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                         ASSESSING CHANGE
                                       IN THE
                        EDISTO RIVER BASIN:

                              An Ecological Characterization













                                         Edited by:

                                     William D. Marshall
                               South Carolina Water Resources Commission
                                    1201 Main Street, Suite 1100
                                   Columbia, South Carolina 29201











                                         LIBRARY
                                       NOAA/CCEH
                                     1990 HOBSON AVE
                                   CHAS
                                         SC 29408-2629


                         South Carolina Water Resources Commission
   
                                       Report No. 177
                                        October 1993
                                                    us Department of Commerce
                                                    NOAA Coastal Services Center Library
                                                    2234 South Hobson Avenue
                                                    Charleston, SC  29405-2413
                                                   
 









                                                                           State of South Carolina
                                                                                                                                                                    CARO,
                                                                 The Honorable Carroll A. Campbell, Jr., Governor
                                                     South Carolina Water Resources Commission

                                                                                   Appointed Members                                                                RCMES
                                                                         Mr. Lynn H. Youmans, Jr., Chairman
                                                                     Mr. Tom W. Dunaway, 111, Vice-Chairman


                                Agriculture
                                                        Mr. Ben M. Gramling, III           ................................................................. Gramling
                                                        Mr. Lewis Walker          ................................................................................  Sumter
                                                        Mr. Lynn H. Youmans, Jr            . ..................................................................  Furman

                                Industry
                                                        Mr. Ralph A. "Nick" Odom, Jr             . ....................................................... Rock Hill
                                                        Mr. Robert M. Rainey           . .................................................................... Anderson
                                                        Mr. Frank B.Winslow           ..............................................................  ....... Hartsville


                                Municipalities
                                                        Mr. H.F. "Dick" Crater          .......................................................................  Gaffney
                                                        Mr. Tom W. Dunaway, III              ............................................................... Anderson
                                                        Vacant


                                Saltwater
                                                        Mr. Whitemarsh S. Smith            ............................................................... Charleston


                                                                         Ex Officio Members and Designees


                                Mr. D. Leslie Tindal, Commissioner                                              Mr. John W. Parris, Executive Director
                                S.C. Department of Agriculture                                                       S.C. Land Resources Conservation
                                Desig: Mr. David L. Tompkins                                                               Commission
                                                                                                                           Desig: Mr. Cary D. Chamblee

                                Mr. Doug Bryant, Commissioner                                                              Mr. Wayne L. Sterling, Director
                                S.C. Department of Health                                                                  S.C. Department of Commerce
                                and Environmental Control                                                                        Desig: Mr. O'Neal Laird
                                Desig: Mr. R. Lewis Shaw

                                Mr. J. Hugh Ryan, State Forester                                                           Dr. Maxwell Lennon, President
                                S.C. Forestry Commission                                                                                 Clemson University
                                Desig: Dr. Tim Adams                                                                                 Desig: Dr. Earl Hayter

                                Dr. James A. Timmerman, Jr., Executive Director                                 Mr. Daniel P. Fanning, P.E., Executive
                                S.C. Wildlife and Marine Resources Department                                              Director
                                Desig: Mr. Larry D. Cartee                                                           S.C. Department of Transportation
                                                                                                                            Desig: Mr. Robert B. Ferrell
                 9;)





























































                                                                                              Staff
                                                                          Alfred H. Vang, Executive Director
                                                                        Hank W. Stallworth, Deputy Director
                                                                         Anne Hale Miglarese, Director of the
                                                                   Research, Assessment and Planning Division







                                   ASSESSING CHANGE IN THE EDISTo RIVER BASIN


            ACKNOWLEDGEMENTS
            This study and the report were made possible through a grant from the National Oceanic and
            Atmospheric Administration, Washington, D.C.
                     The information provided in this report was derived from the research and knowledge
            of many people. In particular, the contribution of Dr. James G. Gosselink is acknowledged.
            His work and writing in recent years, with Dr. Lyndon Lee, led to the development of the
            methods and conceptual approach to this study. Dr. Gosselink provided essential guidance to
            the work group involved with this study, and he made extensive comments on the draft reports.
                     Staff members of the South Carolina Water Resources Commission, Resource
            Assessment and Planning Division, provided essential support. The Division Director, Anne
            Hale Miglarese, provided oversight and consistent encouragement toward development of this
            study and the published report. Catherine E. Vanden Houten contributed to the introduction and
            Basin description presented in the Introduction and Overview chapter, and she provided review
            and editing support for several drafts of this report. Jim Scurry, Floyd Stayner, and Jean Coombs
            provided the spatial-data analysis and map graphics from the Commission's geographic
            information system. Chris Page gathered, sorted, and developed an array of land use and wildlife
            information, assisted in the Natural Area Inventory work, and reformatted many of the map
            graphics. Cindy Brown provided review and comments on draft reports, and contributed to the
            Land Use and Biological Diversity chapters with a literature review used in the chapter
            discussions. Noel Hill helped develop some of the tables presented in the Biological Diversity
            chapter.
                     John White and Cindy Aulbach-Smith provided extensive comments on draft reports
            and contributed to the Biological Diversity chapter with the discussion of methods and results
            from the Natural Area Inventory. The Natural Area Inventory of the Edisto Basin was a
            cooperative project with The Nature Conservancy's Southeast Regional Office. Dorothy Allard
            administered the inventory on behalf of The Nature Conservancy.
                     Susan Moegenburg of the Department of Zoology, University of Florida, conducted
            the Breeding Bird Survey analysis and contributed to the methods, results, and discussiq@ n of this
            analysis as presented in the Biological Diversity chapter.
                     Individuals from other agencies and organizations made significant contributions to
            the study and to the report. Those who provided substantive comments and suggestions on draft
            reports and/or contributed to the meetings of the study work group were: Bob Somers of the
            South Carolina Land Resources Commission; John Cely, Fred Holland, Bert Pittman, and Kathy
            Boyle of the South Carolina Wildlife and Marine Resources Department; Steve Gilbert of the
            U.S. Fish and Wildlife Service; Bill Baughman, Joe Collins, and Bob Fletterman of Westvaco
            Timberlands Division; Jim Couch of the U.S. Environmental Protection Agency; Buddy Atkins,
            Danny Johnson, and Rod Cherry of the South Carolina Water Resources Commission; Lamar
            Sanders of the U.S. Geological Survey; and Dennis DeFrancesco of the U.S. Soil Conservation
            Service, Roy Newcorne of the South Carolina Water Resources Commission and Beverly
            Miller and John White of Ecological Services in Urbana, Illinois provided technical editing on
            most of the report.
                     Cover artwork is provided courtesy of the New-York Historical Society, New York,
            New York. The work is titled Common Snipe (Capella gallinago), painted by John James
            Audubon while visiting South Carolina in 1832. The landscape presented with Audubon's
            Snipe was painted by George Lehman. The illustrations presented at the beginning of each
            chapter in the report were created by Gene Speer of Columbia, S.C. The typesetting and design
            for the report were done by Van Komegay of Columbia, S.C.



                              In the beginning God created the heavens and the earth.
                                         And God saw all that he had made,
                                             and behold, it was very good.

                                                     - Genesis 1: 1, 31






              iv                                                               ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                        ABSTRACT
                                                        This report is a description and evaluation of ecological conditions and historical changes in
                                                        the Edisto River Basin with recommendations for improving natural resource management
                                                        in the future. The methods used to assess ecological conditions emphasize a landscape-level
                                                        approach to address the cumulative effects of human activities on natural processes. The first
                                                        chapter explains the background and purpose of the study, describes the study ared,
                                                        summarizes study methods and results, and outlines optional goals and plans for resource
                                                        management in the region. Chapters 2 through 5 assess land use and land cover, hydrology,
                                                        water quality, and biological diversity in the Edisto River Basin and provide detailed
                                                        discussions of methods, results, and conclusions.
                                                                 The Edisto River Basin is a 3,120 square mile region (about 2 million acres) drained
                                                        by a black-water river system located in the Coastal Plain of South Carolina. The Basin is
                                                        primarily rural in character, but most of the residents are employed in manufacturing and
                                                        service sectors of the economy. Compared to many other regions in the southeastern United
                                                        States, the Edisto River Basin is in exceptional ecological condition.
                                                                 The assessment of land use and land cover showed that currently the Basin is about
                                                        56 percent forested, and that total forest cover has remained relatively stable since 1950. One-
                                                        third of the Basin's forest cover consists of pine plantations - monoculture forests that have
                                                        rapidly expanded in recent decades. Most of the Basin's forests are closely interconnected
                                                        and an irregular pattern of forested corridors extends throughout the landscape. However,
                                                        most of the forests are relatively young and high-quality forest-interior habitats seem to be
                                                        quite limited. The Basin's forest conditions are far from pristine, but remain favorable for
                                                        supporting many indigenous wildlife species and good water quality. Most of the Basin's
                                                        stream edges (riparian zones) are covered in native vegetation. These riparian conditions are
                                                        favorable for providing important wildlife habitats, corridors for wildlife movement, and
                                                        improved water quality that results from the filtration of sediments, nutrients, and other
                                                        contaminants flowing into the streams.
                                                                 From the hydrology assessment, analysis of precipitation and streamflow indicates
                                                        that only minor changes in precipitation and strearnflow have occurred in the Edisto River
                                                        Basin and that changes in streamflow are a result of changes in precipitation. This finding
                                                        indicates that the minor increases in strearnflow did not result from land use changes
                                                        involving forest and vegetative cover losses. Also, there have been no significant modifica-
                                                        tions to the Edisto River stream channels to alter the hydrology. The stable trends in
                                                        hydrology for the Edisto are likely to be related to the predominately natural-cover conditions
                                                        of the Basin's stream-edge habitats.
                                                                 The analysis of historical water quality records indicate's that, while certain areas of
                                                        the Basin have problems, the Edisto Basin overall has very good water quality. Water quality,
                                                        as characterized by total phosphorus concentration, is generally within the EPA criterion of
                                                        0. 1 milligrams per liter total phosphorus and is being maintained throughout the Basin, with
                                                        the exception of the North Fork Edisto River. The North Fork also showed frequent
                                                        violations of state standards for fecal coliform bacteria in the headwaters. Analysis of total
                                                        phosphorus, total suspended solids, and turbidity showed highly significant and negative
                                                        relationships to stream discharge. This concurrent decrease in concentration of pollutants
                                                        with an increase in stream volume (increased water volume resulting from rain and runoff)
                                                        suggests a dilution phenomenon characteristic of undisturbed, forested watersheds.
                                                                 Very little information exists to provide a significant understanding of how the
                                                        abundance and diversity of native species has changed in the Edisto Basin. Breeding Bird
                                                        Surveys were analyzed and showed that no species had plummeting populations or appeared
                                                        threatened with local extinction; however, more species' populations are decreasing than
                                                        increasing at four of the six Breeding Bird Survey routes analyzed. Two routes in particular
                                                        are showing declines for 30 to 40 percent of the species over the last 20 years. These declines
                                                        coincide with land cover changes of forest loss and forest conversion to pine monoculture
                                                        along these routes. The large, wide-ranging mammals native to the Edisto River Basin -
                                                        bears, cougars, and wolves - have been extirpated. However, medium-sized carnivores
                                                        with smaller range requirements - such as bobcats and otters - remain, and most of the
                                                        raptors in the Basin appear to have increasing or stable populations. Several nationally
                                                        threatened and endangered species inhabit the Edisto River Basin, suggesting that certain
                                                        areas serve as a refuge for sensitive or specialized species and that the Basin contains








                                  ASSESSING CHANGE IN THE EDISTo RIVER BASIN





           relatively intact and uncontaminated habitats that are rare or unique in the nation. An
           inventory of natural areas revealed that the relatively undisturbed, high-quality natural
           communities that remain in the Basin are almost all wetlands, and most of these are found in
           the coastal region. Few natural areas and fewer kinds of natural communities are found in
           the more inland portions of the Basin.
                     Based on the findings of this study, a broad set of goals and planning objectives are
           suggested as an option for consideration in future planning efforts. The suggested goals and
           objectives are directed toward ecological protection and enhancement of the Edisto Basin
           through thoughtful conservation, use, and development of the Basin's natural resources.
           Basin-level (or landscape-level) planning is recommended and encouraged because it can
           provide a framework for guiding many decisions and activities that will continue to
           incrementally effect ecological conditions in the Edisto River Basin.







                 Vi                                                                              ASSESSING CHANGE IN THE EDISTo RIVER BASIN

                                                                     TABLE OF CONTENTS

                                 Chapter 1: Introduction and Overview
                                        by William D. Marshall
                                                         Introduction      .........................................................................................................................1
                                                               Background and Context of the Study                 .........................................................................I
                                                               The Problem of Cumulative Impacts on Natural Resources                         ........................................2
                                                               Managing Cumulative Impacts                ....................................................................................3
                                                               Landscape Ecology and Natural Resources Conservation                         ...........................................3
                                                         Purpose of the Study          ...........................................................................................................4
                                                               Goals     ............................................................................................................................4
                                                               Methodology         ................................................................................................................5
                                                               Application      ................................................................................................................... 5'
                                                         Description of the Edisto River Basin              .................................................................................6
                                                               Location and Size        .........................................................................................................6
                                                               Climate and Weather           ....................................................................................................6
                                                               Landforms, Geology, Soils, and Vegetation                  ................................................................8
                                                               People and Economy            ................................................................................................. 10
                                                               Protected Areas        .......................................................................................................... 11
                                                         Results from the Ecological Characterization Study                    ........................................................ 13
                                                               Basin Condition by Indices of Ecological Integrity                   ................................................... 14
                                                               Assets and Problems for Ecological Integrity                 ............................................................ 17
                                                         Development of Goals and Plans               ...................................................................................... 18
                                                               Suggested Goals for Management                 ............................................................................. 18
                                                               Suggested Management Plans               .................................................................................... 19
                                                         References      ......................................................................................................................... 21


                                Chapter 2: Land Use and Land Cover
                                       by William D. Marshall
                                                         Introduction     ..........................................................................................................  ........ 23
                                                         Methods of Assessment               ............................................................... *****'** .... --** ... **  ............. 23
                                                               Information Sources           ................................................................................................... 23
                                                               Assessing Historical Land Use              .................................................................................. 24
                                                               Assessing Current Land Use             ...................................................................................... 25
                                                               Changes in Wetlands           .......................................................................  .......................... 25
                                                               Stream-Edge Habitat Analysis             ................................................................................... 26
                                                               Forest Patch Analysis         ................................................................................................. 27
                                                         Results    ............................................................................................................................... 28
                                                               Historical Changes in Land Use and Land Cover                     ...................................................... 28
                                                               Current Land Use and Land Cover                 ............................................................................ 29
                                                               Changes in Wetland Resources               .................................................................................. 44
                                                               Stream-Edge Habitat           .................................................................................................. 48
                                                               Forest Patch Analysis         ................................................................................................. 51
                                                         Summary and Discussion              .................................................................................................. 57
                                                               Land Use Trends and Structural Change                  ................................................................... 57
                                                               Implications for Ecological Integrity             ......................................................................... 58
                                                               Subbasin Comparisons            ............................................................................................... 63
                                                         References      ......................................................................................................................... 65






                                              ASSESSING CHANGE IN THE EDISTO RIVER BASIN                                                                                                  Vfi


                              Chapter 3: Hydrology Assessment
                                    by Larry Bohman and Glenn Patterson
                                                      Introduction      ....................................................................................................................... 69
                                                            Description of Basin Hydrology              ................................................................................ 69
                                                            Purpose and Scope         ..................................................................................................... 70
                                                            Data Available        ........................................................................................................... 71
                                                      Analyzing Strearnflow and Precipitation                .......................................................................... 71
                                                            Techniques Used for Analysis              ................................................................................... 71
                                                      Results of the Analyses         .................................................................  ................................... 75
                                                            Precipitation      ............................................................................................................... 75
                                                            Strearnflow      ................................................................................................................. 78
                                                      Summary of Findings           ........................................................................................................ 83
                                                      References        ......................................................................................................................... 83


                              Chapter 4: Water Quality
                                     by Jeannie Pickett Eidson
                                                      Introduction      ....................................................................................................................... 85
                                                      Site Description       ................................................................................................................. 85
                                                      Water Quality Data Interpretation             ..................................................................................... 85
                                                      Results and Discussion          ...................................................................................................... 89
                                                            Trends Analysis         ......................................................................................................... 89
                                                            Water Quality Standards           ............................................................................................ 95
                                                            Discharge Relationships           ........................................................................................... 101
                                                            Nitrogen / Phosphorus Ratios             .................................................................................. 101
                                                            Nutrient Fluxes        ........................................................................................................ 102
                                                      Summary           ......................................................................................................................... 109
                                                      References        ....................................................................................................................... 110



                              Chapter 5: Biological Diversity
                                     by William D. Marshall
                                                      Introduction      ..................................................................................................................... 113
                                                      Methods      ........................................................................................................................... 114
                                                            Analyzing Changes in Bird Species Richness                    ......................................................... 114
                                                            Assessing Threatened and Endangered Species, Indicators,
                                                            and Other Wildlife        ................................................................................................... 118
                                                            Natural Area Inventory           ............................................................................................ 118
                                                      Results     ............................................................................................................................. 120
                                                            Changes in Bird Species Richness               ........................................................................... 120
                                                            Changes in Other Wildlife Species Richness                  ........................................................... 123
                                                            Presence of Indicator Species            .................................................................................. 124
                                                            Presence of Threatened and Endangered Species                     .................................................... 125
                                                            Natural Areas        ........................................................................................................... 129
                                                      Discussion and Conclusions             ............................................................................................ 137
                                                            Changes Affecting Bird Species               .............................................................................. 137
                                                            Indicator Species and Threatened and Endangered Species                        .................................... 138
                                                            Natural Areas in the Landscape              ............................................................................... 139
                                                            Ecological Integrity Based on Indicators of Biological Diversity                       ........................... 140
                                                      References        ....................................................................................................................... 142


                              Appendices
                                                      Appendix I        ....................................................................................................................... 144
                                                      Appendix 11       ..................................................................................................................... 145
                                                      Appendix III      .................................................................................................................... 147

















                     Chapter 1
                     Introduction and Overview

                     by;

                     William D. Marshall
                     South Carolina Water Resources Commission







                                            INTRODUCTION AND OVERVIEW


            INTRODUcriON

            The Edisto River Basin Ecological Characterization Study attempts to describe the overall
            ecological conditions of the Edisto River Basin. This study focuses on the land use patterns,
            water quality, hydrologic conditions, and biological diversity of the Basin, and addresses
            issues affecting environmental conservation on a regional level. Some of the most serious
            and difficult problems affecting our environment result from the cumulative effects, or
            impacts, of human activities on natural ecosystems. A description of some of the problems
            associated with cumulative impacts on the Edisto River Basin is provided in the report. In
            order to address the problems of cumulative impacts, this study applies principles of
            landscape ecology to planning issues that affect natural resources.
                 This chapter explains the background and purpose of the study, describes the study area,
            summarizes study methods and results, and outlines optional goals and plans for resource
            management. Detailed discussions of methods and results are found in subsequent chapters
            addressing land use, hydrology, water quality, and biological diversity in the Edisto River
            Basin.


            Background and Context of the Study
            The Ecological Characterization of the Edisto Basin is founded on the objectives of the
            Natural Resources Decision Support System (NRDSS) Project, conducted by the South
            Carolina Water Resources Commission (SCWRC). The NRDSS Project is a multiyear
            research and demonstration project begun in 1988 and funded by the National Oceanic and
            Atmospheric Administration (NOAA) and the State of South Carolina. This project was
            created in response to problems with the existing approach to environmental management
            in South Carolina - the problems of insufficient information about the resources and lack
            of consensus on how they should be managed. The following objectives, mutually agreed
            to by SCWRC and NOAA, guide-the NRDSS Project:

                 ï¿½ Develop a geographic information system for natural resource management
                      applications in the Edisto River Basin of South Carolina; and
                 ï¿½ Develop public policy procedures to identify the public interests in natural
                      resources, classify and prioritize natural resources by value, and formulate
                      alternative approaches to environmental management and regulation.

                 On the basis of the second of these objectives, SCWRC is developing a public policy
            process aimed at natural resources management on a basin-wide scale - the Edisto Basin
            Natural Resource Assessment Process. In short, the Natural Resource Assessment Process
            will provide the citizens of the Edisto Basin with the opportunity to consider what natural
            resources they have and how they can best use and conserve those resources. The process
            will incorporate the following:

                 ï¿½ Baseline studies of ecology (this study), socioeconomics, and public opinion;
                 ï¿½ Classification of resources into categories of use and relative value by various
                      committees of resource experts ; and
                 ï¿½ Recommendation of priorities for resource management by a regionally
                      representative Edisto Basin Task Force.

                 The information and recommendations derived from this Ecological Characterization
            will be provided to participants in the Natural Resource Assessment Process. This
            information, along with information from the other baseline studies, will provide partici-
            pants in the process with a deeper understanding of the problems and issues facing the Basin
            and enable them to reach greater consensus on goals for the future of the Basin and its
            resources.







                                                                             ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                       The Problem of Cumulative Impacts
                                                       on Natural Resources
                                                       Cumulative impacts are the combined effects of individually minor actions and changes on
                                                       the environment. They are the total effect on the environment of small-scale, incremental
                                                       activities that individually seem insignificant. Cumulative impacts are often the product of
                                                       complex physical, chemical, and biological interactions that have synergistic results.
                                                       Cumulative impacts can have positive or negative effects. Positive effects can be seen as
                                                       improvements in environmental quality resulting from a host of individually minor improve-
                                                       ments such as sound land management practices and pollution control technologies applied
                                                       and adhered to by individual landowners. Negative effects can be seen as a relatively slow
                                                       deterioration of environmental quality from a host of seemingly minor assaults on air, water,
                                                       land, and biological resources.
                                                           An example of a cumulative impact can be seen in the eventual degradation of a city's
                                                       air quality through the output of exhaust fumes from numerous automobiles. When viewed
                                                       individually, each automobile poses no significant threat to the overall condition of the city's
                                                       air, however, thousands of automobiles, with engines running simultaneously, can threaten
                                                       air quality. Another example is evident in the deterioration of river water quality through
                                                       the interaction of runoff from urban pavements, agricultural fields, and cleared land,
                                                       combined with the depletion of naturally forested flood plains. While each of these activities
                                                       has some immediate impact on the environment, they also have a combined effect that can
                                                       seriously threaten the ecological condition of the river corridor. Furthermore, the effects are
                                                       felt on a large scale rather than simply where each activity is taking place (in other words, the
                                                       activities affect the conditions downstream as well).

                                                       Contributing Factors
                                                       Cumulative impacts can be widespread and very difficult to deal with, thus posing one of the
                                                       most serious threats to our natural resources and the overall quality of the environment. There
                                                       are several reasons for this.
                                                                First, cumulative impacts may be viewed as "social traps," situations in which the
                                                       short-run, small-scale incentives of an activity are not consistent with the long-term, overall
                                                       best interest of individuals and society (Costanza 1987). For example, the individual actions
                                                       that make up cumulative impacts are driven by relatively short-term profit motives of private
                                                       landowners (for example, forest clearing for row crop production). Over an entire river basin,
                                                       the landscape is divided into thousands of parcels of land where each individual private owner
                                                       follows his or her own distinct land management objectives. Individually, these activities
                                                       usually have minimal environmental costs directly associated with them. However, the
                                                       combined long-term environmental cost of all such actions may be high and these costs
                                                       accrue to the public, not to the landowner. As a result, cumulative impacts are easily created,
                                                       yet not easily avoided.
                                                                Secondly, lack of comprehensive planning contributes to the prevalence of
                                                       cumulative impacts and the difficulty in dealing with them. Comprehensive planning has
                                                       several characteristics: a) considering the widest number of factors related to an issue, b)
                                                       addressing long periods of time, c) including all affected regions and parties, and d)
                                                       increasing the level of consensus on goals and objectives that balance and optimize
                                                       environmental conservation and socioeconomic development. Comprehensive planning has
                                                       the effect of proactively addressing problems and setting limits to certain activities, thus
                                                       controlling cumulative impacts. In South Carolina, however, as in many other states, true
                                                       comprehensive planning is virtually nonexistent. Instead, decisions affecting the natural
                                                       resources of our state are made largely in an incremental, piecemeal approach, with little
                                                       consideration of larger and long-term issues. Thus, South Carolina, like all other states, is
                                                       confronted with the difficult problem of cumulative impacts. Regulatory programs alone do
                                                       not effectively address the problem because they typically are not linked to comprehensive
                                                       planning. The federal program that permits development in wetlands is an example of a
                                                       reactive, rather than proactive, regulatory system that is not able to effectively deal with
                                                       cumulative impacts. The common occurrence is that permitting development at one site
                                                       today sets a strong precedent for permitting development at similar sites everywhere
                                                       tomorrow; thus cumulative impacts continue despite regulatory programs.







                                                 INTRODUCTION AND OVERVIEW


                         A third factor that significantly contributes to widespread cumulative impacts and
               the difficulties associated with them is fragmented decision making. When authority for
               decisions affecting natural resources is divided among numerous entities without coordina-
               tion, the problem of cumulative impacts is even more difficult to manage. Governmental
               responsibility for natural resources management is divided among numerous agencies and
               programs, each with its own specific mission. The result of this political and organizational
               structure is that individual agencies make policy decisions on individual environmental
               issues without the necessary consideration of "the big picture."


               Managing Cumulative Impacts
               Despite the complex nature of cumulative impacts, which the preceding discussion illus-
               trates, they can be successfully managed. However, it must first be understood that the
               problem of cumulative impacts is actually a two-pronged problem - a problem of both
               science and public policy. Thus, any effective solution must necessarily address both the
               scientific and the public management facets of cumulative impacts.

               Science
               On the scientific side of the issue, it is necessary to have appropriate methods, standards, and
               information in order to assess cumulative impacts. The assessment of cumulative impacts
               requires a refocusing from site-specific ecological analyses to broad analyses of the
               landscape. Such an assessment should look beyond the limited organizational or political
               jurisdictions of the associated agencies and encompass a larger ecologically defined
               landscape. Furthermore, the focus of analysis should be on the broad spectrum of natural
               resources within the region, not merely a select few. A solid basis for such an assessment
               is provided by landscape ecology, which is dealt with in greater detail later in this report.

               Public Policy
               On the policy side of the issue, successful management of cumulative impacts requires a new
               public policy approach. First, there needs to be more coordination in developing environ-
               mental policy among the various entities responsible for environmental management.
               Coordination of policy would help counteract the fragmented, piecemeal approach to
               environmental decision-making that contributes to the prevalence of cumulative impacts.
               Second, goals for managing natural resources must be established through meaningful input
               from the public. The goals should be as specific as possible and represent the public's
               interests and aspirations for the area of concern. As one author points out, many valid social
               and economic needs must be considered in addition to scientific facts in assessing the
               tradeoffs that exist among competing resource uses and environmental management goals
               (Stahkiv 1988). Goals for the protection and enhancement of the environment are in the
               public's interest, but such goals must be grounded in the realities of relevant ecological and
               socioeconomic tradeoffs and they should be made to conform with the ecological capabilities
               of the region.
                         Finally, specific plans must be made to ensure the successful implementation of the
               goals decided upon. These plans should reflect a thorough consideration of the ecological
               assessment of the area and the public goals set in the public policy process. The plans should
               be as comprehensive as possible and practical. Public education, landowner incentives, and
               coordination of existing regulatory activities are several areas that could be affected by
               planning efforts. Successful implementation will require ongoing public support and
               advocacy among the citizens of the affected region.


               Landscape Ecology and Natural Resources Conservation
               As mentioned above, landscape ecology provides a conceptual approach to the ecological
               assessment of a region and the analysis of the cumulative impacts. It is therefore helpful to
               take a closer look at the principles of this discipline.
                         Landscape ecology is defined as the study of physical and biological relationships that
               govern the different spatial units of a region (Gosselink and others 1990). More simply put,
               landscape ecology deals with large areas, the interaction of parts within these areas, the landscape







                                                                                ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                       patterns of the areas, and how the patterns influences ecological processes. From a landscape
                                                       ecology perspective, the cumulative effects of development activities are evaluated by examin-
                                                       ing changes in both ecological structure and functional ecological processes in a particular
                                                       landscape unit. While a general landscape ecological approach is helpful in assessing
                                                       cumulative impacts, a related theory - island biogeography - provides further insight into the
                                                       ecology of a region.
                                                                  Island biogeography concerns itself with the size, shape, and pattern of various parts
                                                       (or patches) of the landscape, their isolation from each other, and the influence of these factors
                                                       on ecological processes and natural diversity (Gosselink and others 1990). This particular theory
                                                       is frequently applied in planning nature reserves; however, it also has useful applications in
                                                       overall environmental planning and management. Diamond (1975) presented five principles
                                                       from island biogeography that apply to natural reserves in a forested landscape: 1) species
                                                       richness increases with forest area; 2) for a given total forest area, one large reserve will support
                                                       more native interior species than two or more smaller ones; 3) for a given forest area, separate
                                                       but nearby patches will support more species than patches farther apart; 4) blocks of forest
                                                       connected by strips of protected habitat are preferable to isolated patches of forest; and 5) other
                                                       things being equal, a circular-shaped reserve is preferable to a linear one because the former
                                                       maximizes dispersal distances within the reserve and minimizes the edge relative to the interior
                                                       area.
                                                                  In summary, landscape ecology provides principles that can serve as a means for
                                                       diagnosing the ecological health and conditions of a landscape unit. The focus of landscape
                                                       ecology is on large areas, the patterns and interaction of parts within the areas, and the effects
                                                       of these patterns on natural processes and biological diversity. Because of its focus on large
                                                       areas, landscape ecology usually incorporates humans and human activities. Landscape
                                                       ecology is therefore an applied science that deals with the natural world within which man is one
                                                       actor (Forman and Gordon 1986). The effect of landscape ecology on resource management is
                                                       that it broadens the perspective to a holistic one in which resources such as forests, wetlands,
                                                       agricultural lands, wildlife, water, and human development are not viewed each in isolation but
                                                       rather as a whole.

                                                       Terminology
                                                       In this study, the term landscape structure refers to the shape, pattern, and natural quality of
                                                       the forests and other native vegetation as they are related to the mix of human development
                                                       and land uses in the region. These factors can greatly affect the water quality, hydrology, and
                                                       wildlife populations of a region like the Edisto River Basin. The terms natural processes and
                                                       ecological processes (or functions) as they are used in this study, refer primarily to the
                                                       movement of energy and support of diversity through food chains within the natural plant and
                                                       animal communities; maintenance of the full array of native species, each with particular
                                                       habitat requirements; movement and processing of chemicals from the land into the region's
                                                       streams; and stability (that is, normal seasonal fluctuations in strearnflow) and storage of
                                                       flowing water as it relates to flood control and maintaining a continuous source of water in
                                                       the streams.


                                                       PURPOSE OF THE STUDY
                                                       Goals
                                                       The goals of the Edisto River Basin Ecological Characterization are as follows:

                                                            ï¿½ Establish a baseline description of the relative ecological conditions and historic
                                                                  changes in the Basin by: a) describing the existing and historical landscape
                                                                  structure (land use and land cover) of the Basin; b) describing the ecological
                                                                  processes (functions) of the Basin, specifically regarding hydrology, water
                                                                  quality, and biota; and c) describing the relationship between the structural and
                                                                  functional elements of the Basin.
                                                            ï¿½ Evaluate ecological conditions relative to human values and identify potential
                                                                  problems affecting ecological structure and function in the Basin.
                                                            ï¿½ Make recommendations for improved natural resources management to include
                                                                  suggested goals and an implementation plan.








                                                INTRODUCTION AND OVERVIEW


               Methodology
               The methods of the Edisto River Basin Ecological Characterization are adapted from two
               sources:


                   ï¿½ The manual of a training course offered by the U.S. Environmental Protection
                        Agency's Office of Wetland Protection, titled Cumulative ImpactAssessment
                        in Southeastern Wetland Ecosystems: The Pearl River, and
                   ï¿½ James Gosselink and Lyndon Lee's 1989 article, "Cumulative Impact Assess-
                        ment in Bottomland Hardwood Forests" in Wetlands, Vol. 9, Special Issue.

                        This study takes a relatively new scientific approach and applies principles of
               landscape ecology to evaluate available information for hydrology, water quality, indigenous
               animal populations, and landscape structure (or patterns of land use and land cover). Useful
               types of information include long-term data sets, repeated survey data, and indicators of
               landscape ecological conditions. The methods are designed to assess watersheds of about 1
               to 2 million hectares in size. The Edisto Basin is a 3,120-square-mile area (800,000 hectares).
                        As discussed previously, landscape ecology focuses on large areas, the patterns and
               interactions of parts within the areas, and the effects of these on natural processes and
               biological diversity. Applying landscape ecology to natural resource management broadens
               the perspective to large areas and incorporates a comprehensive approach.


               ApplicAtion
               Human medical science provides a useful analogy that helps explain the purpose of this study
               and helps us understand its application. Various indicators of ecological integrity are
               addressed in this report that point to overall ecosystem health in the same way that pulse and
               body temperature point to the health of a human patient (Gosselink and Lee 1989). The
               purpose of this study is to assess the ecosystem health of the Edisto River Basin. The
               diagnostic procedures used to characterize the Basin's condition focus on changes in
               landscape structure and changes in ecological processes. Landscape structure refers to
               patterns of land use and land cover; ecological processes relate to water quality trends,
               changes in hydrology, and changes in populations of indigenous animals. Where information
               is available (for example, water quality), the ecological indicators are related to standards in
               the same way that human body temperature isjudged by its relationship to "normal." Trends
               or changes, in water quality for example, are a means of judging incremental deterioration
               or improvement of the ecosystem. Analyses of this information are used to provide a baseline
               description of the relative ecological conditions of the Basin, changes that have occurred, and
               activities affecting those changes.
                        The information resulting from this study must be applied to solving problems in a
               new way - using a new public policy approach. To this end, the information from this study
               will be provided to a regionally representative Edisto Basin task force charged with
               developing a vision for the use and conservation of natural resources while considering
               economic development needs of the region. To accomplish this, an open public process is
               proposed to enable citizens to define the vision by identifying resource values, common
               goals, and priorities and to target the goals with strategies for action. The process is referred
               to as the Edisto Basin Natural Resource Assessment Process.
                        Humans need to understand their overall health conditions in order to make
               reasonable choices that will lead to the maintenance and improvement of their health.
               Likewise, the conditions of an ecosystem should be understood in order to make similar
               choices affecting ecological health. The point is that choices - choices made by individuals
               and whole communities - are what will affect a region's ecological health and quality of life.
               Insuring the future ecological health of an ecosystem that is coming under increasing
               pressures, such as the Edisto Basin, calls for some form of regionwide planning, and planning
               requires the establishment of publicly accepted goals and objectives.
                        When goals that specify desired future conditions become understood and estab-
               lished, then courses of action can be identified and selected to achieve those goals. In medical
               terms, a prescription or treatment plan is developed and adhered to by the patient. Similarly,







                                                                         ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                   plans for directing the Edisto Basin's health toward desirable ecological conditions must be
                                                   developed and adhered to by people and institutions that affect it.


                                                   DESCRIPTION OF THEEDISTO RIVERBASIN

                                                   Location and Size
                                                   The Edisto River Basin is located in south-central South Carolina. From its western extreme
                                                   in eastern Edgefield County, the Basin extends southeastward across the Coastal Plain to the
                                                   Atlantic Ocean. The Edisto River Basin is a drainage area of about 3,120 square miles
                                                   (roughly 2 million acres or 800,000 hectares). The region occupies approximately one-tenth
                                                   of the area of South Carolina. (See Figure 1-1 for a general location map.)
                                                            The Basin is approximately 130 miles long from Edgefield County to the ocean. The
                                                   width of the Basin ranges from an approximately 30-mile-wide corridor, common for most
                                                   of the upper portions, to an 8-mile-wide bottle-neck below Givhans Ferry, then to a 10- to 24-
                                                   mile-wide estuarine region at the coast. Portions of 12 counties are encompassed by the
                                                   Basin. These counties are: Edgefield, Saluda, Lexington, Aiken, Barnwell, Bamberg,
                                                   Orangeburg, Calhoun, Dorchester, Berkeley, Charleston, and Colleton.
                                                            The approximately 250 unobstructed river miles from the Atlantic Ocean to the
                                                   headwaters in Edgefield County have distinguished the Edisto as one of the longest free-
                                                   flowing blackwater rivers in the United States. Much of the Edisto River and its tributaries
                                                   is associated with extensive wetland areas. The Edisto River Basin is drained by four major
                                                   river systems: the South Fork Edisto River, North Fork Edisto River, Edisto River (main
                                                   stem) and Four Hole Swamp.

                                                   Subbasins
                                                   The North and South Forks originate in the Upper Coastal Plain, primarily in the Sandhills
                                                   regions of Edgefield, Saluda, and Lexington Counties. The North and South Forks drain two
                                                   subbasins of 750 and 870 square miles, respectively. These subbasins span approximately
                                                   70-75 miles and then join to form the main stem of the Edisto River. The headwaters of Four
                                                   Hole Swamp subbasin originate in the Coastal Plain in Calhoun and Orangeburg Counties
                                                   and drain about 650 square miles. The Four Hole Swamp system spans approximately 50
                                                   miles before it discharges into the main stem of the Edisto River. The Edisto River (main
                                                   stem) eventually receives all the drainage from the North and South Forks and Four Hole
                                                   Swamp. In addition, the main stem receives drainage from its own subbasin area of about
                                                   850 square miles. The main stem extends approximately 65 miles from the confluence of the
                                                   North and South Forks to the Atlantic Ocean. At the coast, the Edisto River is divided by
                                                   Edisto Island to form the North and South Edisto Rivers with two distinct estuaries. Most
                                                   of the freshwater flow is to the south side of Edisto Island. These tidally influenced brackish
                                                   streams also receive drainage from bordering salt marshes, tidal rivers, and tidal creeks. The
                                                   coastal/estuarine portion of the main stem drainage is about 200 square miles.


                                                   Climate and Weather

                                                   The Edisto Basin has a mild climate with plentiful rainfall. The region's low latitudinal
                                                   location coupled with its close proximity to Gulf Stream waters provides for a climate
                                                   dominated by warm, moist air masses from the south. The Appalachian Mountains to the
                                                   north and west of South Carolina help to shield the Basin from cold air masses of the
                                                   northwest.
                                                            The average annual temperature ranges from 610 to 660 F and the average relative
                                                   humidity is 50 to 55 percent in mid-afternoon and about 90 percent at dawn. The summers
                                                   are hot and humid, with an average temperature of 790 F and daily maximum temperatures
                                                   of 89 to 900 F. The winters are cool, with an average temperature of 480 F and an average
                                                   daily minimum of about 360 F. The average annual rainfall for the Basin ranges from 42 to
                                                   52 -inches. The highest precipitation occurs in Charleston, Dorchester, and Colleton
                                                   Counties, about 20 miles inland from the coast, due to the upward flow of moist air moving
                                                   inland from the ocean on hot summer days. Generally, during the months of spring, the Basin
                                                   receives its maximum rate of rainfall. During the autumn months, September through
                                                   November, rainfall is at a minimum.







                                          INTRODUCTION AND OVERVIEW








                                          THE EDISTO RIVER BASIN









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                SOUTH CAROLINA WATER RESOURCES COMMISSION
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           Figure 1-1. General locational map for the Edisto River Basin.







                                                                              ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                                 Extreme weather is usually in the form of violent thunderstorms, tropical storms,
                                                       and hurricanes, as well as occasional droughts. Snowfall may occur once or twice a year in
                                                       the upper portions of the Basin, but rarely near the coast. Thunderstorms are common in the
                                                       summer months. The violent storms, however, usually accompany cold fronts in the spring
                                                       and are characterized by lightning, hail, high winds, and sometimes tornadoes. Hurricanes
                                                       and tropical storms from the Atlantic periodically cross the Basin or pass near it during the
                                                       summer and early fall. They bring several days of heavy and sustained rainfall, as well as
                                                       destructive winds and coastal flooding. Historically, severe droughts occur about once every
                                                       15 years in South Carolina. Less severe and less widespread droughts occur about once every
                                                       7 years (SCWRC 1983).


                                                       Landforms, Geology, Soils, and Vegetation
                                                       The Edisto Basin is underlain by the unconsolidated and consolidated sedimentary forma-
                                                       tions of the Coastal Plain. The Coastal Plain is divided into three physiographic regions, the
                                                       Upper, Middle, and Lower Coastal Plain. These regions are differentiated by topographic
                                                       and geomorphic features formed over millions of years when ocean levels were much higher
                                                       than at present.
                                                                 Beginning at the Fall Line, the Upper Coastal Plain extends southeast to a steep
                                                       slope known as the Citronelle Escarpment. This ancient sand dune region includes the
                                                       Carolina Sand Hills and is characterized by moderately sloped, irregularly shaped, and
                                                       generally rounded terrain. The Middle Coastal Plain lies between the Sand Hills and another
                                                       steep slope known as the Surry Escarpment. The Lower Coastal Plain lies between the Surry
                                                       Escarpment and the Atlantic coastline. These latter two physiographic regions exhibit
                                                       moderate to low relief and are marked by several terraces, each of which represents a former
                                                       sea level.
                                                                 Underlying the sedimentary formations of the Coastal Plain are metamorphic and
                                                       igneous rocks similar in type and age to those of the Piedmont and Blue Ridge provinces of
                                                       South Carolina. This basement rock has an irregular surface that dips to the south and
                                                       southeast. The Coastal Plain formations consist of sediments of alluvial and marine origin
                                                       that thicken from a few feet at the Fall Line to nearly 4,000 feet at Edisto Island. The Coastal
                                                       Plain formations beneath the Edisto Basin include significant aquifer systems of the
                                                       Middendorf, Black Creek, Tertiary limestone, and Tertiary sand formations.

                                                       Land Resource Areas
                                                       The Soil Conservation Service has divided the state of South Carolina into six land resource
                                                       areas based on soil conditions, climate, and land use (U.S. Department of Agriculture 1978).
                                                       These land resource areas are similar to physiographic provinces, but are based primarily on
                                                       soil characteristics that provide a basis for describing potential vegetation and land uses. The
                                                       Edisto Basin encompasses four of the six land resource areas: the Carolina-Georgia
                                                       Sandhills, the Southern Coastal Plain, the Atlantic Coast Flatwoods, and the Tidewater Area
                                                       (Figure 1-2). The two land resource areas outside of the Edisto Basin include the Blue Ridge
                                                       Mountains and Southern Piedmont.
                                                                 Carolina-Georgia Sandhills: This is an area of gently sloping to strongly sloping
                                                       uplands that is synonymous with the Upper Coastal Plain physiographic province. Eleva-
                                                       tions range from about 250 to 450 feet with local relief in tens of feet. About two-thirds of
                                                       the area is forested, predominantly pine with some upland and bottornland hardwood forest
                                                       types. The remainder of the area is in cropland or pasture. The soils are mostly well drained
                                                       and formed in sandy Coastal Plain sediments.
                                                                 Southern Coastal Plain: This area generally corresponds to the Middle Coastal Plain
                                                       physiographic province. The area has gentle slopes with increased dissection and moderate
                                                       slopes in the northwestern part. Elevations range from about 100 to 450 feet with local relief
                                                       in tens of feet. Generally, about half of this region is forested, a mix of mostly pine with
                                                       upland and bottomland hardwood forest types. The other half of the area is mostly cropland.
                                                       The soils are predominantly well drained or moderately well drained and formed in loamy
                                                       or clayey Coastal Plain sediments.
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                                                                 Atlantic Coast Flatwoods: This is an area where a majority of the land surface is
                                                       nearly level and is dissected by many broad, shallow valleys with meandering stream
                                                       channels. Elevations range from about 25 to 125 feet with local relief of a few feet to about







                                         INTRODUCTION AND OVERVIEW







                                              EDISTO RIVER BASIN
                               MAJOR LAND RESOURCE AREAS



                    Johnston          Batesburg








                         Aiken






                                        Williston


                                                          Bamberg







                                      = Carolina and Georgia Sand Hills
                                      = Southern Coastal Min
                                      Ell Atlantic Coast Flatwoods
                                      = Tidewater Area








                 South Carolina Water Resources Commission
                 Natural Resources Decision Support System                                              Edisto Beach
                 Cdr&a, South Carow                     Sotrce: USDA Sol ConservaVion Service






            Figure 1-2. Map of the Major Land Resource Areas of the Edisto River Basin.

                Land Resource Areas compared to Physiographic Provinces: Carolina-Georgia Sandhills is similar to Upper Coastal Plain;
                Southern Coastal Plain is similar to Middle Coastal Plain; and Atlantic Coast Flatwoods combined with the Tidewater Area are
                similar to the Lower Coastal Plain physiographic province.







                                                                              ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                       20 feet. About one-half of the area is forested primarily with pine and bottomland hardwood
                                                       forest types. The remainder of the area is predominantly cropland. The soils are moderately
                                                       well drained to poorly drained and formed in sandy to clayey Coastal Plain sediments.
                                                                 Tidewater Area: This area is nearly level and is dissected by many broad, shallow
                                                       valleys with meandering stream channels. Most of the valleys terminate in estuaries along
                                                       the coast. Elevations range from sea level to about 25 feet, and local relief is usually less than
                                                       5 feet. About two-thirds of the area is forested primarily with pine and bottomland hardwood
                                                       forest types. The remainder of the area is marsh, pasture, or cropland. The soils are
                                                       predominantly somewhat poorly drained to very poorly drained and formed in sandy to
                                                       clayey Coastal Plain sediments.
                                                                 The Atlantic Coast Flatwoods and the tidewater Area are land resource areas that,
                                                       together, generally define the Lower Coastal Plain physiographic province.

                                                       Natural Communities
                                                       The Edisto Basin supports approximately 94 natural ecological communities (not including
                                                       aquatic communities). These include 21 terrestrial communities, 57 palustrine communities,
                                                       and 16 estuarine communities. These communities are associated with the wet soils of the
                                                       swamps and riverine bottomlands, the porous soils of the upland sandhills and coastal plain,
                                                       and the mix of well drained to poorly drained soils of the coastal flatwoods. The lower
                                                       flatwoods and the tidewater areas contain the most diverse assemblage of natural communi-
                                                       ties -including those typically associated with broad floodplain swamps, barrier islands,
                                                       marsh islands, and major estuarine rivers. Natural communities of the Edisto Basin are
                                                       addressed in grater detail in the biological diversity chapter (Chapter 5).


                                                       People and Economy
                                                       Population, education, employment, and income data were not available for the river basin
                                                       alone; therefore, a socioeconomic description of the Edisto Basin is based on data from
                                                       selected counties that compose a major portion of the region. These include Aiken, Bamberg,
                                                       Calhoun, Colleton, Dorchester, Edgefield, Lexington, and Orangeburg Counties. Three
                                                       major metropolitan areas are located just outside the Basin boundaries in Aiken, Dorchester,
                                                       and Lexington Counties. Data from these metropolitan counties can skew the figures used
                                                       to represent the whole Basin; however, the close proximity of the metropolitan areas has
                                                       significant economic and environmental effects on the Basin. More information on
                                                       socioeconomics than can be presented here is provided by a 1992 report entitled The
                                                       Economy of the Edisto River Basin (SCWRC 1992).

                                                       Character and Population of the Study Area
                                                       The Edisto River Basin is primarily rural in character. The major economic use of land in
                                                       the region is forestry related, and the secondmost is for agricultural purposes. Over the past
                                                       30 years, the percentage of forest land has decreased only slightly, while the percentage of
                                                       land used for farming has declined sharply. This decline in farm land has been accompanied
                                                       by an even sharper decline in the number of farms and by an increase in the average size of
                                                       farms.
                                                                 Of the state's nearly 3.5 million residents in 1990, about 8.5 percent (roughly
                                                       300,000 people) lived in this study area. Since 1960, the average annual rate of population
                                                       growth in the region has been above that of the state as a whole. This population growth has
                                                       been accompanied by an increase in total housing units at a rate above the state average.
                                                       Despite this rapid population growth the region remains sparsely populated compared with
                                                       the rest of the State. For example, the average population density of the state was 119 people
                                                       per square mile, while the population density of the Edisto Basin counties averaged 94. These
                                                       figures, however, do not tell the whole story. It is important to recognize that the metropolitan
                                                       areas of Lexington, Dorchester, and Aiken Counties - with population densities of 255, 144,
                                                       and 111 people per square mile, respectively - give us a skewed picture of the river basin.
                                                       Thus, it is useful to look at the population densities of the remaining five counties:
                                                       Orangeburg with 77 people per square mile and Bamberg, Edgefield, Calhoun, and Colleton
                                                       with population densities ranging from 33 to 42 people per square mile. The racial
                                                       composition of the region in 1990 was nearly identical to that of the state as a whole - the







                                                INTRODUCTION AND OVERVIEW


              ratio of whites to non-whites was approximately 7 to 3. It should be noted, however, that the
              regional (12 counties) average masks the significant diversity that exists among the counties.

              Education
              Educational attainment level varies among the Edisto Basin counties, but it is generally below
              the state average. In 1990, the Basin counties with the highest percentage of population with
              at least a high school diploma were Lexington, Dorchester, and Aiken - each with over 70
              percent of the population having graduated from high school. In the more rural areas of
              Orangeburg, Bamberg, Calhoun, Colleton, and Edgefield Counties, these figures ranged
              from a low of 59 percent in Bamberg to a high of about 62 percent in Orangeburg and
              Edgefield. While these five counties have experienced increased levels of educational
              attainment since 1960, largely consistent with the overall statewide trend, they remained
              below the statewide average of 68 percent in 1990.
              Employment and Income
              More than 95 percent of the working population of the Edisto region is employed in
              nonagricultural jobs. Manufacturing has employed the greatest portion of the population
              since 1970, but there has been a substantial shift from the manufacturing sector to the trade
              and service sectors since that time. In the period between 1970 and 1990, nonagricultural
              employment grew at a faster pace in the Edisto Basin region than in the state as a whole.
                        Since 1950, the number of farms and the extent of farmland has steadily decreased
              and agricultural employment has decreased as well. Farming employment in the Basin area
              decreased by about 63 percent between 1960 and 1980 - a decrease from about 16,000 to
              6,000 people. This was a faster rate of decrease than in the state as a whole. While forestry
              employment data are sketchy, it has been estimated that in 1980 and 1990, approximately 740
              and 850 people, respectively - less than 1 percent of the Basin's population - worked for
              the timber industry in the Edisto Basin.
                        Unemployment rates in the Edisto Basin vary among the counties. In 1990,
              unemployment ranged from a low of about 3 percent in Dorchester County to a high of 8
              percent in Bamberg County.
                        Between 1970 and 1989, both total personal income and per capita income grew
              faster in the Edisto region than it did in the state as a whole or in the state's metropolitan areas.
              Despite this faster growth in income, in 1989 most of the counties of the Edisto still had a
              lower per capita income and a larger portion of their population living below the poverty level
              than the state as a whole or the metropolitan areas.
                        Statewide, about 15 percent of the population was be-low the poverty level in 1989.
              The percentage of the Edisto Basin population living below the poverty level in 1989 ranged
              from approximately 8 percent in Lexington County to 28 percent for Bamberg County. Only
              in Lexington, Aiken, and Dorchester Counties were the residents better off than the state
              average in terms of economic status.
                        Farm income and farm-related income constituted a niere 1.6 percent of the region's
              total personal income in 1989. Thus, while agriculture remains an important activity for
              many communities and families throughout the region, the agricultural income and employ-
              ment figures indicate that the farm sector's contribution to the region's economy as a whole
              is relatively small.
                        In 1989, the total cash receipts for natural resources-based products in the counties of
              the Edisto Basin were divided nearly equally among livestock and livestock products (36.7
              percent), crops (32.5 percent), and timber and forest products (30.8 percent). Since 1980, the
              Edisto Basin region has accounted for more than 20 percent of the state's total cash receipts from
              timber and forest products.
                                                                                                                        719





















































              Protected Areas
              The Edisto River Basin contains a variety of protected lands. Areas under official protection
              as state or federal parks and wildlife refuges occupy less than 4 percent of the Basin's total
              area. Figure 1-3 is a map that shows the location of protected lands and land conservation
              projects. Much of the ACE Basin Project Area shown in Figure 1-3 lies outside of the Edisto
              River Basin and is therefore not included in the 4 percent figure mentioned above.







                                                                       ASSESSING CHANGE IN THE EDISTo RIVER BASIN








                                             EDISTO RIVER BASIN
                                               PROTECTED AREAS






                                   SALUDA
                                                      LEXNGTON




                       EDGEFELD
                                                                          CALHOLN


                                         AID STATE PARK


                                 AM                                 UMOR



                                             DMLL
                                                             BAkffRG           FRANCIS BUM FOM             BERKELEY

                                                                                                                         GaESTON
                                                                         STATE PARK          WHANS     STATE PARK

                                                                                             DORDESTER
                                                                           ODLLETON
                        El ACE Bm@ Project Area                             -ACE   NWR

                                                                    BEAR &A @G .A,ME         NA          RESEARCH RESERVE CORE
                                                                                                  0 BEACH STATE PARK


                  South Carolina Water Resources comrrjwm
                  Natural Resources Decision &qxri System
                  Cokimbia, South Corokm











         Figure 1-3. Location of protected areas in the Edisto River Basin.





                                             INTRODUCTION AND OVERVIEW                                                                               3


                      The ACE Basin, the coastal drainage area of the Ashepoo, Combahee, and Edisto
             Rivers, is a region with an exceptional diversity of habitats. These include relatively pristine
             estuaries with extensive marshlands; forestlands with maritime, bottomland hardwood,
             cypress-tupelo, and pine flatwood natural communities; and an extensive system of managed
             estuarine impoundments. The area has been identified as one of the highest priority regions
             for protection under the North American Waterfowl Management Plan. It is virtually
             unpolluted and has an isolated, undeveloped character. These characteristics add consider-
             ably to the ecological significance and uniqueness of this coastal region. The ACE Basin has
             been classified as a nationally significant wildlife ecosystem by the U.S. Fish and Wildlife
             Service and was listed in Significant Wildlife ResourceAreas of South Carolina 1981. The
             exceptional characteristics of this region have resulted in the focus of major national
             conservation efforts.
                      The ACE Basin Project is a conservation effort aimed at a contiguous 350,000-acre
             area in portions of four adjacent counties. The ACE Basin Project is a cooperative land
             conservation effort involving private land owners, U.S. Fish and Wildlife Service, South
             Carolina Wildlife and Marine Resources Department, Ducks Unlimited Foundation, and The
             Nature Conservancy. These groups are working to protect important habitats in the ACE
             Basin through land acquisition and conservation easements on many of the large tracts of land
             in the area. The U.S. Fish and Wildlife Service is working with the other cooperators to
             establish an 18,000-acre ACE Basin National Wildlife Refuge in the heart of the ACE Basin
             (USFWS 1990).
                      Within the Edisto River drainage area, state and federally protected lands which are
             now part of the ACE Basin conservation efforts include the State's 12,000-acre Bear Island
             Wildlife Management Area as well as Edisto Beach State Park and the 1,955-acre Grove
             Plantation, now part of the National Wildlife Refuge. In addition, 9,475 acres of conservation
             easements have been secured along the South Edisto at Hope Plantation (5,232 acres),
             Willtown Bluff Plantation (993 acres), and Pon Pon Plantation (3,250 acres). Other lands
             adjacent to the South Edisto River proposed for protection under ACE Basin efforts include
             Otter, Pine, and Jehossee Islands (slightly more than 10,000 acres, collectively).
                      Within the ACE Basin Project area, a 144,000-acre portion of the estuary of the
             South Edisto River and St. Helena Sound has been designated as a National Estuarine
             Research Reserve by the National Oceanic and Atmospheric Administration. The reserve is
             operated by the South Carolina Wildlife and Marine Resources Department. The core area
             of this reserve will consist of eight islands, predominantly marshlands, of approximately
             16,000 acres that will be the object of long-term baseline research and monitoring.
                      The Four Hole Swamp area of Dorchester and Orangeburg Counties is an 11,000-
             acre braided-riverine bottomland -hardwood swamp that contains the Francis Beidler Forest,
             a National Audubon Society Sanctuary, reported to contain the largest old-growth stand of
             tupelo-cypress in the United States. U.S. Fish and Wildlife Service listed the area in
             Significant Wildlife ResourceAreas ofSouth Carolina 1981 The area supports an extremely
             large variety of birds, mammals, reptiles, and amphibians and many rare plants.
                      Other protected areas include Givhans Ferry State Park, Colleton State Park, and
             Aiken State Park, all located on tracts adjacent to the Edisto River.


             RESULTS FROM THEECOLOGICAL
             CHARACTERIZATION STUDY

             The Ecological Characterization of the Edisto River Basin applies principles of landscape
             ecology to evaluate available information on landscape structure (or patterns of land use and
             land cover), water quality, hydrology, and indigenous animal populations. The information
             that was analyzed included long-term data sets, repeated survey data, and indicators of
             landscape ecological conditions. This section provides a summary of the results by
             describing the status of ecological conditions in the Basin and the associated assets and
             problems.







                                                                             ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                      Basin Condition by Indices of Ecological Integrity
                                                      The indices used to determine ecosystem health, or ecological integrity, of the Edisto Basin
                                                      were: loss of forest and other native vegetation, pattern of forest patches, condition of stream-
                                                      edge habitat, water quality in the streams, stability of stream hydrology, and the presence of
                                                      balanced indigenous plant and animal populations and natural areas. Detailed discussion of
                                                      methods and results related to these indices are discussed in the subsequent chapters
                                                      addressing land use, hydrology, water quality, and biological diversity. A summary of the
                                                      results is provided below.

                                                      Native Vegetation Loss
                                                      Prior to European settlement, the Edisto River Basin was approximately 90 percent forest and
                                                      open woodland. Native upland habitats (natural vegetative communities) covered about 70
                                                      percent of the region and about 30 percent was in native wetland habitats. Current conditions
                                                      indicate that, historically, about three-quarters of the native upland habitats and more than
                                                      one-third of the native wetland habitats have been converted to other land uses and vegetative
                                                      cover types. The conversions were mostly to agriculture and pine plantation forests.
                                                                Today, the Basin is about 56 percent forested. The Basin is composed of 23 percent
                                                      mixed upland forest, 19 percent pine plantation forest, and 14 percent wetland forest. The
                                                      remaining areas of the Basin are managed for agriculture (34 percent) and urban development
                                                      (3 percent), or they support nonforested wetland habitats (4 percent) and open water (2
                                                      percent).   In spite of the changes that have occurred, the structure of the Edisto Basin
                                                      landscape, in terms of total forest cover, is relatively intact and stable compared to other
                                                      regions of the country.
                                                                The forest-cover conditions in the Edisto Basin, landscape are favorable for
                                                      supporting good water quality and many populations of desirable wildlife species. It is
                                                      important to note, however, that much of the Basin's forestlands are intensively managed
                                                      pine plantations. Plantation forests have rapidly expanded in recent decades, and currently
                                                      occupy one-third of the Basin's total forest cover. Pine plantations are simplified forest
                                                      communities, usually representing even-aged, single-species stands that are highly produc-
                                                      tive for timber. Plantation forests typically lack the multilayered canopy, diverse tree sizes,
                                                      abundant snags and fallen trees, and the high species diversity that exist in natural
                                                      communities (Van Lear 1991); however, plantation forest stands can be established and
                                                      maintained in ways that improve their diversity (Hunter 1990). Within distinct forest stands
                                                      biological diversity is enriched by maintaining native herbaceous and shrub plants, complex
                                                      vertical structure in the forest canopy, large living trees, standing dead snags, and large
                                                      downed woody debris (Van Lear 1991, Seymour and Hunter 1992). These types of
                                                      characteristics are determined largely by forest management practices on individual forest
                                                      stands. The landscape, however, remains the critical level at which the fate of wildlife species
                                                      is ultimately determined. In forested landscapes, an interspersed pattern of different
                                                      ecosystems and forest stands of varying sizes, ages, and spe    'cies compositions is believed to
                                                      provide the greatest biological diversity (Hunter 1990). Even though some pine plantation
                                                      stands are quite extensive in the Edisto Basin, they generally remain interspersed within a
                                                      landscape mosaic of native upland and wetland forests that continue to provide some of the
                                                      forest habitats that are otherwise unavailable in the plantations.

                                                      Forest Patch Pattern
                                                      Forest patch analysis of the Basin's total forest cover showed that most of the forest area (56
                                                      percent of the Basin) is in a few large patches that extend through most of the landscape via
                                                      the bottomlands of the streams linkingupland and wetland forests into an irregular, or in some
                                                      cases dendritic (branching), pattern of forested corridors. The total area of forest was
                                                      1,112,600 acres distributed among many (4,025) patches. The majority (about 70 percent)
                                                      of the Basin's forests were found in five patches of 50,000 acres or more. Most of the patches
                                                      were very small (less than 25 acres) and collectively contained very little of the Basin's total
                                                      forest area.
                                                                The large patches in the Edisto Basin result from many narrow connections in a
                                                      mosaic of forested tracts that create the irregular, dendritic pattern of forested corridors
                                                      described above. A substantial portion of the habitats associated with these large patches
                                                      comprises relatively exposed forest corridors and forest edges. In addition, many roads and







                                              INTRODUCTION AND OVERVIEW


             utility corridors crisscross the forest patches causing greater forest fragmentation than is
             indicated by the analysis. Therefore, the Basin's forest pattern is not as favorable for sensitive
             forest-interior species as may be indicated by the large patch acreages; in fact, high-quality
             forest-interior habitats seem to be quite limited.
                       Forest patch characteristics indicate that the Basin's forest pattern, although far
             from being in pristine condition, remains favorable for supporting many indigenous wildlife
             species because of extensive forest connectivity throughout the Basin. The region's
             extensive pine plantations contribute to the pattern of large forested patches on the landscape.
             The wetland forests (bottomland hardwood forests), however, are the critical link in the
             overall connectivity of forests in the landscape and they also appear to provide the best forest-
             interior habitats available in the Basin. The largely intact bottomland forest system remains
             favorable for supporting very good water quality in the Basin's streams.
                       Forest stands with older, larger trees are thought to support more wildlife species
             than those with younger, smaller trees (O'Neil and others 1991). Because much of the
             Basin's upland forests are intensively managed planted pine, the overall age of the Basin's
             forests is relatively young. Most (more than 70 percent) of the Basin's older forest stands
             (stands more than 80 years old) are bottomland hardwoods. These stands, however, only
             amounted to about 4 percent of all the forestland in the Basin. Twenty-four percent of all
             forestland in the Basin had mature stands (stands from 40 to 80 years old). Over half of these
             mature stands were bottomland hardwoods. These conditions further illustrate the relative
             importance of the bottomland hardwood forests for the maintenance of environmental quality
             in the Edisto Basin.

             Stream-Edge Habitat Condition
             Riparian ecosystems are often the most valuable ecological components of a forested
             landscape (Hunter 1990). The evaluation of riparian ecosystems involved a "buffer" analysis
             that tallied the land use and land cover types within two stream-edge zones of different
             widths: one at 60 meters (about 200 feet) and the other at 125 meters (about 400 feet) from
             either side of the Basin's streams. The 60- and 125-meter analyses showed that a minor
             proportion (15 to 25 percent respectively) of the stream edges are under intensive land uses.
             The intensive land uses are urban (2 percent of the Basin's stream edges), agriculture (9 to
             15 percent of the Basin's stream edges), and pine plantation (4 to 8 percent of the Basin's
             stream edges). Most of the stream-edge habitats (75 to 85 percent) are in natural cover: 33
             percent as forested wetland, 14 to 19 percent as mixed upland forest, 14 to 27 percent as
             palustrine nonforested wetland, and 9 to II percent as estuarine wetland. It has been
             estimated that over 70 percent of the riparian ecosystems in the continental United States have
             been converted to other land uses (Brinson and others 1981). Because the Edisto Basin's
             stream edges are largely in natural cover, their condition is favorable for supporting viable
             riparian wildlife habitat corridors and improving water quality by reducing sediment,
             nutrients, and other contaminants coming into the streams.

             Water Quality in the Streams
             The analysis of historical water quality records from 1975 to 1991 indicates that while certain
             areas of the Basin have problems, the Edisto Basin overall has very good water quality. The
             most consistent trends observed were declining concentrations of total phosphorus and
             biochemical oxygen demand. This is consistent with nationwide trends resulting from
             municipal and industrial pollution control programs during the 1970s and 1980s.
                       Generally, acceptable water quality (based on the EPA criterion of 0.1 milligrams
             per liter total phosphorus) is being maintained throughout the Basin, with the exception of
             the North Fork Edisto River. The North Fork exhibited the highest mean total phosphorus
             concentration (0.29 mg/1) and usually exceeded the 0. 1 mg/I criterion both in the headwaters
             and below Orangeburg. The North Fork also showed frequent violations of state standards
             for fecal coliform bacteria in the headwaters. The North Fork's problems are derived
             primarily from a combination of point and nonpoint sources (livestock and feedlot activity).
                       Analysis of total phosphorus, total suspended solids, and turbidity showed highly
             significant and negative relationships to stream discharge. This concurrent decrease in
             concentration of pollutants with an increase in stream volume (increased water volume
             resulting from rain and runoff) suggests a dilution phenomenon characteristic of undisturbed,
             forested watersheds. The low turbidity and total suspended solids concentrations observed







                                                                            ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                     throughout the Basin also indicate that erosion loading during storm events is minimal. The
                                                     ratio of nitrogen to phosphorus (N/P ratio) in the Basin's streams has been between 10 and
                                                     15 since 1983. This N/P ratio indicates a balanced aquatic ecosystem, also characteristic of
                                                     an undisturbed watershed. The North Fork Edisto River, however, had the lowest N/P ratios
                                                     (in other words, an excess of phosphorus) because of phosphorus entering the streams from
                                                     both point and nonpoint sources.
                                                     Stability of Stream Hydrology
                                                     Analysis of precipitation and streamflow during the period 1939 to 1990 indicates that only
                                                     minor changes in precipitation and strearnflow occurred in the Edisto River Basin and that
                                                     changes in strearnflow are a result of changes in precipitation. This indicates that the minor
                                                     increases in strearnflow did not result from land use changes involving forest and vegetative
                                                     cover losses. Also, there have been no significant modifications to the Edisto River stream
                                                     channels to alter the hydrology, such as navigation or flood control projects to widen,
                                                     straighten, levee, or dam the river. Stable trends in hydrology for the Edisto are likely to be
                                                     related to the land use and land cover along the Basin's stream edges. The stream edges are
                                                     mostly forested or in other natural vegetative cover, conditions that are favorable for water
                                                     storage that supports year-round base flows (groundwater discharge to streams) and retains
                                                     flood water.

                                                     Balanced Indigenous Populations and Natural Areas
                                                     Very little information exists to provide a significant understanding of how the abundance
                                                     and diversity of native species have changed in the Edisto Basin. The only long-term,
                                                     systematic data available are for birds, primarily the North American Breeding-Bird Surveys.
                                                     Analysis of Breeding-Bird Surveys (BBS) identified 98 species of birds that were seen six
                                                     or more times on one of the six BBS routes in the Edisto Basin. Of the 98 species analyzed,
                                                     24 species have populations that appear to be increasing, 37 species have populations that
                                                     appear to be decreasing, and 37 species have populations that appear relatively stable. Only
                                                     a few species show consistency in the direction or strength of change at all six routes;
                                                     specifically, 10 species are declining and three species are increasing on most of the routes.
                                                     No species had plummeting populations or appeared threatened with local extinction.
                                                     However, more species' populations are decreasing than increasing at four of the six BBS
                                                     routes analyzed. Two routes in particular are showing declines for 30 to 40 percent of the
                                                     species over the last 20 years, which may indicate ecological instability in the lower portions
                                                     of the Basin. These declines coincide with land cover changes of forest loss and forest
                                                     conversion to pine monoculture along these routes.
                                                               The large wide-ranging mammals native to the Edisto River Basin - bears,
                                                     cougars, and wolves - have been extirpated. Stable populations of medium-sized carnivores
                                                     with smaller range requirements, such as bobcats and otters, are found in the Edisto Basin.
                                                     The apparent trend of increasing and stable populations for most of the raptors in the Basin
                                                     serves as evidence that the region provides stable food web support for these top-level
                                                     carnivores.
                                                               There are several nationally threatened and endangered species in the Edisto River
                                                     Basin which may be a positive sign of ecological integrity - showing that certain areas serve
                                                     as a refuge for sensitive or specialized species. The presence of the Red-cockaded
                                                     Woodpecker, Southern Bald Eagle, Loggerhead Turtle, and Shortnosed Sturgeon suggests
                                                     that the Edisto River Basin contains relatively intact and uncontaminated habitats that are rare
                                                     or unique in the nation.
                                                               A Natural Area Inventory (conducted by The Nature Conservancy and SCWRC)
                                                     revealed that the relatively undisturbed, high-quality natural communities that remain in the
                                                     Edisto River Basin are almost all wetlands, and most of these are found in the coastal region.
                                                     Most of the Edisto landscape has a long history of intensive land management for agriculture
                                                     and forestry; therefore, very few native upland communities of any size remain intact. The
                                                     greatest number and diversity of the 132 natural areas is concentrated in the coastal region,
                                                     which spans the most ecologically diverse portion of the Basin. The coastal region has nearly
                                                     80 percent of the natural areas: sites that contain flatwoods, Carolina bays, bottomland
                                                     hardwoods, a full array of intertidal wetlands, and barrier island communities. Few natural
                                                     areas and fewer kinds of natural communities are found in the more inland portions of the
                                                     Basin.







                                                INTRODUCTION AND OVERVIEW


              Assets and Problems for Ecological Integrity
              In further summarizing the results of the Ecological Characterization, a listing of the Edisto
              Basin's assets and problems was developed at a workshop held by the South Carolina Water
              Resources Commission in October 1992. The workshop was intended to develop a summary
              and synthesis of the Edisto ecological characterization study. Participants included profes-
              sional and technical staff representing several state and federal agencies and a corporate
              landowner. Each of the participants was knowledgeable of the Edisto River Basin and
              environmental management issues affecting the area. The workshop participants discussed
              results from the land use, hydrology, water quality, and biological diversity chapters of this
              report and then identified assets and problems of the Basin.

              Assets
              Assets are characteristics or attributes that define or support and enhance the Basin's
              ecological integrity. Workshop participants identified the following assets for the Edisto
              Basin:


                   ï¿½   Relative to other areas in the southeastern United States, the Edisto Basin is one
                        of the most intact drainage basins; it is outstanding in terms of natural
                        conditions.
                   ï¿½   The Basin is relatively undeveloped (particularly on the coastal end).
                   ï¿½   Large blocks of land are in single ownerships.
                   ï¿½   Some areas are not suitable for anything but forest.
                   ï¿½   The Basin has a low density of human population.
                   ï¿½   The Basin is not heavily industrialized.
                   ï¿½   Forest land coverage is fairly high.
                   ï¿½   The forests are highly interconnected (when excluding most roads and utility
                        corridors) and extend through much of the landscape following the Basin's
                        stream network.
                   ï¿½   Stream edges (riparian zones) are largely in good condition, covered primarily
                        with native vegetation.
                   ï¿½   Upland sandy soils in the area enhance water quality (through high infiltration),
                        and the bottomland's muck soils inhibit exploitation.
                   ï¿½   Water quality is generally good or improving, with only a few problem areas.
                   ï¿½   The estuary exhibits a good tidal range and therefore good flushing (the area
                        of estuary is 80 percent marsh, 20 percent water).
                   ï¿½   The Sandhills region is an important groundwater recharge area and is
                        relatively undeveloped.
                   ï¿½   There are no dams on the major river system.

              Problems
              Problems are characteristics related to degradation of the Basin's ecological integrity.
              Workshop participants identified the following problems in the Edisto Basin:


                   ï¿½ There is a poor dispersion of intact ecological communities (very few intact
                        upland communities, but many more intact wetland communities).
                   ï¿½ Many upland communities are degraded, are experiencing widespread loss, or are
                        threatened with extinction.
                   ï¿½ Harvest pressures on fisheries and other selected wildlife are significant.
                   ï¿½ Rare and endangered plants are found invulnerable habitats, specifically Carolina
                        bays.
                   ï¿½ There is a loss of natural transitional cover on outer/higher floodplains between
                        uplands and the lower floodplains; intensive land uses have encroached on these
                        areas.
                   ï¿½ Pine plantations are expanding, replacing native hardwood and mixed forest
                        stands; typically, they are simplified forest habitats with lower species diversity.
                   ï¿½ Four Hole Swamp seems to be the most degraded of the four subbasins, yet it
                        contains the ecologically significant Beidler Forest and adjacent swamp forest.







                                                                           ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                             Only a few   large forested tracts could provide high quality interior-forest
                                                              habitats for area-sensitive species.

                                                    PossiblelQuestionable Problems
                                                    A number of items were identified as possible problems by workshop participants, but little
                                                    or no information was available to assess them. Therefore, the following are considered
                                                    questionable and should be examined further.


                                                         ï¿½ Rural sprawl, increased expansion of low-density development dispersed
                                                              throughout rural areas, will further fragment the remaining forests and natural
                                                              habitat.
                                                         ï¿½ River corridor development pressures, from second homes and recreational
                                                              dwellings, seem to be increasing.
                                                         ï¿½ Headwater impoundments may have a negative impact on fisheries-and a
                                                              positive impact on water quality.
                                                         ï¿½ Water supply for the cities of Charleston and Orangeburg may be threatened
                                                              by the minimum flows of the Edisto River that occur during periods of
                                                              drought.
                                                         ï¿½ Agricultural chemicals maybe a water quality concern (but were not evaluated
                                                              in this study).
                                                         ï¿½ Acid precipitation may be a water quality concern.


                                                    DEVELOPMENT OFGOALS AND PLANS

                                                    The need for setting goals to manage the widespread incremental deterioration of environ-
                                                    mental quality, known as cumulative impacts, has been emphasized by nearly everyone who
                                                    hasstudied these problems. The technically supported findings about ecosystem health and
                                                    condition, and the human activities affecting the environment, must at some point be
                                                    translated into societal valuejudgmems regarding the appropriate balance of natural resource
                                                    conservation and development. Goals, backed by specific, spatially based plans for a
                                                    watershed are believed to be necessary to guide and improve decisions that are made in the
                                                    environmental regulatory process (Gosselink and Lee 1989). Goals can provide consistency
                                                    and direction to all sorts of programs affecting environmental management - programs of
                                                    regulation, incentives, education, land acquisition, and economic development. The point is
                                                    that the assessment of the Basin's ecological health should not be used simply to set new
                                                    regulatory criteria, but rather to influence the formulation of management and protection
                                                    objectives. Wetlands, forests, water, and wildlife are important and valuable resources, as
                                                    are economic goods and services. The public ultimately must choose among objectives that
                                                    will affect all of these resources (Stakhiv 1988).
                                                              Goal-setting - that is, choosing among objectives - mustbe done in apublicplanning
                                                    process that includes all groups with an interest in the region under study. These groups would
                                                    include relevant government agencies, local business andconservation interests, andpeoplewho
                                                    live in the region. Currently, no such goals and recommendations from a public planning process
                                                    exist for the Edisto River Basin. However, the information derived from this study is intended
                                                    for use by participants in such a process, referred to as the Edisto Basin Natural Resource
                                                    Assessment Process, to be conducted by the Water Resources Commission in 1993-95.
                                                    Anticipating this public planning process, the October 1992 workshop participants agreed to
                                                    suggest broad goals and planning recommendations to be considered by those who would be
                                                    involved in the Natural Resource Assessment Process and by the public in general.
                                                              These goals and planning recommendations are intended to stimulate ideas among the
                                                    readers and citizens of the Edisto Basin. The recommendations represent potential approaches
                                                    that should be considered as part of an overall basinwide plan; however, no obligation to these
                                                    is intended. The suggestions are presented below.


                                                    Suggested Goals for Management
                                                    The Edisto Basin is one of the few remaining blackwater stream systems in the United States
                                                    that is in good ecological condition. As such, it is both a state and national resource of great







                                               INTRODUCTION AND OVERVIEW


              value to the citizens and to our children. It should therefore be preserved; maintained, and
              enhanced as an important natural resource area for future generations, where the resident
              population can live in a mutually sustaining relationship with the environment and visitors
              can have an opportunity to understand and enjoy a unique natural system. Suggested goals
              are:
                   ï¿½ Develop strategies for a harmonious association of man and nature by which
                       people can live in a mutually sustaining relationship with their environment;
                   ï¿½ Stop landscape degradation and, at minimum, maintain current ecological
                       conditions; and
                   ï¿½ Strive to improve ecological conditions with regard to biological diversity,
                       water quality, hydrology, and landscape structure.

                       These goals are very broad and general. It was agreed that the goals to maintain and
              improve the current level of ecological conditions in the Basin should be achieved by using a
              landscape approach. In this case, using a landscape approach implies having a basinwide focus
              concerned with the spatial pattern and interaction of different land uses and land cover types and
              the effect of these on ecological processes. Generally, in this report, ecological processes relate
              to how natural ecosystems support good water quality, water storage, flood control, and natural
              biotic diversity. Therefore, the goal implies managing the whole Basin as an integrated unit and
              managing the pattern of land use and natural cover in order to maintain and improve the overall
              ecological health of the Basin.
                       The goal of developing strategies (goal 1) implies the need for a comprehensive
              approach to managing natural resources and development in the region, an approach that is fair
              and of long-term benefit to all citizens.
                       The goals of maintaining and improving the ecological conditions of the Basin (goals
              2 and 3) could be made more specific (goals must be more specific for practical use) by targeting
              standards that relate to the indices of ecological integrity, and by applying the standards to
              policies affecting land management. An example of such a standard might be to maintain 30-
              to 60-meter naturally vegetated buffers on all streams.


              Suggested Management Plans
              Goals and objectives may be implemented through the use of federal, state, and local
              governments, and private approaches that include education, persuasion, land purchase,
              easements, incentives and disincentives, and regulation. An implementation plan should be
              carefully developed to meet clearly stated and specific basin goals. Some options are listed
              below to illustrate the kinds of steps that can be taken. These options were thought to be useful
              for attaining the goals and managing the environmental assets and problems of the Edisto River
              Basin previously addressed, but by no means is this an exhaustive list. These options reflect the
              ideas of the workshop participants and do not constitute a management prescription endorsed
              by the South Carolina Water Resources Commission or any other public agency.

                   1. Protect natural areas.
                       a. Alert The Nature Conservancy and South Carolina Heritage Trust to seek out land
                       purchases, land trusts, management agreements, conservation easements, and
                       donations.
                       b. Use existing regulatory means.
                       c. Seek technical assistance such as the Man and the Biosphere Program adminis-
                       tered by the National Park Service.
                   2. Maintain and improve riparian/stream -edge habitats.
                       a. Use existing regulatory means (for example, Clean Water Act Non-Point Source
                       Program, Section 404 best management practices (BMPs) for forestry, floodplain
                       zoning through the Federal Emergency Management Agency (FEMA), and the
                       Conservation Reserve Program or "Swampbuster").
                       b. Promote conservation through county agents (for example, Conservation District
                       agents, Clemson Extension agents, etc.)_
                   3. Forestry and agricultural management that supports natural diversity and abundance.
                         a. Promote conservation through county agents (for example, Conservation
                         District agents, Clemson Extension agents, etc.).
                         b. Develop BMPs and educate farmers and foresters in their use.







                                                                         ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                        4. Restore and maintain natural fish and wildlife populations at sustainable levels.
                                                              Promote through South Carolina Wildlife and Marine Resources Department and
                                                              their enforcement of regulatory programs.
                                                        5. Protect instream water flow for natural uses
                                                              Promote through South Carolina Water Resources Commission's authority to
                                                              protect navigable waters.
                                                        6. Promote ecologically compatible industry and land use.
                                                              a. Work with South Carolina State Development Board and other parties.
                                                              b. Encourage local entities to promote sustainable development and land uses.
                                                        7. Promote ecological understanding and stewardship.
                                                              a. Bring environmental education to schools.
                                                              b. Establish public outreach component to Edisto Basin Natural Resource Assess-
                                                              ment Process.
                                                              c. Involve volunteer citizens in monitoring programs (for example, Waterwatch).
                                                        8. Maintain and increase the extent of forest and other native vegetation cover.
                                                              a. Work with large land owners for sustained yield management.
                                                              b. Check with South Carolina Forestry Commission about reforestation
                                                               (Federal incentive programs).
                                                              c. Develop strategies to aid farmers to diversify their source of income (for
                                                              example, timber, hunting leases, etc.).
                                                        9. Maintain large contiguous blocks of forest and natural vegetation in bottomland alon
                                                              the maior streams.
                                                              a. Alert The Nature Conservancy and South Carolina Heritage Trust Program to
                                                              seek out: land purchases, easements, land trusts, management agreements,
                                                              conservation easements, and donations.
                                                              b. Use existing regulatory means (regulate against conversion and for BMPs).
                                                        10. Manage for rare and sensitive indigenous species (also those with unusual
                                                              habitat requirements).
                                                              a. Promote through The Nature Conservancy and South Carolina Heritage Trust
                                                              Program.
                                                              b. Use existing regulatory means (for example, Endangered Species Act).
                                                              c. Identify species that are important to the public.
                                                        11. Increase protection of Beidler Forest and the Four Hole Swamp.
                                                              a. Promote development of cooperative community conservation and protection
                                                              strategies (for example, a community-based land trust).
                                                              b. Use existing regulatory means (for example, Clean Water Act Non-Point
                                                              Source Program, Section 404 BMPs for forestry, floodplain zoning through
                                                              FEMA, Conservation Reserve Program, etc.)-
                                                              c. Promote conservation through county agents (for example, Conservation
                                                              District agents, Clemson Extension agents, etc.).
                                                              d. Contact appropriate landowners about donating conservation easements on
                                                              Four Hole Swamp.
                                                              e. Promote actions of The Nature Conservancy and Heritage Trust Program to seek
                                                              out: land purchases, land trusts, management agreements, conservation ease-
                                                              ments, and donations.
                                                              f. Use existing regulatory means ( regulate against conversion and for BMPs).
                                                        12. Maintain Class-A Water Quality Standards
                                                              a. Promote through the S.C. Department of Health and Environmental Control's
                                                              authority.
                                                              b. Enforce regulations of Clean Water Act requirements for point and non-point
                                                              sources.
                                                              c. Increase and improve analysis for toxins in Basin streams and water wells.
                                                        13. Develop an Edisto Basin planning authority through citizen action and commitment.
                                                              Such a group could administer the basin goals and plans, seek funding sources for
                                                              implementation, monitor progress toward the goals, develop an educational
                                                              program for the Basin, and otherwise work to insure the future health of the Edisto
                                                              Basin landscape.







                                              INTRODUCTION AND OVERVIEW


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                  and status. U.S. Department of the Interior, Fish and Wildlife Service, FWS/OBS-81/17.

             Costanza, R. 1987. Social traps and environmental policy. BioScience 37 (6): 407-412.

             Diamond, J.M. 1975. The island dilemma: lessons of modern biogeographical studies for the
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             Foreman, R.T.T. and M. Gordon. 1986. LandscapeEcology. J. Wiley and Sons, New York, N.Y.

             Gosselink, J.G, C.E. Sasser, L.A. Creasman, S.C. Hamilton, E.M. Swenson, and G.P. Shaffer.
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             Gosselink, J.G. and L.C. Lee. 1989. Cumulative impact assessment in bottomland hardwood
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             Hunter, M.L., Jr. 1990. Wildlife, forests, and forestry: principles of managing forests for
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             O'Neil, L. J., T.M. Pullen, Jr., R.L. Schroeder. 1991. A wildlife community habitat evaluation
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             Seymour, R.S. and M.L. Hunter, Jr. 1992. Newforestry in eastern spruce-firforests:principles
                  and applications to Maine. Miscellaneous Publication 716, Maine Agricultural Experi-
                  ment Station, University of Maine, Orono.

             South Carolina Water Resources Commission 1992. The Economy of the Edisto River Basin.
                  Vols. I-IV and Executive Summary (draft reports prepared by The Fontaine Company).
                  Columbia, S.C.

             South Carolina Water Resources Commission. 1983. South Carolina WaterAssessment, State
                  WaterPlan. South Carolina Water Resources Commission Report No. 140. Columbia, S.C.

             Stakhiv, E. Z. 1988. An evaluation paradigm for cumulative impact analysis. Environmental
                  Management 12 (5): 725-748.

             U.S. Department of Agriculture. 1978. General soil map of South Carolina. USDA Soil
                  Conservation Service.


             U.S. Environmental Protection Agency. 1988. Manual from the workshop: "Cumulative impact
                  assessment in southeastern wetland ecosystems: the Pearl River." October 17-21, 1988,
                  Slidell, La. Sponsored by the U.S. Environmental Protection Agency, Washington, D.C.

             U.S. Fish and Wildlife Service. 1990. ACEBasinNational WildlifeRefugeFinalEnvironmentaI
                  ImpactAssessmentandLandProtectionPlan. U.S. Department of the Interior, Atlanta, Ga.

             U.S. Fish and Wildlife Service. 1981. Significant Wildlife Resource Areas ofSouth Carolina.
                  U.S. Department of the Interior, Asheville, N.C.

             Van Lear, D.H. 1991. Integrating structural, compositional, and functional considerations into
                  forest ecosystem management. In: Ecosystem Management in a Dynamic Society,
                  Proceedings of a conference held by the Department of Forestry and Natural Resources,
                  Purdue University, West Lafayette, Indiana.











































                                                                                                                          CV





                                                                                                                                  Chapter 2
                                                                                                                                  Land Use and Land Cover

                                                                                                                                  by:

                                                                                                                                  William D. Marshall
                                                                                                                                  South Carolina Water Resources Commission









                                                                                                                                        ff               MI    Jul         41

                                                                                                                                        'A                 F-@







                                               LAND USE AND LAND COVER


               INTRODUCTION
               The distribution and proportions of various types of land use and land cover have a great effect
               upon the ecological functions and conditions of a landscape. As demonstrated and discussed
               by Gosselink and Lee (1989), the stability and character of the biological communities, the
               water quality, and the hydrology of a region depend largely on land uses and the proportions
               of different types of land cover.
                        This chapter will provide two things: (1) a baseline description of the current land
               use and land cover characteristics of the Edisto Basin, and (2) a description of historical land
               use changes that have occurred. The information is presented in a way that will allow for an
               evaluation of land use changes in the Basin and the resulting cumulative effects on ecological
               conditions, specifically in regard to hydrology, water quality, and populations of indigenous
               animals.


               METHODS OFAsSESSMENT
               Information Sources
               The South Carolina Water ReSOUTCeS Commission (SCWRC), through the NRDSS Project,
               has developed a natural-resource based geographic information system for the Edisto River
               Basin. The spatial data being developed for the system are mapped at 1:24,000 scale and
               conform to National Map Accuracy Standards. These data were the most up-to-date available
               and include SCWRC 1989 land use and wetlands data as well as soils, transportation routes,
               hydrography, and political boundaries, all specified below.
                        Historical spatial data for land use and land cover in the Edisto Basin were available
               only since the mid-1970s. Known sources of historical land use data included satellite
               imagery from NASA's Landsat programs and the U.S. Geological Survey's 1977 land use
               data, often referred to as LUDA, which was derived from aerial photography. Another
               limited source included wetlands data from 1981, available only for the coastal counties and
               obtained in digital format from the South Carolina Coastal Council and the South Carolina
               Land Resources Commission.
                        No satellite imagery was analyzed for this study. The LUDA data, which are based
               on the Anderson Level 11 land use and land cover classification system (Anderson and others
               1976), were analyzed and found to be substantially different in the level of resolution from
               the SCWRC 1989 land use and wetlands data. In addition, the LUDA data are of questionable
               quality because the source photography is quite variable in type and scale. Because of these
               differences and the questionable quality of LUDA, comparisons between these two spatial
               data sources were limited to basinwide comparisons of general land use statistics addressed
               later in this section.
                        The SCWRC 1989 land use and wetlands data were the primary source used to
               provide a description of current conditions of landscape structure in the Basin. The other
               sources used to describe historical changes are county or regional survey statistics.

               Land Use and Land Cover Mapping
               Digital spatial data that were used for purposes of evaluating changes in land use and land
               cover in the Edisto Basin are described below. These data were used in analyses conducted
               by staff at the South Carolina Water Resources Commission using ArcInfo software on a
               VAX minicomputer system. The data were as follows:

                   0 1989 land use data - SCWRC, based on Anderson Level 11 classification
                        (Anderson and others 1976), 1:24,000 scale, 10 acre resolution.
                   0   1989 wetlands data - SCWRC, based on National Wetlands Inventory (NWI)
                        classification (Cowardin and others 1979), 1:24,000 scale, I to 5 acre
                        resolution. The land use and wetlands data were derived from 1989 National
                        Aerial Photography Program (NAPP) 1:40,000 scale color infrared photog-
                        raphy.
                   0 Soils data - U.S. Soil Conservation Service (SCS), 1:24,000 scale, 5 acre
                        resolution. The soils were derived from SCS county s6il surveys and







                                                                            ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                               represented conditions in the 12 counties of the Edisto Basin in different years
                                                               as follows: Orangeburg- 1984; Aiken-1981; Dorchester- 1985; Lexington-
                                                               1970; Charleston- 1966; Colleton-1980; Calhoun-1963; Bamberg-1964;
                                                               Barnwell-1973; Edgefield-1978; Berkeley-1974; Saluda-1958.
                                                          * Digital line graphs (DLGs) - U.S. Geological Survey (USGS), 1:24,000
                                                               scale. The DLG's were derived from USGS topographic quadrangle maps
                                                               and include transportation features, political boundaries, and hydrography.
                                                          * 1981 wetlands data - NWI, Cowardin classification (Cowardin and others
                                                               1979), 1:24,000 scale, 1-5 acre resolution. These maps were derived from
                                                               1981 National High Altitude Photography 1:58,000 scale color infrared
                                                               photography.
                                                          * 1977 USGS land use data (LUDA) - 1:250,000 scale, 40 acre resolution.

                                                               The SCWRC 1989 land use and wetlands data, the soils, and the DLG's conform
                                                     to standard federal classification systems. The Anderson Level 11 classification (Anderson
                                                     and others 1976) was used for land use and land cover in upland areas. The Cowardin
                                                     classification (Cowardin and others 1979) was used for wetlands and deep water habitats;
                                                     these data conform to U.S. Fish and Wildlife Service, NWI standards and specifications. The
                                                     DLG's conform to USGS standards and specifications. The soils data, derived from the
                                                     1:20,000 scale SCS county soil survey maps, were remapped to 1:24,000 scale, reviewed by
                                                     the SCS for map accuracy, and then were digitized. Zoom Transfer Scope methods were used
                                                     for remapping soils in order to reduce the mapping scale and to remove the distortion inherent
                                                     in the original county soil survey maps.

                                                     Other Information
                                                     Evaluations of historical changes and existing conditions in land use were also derived from
                                                     the following additional sources of information:

                                                          0 Forest Survey data - U.S. Forest Service, Forest Inventory and Analysis
                                                               Research Unit; data on the extent and conditions of forest lands for 1947,
                                                               1958, 1968, 1978, and 1986. These data were obtained from the Forest
                                                               Service grouped as summary statistics for the 12 counties, and as summary
                                                               statistics for the four subbasins of the Edisto region.
                                                          M Census ofAgriculture data - U.S. Department of Commerce, Bureau of the
                                                               Census, available every 5 years since 1925; data for the extent of agricultural
                                                               land, specific crops, and other farmland uses. These data were obtained as
                                                               summary statistics for the 12 counties of the Edisto region.


                                                     Assessing Historical Land Use
                                                     Historical changes in the extent of forests and natural cover, agriculture, and urban development
                                                     were assessed by comparing data compiled for the U.S. Forest Service's Forest Survey and the
                                                     U.S. Department of Commerce, Bureau of the Census' Census of Agriculture. These data were
                                                     evaluated for an area composed of all twelve counties of the Edisto River Basin and for three
                                                     individual counties to assess sub-area differences. General ownership and related land use trends
                                                     were assessed from the Forest Survey and the Census of Agriculture. The categories of general
                                                     land use derived from the Census of Agriculture and the Forest Survey data were as follows:

                                                          ï¿½ Land in farms - a Census of Agriculture term that represents the acreage of all
                                                               land in farmer owned operations. Land in farms includes subsets of acreage for
                                                               crops, pasture, and grazing lands and also woodland or "wasteland" not actually
                                                               under cultivation nor used for grazing or pasture.
                                                          ï¿½ Agricultural land - this term refers to a subset of acreage derived from the
                                                               Census of Agriculture data for "land in farms." Figures for Agricultural Land
                                                               were derived by subtracting "woodland not pastured" acreage from the "land in
                                                               farms" acreage; each of these were listed in the Census of Agriculture. Thus
                                                               derived, Agricultural Land represents farmer owned acreage for all cropland, all
                                                               pastureland, and all other farmland such as house lots, bam lots, roads, ditches,
                                                               and ponds.







                                                 LAND USE AND LAND COVER



                    ï¿½ Forestland - a Forest Survey term for land at least 16.7 percent stocked by
                         forest trees of any size, or formerly having such tree cover, and not currently
                         developed for nonforest use.
                    ï¿½ Urban land - includes urban or built-up areas inventoried in the initial phase
                         of the U.S. Forest Service's Forest Survey procedures.
                    ï¿½ Other land - where county-based land use statistics are used, this term refers
                         to the county land area unaccounted for after summing forest land, agriculture
                         land, and urban land.


               Assessing Current Land Use
               To focus on the primary elements of concern and to provide a general perspective on the mix
               of land uses in the Basin, the 1989 spatial data were simplified into broad, categories. The
               broad categories were derived by lumping similar Cowardin wetland classification types and
               similar Anderson land use and land cover classification types. The categories of general land
               use derived from the 1989 data are as follows:


                    ï¿½ Native Forested Wetlands - includes all Cowardin palustrine (freshwater)
                         forested wetlands, excluding pine plantations.
                    ï¿½ Nonforested Wetlands - includes all Cowardin palustrine emergent wetlands,
                         and palustrine scrub-shrub wetlands.
                    ï¿½ Open Water - includes all Cowardin palustrine, lacustrine, riverine, estua-
                         rine, and marine open water.
                    ï¿½ Mixed Upland Forest - includes all Anderson upland forest types as well as
                         the rangeland types of shrub-brush and mixed rangeland; does not include
                         pine plantations.
                    ï¿½ Pine Plantation (plantedpine) UplandForest -includes planted pine forests,
                         as distinquished from the Anderson forestland classifications.
                    0 Agriculture - includes all Anderson agricultural land uses as well as the
                         herbaceous rangeland type.
                    ï¿½ Urban - includes all Anderson urban or built-up land uses as well as mines
                         and transitional areas.
                       Estuarine Wetlands - includes all Cowardin estuarine brackish and saltwater
                         wetlands, excludes open water.

                         Existing conditions of the landscape structure were derived from the SCWRC 1989
               land use and wetlands data by analyzing the distribution and extent of the broad categories
               of land uses and cover types. These data were analyzed for the entire Edisto River Basin and
               for each of the subbasins: the North Fork, South Fork, Four Hole Swamp, and the main stem
               of the Edisto.


               Changes in Wetlands
               Several different analyses were conducted to assess changes in the extent of wetland habitats
               as well as land uses and alterations affecting wetland habitats of the Edisto Basin.

               Rationale
               Generally, wetlands are areas where saturation with water is the dominant factor determining
               both the nature of soil development and the types of plant and animal communities living in
               and on the soil. Soil that is at least periodically saturated with or covered by water is the single
               feature that most wetlands have in common. "Wetlands are lands transitional between
               terrestrial and aquatic systems where the water table is usually at or near the surface or the
               land is covered by shallow water" (Cowardin and others 1979).
                         Hydric soil, soil that is saturated, flooded, or ponded long enough during the growing
               season to develop anaerobic conditions in the upper part, is one attribute used to identify an area
               as wetland. The technical criteria for identification of jurisdictional wetlands under Section 404
               of the Clean Water Act are tied to three attributes that wetlands possess: hydrophytic vegetation,
               hydric soils, and wetland hydrology (FICWD 1989). Regulatory jurisdiction for wetlands must
               be determined in the field by judging the presence or absence of these three attributes. The







                                                                             ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                      presence of hydric soil, alone, does not determine whether an area is ajurisdictional wetland, but
                                                      it can indicate the type of native vegetation likely to have been found on that soil.
                                                                The purpose of this study was to assess changes in land use and land cover in the
                                                      Edisto Basin, but the study did not to determine the extent ofjurisdictional wetlands. Because
                                                      saturated soil conditions are the key factor in determining the presence of native wetland
                                                      vegetation, it was assumed that the historical extent of wetland vegetation communities could
                                                      be estimated by assessing the extent of selected hydric soils from the Soil Conservation
                                                      Service's (SCS) county soil surveys. Likewise it was assumed that historical changes in the
                                                      extent of native wetland vegetation could be estimated by comparing selected hydric soils
                                                      with the 1989 NWI data.
                                                                Note that the resolution of the SCS county soil survey mapping units inevitably
                                                      leads to the inclusion of some nonhydric soil areas within the map units that SCS designates
                                                      as hydric. The SCS National Soils Handbook addresses this factor as follows: "The total
                                                      amount of dissimilar inclusions generally does not exceed about 25 percent. Limiting
                                                      inclusions should not exceed about 15 percent, and no one dissimilar soil may make up more
                                                      than 10 percent of the map unit" (USDA 1983). Therefore the worst case condition for
                                                      mapping accuracy means that only about 75 percent of the area mapped as hydric soil would
                                                      actually be hydric. However, according to SCS soil scientists, hydric soils generally tend to
                                                      have fewer inclusions and dissimilarities than other soils and would therefore be more
                                                      accurate, around 85-90 percent mapping accuracy.

                                                      Assessing Wetland Change
                                                      A selected set of hydric soils from the Edisto Basin was analyzed in this study to estimate the
                                                      historical extent of native wetland vegetation. The selected set of hydric soils was derived
                                                      from the county hydric soils lists developed by the Soil Conservation Service. The selected
                                                      set included only those hydric soils with "map unit names" determined to have a "hydric soil
                                                      component" for the "whole map unit" (USDA 1986). In other words, the analysis included
                                                      only those soil types determined by SCS to be uniformly hydric (see Appendix I for hydric
                                                      soilslist). The selected set of hydric soils was compared with the NWI wetlands data to assess
                                                      changes in the extent of native wetland vegetation.
                                                                Conversion of native wetland vegetation communities to other land uses and cover
                                                      types was assessed by quantifying the acreage of various land uses and cover types occurring
                                                      on the hydric soils. This was determined by overlaying the 1989 land use and NWI wetlands
                                                      data on the selected set of hydric soils, derived from the SCS soils data. In conducting this
                                                      analysis about 68 percent of the Basin's area was derived from soil surveys of the 1980s; most
                                                      of remaining area was evenly split among soil surveys from the 1970s and from the 1960s.
                                                                Changes in the spatial extent of native wetlands vegetation was assessed in the
                                                      coastal area of the Basin by comparing the 1981 and 1989 NWI wetlands data. This
                                                      comparison was made for only 17 quadrangles in the coastal zone because the 1981 data were
                                                      available only for this area of the Basin.
                                                                In addition to determining changes in the extent of wetland vegetation, partial
                                                      alterations to wetland resources were evaluated. This was done for each subbasin using 1989
                                                      NWI data to identify and quantify the partially drained/ditched wetlands and the dikedl
                                                      impounded wetlands in the Basin.


                                                      Stream-Edge Habitat Analysis
                                                      The contiguity of streams and stream-edge habitat for each of the perennial stream corridors
                                                      of the Basin was evaluated to assess the extent to which forests and natural cover potentially
                                                      protect and shelter associated streams and provide habitat for wildlife. This analysis was
                                                      performed by using a GIS technique called "buffering." Buffering creates a strip along the
                                                      edges of a mapped feature to any desired width. In this case the Basin's stream network was
                                                      buffered, and then the buffered streams were overlayed with the land use and wetlands
                                                      information to determine the percentage of various land use and cover types found within the
                                                      strip of land adjacent to the stream edges.
                                                                The width of the buffers for each stream analyzed in this study was 250 meters (125
                                                      meters (about 400 feet) on each side of a stream) and 120 meters (60 meters (about 200 feet)
                                                      on each side). The 250 meter buffer was a relatively wide strip for stream-edge analysis, but
                                                      it was chosen in order to assess more than just the minimum areas recommended in the







                                               LAND USE AND LAND COVER


              literature and in Best Management Practices. Gosselink and others (1990) applied a 250
              meter buffer in assessing stream edges of the Pearl River in Mississippi, and a comparison
              with those findings was desired. The dimension of the buffer applied to the Pearl River was
              apparently based on constraints resulting from the resolution of the satellite data that was used
              rather than on particular standards derived from scientific literature. Howard and Allen
              (1989) summarized recent literature concerning the value of strearnside forested wetlands in
              the southern United States. They reported on a number of sources that suggest buffers from
              8 to 31 meters may be needed to protect and maintain water quality and fisheries, and buffers
              up to 104 meters may be needed for wildlife. Brinson and others (1981) report that the zone
              within 200 meters of a stream or open water appears to be the most heavily used by terrestrial
              wildlife. Howard and Allen recommended, for fish and wildlife management purposes, that
              protected zones along perennial and small streams (streams no wider than about 10 meters)
              be at least 60 meters wide (30 meters on each side). For larger streams, 60 meters on either
              side was recommended. Because of these specific recommendations, a second buffer, of 120
              meters, was included in the analysis of stream-edge habitats.
                       The USGS Digital Line Graphs bydrography data were used to interpret stream-
              order using methods described by Strahler (1964). The strearns were then grouped by order
              to evaluate conditions among the different size classes of streams. In this analysis stream-
              order refers to the sequence of stream formation, beginning at the headwaters, i.e. the initial
              formation of a stream. The initial formation of a stream from surface or groundwater drainage
              would be classified as "first-order." A "second-order" stream forms after the confluence of
              two first-order streams. A "third-order" stream forms after the confluence of two second-
              order streams. A "fourth-order" stream forms after the confluence of two third-order streams.
              A "fifth-order" stream forms after the confluence of two fourth-order streams; and so on.
                       The streams were grouped as third-order, fourth-order, and fifth-order and greater.
              First- and second-order streams were not included in the analysis because many of these
              features were determined to be intermittent and were of greater spatial complexity than this
              analysis required.
                       Generally, the "fifth- and greater-order" (large streams) represented the primary
              river segments of the Edisto: the North Fork and South Fork of the Edisto River; the Edisto
              River; North Edisto River; South Edisto River; Four Hole Swamp; as well as all the major
              intertidal rivers and creeks on the 1:24,000 scale maps. The "fourth-order streams" (medium
              streams) were generally the primary tributaries of the river system - the major creeks that
              feed into the rivers mentioned above. The "third-order streams" (small streams) were
              generally the tributaries to the major creeks of the Basin.


              Forest Patch Analysis
              The sizes and frequency of forest patches within the Edisto Basin were derived for each
              subbasin and for the entire Edisto River Basin from the SCWRC 1989 land use and wetlands
              data. Three categories of forest were analyzed for each subbasin:

                  ï¿½ Total forest - includes upland mixed forests, native wetland forests, and
                       planted pine forests (these forest types are defined above under "Assessing
                       Current Land Use"),
                  ï¿½ Total forest excluding the planted pine forests, and
                  ï¿½ Native forested wetland - includes native wetland forests and excludes
                       planted pine forests and mixed upland forests.

                       Total forest was the only forest category for which the subbasins were merged in
              order to analyze forest patches for the entire Edisto Basin. The other two forest categories
              were analyzed for the subbasins only.
                       Patch analysis was done to assess forest fragmentation and to identify large "natural
              patches" of contiguous wetland and upland forest, important for supporting wildlife -
              particularly sensitive or threatened species. Forest fragmentation results from many different
              natural conditions as well typical land use patterns associated with human settlement and land
              development. An important point to note regarding this analysis is that the available land use
              and wetlands data were mapped so that most roads and utility corridors are not shown. It was
              obvious from other map information, however, that many roads and utility corridors fragment







                                                                              ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                       the forests and natural cover of the Edisto Basin. In this forest patch analysis the Interstate
                                                       and other four-lane divided highways were overlaid on the land use and wetlands data to
                                                       dissect the forest patches. Only these large highways were considered because they were
                                                       believed to be obvious breaks in forest connectivity and barriers to most wildlife movement.


                                                       RESULTS
                                                       Historical Changes in Land Use and Land Cover

                                                       Trends from County-Based Survey Data
                                                       Most of the historical land use data used in this study was derived from the Forest Surveys
                                                       and the Census of Agriculture. These were county-based survey data (statistics representing
                                                       whole counties) and provided only a general representation of land use trends in the
                                                       hydrologically defined Edisto River Basin. The county-based statistics were available
                                                       beginning around 1930 for agriculture and about 1950 for forests; these were published about
                                                       every 5 and 10 years respectively. Figure 1-1 (in previous section) shows the hydrologically
                                                       defined basin of 2 million acres in relation to the 12 county area of about 5.7 million acres.
                                                                The total acreage of all land within the 12 county area varied between 1930 and
                                                       1990, but the average land area during this period was about 5.7 million acres. The sum of
                                                       acreage figures from the Census of Agriculture and the Forest Survey for any given year from
                                                       1950 to 1990 accounted for only about 80 to 90 percent of all land; i.e. an acreage gap ranging
                                                       from 0.5 to 1 million acres was unaccounted for using these data. The data for agricultural
                                                       land use are likely the primary source of this acreage gap. Further explanation of problems
                                                       with these data is given later in this chapter (see "Current Land Use and Land Cover").
                                                       Related to the acreage gap was a sharp reduction of agricultural land uses that occurred
                                                       between 1950 and 1960 due, in part, to the establishment of the Savannah River Plant (SRP)
                                                       in 1952. SRP, an area of about 200,000 acres, was removed from the agricultural land use
                                                       inventories in Aiken and Barnwell Counties. Forestland management continued in SRP, and
                                                       the Forest Survey inventory continued as well. However, agricultural land uses in SRP were
                                                       abruptly ceased in the early 1950's and the Census of Agriculture data for agricultural land
                                                       reflect this change (Figure 2-1).
                                                                The extent of agriculture was fairly stable from about 1930 to 1950. Since 1950 the
                                                       extent of forest cover has changed very little, but agricultural land area, even after accounting
                                                       for the affects of SRP, has steadily declined. In 1950 about 3.S million acres (62 percent)
                                                       of the 12-county area of the Edisto River Basin were considered forest land (Figure 2-1).
                                                       Forest acreage slowly increased in the 1950s, 1960s, and 1970s but declined in the 1980s. By
                                                       the late 1980s forest acreage was nearly the same as in 1950.
                                                                Historical data for urban-related land uses were available from about 1970 to 1990.
                                                       These urban land use data (see Figure 2-1) show there was a 62 percent increase in urban-
                                                       related land in the 12-county area of the Edisto during this period, an increase from 265,000
                                                       acres to 430,000 acres. During this same period, agricultural land decreased 27 percent and
                                                       forest land decreased 3 percent.
                                                                Figure 2-2 compares the percentages of general land use categories for 1968 and
                                                       1986 for the 12 Edisto Basin counties combined, and individually for Aiken, Orangeburg and
                                                       Dorchester Counties. These three counties represent different regions of the Edisto River
                                                       Basin. Aiken is representative of the upper Basin, Orangeburg represents the middle Basin,
                                                       and Dorchester represents the lower Basin. As stated above, the overall trend for this 18-year
                                                       period was a decrease in forest land and agricultural land with an increase in urban and other
                                                       land uses. Orangeburg County was an exception for forest land use, showing a small increase
                                                       since 1968.

                                                       Changes in Land Ownership
                                                       Land ownership in the counties of the Edisto Basin reflects the socioeconomic changes that
                                                       have affected land use. The decline in agricultural land use since 1950 was associated with
                                                       the loss of "land in farms," a Census of Agriculture statistic that represents all land in farmer-
                                                       owned operations. From about 1950 to 1990, nearly 66 percent of the land in farms was lost
                                                       to other land uses and ownerships, a decline from 3.3 million acres to 1.3 million acres for







                                              LAND USE AND LAND COVER



                4000000-



                                                                                       h    Agricultural land
                3000000-
                         -                                                            F     Forestland

                                                                                            Urbanland
                2000000-


                                                                                                                  Figure 2-1. Trends in general land
                                                                                                                  use categories for the12 counties of
                1000000-                                               ---A
                         -                                                                                        the Edisto Basin, 1930 to 1990.
                                                                                                                  Sources: U.S. Forest Service, Forest
                        01                                                                                        Survey and U.S. Bureau of the
                           1930    1940   1950    1960    1970   1980    1990                                     Census, Census of Agriculture.
                                                  Year


              the 12 counties of the Edisto Basin. The U.S. Forest Service data in the Edisto River Basin
              also showed a decline in farmer ownership for forestlands. From 1968 to 1986, farmer-
              owned forestland declined nearly 50 percent with increased ownership going to forest
              industry and "miscellaneous private entities," corporate land owners and individuals other
              than farm operators (Figure 2-3).

              ChangesBased on Spatial Data
              Figure 2-4 provides a comparison of the LUDA land use data from 1977 with the SCWRC
              1989 land use and wetlands data for the hydrologically defined Edisto River Basin. This
              information was derived from land use maps and statistics rather than the county-based
              survey data discussed above. As previously mentioned (see "Methods") the LUDA data are
              ofquestionable quality and were analyzed and found to be substantially different in their level
              of resolution from the SCWRC 1989 land use and wetlands data. However, the LUDA data
              did seem to provide a useful comparison for general land use changes at a basinwide scale,
              but not for evaluating or comparing sub-areas of the Basin . The comparison indicates that
              the Edisto River Basin, hydrologically defined, had similar land use trends as the 12-county
              area of the Edisto Basin, i.e., relative stability with only slight changes. Overall, there was
              a decrease in forest land (specifically upland forests), a decrease in agricultural land, and an
              increase in urban and other land uses (particularly nonforested wetlands).

              Changes in Forest Type
              As previously discussed, the extent of forest land in the Edisto River Basin declined slightly
              in recent decades. According to the Forest Survey data, overall forest acreage decreased
              about 5 percent (1,200,735 acres to 1,144,330 acres) in the Edisto drainage from 1968 to
              1986. The composition of the forests, however, changed more dramatically during this
              period. Figure 2-5 shows that seven out of ten of the forest types inventoried by the U.S.
              Forest Service declined in total area since 1968 (U.S. Forest Service 1991). Three forest
              types, Loblolly Pine, Oak-Hickory, and Elm-Ash-Cottonwood, increased in area. The
              Loblolly Pine forests showed the greatest expansion (73 percent increase in area) and
              represents the increased use of pine plantations for timber production in the Basin. In 1968
              Loblolly Pine comprised about 15 percent of the Basin's forests; its area increased to 27
              percent of the Basin's forest by 1986 (from 179,000 acres to 309,000 acres). The Oak-
              Hickory forests increased by 41 percent (120,000 acres to 170,000 acres) and may have
              expanded because of natural forest succession in abandoned agricultural fields or fire
              suppression in former pine-dominated stands.


              Current tAnd Use and LAnd Cover
              Based on 1989 land use data (Figures 2-6 and 2-7), the Edisto River Basin area was 56 percent
              forested. Three-quarters of the Basin's forestlands were mixed upland forest and pine
              plantation with the remainder in native forested wetlands. The native forested wetlands
              comprised about 14 percent of the Basin area; mixed upland forest, 23 percent; and planted
              pine forest, 19 percent. Agricultural land uses (which includes grasslands) made up 34







                                                                            ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                      percent of the Basin area; 7 percent was in non-forested wetland (including estuarine, scrub-
                                                      shrub, emergent, and open water); and 3 percent was in urban uses.

                                                      Patterns of Land Use
                                                      There are distinct patterns of land use and land cover in the Edisto River Basin that correspond
                                                      to the natural characteristics of the landscape. Broad patterns of land use and cover generally
                                                      correspond to the character of the soils, which is related to topography and drainage. "Land
                                                      resource areas" as described by the U.S. Soil Conservation Service (see "Soils and Vegeta-
                                                      tion" and Figure 1-2 in Chapter 1) are regions based primarily on soil characteristics that
                                                      provide a basis for describing the dominant vegetation and land uses in different parts of the
                                                      state. Land use and land cover in the Edisto Basin (Figure 2-7) corresponds remarkably well
                                                      with the land resource areas (see Figure 1-2 of the Introduction chapter).
                                                               The Edisto Basin encompasses four of the six land resource areas in South Carolina.
                                                      The Carol ina-Georgia Sandhills, an area that crosses the Basin near the western end, is mostly
                                                      forested with a mix of pines and scrub-oaks. There are only small scattered locations of
                                                      agriculture in the Sandhills area due to widespread excessively drained and infertile sandy
                                                      soils. The Southern Coastal Plain, found at both the Basin's western tip and through a broad
                                                      band in the middle Basin, is dominated with agricultural land uses. The fertile loamy and
                                                      clayey soils of this Southern Coastal Plain area support some of the most productive
                                                      agricultural land in South Carolina. The sandy and clayey soils of the Atlantic Coast
                                                      Flatwoods support some very large agricultural areas; however, as the Basin narrows into a
                                                      "neck" at its southeastern end, the Flatwoods become dominated with forestland - primarily
                                                      pine plantations. Much of the pine plantation forests in the Flatwoods area is owned by the
                                                      forest products industry that has expanded these forests over the past 25 years. The Tidewater
                                                      Area supports a variety of land use and land cover, but mostly consists of forests and estuarine
                                                      wetlands with some agriculture on the better drained sandy and clayey soils. Agriculture in
                                                      the Tidewater Area is mostly vegetable farming.
                                                               The riverine bottomlands or floodplains remain mostly forested, and they form a
                                                      dendritic or branching pattern of forested wetland corridors throughout the Basin. In many
                                                      areas it can be seen that these corridors have been encroached upon, and the native vegetative
                                                      cover has been converted to agriculture, pine plantation forest, and - adjacent to Orangeburg
                                                      - to urban land uses (see Figure 2-7).
                                                               The city of Orangeburg is the only large urban area within the Edisto Basin and this
                                                      location is likely no accident. Orangeburg lies within the heart of the productive agricultural
                                                      lands and on the banks of the North Fork Edisto River, two factors that have continued to
                                                      support growth and economic development in this city for more than 150 years. The river
                                                      supported commerce through transportation in the past, and today the river's water supply
                                                      supports a significant industrial base for the city

                                                      Land Use in the Subbasins
                                                      Maps, acreages, and percent of total area for land use and land cover categories in the Edisto
                                                      River Basin and its four subbasins are provided in Figures 2-6 through 2-15.
                                                               The North and South Fork subbasins were generally very similar in land use
                                                      characteristics; both were 56 percent forested and had nearly 40 percent in agricultural land
                                                      (Figures 2-8 and 2-10). Proportionally, the differences between the North and South Forks
                                                      were only 2 to 3 percentage points, with the North Fork having more urban land (5 percent
                                                      of the area and greatest among all subbasins), and more pine plantation (19 percent) and
                                                      mixed upland forest lands (29 percent). The South Fork had more forested wetlands (10
                                                      percent) and more agricultural land (40 percent).
                                                               The Four Hole Swamp subbasin had agricultural uses that occupied 42 percent of
                                                      the area (Figures 2-12 and 2-13). This was the highest proportion of agricultural land among
                                                      the four subbasins. Forests covered 52 percent of the area and more than one-third of the
                                                      forests were forested wetlands. Pine plantations were found to be more extensive than mixed
                                                      upland forests in the Four Hole Swamp and in the main stem subbasins.
                                                               Overall, the main stem had proportionally more forest area (60 percent of the area)
                                                      and less agricultural area (20 percent) than the other subbasins (Figures 2-14 and 2-15). The
                                                      forest lands of the main stem were equally distributed among forested wetland and mixed
                                                      upland forestland with slightly more pine plantation forestland. Nonforested wetlands,
                                                      primarily estuarine marsh and intertidal open water areas covered 19 percent of the main stem
                                                      area - greater than six times as much as was found in the other subbasins.







                                          LAND USE AND LAND COVER



                                                                                                                          "Aw







                                All Counties of the Edisto Basin
                  Urban Land    p" I
                  Forest Land

           Agricultural Land
                  Other Land                                                                 1968
                                0      10       20      30       40       50      60
                                                      Percent of Area                        1987


                                Aiken County
                  Urban Land)W7
                  Forest Land

           Agricultural Land

                  Other Land


                                0      10       20      30       40       50      60        70
                                                      Percent of Area


                                Orangeburg County

                  Urban Land

                  Forest Land

           Agricultural Land

                  Other Land

                                0      10       20      30       40       50      60        70
                                                      Percent of Area
                                Dorchester CQu-nty

                  Urban Land

                  Forest Land                                                                              Figure 2-2.
           Agricultural Land                                                                               Change in land uses for counties of
                                                                                                           the Edisto Basin, 1968 to 1986.
                  Other Land                                                                               Sources: U.S. Forest Service, For-
                                let I                               .... ....      I .....                 est Survey and U.S. Bureau of the
                                0      10       20      30       40       50      60        70             Census, Census of Agriculture.
                                                      Percent of Area







                                                                           AsSESSING CHANGE IN THE EDISTo RIVER 13ASIN



                                                        800000-

                                                        700000_@
                                                                                                                                Public
                                                        600000-                                                                 Forest Industry
                                                        500000-
                                                                                                                         -F- Farmer
                                                        400000---
                                                        300000--T,1-__'-'                                                       Misc. Private
            Figure 2-3. Trends in the ownership         200000
            of forestland acreage in the Edisto
            River Basin, 1968 to 1986.                  100000
            Source: U.S. Forest Service,                                                 P               P
            Forest Survey.                                             1968             1978            1986
                                                                                        Year




                                                                                    Urban
                                                                            Open Water                                            1977

                                                      Nonforest & Estuarine Wetland                                               1989

                                                                      Forested Welland
            Figure 2-4. Changes in the percent-
            age of land use categories for the        Mix Upland & Plantation Forest
            Edisto River Basin, 1977 to 1989.
            Sources: 1977 USGS LUDA data                                      Agriculture
            and 1989 land use and wetlands data
            from SCWRC.
                                                                                           0    5    10 15 20 25 30 35 40 45 50
                                                                                                              Percent of Area


                                                        350000




                                                        300000-
                                                                                                                       Longleaf Pine

                                                                                                                       Slash Pine
                                                        250000-                                                  L     Loblolly Pine

                                                                                                                       Shortleaf Pine

                                                        200000-                                                  P     Pond Pine

                                                      U                                                                Oak Pine

                                                        150000-                                                  !1    Oak-Hickory

                                                                                                                       Southern Scrub Oak

                                                        100000                                                   E)    Oak-Gum-Cypress

                                                                                                                       Elm-Ash-Cottonwood


            Figure 2-5. Changes in area of forest         50000-
            types in the Edisto River Basin, 1968                 -
            to 1986.
            Source: U.S. Forest Service,
            Forest Survey.                                     0
                                                                         1968               1986







                                               LAND USE AND LAND COVER


             Disparities Between Data Sources
             There is a disparity between the 1989 land use data and the 1986 land use statistics previously
             mentioned and shown in Figure 2-2. The 1989 data show 34 percent agricultural land,
             substantially more than the 1986 data that show only 14 percent in agriculture. Urban land
             differs as well; 1989 data show 3 percent and 1986 show 7 percent. Part of the reason for the
             disparity is that these are two completely different data sets, both in terms of quality and the
             area represented. The 1.989 data are spatial data derived from aerial photography and
             represent the hydrologically defined basin. The 1986 data are census survey statistics derived
             from a representative sample of landowners and represent the 12 counties of the basin, a
             region that is more than twice the size ofthe Edisto drainage basin. Given these differences
             in the data, the disparity in urban land can be explained by the fact that the 12 county area
             encompasses portions of the metropolitan areas of Charleston, S.C., Columbia, S.C., and
             Augusta, Ga. The hydrologically defined basin area is distinct from these areas and is
             definitely more rural. For agricultural land, the disparity is due, in part, to the area differences
             but probably more related to differences in the quality of the data. Because the Census of
             Agriculture data are census survey statistics they are probably less accurate. It is interesting
             to note that for 1986 the proportion of "other land" (land apparently unaccounted for by the
             available survey data) was about 20 percent of the 12 county area. The same proportion, 20
             percent, represents the full disparity between the 1986 and 1989 data sources for agricultural
             land area. This indicates that the Census of Agriculture data may simply omit some of the
             agricultural land inventoried by photointerpretation. This may be due to definitional
             differences or survey sampling limitations.






                                                          ASSESSING CHANGE IN THE EDISTo RIVER BASIN







                                 Edisto River Basin - 1989 Land Use              Land Cover





                                                        Urban

                                  Nonforested Wetlands



                            Forested Wetlands                                        Agriculture









                            Mixed Upland Forest


                                                                          Pine Plantation Forest








                    Land Use / Land Cover Types                            Acres      Percent of Total Area
                    Nonforested Wetland
                        Estuarine Wetland                                44,730                2%
                        Palustrine Emergent Wetland                      12,831                1%
                        Palustrine Scrub-Shrub                           28,184                1%
                    Open Water                                           47,251                2%
                    Forested Wetland                                    278,889               14%
                    Upland Forest / Mixed                               458,189               23%
                    Upland Forest / Pine Plantation                     377,562               19%
                    Agriculture                                         671,123               34%
                    Urban                                                63,688                3%
                    Total Area                                         1,982,446






         Figure 2-6. Edisto River Basin: acreage and percentage of total Basin for land use and land cover types, 1989. Source: SCWRC 1989
         land use and wetlands data.










                                                                                        1989 LAND USE/LAND COVER TYPES


                                                                                                                 Edisto River Drainage Basin









                                                                                  AL






















                                                                                                                      LAND USEILAND COVER TYPE          ACRES   PERCENT

                                                                                                                      NON-FORESTED WTLANDS            85, 745     4. 33%

                                                                                                                      FORESTED WTIANDS               278, 889    14. 07%

                                                                                                                      UPLAND FORESTED/ M XED         458,189     23.11%

                                                                                                                      UPLAND FORESTED/PLANTATION     377, 562    19. 05%
                                                                                                                 F-1  OPEN MATER                      47, 251     2. 38%
                                                                                                                 M    AGRICULTURE                    671, 123    33. 85%
                                                                                                                 E@   URBAN                           63, 688     3. 21%




                      S-h C-Ii-        R........ Co@--
                                                                                                                                  5
                      N-111 R11111111 D-ilill SIPPolt Syst"                                                                     Mw6m@@@@
                      C,1,@i,, S- h C-1 i-









              Figure 2-7. Land use and land cover map of the Edisto River Basin, 1989.







                                                         ASSESSING CHANGE IN THE EDISTo RIVER BASIN







                           North Fork Subbasin - 1989 Land Use                    Land Cover





                                                        Urban
                                 Nonforested Wetlands

                              Forested Wetlands



                                                                                     Agriculture





                     Mixed Upland Forest






                                                                   Pine Plantation Forest







                 Land Use / Land Cover Types                              Acres       Percent of Total Area
                 Nonforested Wetlands
                     Estuarine Wetland                                         0               0%
                     Palustrine Emergent Wetland                          1,144               <1%
                     Palustrine Scrub-Shrub Wetland                       3,783               <1%
                 Open Water                                               5,141                1%
                 Forested Wetland                                        40,448                8%
                 Upland Forest / Mixed                                  142,025               29%
                 Upland Forest / Pine Plantation                         93,535               19%
                 Agriculture                                            178,277               37%
                 Urban                                                   22,605                5%
                 Total Area                                             486,957






    Figure 2-8. North Fork subbasin: acreage and percentage of total subbasin for land use and land cover types, 1989.
    Source: SCWRC 1989 land use and wetlands data.







                                                                   LAND USE AND LAND COVER











                                                         1989 LAND USE/LAND COVER TYPE


                                                                                                         North Fork Sub-Basin






























                                                   [AND USE/LAND COVER TYPE               ACRES     PERCENT

                                                   NON@ FORESTED wrLANw                   4,927      1.00%

                                                   FORESTED METIANDS                    40,448       8. 31%

                                                   UPLAND FORESTEDI M XED              142,025      29. 17%

                                                   UPLAND FORESTED/PLANTATION            93,535     19.21 %

                                                   OPEN VATER                             5,141      1. 06%

                                                   A(M CULTURE                        178, 277       36.61%

                                                   URBAN                                22, 605      4. 64%























                   Figure 2-9. Land use and land cover map of the North Fork subbasin in the Edisto River Basin, 1989.







                                                             ASSESSING CHANGE IN THE EDISTo RIVER BASIN








                              South Fork Subbasin - 1989 Land Use                    Land Cover





                                                                Urban
                                        Nonforested Wetlands

                                   Forested Wetlands





                                                                                         Agriculture




                         Mixed Upland Forest







                                                                      Pine Plantation Forest







                    Land Use    Land Cover Types                            Acres      Percent of Total Area
                    Nonforested Wetlands
                        Estuarine Wetland                                         0                0%
                        Palustrine Emergent Wetland                           1,698              <1%
                        Palustrine Scrub-Shrub Wetland                        4,974                1%
                    Open Water                                                1,587                1%
                    Forested Wetland                                        57,559               10%
                    Upland Forest / Mixed                                  154,269               28%
                    Upland Forest / Pine Plantation                         93,538               17%
                    Agriculture                                            217,875               40%
                    Urban                                                   13,856                 3%
                    Total Area                                             548,452
                                             (@L






























        Figure 2-10. South Fork subbasin: acreage and percentage of total subbasin for land use and land cover types, 1989.
        Source: SCWRC 1989 land use and wetlands data.








                                                                                                                                                                                                                                            too
                                                                         LAND USE AND LAND COVER











                                                                 1989 LAND USE/LAND COVER TYPES


                                                                                                                 South Fork Sub-Basin















                                                                                                                                                SIM











                                    LAND US I) LAND COVER 'I YPE             ACRES      PERCENT                                                                                                                         %A
                                    NON- FORESTED WfLANDS                   6, 673        1. 22%

                                    FORESTED WFLANDS                       57, 559      10. 49 %

                                    UPLAND FOR1,STED/ MIXED               154, 269      28. 13%
                              L     UPLAND FORESr   FEW PLANTATI ON        93, 538      17. 05%
                              0     OPEN VWI'ER                              4,681          .85%

                                    AQU CULFURIE.                          217,876      39. 73%

                                    UR13AN                                  13,857       2. 53%
                                                                                                                                                                                                       Jr

















                     Figure 2-11. Land use and land cover map of the South Fork subbasin in the Edisto River Basin, 1989.







                                                          ASSESSING CHANGE IN THE EDISTo RIVER BASIN







                         Four Hole Swamp Subbasin - 1989 Land Use                     Land Cover




                                                             Urban
                                     Nonforested Wetlands




                            Forested Wetlands



                                                                                    Agriculture






                         Mixed Upland Forest





                                         Pine Plantation Forest







                         Land Use / Land Cover Types                            Acres       Percent of Total Area
                         Nonforested Wetlands
                             Estuarine Wetland                                       0               0%
                             Palustrine Emergent Wetland                        1,502              <1%
                             Palustrine Scrub-Shrub Wetland                     7,354                2%
                         Open Water                                             1,902              <1%
                         Forested Wetland                                     78,068               19%
                         Upland Forest / Mixed                                60,370               15%
                         Upland Forest / Pine Plantation                      72,511               18%
                         Agriculture                                          167,108              42%
                         Urban                                                13,607                 3%
                         Total Area                                           402,424
                                          All&
                                          @@L
































       Figure 2-12. Four Hole Swamp subbasin: acreage and percentage of total subbasin for land use and land cover types, 1989.
       Source: SCWRC 1989 land use and wetlands data.







                                                     LAND USE AND LAND COVER










                                       1989 LAND USEILAND COVER TYPES


                                                                                               Four Hole Sub-Basin





                                                                   *k                                                          F- H,le S.b.S,,I,



                                                                 jjr,
                                                                                              41



                                                                                                                                to
                                                                               N                                 411





                                                                                                                                                    J=


                                       LAND USE/ LAND COVER TYPE           ACRES    PERCENT

                                       NON- FORESTED VIETLANDS             8.856     2. 20%

                                       FORESTED NWULANDS                 78, 069    19. 40%

                                                                         60. 370    15. 00%
                                       UPLAND FORESTED/ M XED
                                 F_ I  UPLAND FORESTED/PLANIA11ON        72,511     18.02%

                                       OPEN WNTER                         1, 902       .47%
                                       AGRicuurURE                      167. 109    41. 53%                                    IN'

                                       URBAN                             13, 607     3. 38%









                                S- h -.1 1  Mt  R@ ....... C--
                                N.t.- R..... - D.-- S.pp.,t Sy-.
                                        -1h C.1.1-













              Figure 2-13. Land use and land cover map of the Four Hole Swamp subbasin in the Edisto River Basin, 1989.







                                                             ASSESSING CHANGE IN THE EDISTo RIVER BASIN







                                   Main Stem Subbasin - 1989 Land Use / Land Cover





                                                           Urban
                               Nonforested Wetlands                              Agriculture







                            Forested Wetlands                                           Pine Plantation Forest





                                            Mixed Upland Forest







                            Land Use / Land Cover lypes                              Acres       Percent of Total Area
                            Nonforested Wetlands
                                Estuarine Welland                                  44,730                 8%
                                Palustrine Emergent Welland                          8,486                2%
                                Palustrine Scrub-Shrub Wetland                     12,073                 2%
                            Open Water                                             35,527                 7%
                            Forested Welland                                      102,814                19%
                            Upland Forest / Mixed                                 101,525                19%
                            Upland Forest / Pine Plantation                       117,977                22%
                            Agriculture                                           107,862                20%
                            Urban                                                  13,619                 2%
                            Total Area                                            544,613






        Figure 2-14. Edisto (main stem) subbasin: acreage and percentage of total subbasin for land use and land cover types, 1989.
        Source: SCWRC 1989 land use and wetlands data.







                                                                                       LAND USE AND LAND COVER                                                                                                                                                                          rl a

                                                                                                                                                                                                                                                            ......... ...









                                                                                            1989 LAND USE/LAND COVER TYPES



                                                                                                                                      Main Stem Sub-Basin











                                                                                                                     j























                                                                                     11.1       C-E. I                             PE-
                                                                                    1-1 E. WN IINW                   65,288        ". I-
                                                                               F-rED wr@i@                           1.2. -        18.88%
                                                                               - R-EM                                -, -          -64%
                                                                               UP- -TEU P- I                         1 17, 977     21. 66%                                   7
                                                                               (IEI       1                          35. S27       6. -
                                                                                                                     W, 862        19...%
                                                                                                                     13, 619       2. 50%

























                        Figure 2-15. Land use and land cover map of the main stem subbasin in the Edisto River Basin, 1989.






                                                                            ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                     Changes in Wetiand Resources
                                                     The National Wetlands Inventory data were derived from color infrared photography and
                                                     primarily represent existing native wetland vegetation and surface water. Based on the 1989
                                                     National Wetlands Inventory (NWI) data, the Edisto River Basin contained 364,634 acres of
                                                     wetland habitats, an area equal to approximately 18 percent of the region. Three-quarters of
                                                     these wetland habitats were palustrine forests. Table 2-1 describes the proportion of general
                                                     wetland types found in the Basin.

                                                     Table 2-1. 1989 National Wetlands Inventory acreage for the Edisto River Basin.


                                                     Wetlands of the Edisto River Basin                               Acres     % of total wetlands
                                                     Palustrine (freshwater) Forested Wetlands                       278,889             76%
                                                     Estuarine (salt and brackish water) Wetlands                     44,730             12%
                                                     Palustrine (freshwater) Scrub-Shrub Wetlands                     28,184              8%
                                                     Palustrine (freshwater) Emergent (herb aceous)Wetl ands          12,831              4%
                                                     Total Wetlands in 1,989                                         364,634-
                                                          * Total wetland acreage equals 18 percent of the total Basin area of approximately
                                                          2 million acres.


                                                               The wetland habitats of the Edisto River Basin have been affected by a variety of
                                                     human land use activities. Some of these activities have resulted in a loss of area for native
                                                     wetland vegetation because of conversion to other land uses and cover. Evaluating the extent
                                                     of a selected set of the hydric soils in the Edisto River Basin (see "Methods" for an explanation
                                                     of how the selected set was determined) provides an indication of the historical extent of
                                                     native wetland vegetation. Assuming that the selected set of hydric soils chosen for this
                                                     analysis is a conservative indicator of the historical extent of native wetland vegetation, then
                                                     the 1989 wetland acreage compared to the hydric soil acreage suggests a conversion of
                                                     roughly 39 percent of the Basin's native wetland vegetation has occurred (Figure 2-16).
                                                     Comparing these data for the subbasins suggests that the greatest wetland vegetation
                                                     conversions have occurred in the main stem and Four Hole Swamp - a conversion of 41
                                                     percent and 45 percent of former native wetland vegetation acreage respectively.
                                                               Note that the historical conversions indicated by the hydric soils analysis refer to
                                                     habitat changes from "native wetland vegetation" to other land uses and cover types, and not
                                                     necessarily to the hydrologic changes associated with filling, ditching, draining, or impound-
                                                     ing wetlands. Some of these areas of lost native wetland vegetation may still retain saturated
                                                     soil conditions (i.e. hydric soils), and depending upon the new land use, may continue
                                                     important wetland ecological processes. However, food web support and biological diversity
                                                     would certainly be altered by the conversion of native wetland vegetation to other cover
                                                     types.

                                                     Land Uses on Hydric Soils
                                                     Comparing the selected set of hydric soils overlayed with the 1989 SCWRC land use and
                                                     wetlands data provides an acreage estimate of the total conversion of native wetland
                                                     vegetation to various types of land use practices in the Basin. Table 2-2 shows the results of
                                                     the overlay of these two data layers. Aside from the wetlands (which were obviously
                                                     expected), upland forests and pine plantations were the predominant land use/cover associ-
                                                     ated with the extent of hydric soils; these were followed by agriculture. When comparing the
                                                     subbasins, agriculture, pine plantation, and urban land (the more intensive land uses) were
                                                     associated with a greater portion of the hydric soils in Four Hole Swamp (36 percent of the
                                                     hydric soils) followed by the main stem (at 28 percent), then the North Fork (at 20 percent)
                                                     and the South Fork (at 18 percent). The large acreage of upland forests found on hydric soils
                                                     may seem odd; however, these areas could represent drained wetland areas that were
                                                     abandoned to natural forest succession, leading to the establishment of a mixed upland forest
                                                     community on former wetlands. Mapping and classification errors also may have affected
                                                     these results. The areas identified as upland forests may have actually been pine plantation
                                                     forests, possibly even wetland forests. Also, a minor portion of the soils maybe misidentified.







                                                  LAND USE AND LAND COVER


                         Disparity between the wetlands and soils data was evident when comparing the two
               data sets. For the entire Basin about 54,500 acres (or 15 percent) of the NWI wetlands did not
               correspond with any of the hydric soils in the overlay process. Of the 54,500 acres not associated
               with hydric soils, 79 percent were forested wetlands, 11 percent were scrub-shrub wetlands, 6
               percent were estuarine wetlands, and 4 percent were palustrine emergent wetlands. Part of this
               disparity could have been due to the selection of only a subset of the hydric soils for this analysis.
               Other reasons for the disparity are likely the fundamental differences in methods, dates and
               sources of raw data, and the overall purposes of developing the two different data bases. The
               discrepancy may also be due to the limitations and/or errors of photo interpretation for the NWI
               data where transitional and/or other areas could be misidentified. In spite of the disparities,
               major losses of wetland vegetation due to conversion to other land uses are evident.



                   600-



                   500-



                   400


                                                                                              North Fork
                   300-                                                                 Fj SouthFork
                         -                                                                                                 Figure 2-16. Historic acreage of
                   200-                                                                       Four Hole Swamp
                         -                                                                                                 native wetland vegetation (as indi-
                                                                                              Main Stem                    cated by a selected set of hydric
                   too-                                                                                                    soils) compared to 1989 National
                                                                                                                           Wetlands Inventory for the Edisto
                                                                                                                           River Basin.
                      0-1
                   Historic Wetland Vegetation                1989 NWI Wetland Habitat

                         Subbasins                 Historic Wetland Veg. (hydric soils)*                   1989 Wetlands
                      of Edisto Basin                         Acreage      % of total               Acreage       % of total               % change
                      North Fork                              65,584           11%                   45,375           12%                    -31%
                      South Fork                              88,340           15%                   64,232           18%                    -27%
                      Four Hole Swamp                        157,043           26%                   86,924           24%                    -45%
                      Edisto (main stem)                     283,611           48%                  168,103           46%                    -41%
                      Total Edisto River Basin               594,578                                364,634                                  -39%
                            * Date of soils data - about 68 percent of the Basin's area was derived from soil surveys of the 1980s;
                            most of remaining area was evenly split among soil surveys of the 1970s and the 1960s
                            (See "Methods, Data Sources").


               Table 2-2. Area of different land use types found on a selected set of the hydric soils in the
               Edisto River Basin and subbasins.


                                                      Acres of HVdric Soils and % of Total by Basin and Subbasin
                      Land Uses found           Entire               North                  South                Four                  Main
                      on Hydric Soils           Basin     %          Fork       %           Fork     %           Hole %                Stem      %
                      Wetlands / Water a        320803     54%         38,020 58%           55,372   63%          73,358 47%           154,052   55%
                      Upland Forests            104:578 18%            14,414 22%           16,148   18%          26,276 17%             47,740  17%
                      Pine Plantations           98,984 17%              6,032    9%          5,852     6%        27,469 17%             59,631  21%
                      Agriculture                 61,512   10%           5,910    9%        10,136   11%          27,237 17%             18,229    6%
                      Urban                       8,702     1%          1,208 2%                 832    1%          2,703 2%             3,959 1%
                      Total                     594,578                65,584               88,340               157,043               283,611
                            a Water alone overlays about 10,700 acres or        1.8 percent of the hydric soils in the Basin







                                                                          ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                    Changes in the Coastal Region
                                                    Comparing the 1989NWI data with the 198INWI data that were available for 17 quadrangles
                                                    in the coastal region indicated about a 5 percent loss in total acreage of native wetland
                                                    vegetation over the 8-year period (Table 2-3). These data showed both increases and
                                                    decreases in acreage for various types of wetland habitats. Because the 1989 and 1981
                                                    wetlands data were derived from different scales of photography, comparing the differences
                                                    among the various wetland types can be subject to error. The 1989 data were derived from
                                                    1:40,000 scale photography while the 1981 data were from 1:58,000 scale photography. The
                                                    differences in photo resolution affect the accuracy of quantifying absolute changes among
                                                    the various wetland habitat types. Also variable conditions of ground saturation at the time
                                                    of aerial photograph acquisition could lead to different results for wetland acreages. These
                                                    data do, however, provide a basis for describing general patterns of change.
                                                             In general, the patterns of change among the native wetland vegetation in the coastal
                                                    region indicated decreases in forested wetlands and increases in palustrine emergent and
                                                    scrub-shrub wetlands. The acreage of estuarine wetlands appears to have remained relatively
                                                    stable.


                                                    Table 2-3. Changes in wetlands in the coastal region of the Edisto River Basin from 1981
                                                    to 1989.


                                                    Wetlands of the Edisto Coastal Region              1981. Acres     1989 Acres      % change
                                                    Palustrine Forested Wetlands                           82,735          71,355           -14%
                                                    Estuarine Wetlands                                     43,999          44,730            +2%
                                                    Palustrine Emergent (herbaceous) Wetlands               6,325           7,778           +23%
                                                    Palustrine Scrub-Shrub Wetlands                         4,682           7,330           +57%

                                                    Total Wetlands                                       137,741         131,193             -5%



                                                    Altered Wetlands
                                                    About thirteen percent of the 1989 inventory of wetland habitats in the Edisto River Basin
                                                    was in an altered condition due to diking and impounding or partial draining and ditching
                                                    activities. Diked or impounded wetlands are created or modified by a constructed barrier or
                                                    dam that obstructs the outflow of water (beaver dams are included). Partially drained or
                                                    ditched wetlands are areas where the water level has been artificially lowered. Partially
                                                    drained areas are still classified as wetlands because soil moisture is sufficient to support
                                                    some hydrophytic species at the time of the inventory. The National Wetlands Inventory does
                                                    not consider drained areas as wetlands if they no longer support hydrophytes (Cowardin
                                                    1979).
                                                             A summary of "altered wetlands" from the 1989 National Wetlands Inventory data
                                                    (Table 2-4) provides acreage figures for impounded and partially drained wetlands. Overall,
                                                    there were about 49,000 acres of altered wetlands in the Edisto River Basin. Slightly more
                                                    than one-half of this acreage was impounded; the balance was partially drained.
                                                             Nearly 50 percent of the Edisto Basin's altered wetlands acreage was located in the
                                                    main stem subbasin. Half of the altered wetlands of the main stem were found in
                                                    impoundments and half were in partially drained conditions. Most of the main stem's coastal
                                                    impoundments originated with the intertidal rice planting culture established in the 18th
                                                    century, but are now maintained as waterfowl habitat. The partially drained wetlands are
                                                    primarily a result of more recent agricultural and forestry practices.
                                                             Most of the altered wetland acreage of the North and South Fork subbasins was
                                                    impounded. Most of these impounded wetlands were found in the headwaters streams where
                                                    the relatively steep, narrow valleys in the sandhills make good farm pond sites. There were
                                                    very few headwater streams without impoundments. In Four Hole Swamp most of the altered
                                                    wetland acreage was partially drained due primarily to the relatively intensive agriculture
                                                    development that has occurred in the subbasin.







                                                               LAND USE AND LAND COVER









                 Table 2-4. Altered Wetland in the Edisto River Basin and subbasins from 1089 National Wetlands Inventory data.


                         Subbasin                     Altered Wetland Types                                    # of sites                  Acreage                  Total Acreage
                         Edisto (main stem) Diked / impounded                       ....................................... .......................................................... 11,557
                                                         Palustrine Nonforest                                         225                     5,854
                                                         Palustrine Forested                                            95                    1,437
                                                         Lacustrine                                                       7                      168
                                                         Estuarine                                                    115                     4,098
                                                      Partially drained / ditched            ....................................................................................... 12,484
                                                         Palustrine Nonforest                                         358                     4,147
                                                         Palustrine Forested                                          613                     8,324
                                                         Lacustrine                                                       0                          0
                                                         Estuarine                                                        1                         13

                         --------------------------------------------------------------------------

                         North Fork                   Diked / impounded             ................................................................................................... 6,607
                                                         Palustrine Nonforest                                        1,917                    4,155
                                                         Palustrine Forested                                          309                        963
                                                         Lacustrine                                                     54                    1,489
                                                      Partially drained / ditched            ............................................................................................  502
                                                         Palustrine Nonforest                                           68                       218
                                                         Palustrine Forested                                            33                       284

                         --------------------------------------------------------------------------

                         South Fork                   Diked / impounded             ................................................................................................... 6,052
                                                         Palustrine Nonforest                                        1,677                    4,152
                                                         Palustrine Forested                                          368                     1,002
                                                         Lacustrine                                                     47                       898
                                                      Partially drained / ditched            ......................................................................................... 2,012
                                                         Palustrine Nonforest                                         147                        815
                                                         Palustrine Forested                                          116                     1,197

                         --------------------------------------------------------------------------

                         Four Hole

                         Swamp                        Diked / impounded             ................................................................................................... 1,431
                                                         Palustrine Nonforest                                         285                        716
                                                         Palustrine Forested                                            89                       373
                                                         Lacustrine                                                       9                      342
                                                      Partially drained / ditched            ......................................................................................... 8,509
                                                         Palustrine Nonforest                                         229                     1,705
                                                         Palustrine Forested                                          562                     6,804


                         Entire Edisto

                         River Basin                  Diked / impounded             ................................................................................................. 25,647
                                                      Partially drained / ditched            ....................................................................................... 23,507

                                                                Edisto River Basin Total              .............................................................................. 49,154







                                                                              ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                       Stream-Edge Habitat
                                                       The land use and land cover adjacent to the stream edges of the Edisto River Basin was
                                                       determined from a 250-meter buffer and a 120-meter buffer of the Basin's stream network.
                                                       The buffered streams were then overlaid on the 1989 land use and wetlands data. Figure 2-
                                                       17 and Tables 2-5 and 2-6 show the results of this procedure grouped by the stream-order and
                                                       subbasins.
                                                                 For the entire Edisto River Basin, the 250-meter stream-edge buffer area was in 75
                                                       percent natural cover (see Table 2-5). The stream edges consisted of 52 percent natural
                                                       forestland (forested wetlands + mixed upland forest), 14 percent open water and nonforested
                                                       wetlands, and 9 percent estuarine wetlands. The intensively managed land use categories of
                                                       urban, agriculture, and pine plantations covered a total of 25 percent of the stream-edge buffers
                                                       in the Basin; 15 percent was in agricultural land, 8 percent in pine plantations, and 2 percent in
                                                       urban land uses. The 120-meter buffer results (Table 2-6) showed proportionally more natural
                                                       cover (85 percent) and less of the intensive land uses (15 percent) compared with the 250-meter
                                                       buffer. The 120-meter analysis evaluated a narrower strip of land along the Basin's stream edges
                                                       compared with the 250-meter analysis. The net result was that upland land uses and cover types
                                                       (including the intensive land uses) were proportionally reduced and the wetland cover types were
                                                       increased with the 120-meter buffer analysis of the Basin.
                                                                 The proportion of the different land uses within the stream-edge buffers varied among
                                                       the four subbasins (Figure 2-17). Wetland forests were a major component of the stream edges
                                                       of the North Fork, South Fork, and Four Hole Swamp subbasins; each with 40+ percent forested
                                                       wetlands in the 250-meter buffer, and 60+ percent in the 120-meter buffer. Stream edges of the
                                                       main stem, however, were covered with mostly nonforested and estuarine wetlands. Within the
                                                       250-meter buffer, mixed upland forests were more prevalent in stream-edge buffers of the North
                                                       and South Fork (25 percent and 29 percent, respectively) due to greater relief and better drainage,
                                                       compared to Four Hole Swamp and the main stem subbasins (13 percent and 15 percent,
                                                       respectively) that have relatively flat terrain. However, the 120-meter buffer analysis showed
                                                       much more similar proportions of mixed upland forests among the subbasins.
                                                                 Both the 250-meter and the 120-meter buffer analysis of the Edisto Basin's third-order
                                                       streams (small streams) and fourth-order streams (medium streams) showed that agricultural
                                                       land was most extensive along these stream edges in the Four Hole Swamp subbasin. The 250-
                                                       meter analysis, in particular, showed that agriculture was the predominant land cover type found
                                                       adjacent to the small streams of Four Hole Swamp subbasin, and the intensive land uses covered
                                                       more than half of its small stream buffers. In contrast however, among all the large streams of
                                                       the Edisto Basin, the Four Hole Swamp subbasin had the smallest portion of intensive land uses.
                                                       This is because of its uniquely wide and saturated floodplain. Basin-wide, the South Fork
                                                       subbasin seemed to have had stream-edge habitats that were in the best condition overall. This
                                                       was indicated by the relatively low proportion of intensive land uses found in stream buffers of
                                                       the South Fork among the different stream-size categories.
                                                                 Among the four subbasins, mixed upland forested stream edge was consistently greater
                                                       in the North and South Forks along the small and medium size streams. Forested wetland stream
                                                       edges were most extensive on the small and medium streams of the main stem and Four Hole
                                                       Swamp, and on the large streams of Four Hole Swamp. Pine plantations were found to be most
                                                       extensive on the edges of the small and medium streams of the main stem subbasin. The largest
                                                       proportion of open water and nonforested wetland stream edges and all of the estuarine wetland
                                                       edges were found along the large streams of the main stem subbasin. These were primarily the
                                                       major streams of the intertidal system.
                                                                 Human impacts on stream-edge habitats seem to have been greatest in the Four Hole
                                                       Swamp subbasin, primarily along its creeks and small streams (third-order streams). Overall,
                                                       the proportion of agricultural land within the 250-meter stream-edge buffers was greatest in the
                                                       Four Hole Swamp subbasin; with 26 percent compared to only 12 percent in the other three
                                                       subbasins. The more intensively managed land use categories of urban, agriculture, and pine
                                                       plantations covered a total of 38 percent of the stream-edge buffers in the Four Hole Swamp
                                                       subbasin compared to the other- subbasins that ranged from 21 percent to 26 percent. Results
                                                       from the 120-meter buffer analysis confirmed that stream edges of the Four Hole Swamp
                                                       subbasin exhibit the greatest human impacts. However the 120-meter analysis also revealed that,
                                                       overall, the main stem stream edges contained the same proportion of agricultural land as the
                                                       Four Hole Swamp subbasin.







                                            LAND USE AND LAND COVER






            Table 2-5. Percentage of land use and land cover types bordering stream edges in the Edisto River Basin within a 250-meter buffer
            (125 meters from each side of stream).

                                                        All Streams (Third- and Larger-Order Streams)
            Land Use/Cover                         Entire Basin     North Fork      South Fork        Four Hole       Main Stem

                 Agriculture                            15%             t2%             12%              26%               12%
                 Urban                                   2%              3%              1%                2%               2%
                 Upland Forest / mixed                  19%             25%             29%              13%               15%
                 Forest / Pine Plantation                8%             tl%              9%              10%                7%
                 Palustrine Forested Wetland            33%             42%             43%              44%               21%
                 Open Water & Nonforest Wtld.           14%              7%              6%                4%              24%
                 Estuarine Wetland                       9%              -               -                 -               19%
                 Intensive Land Uses a                  25%             26%             22%              38%               21%



                                                         Third-Order Streams*    Small Streams

            Land Use/Cover                         Entire Basin     North Fork      South Fork        Four Hole       Main Stem

                 Agriculture                            24%             18%             17%              37%               26%
                 Urban                                   2%              2%              1%                2%               2%
                 Upland Forest / mixed                  28%             33%             39%              16%               21%
                 Forest / Pine Plantation               14%             .13%            12%              14%               18%
                 Palustrine Forested Wetland            27%             26%             26%              28%               30%
                 Open Water & Nonforest Wtld.            5%              8%              6%                3%               3%
                 Intensive Land Uses                    40%             31%             30%              55%               40%


                                                         Fourth-Order Streams"      Medium Streams
            Land Use/Cover                         Entire Basin     Nopth Fork      South Fork        Four Hole       Main Stem

                 Agriculture                            15%             11%             10%              29%               11%
                 Urban                                   2%              4%              1%                4%               1%
                 Upland Forest / mixed                  20%             26%             25%              16%               13%
                 Forest / Pine Plantation               11%             11%              9%                9%              16%
                 Palustrine Forested Wetland            45%             37%             48%              39%               54%
                 Open Water & Nonforest Wtld.            7%             11%              7%                4%               6%
                 Intensive Land Uses                    28%             26%             20%              42%               28%


                                                         Fifth-Order and Greater Streams"       Large Streams
            Land Use/Cover                         Entire Basin     North Fork      South Fork        Four Hole       Main Stem

                 Agriculture                             8%              3%              4%                3%              10%
                 Urban                                   2%              3%              2%                1%               2%
                 Upland Forest / mixed                  13%             11%             11%                5%              14%
                 Forest / Pine Plantation                4%              7%              4%                4%               3%
                 Palustrine Forested Wetland            32%             72%             76%              83%               14%
                 Open Water & Nonforest Wt1d.           23%              5%              3%                4%              31%
                 Estuarine Wetland                      18%              -               -                 -               26%
                 Intensive Land Uses                    14%             13%             10%              8%                15%


                 a Intensive Land Uses = agriculture + urban + pine plantation land uses.
                      Fifth-order and greater (large-order streams) - the primary river segments and the major intertidal rivers and creeks labeled
                      on the 1:24,000 scale maps.
                    Fourth-order streams - generally, the primary tributaries of the river system and the major creeks that feed into the rivers (fifth-
                      order) mentioned above.
                   Third-order streams - generally, the tributaries of the major creeks of the Basin.







                                                                         ASSESSING CHANGE IN THE EDISTo RIVER BASIN






          Table 2-6. Percentage of land use and land cover types bordering stream edges in the Edisto River Basin within a 120-meter buffer
          (60 meters from each side of stream).

                                                      All Streams (Third- and Larger-Order Streams)
          Land Use/Cover                        Entire Basin     North Fork       South Fork       Four Hole       Main Stem

              Agriculture                              9%              5%                5%             11%              11%
              Urban                                    2%              2%                1%              2%               2%
              Upland Forest / mixed                   14%             13%              16%               8%              15%
              Forest / Pine Plantation                 4%              5%                4%              7%               3%
              Palustrine Forested Wetland             33%             60%              63%              67%              16%
              Open Water & Nonforest Wtld.            27%             15%              11%               6%              36%
              Estuarine Wetland                       11%                -                -                -             18%
              Intensive Land Uses a                   15%             12%              10%              20%              16%



                                                      Third-Order Streams*     Small Streams

          Land Use/Cover                        Entire Basin     North Fork       South Fork       Four Hole       Main Stem

              Agriculture                             11%              8%                7%             19%              11%
              Urban                                    2%              2%                1%              2%               2%
              Upland Forest / mixed                   19%             21%              25%              12%              19%
              Forest / Pine Plantation                 9%              7%                6%             11%              15%
              Palustrine Forested Wetland             48%             44%              47%              51%              51%
              Open Water & Nonforest Wtld.            11%             18%              14%               5%               3%
              Intensive Land Uses                     22%             17%              14%              32%              28%


                                                      Fourth-Order Streams"       Medium Streams

          Land Use/Cover                        Entire Basin     North Fork       South Fork       Four Hole       Main Stem

              Agriculture                              5%              4%                3%              9%               2%
              Urban                                    2%              3%                1%              4%               1%
              Upland Forest / mixed                    9%             12%              12%               7%               4%
              Forest / Pine Plantation                 5%              5%                2%              5%               9%
              Palustrine Forested Wetland             67%             55%              68%              69%              76%
              Open Water & Nonforest Wtld.            -12%            22%              13%               6%               8%
              Intensive Land Uses                     12%             12%                6%             18%              12%


                                                      Fifth-Order and Greater Streams* * * / Large Streams
          Land Use/Cover                        Entire Basin     North Fork       South Fork       Four Hole       Main Stem

              Agriculture                              9%              0%                2%              0%              11%
              Urban                                    2%              2%                1%              1%               2%
              Upland Forest / mixed                   13%              3%                4%              1%              15%
              Forest / Pine Plantation                 2%              1%                2%              1%               2%
              Palustrine Forested Wetland             22%             87%              88%              91%              10%
              Open Water & Nonforest Wtld.            35%              7%                3%              6%              40%
              Estuarine Wetland                       17%                -                 -               -             21%
              Intensive Land Uses                     13%              3%                5%              2%              15%


              a Intensive Land Uses = agriculture + urban + pine plantation land uses.
                   Fifth-order and greater (large-order streams) - the primary river segments and the major intertidal rivers and creeks labeled
                   on the 1:24,000 scale maps.
                 Fourth-order streams - generally, the primary tributaries of the river system and the major creeks that feed into the rivers (fifth-
                   order) mentioned above.







                                               LAND USE AND LAND COVER




                  100-

                  90-                                                                  Urban
                  80-                                                                  Pine Plantation

                  70-
                                                                                       Agriculture
               E  60
                                                                                       Forested Wetland
                  50--
               41
               0       -                                                               Estuarine Wetland            Figure 2-17. Percentage of land use
               @5 40--                                                                                              and cover types bordering stream
               11.)    -
               U       -
                  30-                                                                  Open Water/                  edges within a 120 meter buffer (60
                       -                                                               nonforest Wetland            meters on each side of stream) for the
                  20-                                                                                               Edisto River Basin.
                  10                                                                   Upland forest                Small Streams = third-order streams;
                                                                                                                    Medium Streams = fourth-order
                    0                                                                                               streams; and Large Streams         fifth-
                          Small       Medium         Large     All Streams                                          order and greater streams.
                         Streams      Streams       Streams



                    Third-order streams - generally, the tributaries of the major creeks of the Basin.


             Forest Patch Analysis
             The sizes and frequency of forest patches were determined for each of the four subbasins, and
             for the entire Edisto Basin using SCWRC 1989 land use and wetlands data. The categories
             of forest included in the patch analysis of the subbasins were total forest, total forest excluding
             planted pine forest (hereafter referred to as "native forest"), and forested wetland (see
             "Methods" for definition of categories). Total forest was the only category where the forest
             cover for all the subbasins was merged and analyzed for the entire Edisto River Basin.
                       The area of total forest for the Edisto Basin was 1,112,600 acres (56 percent of the
             Basin) and was distributed among 4,025 patches. Most of the patches for total forest were
             small (less than 25 acres) and, proportionally, the small patches occupied relatively little total
             area. The majority of the Basin's forest area was found in a few very large patches: 5 patches
             that were each over 50,000 acres in size contained over 70 percent of the Basin's total forest
             area; one patch, the largest, was nearly 376,000 acres in size (see Figure 2-19). Subbasin
             analyses of total forest patch sizes and frequencies for the North and South Fork (see Figure
             2-20) showed a similar pattern - most of the total forest area was found in a few very large
             patches. Total forest area in the Four Hole Swamp and the main stem subbasins was a little
             more distributed among the various patch size classes but was still predominantly associated
             with large patches.
                       The appearance of very large patches from this analysis is misleading because it
             suggests large blocks of forest, providing an abundance of isolated interior forest habitats.
             Figure 2-18 shows that the forest patch pattern is characterized more accurately as an
             irregular, or in some cases dendritic, pattern of forested corridors.
                       The native forest category (total forest excluding planted pine forest) was more
             patchy than was the total forest. Native forests covered 735,800 acres of the Basin and was
             distributed among 7,738 patches, nearly twice the patches of total forest. The total area of
             native forest was more distributed among the different patch size categories than for total
             forest (see Figure 2-21). However, most of the patches were still among the smallest size
             category (less than 25 acres). The North Fork had one native forest patch that exceeded
             100,000 acres. Forested wetland was the most patchy category of the three forest coverages
             analyzed. Forested wetland covered 279,000 acres with 11,594 patches. As with the other
             analyses, most of the patches were less than 25 acres in size. No large (25 to 200 thousand
             acres) forested wetland patches were found. The largest forested wetland patch was a 13,000
             acre area located in Four Hole Swamp (see Table 2-7).







                                                                                                                 ASSESSING CHANGE IN THE EDISTo RIVER BASIN







                                                                1989 FOREST PATCH CATEGORIES


                                                                                                      Edisto River Drainage Basin









                                                                                                                                                                                                                          P,



                                                                               j                                                                                              Z@              S




























                                                         So,t h C. . . I I na Vbt   Resour . . .CamW ssl o,
                                                         Nat . . . IResour-1 Decl S1 a, Supp- t Syst 11
                                                         Cat .,abi    S.U1 h Car a, I








                Figure 2-18. Distribution of forest patches (total forest) in the Edisto River Basin, showing patches by size categories, 1989.







                                                 LAND USE AND LAND COVER


















                          ik I V..





                                                                                             U   Rml Dminage Basin



             r













                                              all






                            PATCH SIZE            NUNBER    TOTAL AREA

                            <25                    3,321        17,235

                            25-250                   581        41,520

                            250- 1250                   89      48,634
                        F   1250-2500                   11      18,144
                        F-1 2500-12500                  13      79,904
                                                                                                            Ir.
                            12500-25K                   3       58,372
                        F-1 25K- 50K                    2       68,855
                                                                                                              ..4
                        F-1 75K- 100K                   3      261, 944
                        El  125K- 250K                  1       142,072
                        m   >250K                       1       375,923


                        0         S         10          15           MILES







                                                                         ASSESSING CHANGE IN THE EDISTo RIVER BASIN






                                                      Edisto River Basin Forest Patches     Total Forest

                               40


                               30-


                          e    20-


                               10


                               0
               Patch size (acres)    <25      25-250      250-      1,250-    2,500-   12.5k- 25k-50k       50k-      I OOk-    >200k
                                                          1,250     2,500     12.5k      25k                I 00k     200k
               Total patch area      17,000   42,000     49,000   18,000 80,000        58,000    69,000 262,000 142,000 376,000
               No. of patches        3.321      581       89         11        13        3          2         3           1         1

          Figure 2-19. Forest patch size categories for total forest cover, presented as percentage of the total Basin area with total patch area
          and total number of patches given for each size category.
          (k =thousands)


          Table 2-7. Forest patch size categories for forested wetlands by percentage of subbasin area, total patch area (acres), and total number
          of patches for each size category.


              Patch size (acres)     <25        25-       250-       1,250-      2,500-     12.5k-        25k-        50k-      100k-
              Categories                        250       1,250      2,500       12.5k       25k          50k         100k      200k

              North Fork
              Percent of area        1.5        2.5        1.5        1.4         1.4          0           0           0          0
              Total patch area       7,100    12,000      7,400      6,900       7,000         0           0           0          0
              No. of patches         1,470      193        15          4            2          0           0           0          0

              South Fork
              Percent of area        1.5        2.7        2.0        1.5         2.8          0           0           0          0
              Total patch area       8,500    15,000      11,000     8,400       15,000        0           0           0          0
              No. of patches         1,738      216        20          5            3          0           0           0          0

              Four Hole Swamp
              Percent of area        3.0        4.9        4.0        2.6         1.8        3.1           0           0          0
              Total patch area       12,000   20,000      16,000     10,000      7,100      13,000         0           0          0
              No. of patches         2,656      294        34          6            2          1           0           0          0

              Main Stem
              Percent of area        2.9        6.5        6.2        1.6         1.7          0           0           0          0
              Total patch area       16,000   35,000      34,000     8,900       9,100         0           0           0          0
              No. of patches         4,398      471        59          5            2          0           0           0          0


              (k =thousands)







                                            LAND USE AND LAND COVER







                                                           North Fork Subbasin - Total Forest
                        as   40-

                             30
                        15


                             10

                               0
            Patch size (acres)       <25      25-250 250-1,250      1,250-    2,500-     12.5k-   25K-50k     50k-      100k-
                                                                    2,500     12.5k      25k                  100k      200k
            Total patch area        3,300     8,400      9,600      5,200     9,300      15,000    37,000       0      188,000
            No. of patches           555       124         20         3         1          1         1          0          1

                                                         South Fork Subbasin - Total Forest
                             40-




                             20

                             10

                                                                                         MW
                        40     0
            Patch size (acres)       <25      25-250 250-1,250      1,250,-   2,500-     12.5k- 25k-50k       50k-      100k-
                                                                    2,500     12.5k      25k                  100k      200k
            Total patch area        3,700     9,100      5,800      6,200     11,000     20,000      0        61,000 188,000
            No. of patches           658       134         9          4         1          1         0          1          1

                                                       Four Hole Swarrip Subbasin - Total Forest
                             40-



                        0
                             20
                        0

                             10

                               0
            Patch size (acres)       <25      25-250 250-1,250 1,250,-        2,500-     12.5k-  25k-50k      50k-      100k-
                                                                    2,50Q     12.5k      25k                  100k      200k
            Total patch area        5,500     14,000    23,000      5,400     33,000     14,000    32,000     82,000       0
            No. of patches           984       191         45         3         7          1         1          1          0

                                                           Main Stem StIbbasin - Total Forest
                             40-

                             30




                             10


                               0-
            Patch size (acres)       <25      25-250 250-1,250      1,250-    2,500-     12.5k- 25k-50k       50k-      100k-
                                                                    2,500     12.5k      25k                  100k      200k
            Total patch area        5,300     11,000     12,000     4,600     47,000     24,000 117,000         0      100,000
            No. of patches          1,277      152         19         3         7          1         3          0          1
            Figure 2-20. Forest patch size categories for total forest cover, presented as percent of subbasin area with total patch area and total
            number of patches given for each size category.







                                                                         ASSESSING CHANGE IN THE EDISTo RIVER BASIN






                                                  North Fork Subbasin - Total Forest Excluding
                                                          Planted Pine (Native Forests)*
                              20-

                        'a    15
                        q
                        4.    to-


                              5-

                              0
           Patch size (acres)       <25     25-250 250-1,250       1,250-    2,500-   12.5k- 25k-50k        50k-      100k-
                                                                   2,500     12.5k       25k                100k      200k
           Total patch area         5,200    21,000    27,000      6,600     27,000 44,000           0      52,000        0
           No. of patches           813       256         48        4          6          2          0        1           0
                                                South Fork Subbasin - Total Forest Excluding Planted Pine
                              20-

                        1;    15-
                        2
                        4.    to-
                        0

                              5

                              0
           Patch size (acres)       <25     25-250 250-1,250      1,250-     2,500-   12.5k- 25k-50k        50k-      100k-
                                                                   2,500     12.5k      25k                 100k      200k
           Total patch area         5,400     17,000   22,000      10,000    35,000    15,000        0        0       107,000
           No. of patches           939       234         39        5          5          1          0        0           1
                              20-            Four Hole Swamp Subbasin - Total Forest Excluding Planted Pine

                              15

                              10-

                              5

                              0
           Patch size (acres)       <25      25-250  250-1,250 1,250-        2,500-   12.5k- 25k-50k        50k-      100k-
                                                                   2,500     12.5k      25k                 100k      200k
           Total patch area         8,900    23,000    24,000     10,000     49,000 22,000           0        0           0
           No. of patches           1,833    318          51        6          7          1          0        0           0
                              20-               Main Stem Subbasin - Total Forest Excluding.Planted Pine

                              15-

                              to-

                              5

                        U
                        914   0
           Patch size (acres)       <25    25-250 250-1,250       1,250-     2,500-   12.5k- 25k-50k        50k-      100k-
                                                                  2,500      12.5k      25k                 100k      200k
           Total patch area         10,000   25,000    32,000     22,000     59,000    18,000   39,000        0           0
           No  of patches           2, 751   335          56       12         12          1          1        0           0

         Figure 2-21. Forest patch size categories for all forests excluding planted pine by percentage of subbasin area with total patch area and
         total number of patches for each size category.
           *Native forests includes mixed upland and wetland forests types.







                                              LAND USE AND LAND COVER


             SUMMARY ANDDISCUSSION


             Land Use Trends and Structural Change
             Prior to European settlement, the land of the Edisto River Basin was probably covered with
             greater than 90 percent forest and open woodland (Kuchler 1964). Approximately 70 percent
             of the region was covered in native upland vegetation communities and about 30 percent was
             in native wetland communities. Settlement in the Basin began first in the coastal region along
             the intertidal rivers in the 1700s and slowly expanded to the inland areas, Most of the clearing
             of forests occurred prior to the twentieth century. Based on the available data for the 12
             counties that encompass the Edisto Basin, the region was about 60 percent forested in 1950
             and nearly the same in 1987. Prior to 1950 the only land use data available are for agricutture.
             These data indicate that the extent of agricultural land was fairly constant back to 1930.
             However, since 1950 there was apparently a steady decrease in agricultural land in the 12-
             county region, falling from 30 percent in 1950 to 16 percent in 1987. This decline in
             agricultural land coincided with socioeconomic changes during this period that were
             reflected by a 60 percent decline of land acreage in farmer-owned operations. In contrast to
             agricultural lands, the extent of urban land increased within the 12 counties of the Edisto
             Basin from about 5 percent of the area in 1968 to 8 percent in 1987.
                      These survey data for the counties of the Edisto Basin were not a precise measure
             of change in the Edisto River Basin because well over half of the 12-county area lies outside
             the Basin boundaries. These county-based data do, however, indicate the general pattern of
             change that has occurred in the Edisto region. The general pattern since 1950 has been a
             steady decline in the extent of agricultural land with forestland remaining relatively stable
             and urban land gradually expanding.
                      A comparison of spatial data (land use maps and statistics) from 1977 and 1989 for
             the hydrologically defined Basin area indicates that agricultural land decreased 4 percent
             (26,000 acres), forestland decreased 2 percent (24,200 acres), and urban land increased 31
             percent (15,100 acres) in this 12-year period. The 1989 spatial data show that the current mix
             of land uses in the hydrologically defined Edisto River Basin was 56 percent forest, @4 percent
             agriculture, 7 percent nonforested wetland and open water, and 3 percent urban land. About
             a quarter of the Basin's forests were forested wetland.
                      These findings indicate there has been no dramatic or rapid change in general
             categories of land use and land cover in Edisto River Basin over the past 50 years. The major
             losses in acreage of forest cover for the Edisto Basin likely occurred during the 1800s; these
             losses resulted mostly from conversion of upland forest to agriculture. In recent decades, the
             changes that have occurred were the gradual expansion of urban-related land and the steady
             decline of agricultural land. These changes have been relatively minor compared to other
             areas in the country where there has been major forest clearing and conversion to agricultural
             development (e.g., Yazoo River Basin and Tensas River Basin discussed in Gosselink and
             Lee 1989 and Gosselink and others 1989).

             Change in Forest Composition
             Though the extent of forest cover in the Edisto Basin has remained fairly stable at between
             about 55 percent to 60 percent of the area for nearly 50 years, the composition of these forests
             has not remained the same. Conversion of natural forestand agricultural land to planted
             Loblolly Pine has occurred at a very rapid rate. Since 1968, seven out of ten of the forest types
             found in the Edisto Basin have declined in acreage; yet Loblolly Pine has nearly doubled from
             15 percent of total forest area in 1968 to 27 percent in 1986. In 1968, the Oak-Gum-Cypress
             (bottomland hardwood) forest type was by far the most extensive in the Basin. By 1986, due
             to widespread planting, Loblolly Pine forests equaled the acreage of the Oak-Gum-Cypress
             forest that had decreased by 3 percent since 1968. The Oak-Hickory forests' showed a 41
             percent increase in acreage that may be the result of forest succession and fire suppression
             in many areas.
                      The changes in forest composition are directly related to changes in forestland
             ownership. Between 1968 and 1986, nearly 400,000 acres of forestland (33 percent of total
             forestland) changed hands from farmer ownership to industry, corporate, and other private







                                                                           ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                     ownerships. In 1968 the forest industry owned about 25 percent of the Basin's forestland and
                                                     by 1986 it had increased to 45 percent. Public ownership of forestland increased but currently
                                                     remains well below one-percent of the Basin's total forestland.
                                                     Change in Wetland Resources
                                                     In 1989, 18 percent of the Edisto River Basin was covered in native wetland vegetation
                                                     according to the National Wetlands Inventory (NWI) data. Three-quarters of these wetland
                                                     habitats were forested wetlands distributed along the river bottoms and in the swamps, bays,
                                                     and depressions of the Basin. About one-eighth of the wetlands were estuarine wetlands
                                                     found in the intertidal region of the lower Basin, and the remainder were palustrine scrub-
                                                     shrub and emergent types. The history of agricultural and forestry development in the region
                                                     has changed the wetland habitats of the Edisto Basin.
                                                              It is assumed that certain hydric soils can serve as an indication of the historical
                                                     extent of native wetland vegetation. Comparing the existing native wetland vegetation base,
                                                     from 1989 NWI data, with the extent of a selected subset of hydric soils indicated that 39
                                                     percent of the Basin's native wetland vegetation (roughly 200,000 acres) has been converted
                                                     to some other land use and land cover, primarily by forestry and agricultural practices. The
                                                     1989 NWI data showed that an additional 13 percent of the Basin's native wetland habitats
                                                     had not been converted but were in an altered condition. About half of the altered wetlands
                                                     were diked and impounded and the other half were partially drained. Impoundments were
                                                     found primarily on the headwater streams as farm ponds and in the intertidal areas as former
                                                     rice fields, now used for waterfowl attraction. The ditching activities were primarily
                                                     associated with the intensive agricultural and forestry activities of the Four Hole Swamp and
                                                     main stem subbasins. The partially ditched and drained areas may be totally lost from the
                                                     region's wetlands resource base, depending upon the degree of the alteration.
                                                              Comparative data for wetland habitats were available for the coastal region of the
                                                     Basin. The comparison showed differences between 1981 and 1989 NWI data: overall, a 5-
                                                     percent decline in the acreage of native wetland vegetation over the 8-year interval.
                                                     Generally, the estuarine wetlands remained relatively stable, The declines were in forested
                                                     wetlands; the increases were in palustrine emergent and scrub-shrub wetlands. These trends
                                                     may reflect forestry activities in the area - the apparent declines in forested wetlands may
                                                     be due to forest clearcut harvesting which, in turn, produces more area that has regenerating
                                                     bottornland hardwood forests. The additional areas of regenerating bottomland hardwood
                                                     forests are photointerpreted as scrub-shrub wetlands, therefore the inventory reflects an
                                                     increase in scrub-shrub wetlands which may, in fact, represent young forested wetlands.


                                                     Implications for Ecolo ical Inte I
                                                                                         91              grity
                                                     Several indicators of ecological integrity were proposed by Gosselink and Lee (1989) for
                                                     assessing the condition of a landscape unit such as the Edisto River Basin. Proposed indices
                                                     related to landscape structure were forest conversion, forest pattern, and bottomiand forest
                                                     contiguity - in this study, contiguity was treated as the condition of stream-edge habitat.
                                                     Landscape structure has been assessed in this study by analyzing various datarelated to land
                                                     use and land cover in the Edisto Basin.


                                                     Forest Conversion
                                                     Forest conversion was proposed as an indicator of ecological integrity in forested landscapes
                                                     because from an ecological perspective the functional integrity of forested ecosystems was
                                                     directly related to remaining forest area. Scientific study, however, has not developed any
                                                     particular standards by which to assess forest loss as it relates to ecological integrity
                                                     (Gosselink and Lee 1989). For a perspective on forest conversion, Gosselink and Lee
                                                     reported that 80 percent of all bottomland hardwood forests, nationwide, have been cleared
                                                     for agriculture, although along the Atlantic coastal plain some watersheds remain relatively
                                                     intact. Biological diversity and water quality in streams are known to be adversely affected
                                                     by forest loss. Biogeographic studies indicate that a loss of 90 percent of a habitat may result
                                                     in roughly a 50 percent reduction in the numbers of animal species (Diamond 1975). Nutrient
                                                     concentrations in streams generally violate EPA water quality criteria when more than 50
                                                     percent of the forests in a watershed are cut (Omernik 1977, in Gosselink and Lee 1989).







                                             LAND USE AND LAND COVER


                      Findings from this study of the Edisto Basin indicate that, historically, about one-
             third of the native wetland vegetation communities (in terms of acres) have been converted
             and about two-thirds of the native upland communities have been converted to other land uses
             and cover types. The conversions have gone mostly to agriculture and pine plantation forest
             land uses. In spite of these changes, the structure of the Edisto Basin landscape, in terms of
             forest cover, is relatively intact and stable compared to other regions of the country. The
             forest cover conditions in the Edisto Basin probably support good water quality and many
             populations of desirable wildlife species.
                      It is important to note, however, that much of the Basin's forestlands are intensively
             managed pine plantations. Pine plantation forests are widespread, having rapidly expanded
             in recent decades; they currently occupy one-third of the Basin's total forest cover. Pine
             plantations are simplified forest communities, usually representing even-aged, single-
             species stands that are highly productive for timber. When managed on short rotations,
             plantations can produce more wood fiber than just about any forestry system; however,
             plantation forests typically lack the multilayered canopy, diverse tree sizes, abundant snags
             and fallen trees, and the high species diversity that exist in natural communities (Van Lear
             1991). Plantations have a widespread reputation for suppotting a relatively low diversity of
             wildlife; however, they can be established and maintained in ways that improve their
             diversity (Hunter 1990). Thill (1990) reports that when size, shape, and spatial distribution
             of clearcuts are considered, and frequent thinning and burning are practiced after pine canopy
             closure, intensively managed plantations furnish suitable habitat for many early-succes-
             sional wildlife species - species such as deer, quail, and rabbits. However, intensive even-
             aged silviculture is detrimental to species requiring hardwoods, snags and cavity trees, and
             large, downed woody material.
                      Where maintaining biological diversity is a goal, @,ilviculture practices must enrich
             forest structure (Sharitz and others 1992). Some important features of forest structure include
             the presence of native herbaceous and shrub plants, complex vertical structure in the forest
             canopy, some large living trees, standing dead snags, and large, downed woody debris (Van
             Lear 1991, Seymour and Hunter 1992). These forest structure features are site specific
             characteristics - they are determined largely by forest management practices on individual
             forest stands, and they can improve diversity at the stand-level. However, the landscape scale
             is the level at which the fate of wildlife species is ultimately determined (Hunter 1990).
             Hunter suggests that the interspersion or juxtaposition of different ecosystems, and forest
             stands of varying sizes, ages, and species compositions will provide the greatest biological
             diversity in a forested landscape. Even though some pine plantation stands are quite
             extensive in the Edisto Basin landscape, they generally remain interspersed with agricultural
             lands and other types of upland and wetland communities. Therefore, as Thill (1990)
             recommends, the habitats that are lacking in the pine plantations may best be provided
             through retention and management of the riparian forests or upland hardwoods interspersed
             within plantations.

             Stream-E-4-e Habitat
             The condition of forested and natural habitats along stream edges was suggested by Gosselink
             and Lee (1989) as an indicator of landscape ecological ii     'itegrity because these areas are
             positively correlated with water quality, and they function as unique habitats and migration
             corridors for wildlife. The exact relationship of various percentages of stream-edge cover
             types to water quality and wildlife has not been defined. As discussed previously in the
             "Methods" section, the width of the stream-edge buffer appropriate for basinwide analysis
             has not been defined by scientific study. An optimal stre4m-edge buffer width to use for
             analysis might reflect the width of the riparian zone, and would therefore vary greatly
             depending on stream order and topography. Maintenance of at least a 60 meter (about 200
             feet) buffer along both stream edges has been suggested for managing wildlife and would
             likely be adequate for protecting water quality as well (Howard and Allen 1989). Seymour
             and Hunter (1992) believe that intensive forestry should rarely take place within 50 to 100
             meters of a water body because: riparian zones serve as buffers to protect water quality from
             upland disturbances; they provide visual screens for aquatic recreationists; they serve as
             corridors for forest species movement across the landscape; and often they support unique,
             diverse, and productive ecosystems. For these reasons, and because of their rarity, riparian
             ecosystems are often the most valuable components of a forested landscape (Hunter 1990).







                                                                             ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                               Two sizes of stream-edge buffer were used for analysis in this study: a 120-meter
                                                      buffer, 60 meters (about 200 feet) on either side of stream (taken from Howard and Allen
                                                      1989), and a larger buffer of 250 meters, 125 meters (about 400 feet) on either side of the
                                                      stream (Gosselink and others 1990). The 250-meter stream-edge analysis showed that about
                                                      25 percent of these areas were under intensive land uses. Intensive land uses within the buffer
                                                      were urban (2 percent), agriculture (15 percent), and pine plantation (8 percent). The
                                                      remaining 75 percent of the stream-edge buffers were in natural cover (33 percent forested
                                                      wetland, 19 percent mixed upland forest, 14 percent palustrine nonforested wetland, and 9
                                                      percent estuarine wetland). The 120-meter analysis showed that 15 percent of the Basin's
                                                      stream edge was in intensive land uses (2 percent urban, 3 percent pine plantation, and 11
                                                      percent agriculture) and 85 percent was in natural cover (15 percent mixed upland forest, 16
                                                      percent forested wettand, 18 percent estuarine wetland, and 36 percent open water and
                                                      nonforested wetland).
                                                               In theirstudy of the Pearl RiverBasin, Gosselinkand others (1990) found the stream
                                                      edges, overall, to be about 85 percent forested, 10 percent agriculture, and the remainder was
                                                      marsh, urban, and other uses. Though the extent of individual categories of land use varies
                                                      considerably, the Edisto and Pearl basins have a similar proportion of stream edges in natural
                                                      cover. In contrast, the Tensas River Basin study (Gosselink and others 1989) showed a
                                                      dramatic declining trend in the percentage of forested stream edges from 54.5 percent in
                                                      1957, to 23.1 percent in 1972, to 20.9 percent in 1979, and finally to 14.7 percent in 1987.
                                                      It has been estimated that over 70 percent of the riparian ecosystems in the continental United
                                                      States have been converted to other land uses (Brinson and others 1981). Because the Edisto
                                                      Basin's stream- edge habitats are largely in natural cover, they are considered to be relatively
                                                      intact and in good condition; therefore, they are favorable for protecting water quality in the
                                                      streams and providing viable riparian wildlife habitat, as discussed by Gosselink and Lee
                                                      (1989).

                                                      Forest Pattern
                                                      Gosselink and Lee (1989) define forest pattern as "the size frequency distribution of forest
                                                      patches" in the landscape unit. They consider forest pattern a key index of the "island" effect
                                                      of biogeography that can be used to infer general conclusions about regional habitat support
                                                      for sensitive and specialized wildlife species and also the maintenance of water quality.
                                                      Generally, the more favorable forest patterns suggested for maintaining wildlife in a forested
                                                      landscape include large blocks that contain most of the region's total forest area interspersed
                                                      with smaller forested tracts - all having a high degree of connectivity to facilitate movement
                                                      of species. The authors demonstrate that large blocks of forests are critical for maintaining
                                                      populations of "area sensitive" and specialized species such as neotropical migrant birds and
                                                      large, far-ranging mammals and raptors. Forest pattern that is characterized by continuous
                                                      and intact riparian bottomland forests is also shown to be important for supporting corridors
                                                      for wildlife movement, habitat for terrestrial and aquatic species, flood water retention, and
                                                      water quality improvement through sediment and nutrient reduction.
                                                               The forest patch analysis showed that most of the forest area (56 percent of the
                                                      Basin) is found in a few large patches that extend through most of the landscape via the
                                                      bottomlands of the Basin's streams, linking upland and wetland forests into an irregular, or
                                                      in some cases dendritic, pattern of forested corridors. The total area of forest (all upland
                                                      mixed forest, planted pine forest, and wetland forest) was 1, 112,600 acres, distributed among
                                                      many (4,025) patches. Most (about 70 percent) of the Basin's forests were found in 5 patches
                                                      of 50,000 acres or more. Two patches, one 142,000 acres and the other 376,000 acres,
                                                      contained nearly half of the total forest area. Most of the patches were very small (less than
                                                      25 acres) and collectively contained very little of the Basin's total forest area.
                                                               The appearance of very large patches from this analysis is misleading because it
                                                      suggests large blocks of forest, providing an abundance of isolated interior forested habitats.
                                                      These types of habitats, which are generally rare in developed landscapes, are important for
                                                      many species of birds, small mammals, reptiles, and amphibians (O'Neil and others 1991).
                                                      However, in the Edisto Basin the large patches result from many narrow connections in a
                                                      mosaic of forested tracts creating the irregular, dendritic, pattern of forested corridors
                                                      described above. A substantial portion of the habitats associated with these large patches are
                                                      relatively exposed forest corridors and forest edges.
                                                               In addition, roads and utility corridors can present substantial breaks and barriers in







                                              LAND USE AND LAND COVER


             forest patch contiguity. In this study, the Interstate and four-lane divided highways were
             included in the patch analysis to further divide the forests because these large roads were
             thought to be definite barriers to most wildlife migration. It should be noted, however, that
             many other roads and utility corridors crisscross the forest patches causing greater forest
             fragmentation than is indicated by the patch analysis. All roads, particularly well-maintained
             and heavily traveled roads, can inhibit wildlife migration to some extent. The specific effects
             of roads on wildlife depend upon the groups of species in question (Oxley and others 1974,
             Schreiber and Graves 1977, Henderson and others 1985, Lynch and Whigham 1984, all in
             O'Neil and others 1991).
                      Two subsets of total forest were analyzed: total forest excluding planted pine forest,
             and forested wetland. This was done to assess the contribution of various forest types to
             overall landscape forest pattern. The results of analyzing these subsets of the total forest area
             were substantial increases in the number of very small patches (less than 25 acres) and a
             decrease in size or elimination of the very large patches (greater than 50,000 acres); also,
             more patches and a greater proportion of the forest area was distributed among the medium
             categories of patch size (250 to 50,000 acres). Pine plantation forests contributed signifi-
             cantly to the pattern of large forested patches on the landscape. The wetland forests were
             found to be critical to overall connectivity of forest patches in the landscape.
                      Forest stands with older, larger trees are thought to support more wildlife species
             than those with younger and smaller trees (O'Neil and others 1991). The reasons for this are
             due to increased surface area of bole, branches, and foliage, increased production of leaves,
             twigs, branches, fruits, and seeds; and increased probability. of decay leading to cavities and
             cavities of different sizes. Because much of the upland forests are intensively managed
             planted pine, the overall age of the Basin's forests is relatively young. As a general rule,
             forested landscapes with stands of many ages will support more species than a single-age
             landscape because various plants and animals are associatedwith the different stages of forest
             succession. Maintaining a balanced age structure (an even mix of different-age stands) in a
             forested landscape can accomplish two objectives: achieving a sustained yield of forest
             products, and providing diverse wildlife habitat (Hunter 11990). Currently, the forest-age
             structure in the Edisto Basin appears unbalanced (see Figure 2-22); it is dominated by
             younger, early successional, forest stands. Older forest stands (stands greater than 80 years
             old) are rare in the Edisto Basin; they compose about 4 percent (about 45,000 acres) of total
             forestland in the region. Most (over 70 percent) of the Basin's older forest stands were found
             in bottomland hardwoods. Twenty-four percent of all forestland in the Basin had mature
             stands (stands from 40 to 80 years old). Over half (54 percent) of these mature stands were
             in bottomland hardwoods. These findings illustrate the relative importance of the Basin's
             bottomland hardwood forests for maintenance of species diversity by providing most of the
             older forest habitats, habitats that are rare in the Edisto Basin. Because old-growth stands
             (stands roughly 200 year old or older) are very rare in the South it has been recommended that
             they be protected in order to ensure the biological integrity of southern forests (Sharitz and
             others 1992).
                      As suggested previously, the landscape scale is the critical level at which forest
             patterns must be assessed. There is no way that careful management of one small forest stand
             by an individual can overcome landscape-scale patterns imposed by the cumulative result of
             hundreds of other individuals' decisions. The interspersion of different ecosystems and
             forest stands of varying sizes, ages, and species compositions will provide the greatest
             biological diversity in a forested landscape. Note that very large forested habitats are an
             important landscape feature because they are required by some of the most threatened
             species; therefore, further forest fragmentation should be avoided (Hunter 1990). In the
             Edisto Basin there is substantial interspersion of forests and other habitat types; however, the
             balance of forest conditions seems to be leaning towards smaller and younger stands, and
             more Loblolly Pine plantations. The forested wetlands associated with the stream network
             are a vital component in the Edisto Basin landscape, creating a dispersion of different forests
             and ecosystems throughout the Basin. In summary, forest patch characteristics indicate that
             the Basin's forest pattern, though far from pristine, remains favorable for supporting many
             indigenous wildlife species and good water quality. The forest pattern, however, is not as
             favorable for sensitive forest-interior species as may be indicated by the patch analysis; in
             fact, high-quality forest-interior habitats seem to be quite limited.







                                                                            ASSESSING CHANGE IN THE EDISTo RIVER BASIN



                                                      Protected Lands
                                                      Another suggested criterion for ecological integrity was the proportion of protected land
                                                      found in the landscape unit (USEPA 1988). Only a very small portion of the Basin area (less
                                                      than 4 percent) is officially protected as public or privately owned land for parks, wildlife
                                                      refuges, or forestland. However, the state and federal governments have dominion over an
                                                      additional 2 percent of the Basin on the open waters and intertidal zones, and jurisdiction for
                                                      wetlands regulation on some portion of the 18 percent of the Basin determined to support
                                                      wetland vegetation. These protected and regulated lands overlap to a degree, so in total they
                                                      may amount to around 20 percent of the Basin area. Since practically all the Basin's land is
                                                      in private ownership, the collective actions of all the landowners has been, and will continue
                                                      to be the primary factor that determines the ecological integrity of the Edisto Basin.







                                                               81+






                                                            61-80
                                                                                                                                  All Classes


                                                                                                                                  Bottornland
                                                                                                                                  Hardwood
                                                      >1    41-60

                                                                                                                                  Upland
                                                      M
                                                      U                                                                           Hardwood
                                                      U
                                                            21-40                                                            E]   Oak-Pine

         Figure 2-22. Area of forestland, by                                                                                 El   Natural Pine
         stand age and broad management
         classes, in the Edisto River Basin,                  0-20                                                                Pine
         1986.                                                                                                               El   Plantation
         *NMS = no manageable stand; a U.S.
         Forest Service term for forestland that
         is less than 60% stocked with com-
         mercial species that can be featured
         under a single management scheme.                  NMS
         Total Area of forestland in 1986 esti-
         mated at 1.15 million acres.
         Source: U.S. Forest Service,                               0       50     100     150     200      250     300      350
         Forest Survey.                                                                Acres (thousands)







                                             LAND USE AND LAND COVER


             Subbasin Comparisons

             Land Use and Structural Changes
             There were very few data available to accurately compare changes in landscape structure
             among the different subbasins of the Edisto. The available historical data were primarily
             based on counties, and the county boundaries do not correspond well with the subbasins.
             Some comparison of change can be made using the Forest Survey data, hydric soils data, and
             the 1989 wetlands data. The SCWRC 1989 land use and wetlands data provide a solid
             baseline of current landscape structure for comparison - but again, there is limited data to
             compare changes or trends among the subbasins.
                       The U.S. Forest Service (1991) Forest Survey was one source of data available for
             the subbasins. This information showed that the declines in forestland since 1968 were
             occurring mainly in the South Fork subbasin - an area decrease of 11.5 percent between
             1968 and 1986. The extent of forestland was nearly constarlit in both the main stem and Four
             Hole Swamp subbasins from 1968 to 1986. The North Fork showed a small area decline of
             3.7 percent These forestry data also showed that, among the subbasins, Four Hole Swamp
             had the greatest increase in the Loblolly Pine forest type (123 percent increase in area from
             1968 to 1986) while the North Fork had the smallest increase (about 34 percent). Loblolly
             Pine comprised the greatest portion of the forests in Four Hole Swamp subbasin, where 32
             percent of total forestland was Loblolly Pine in 1986.
                       Changes in the acreage of native wetland vegetation, based on a comparison of the
             1989 NWI wetlands data with a selected set of hydric soils,Varied among the subbasins. The
             Four Hole Swamp subbasin seems to have experienced the greatest changes with 34 percent
             of its historical extent of native wetland vegetation (as determined by the extent of hydric
             soils) converted to pine plantations and agricultural land (Table 2-5). The Edisto (main stem)
             follows the Four Hole Swamp subbasin in the degree of change in native wetland vegetation
             acreage; 27 percent of these wetland areas were converted to agriculture and pine plantation.
             The North and South Forks showed less wetland habitat conversion to agriculture and pine
             plantation, with 18 and 20 percent conversion, respectively. In terms of altered wetlands,
             in 1989 proportionally more of the North Fork's wetlands had been altered compared to the
             other subbasins. Sixteen percent of the North Fork's wetlands were altered - most were
             impounded. In the main stem, 14 percent of the wetlands were altered; in the South Fork,
             13 percent; and in Four Hole Swamp, 11 percent.

             Current Structure
             The SCWRC 1989 land use and wetlands data showed that the North Fork and South Fork
             subbasins were similar in structure. Both were 56 percent forested, and less than one-fifth
             of the forests were wetlands. The South Fork contained a Ilittle more forested wetland, and
             the North Fork had a little more pine plantation. The South Fork also had more agricultural
             land, at 40 percent, than the North Fork, at 37 percent. The North Fork had the most urban
             land among all four subbasins - 22,605 acres (5 percent of the area). The South Fork, along
             with the other two subbasins, each had about 13,000 acres of urban land, 2 to 3 percent of
             the total area.
                       The Four Hole Swamp subbasin had the smallest portion of forestland (at 52
             percent) and the greatest portion of agriculture (42 percent)4 The forests of Four Hole Swamp
             were more than one-third forested wetland, and about one-third pine plantation and one-third
             mixed upland forest.
                       The Edisto (main stem) subbasin contained the most forestland, comprising 60
             percent of its total area. The mix of forests was similar to Four Hole Swamp subbasin, with
             over one-third as pine plantation, but with slightly less than one-third wetland. The main
             stem had the smallest proportion of agriculture among the subbasins, only 20 percent.
             Compared to the other subbasins, wetlands were a much more dominant feature on the
             landscape of the main stem, with nearly 38 percent of the area in wetlands; half were forested
             and half were non-forested.
                       The stream-edge habitat within the 250 meter buffers for each of the subbasins,
             except Four Hole Swamp, was nearly 75 percent or greater in natural cover. Four Hole
             Swamp showed only 62 percent in natural cover, with the remaining stream edge used for
             agriculture, pine plantation, and urban land. Stream edges of the North Fork and particularly







                                                                            ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                     in the South Fork subbasin had the greatest proportion of natural cover and the smallest
                                                     proportion of intensive land uses in the Basin.
                                                               The size, proximity, and continuity of forest patches in the North and South Forks
                                                     were nearly the same. Most of the total forest area was confined to a few very large patches
                                                     that spread out over most of the landscape. The forests of the Edisto (main stem) were
                                                     distributed into more patches toward the medium-size categories, but still most of the forest
                                                     area was in large patches. Among the subbasins, forests in Four Hole Swamp were the most
                                                     distributed among various patch sizes. Also, the upper portions of the Four Hole Swamp
                                                     subbasin and the adjacent lower portions of the North and South Forks appear to have the
                                                     greatest fragmentation and isolation of forests in the Basin's inland areas. The coastal areas
                                                     of the main stem show a high level of forest fragmentation; however, much of this is a
                                                     reflection of the natural complexity of the coastal landscape with its network of intertidal
                                                     rivers and creeks and associated marshlands that dissect the landscape. Judging whether
                                                     fragmentation is a positive or negative characteristic is generally determined in reference to
                                                     the original natural condition of the landscape. Much of the coastal area in the main stem has
                                                     naturally fragmented habitats that are undisturbed, and are therefore positive in terms of
                                                     ecological integrity. In the inland areas of the Basin where extensive natural forested habitats
                                                     have been lost, or are rare due to land use and development activities, fragmentation would
                                                     generally be viewed in negative terms because many rare and sensitive native wildlife species
                                                     require large, undisturbed habitats.
                                                     Ecological Integrity of the Subbasins
                                                     Applying the above indicators of ecological integrity to each of the subbasins does not yield
                                                     markedly distinguishable results. Most of the subbasins' characteristics indicate moderate
                                                     integrity. The subbasin with the greatest level of ecological integrity may be the Edisto (main
                                                     stem). This subbasin had the lowest ratio of agricultural and urban land to forestland, though
                                                     one-third of these forests were planted pine. More of the main stem's stream-edge habitat
                                                     was in natural cover, and more land was protected and regulated than in the other areas. The
                                                     main stem does, however, benefit substantially from the stable ecological conditions
                                                     upstream in the other subbasins, particularly in terms of the quality of water it receives.
                                                               Four Hole Swamp would appear to be lowest among the subbasins in structural
                                                     ecological integrity due to the following: the highest ratio of agricultural and urban land to
                                                     forestland; the lowest percentage of natural stream-edge habitat; the greatest conversion of
                                                     potential wetland to other land uses; and the most fragmented forest cover.







                                            LAND USE AND LAND COVER


             REFERENCES

             Anderson, J.A., E.E. Hardy, J.T. Roach, and R.T. Witmer. 1976. A land use and land cover
                 classification system for use with remote sensor data. U.S. Geological Survey Profes-
                 sional Paper 964.

             Brinson, M.M., B.L. Swift, R.C. Plantico, and J.S. Barclay. 1981. Riparian ecosystems: their
                 ecology and status. U.S. Department of the Interior, Fish and Wildlife Service, FWS/
                 OBS-81/17.


             Cowardin, L., V. Carter, F. Golet, and E. LaRoe. 1979. Classification of wetlands and deep
                 water habitats of the United States. U.S. Fish and Wildlife Service, Washington, D.C.,
                 FWS/OBS-79/31.


             Diamond, J.M. 1975. The island dilemma: lessons of modern biogeographical studies for the
                 design of natural reserves. Biological Conservation 7:129-146.

             FICWD (Federal Interagency Committee for Wetland Delineation). 1989. Federal Manual
                 forIdentifying andDelineatingJurisdictional Wetlands. U.S. Army Corps of Engineers,
                 U.S. Environmental Protection Agency, U.S. Fish and Wildlife Service, and U.S.
                 Department of Agriculture Soil Conservation Service, Washington, D.C. Cooperative
                 technical publication.

             Gosselink, J.G, G.P. Shaffer, L.C. Lee, D.M. Burdick, D.L. Childers, N. Taylor, S. Hamilton,
                 R. Bournans, D. Cushman, S. Fields, M. Koch, and J. Visser. 1989. Cumulative impact
                 assessment and management in a forested wetland watershed in the Mississippi River
                 flood plain. Marine Science Department, Louisiana State University, Baton Rouge.
                 LSU-CEI-89-02.131pp.

             Gosselink, J.G, C.E. Sasser, L.A. Creasman, S.C. Hamilton, E.M. Swenson, and G.P.
                 Shaffer. 1990. Cumulative impact assessment in the Pearl River Basin, Mississippi and
                 Louisiana. Coastal Ecology Institute, Louisiana State University, Baton Rouge. LSU-
                 CEI-90-03. 260pp.

             Harris, L.D., L.D. White, J.E. Johnson, and D.G. Milchunas. 1974. Impact of forest
                 plantations on north Florida wildlife and habitat. In: Proceedings of the 28th Annual
                 Southeastern Association of Game and Fish Commissions 28:659-657.

             Howard, R.J. and J.A. Allen 1989. Strearnside habitats in southern forested wetlands: their
                 role and implications for management. In: Proceedings of the symposium on the
                 forested wetlands oftheSouthern UnitedStates. U.S. Departmentof Agriculture, Forest
                 Service, General Technical Report SE-50.

             Hunter, M. L., Jr. 1990. Wildlife, forests, and forestry: principles of managing forests for
                 biological diversity. Regents/Prentice Hall, Englewood Cliffs, New Jersey.

             Kuchler,A.W. 1964. Potential natural vegetation ofthe conterminous UnitedStates. Manual
                 to accompany the map. American Geographic Society, Special Publication No. 36.
                 Revised edition of map, 1965.

             Langley, A.K. Jr., and D.J. Shure. 1980. The effects of loblolly pine plantations on small
                 mammal populations. American Midland Naturalist 103 (1): 59-65.

             Noble, R.E. and R.B. Hamilton. 1975. Bird populations in even-aged loblolly pine forests
                 of southeastern Louisiana. In: Proceedings ofthe 29thAnnualSoutheasternAssociation
                 of Game and Fish Commissions 29: 441-450.







                                                                         ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                   Omernik, J.M. 1977. Nonpoint source stream nutrient level relationships: a nationwide
                                                        study. Corvallis Environmental Research Lab., Office of Res. Dev., USEPA Corvalis,
                                                        Oregon. EPA-600/3-77-105.

                                                   O'Neil, L. J.,T.M. Pullenjr., R.L. Schroeder. 1991. A wildlife community habitat evaluation
                                                        model for bottomland hardwood forests in the southeastern United States, Draft
                                                        Biological Report dated 6/17/91. U.S. Department of the Interior, Fish and Wildlife
                                                        Service, Research and Development, Washington D.C.

                                                   Seymour, R.S. and M.L. Hunter, Jr. 1992. New forestry in eastern spruce-fir forests:
                                                        principles and applications to Maine. Miscellaneous Publication 716, Maine Agricul-
                                                        tural Experiment Station, University of Maine, Orono.

                                                   Sharitz, R.A., L.R. Boring, D.H. Van Lear, and J.E. Pinder 111. 1992. Integrating ecological
                                                        concepts with natural resource mangement of southern forests. EcologicalApplications
                                                        2(3): 226-237.

                                                   Strahler, A.N. 1964. Quantitative geomorphology of drainage basins and channel networks.
                                                        In: Handbook ofApplied Hydrology, edited by Ven Te Chow. McGraw-Hill, Inc. New
                                                        York, N.Y.

                                                   Thill, R.E. 1990. Manageing southern pine plantations for wildlife. Proceedings oftheXIXth
                                                        IUFRO World Congress, Vol. 1: 58-68.

                                                   U.S. Department of Commerce. 1925-87. United States Census of Agriculture for South
                                                        Carolina. Bureau of the Census.


                                                   U.S. Department of Agriculture. 1986. Soil Conservation Service County Hydric Soils Lists.
                                                        SCS, Columbia, S.C.

                                                   U.S. Department of Agriculture. 1983. National Soils Handbook, SCS, Washington, D.C.

                                                   U.S. Environmental Protection Agency. 1988. Manual from the workshop: "Cumulative
                                                        impact assessment in southeastern wetland ecosystems: the Pearl River." October 17-
                                                        21, 1988, Slidell, LA. Sponsored by the U.S. Environmental Protection Agency,
                                                        Washington, D.C.

                                                   U.S. Forest Service. 1991. Forest Survey statistics for the Edisto River Basin from the 4th,
                                                        5th, and 6th forest survey. Prepared by: Southeastern Forest Experiment Station, Forest
                                                        Inventory and Analysis, Asheville, N.C.

                                                   Van Lear, D.H. 1991. Integrating structural, compositional, and functional considerations
                                                        into forest ecosystem management. In: Ecosystem Management in a Dynamic Society,
                                                        Proceedings of a conference held by the Department of Forestry and Natural Resources,
                                                        Purdue University, West Lafayette, Indiana.































                                               i




                                                                             Chapter 3                      sInent
                                                                             Hydrology )ksses

                                                                              by:
                                                                              LarrY Bohnan
                                                                               &           erson
                                                                               Glenn Patt
                                                                               U.S, G1010gical S""'y







                                                        1
                                                        Ii
                                                        0                               "12,







                                                  HYDROLOGY AsSESSMENT


              INTRODUCTION

              Strearnflow is the long-term residual of precipitation after evapotranspiration demands and
              deep aquifer losses have been satisfied. Trends in streamflow reflect an integration of many
              hydrologic factors. A change in the location, timing, and amount of strearnflow in a basin
              may be caused by manmade changes such as channelization, construction of reservoirs, or
              change in land use.
                        Precipitation, by contrast, is largely independerit of the works of mankind and
              therefore provides an index for evaluating strearnflow (Searcy and Hardison 1960). Achange
              in the amount of precipitation over a period of time should cause a change in strearnflow
              during the period.


              Description of Basin Hydrology
              The Edisto River Basin extends over the length of the Coastal Plain physiographic province
              in South Carolina. The Coastal Plain is characterized by sandy soils and gentle slopes. The
              ground in the Basin is like a sponge. Nearly all of the Basin's abundant rainfall infiltrates the
              porous soil, from which it later emerges as evapotranspiration or as strearnflow.
                        From the headwaters to Orangeburg on the North Fork and to Bamberg on the South
              Fork, the Basin is in the Upper and Middle Coastal Plain (hereafter referred to as the upper
              Coastal Plain). This upper part of the Coastal Plain includes the Carolina Sand Hills and has
              higher hills (up to 600 ft above sea level), deeper valleys, and steeper slopes than the Lower
              Coastal Plain, which lies to the southeast of Orangeburg and Bamberg. The Lower (lower)
              Coastal Plain includes the Coastal Flatwoods and Tidewater land resource areas described
              in Chapter 1. The different topographic characteristics of the upper and lower regions of the
              Coastal Plain result in different patterns of groundwater flow and different interactions of
              groundwater and surface water. These differences are related to the length of the groundwater
              flow path and especially to the thickness of the unsaturated zone.

              Upper Coastal Plain Hydrology
              In the upper Coastal Plain the uplands between the stream valleys are high enough and porous
              enough to have thick unsaturated zones. Infiltrating rainwater quickly percolates below the
              root zone, leaving little water near the ground surface to sustain plants. Vegetation on these
              uplands, particularly in the Sand Hills, tends to be scrubby, sparse, low, and adapted to dry
              conditions. Common plants include scrub oaks, longleafipine, and sparkleberry.
                        Although the surface soils in the upper Coastal Plain tend to be dry, the shallow
              aquifer below the water table receives abundant recharge, precisely because so little water
              is lost to evapotranspiration. The aquifer discharges to streams whose valleys are incised
              deeply enough to intersect the water table, providing some of the best-sustained strearnflows
              in the State.
                        Streams in the upper Coastal Plain receive natural flow regulation because of the
              porous soils. There is little surface runoff, so flood peaks tend to be attenuated. The well-
              sustained low flows keep the streams from drying out in droughts.
                        Deeply incised streams are common in the upper Coastal Plain, so groundwater flow
              paths from the intervening ridges to the streams tend to be relatively short, on the order of 1
              to 2 miles. The age of groundwater discharging to these streams as baseflow is on the order
              of years or decades. Just after a heavy rain significant strearnflow is derived from temporarily
              saturated soils near the streams. Groundwater flow paths and ages in these temporarily
              saturated soils are much shorter.
                        Groundwater discharging to the upper Coastal Ph      iin streams spends relatively little
              time in contact with soluble minerals, so the dissolved-sollids content in the streams is low.
              In summary, the upper Coastal plain streams tend to have 'low flood peaks, high baseflows,
              and good water quality.

              Lower Coastal Plain Hydrology
              In the lower portion of Coastal Plain (the Coastal Flatwoods and Tidewater land resource
              areas) the land between the streams is much lower and flatter than in the upper Coastal Plain.







                                                                           ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                     The water table is nearer to the land surface, and is often within the root zone. The greater
                                                     availability of soil moisture is reflected in the taller, denser, hydrophytic vegetation
                                                     characteristic of the area, including baldcypress, tupelo, other hardwoods, and large pines.
                                                              A proportion of the infiltrating rainwater in the lower Coastal Plain returns to the
                                                     atmosphere as evapotranspiration. Recharge to the shallow aquifer is therefore less than in
                                                     the upper Coastal Plain. During droughts, baseflow in the streams here is not as well
                                                     sustained, and some streams go dry.
                                                              When rainfall is heavy, the water table may rise, causing flooding in low areas at the
                                                     land surface. Drainage is sluggish, so floodwaters recede slowly.
                                                              The lack of high ridges between streams allows groundwater flow paths to cross
                                                     drainage divides and attain greater length than in the upper Coastal Plain. In addition, in the
                                                     lower Coastal Plain the deep regional aquifers discharge upward to shallower aquifers and
                                                     to streams. Ground water flow paths in the lower Coastal Plain can therefore range from
                                                     several miles to several tens of miles. The age of groundwater discharging to the streams as
                                                     baseflow is on the order of hundreds to thousands of years.
                                                              The longer contact time with subsurface materials results in higher concentrations
                                                     of dissolved substances, both organic and inorganic. The large amount of vegetation around
                                                     streams in the lower Coastal Plain results in relatively high concentrations of organic acids.
                                                     Concentrations of inorganic dissolved constituents, though higher than in the upper Coastal
                                                     Plain, are still relatively low. Streams in both the upper and lower Coastal Plain are low in
                                                     suspended sediments because of the gentle slopes, high infiltration, good vegetative cover,
                                                     and coarse soils of the Coastal Plain.
                                                              The low dissolved-solids content makes Coastal Plain streams relatively poor
                                                     buffers against changes in pH. The abundant organic acids in these characteristic blackwater
                                                     streams causes a natural acidic condition. The streams are therefore susceptible to further
                                                     decreases in pH, as from acid precipitation.

                                                     Hydrology of Blackwater Rivers
                                                     In profiling the ecology of bottomland hardwood swamps Wharton and others (1982)
                                                     described the hydrology of blackwater rivers:

                                                             "These streams have narrower, less well-developed floodplains and reduced
                                                                  sediment loads compared to those of alluvial rivers. The waters are
                                                                  relatively clear, but highly colored (coffee -colored) due to the presence of
                                                                  organics (humic substances) derived from swamp drainages. A hydrograph
                                                                  of a blackwater stream is characterized by irregular discharge peaks that
                                                                  are due almost wholly to frontal or local weather events. Surnmerflooding,
                                                                  as well as more typical winter-spring flooding, may result from local
                                                                  storms. Unlike that of larger alluvial streams, the hydrograph of a smaller
                                                                  blackwater stream may register dry periods during which discharge may
                                                                  dwindle to near zero.
                                                              Groundwater seepage, or base flow, is a particularly important component of
                                                                  the discharge of blackwater streams. A study (Winner and Simmons 1977)
                                                                  of a small North Carolina Coastal Plain blackwater stream (Creeping
                                                                  Swamp, N.C.) resulted in a water budget in which overland runoff
                                                                  accounted for 6.99 inches (17 percent) and base flow runoff for 8.54 inches
                                                                  (20 percent) of the total precipitation of 42.24 inches. Evapotranspiration
                                                                  accounted for 25.91 inches (61 percent) of the rainfall. A negligible 2
                                                                  percent seeped underground and was I ost to the watershed" (in other words
                                                                  - lost to the deep aquifer system).


                                                     Purpose and Scope
                                                     The purpose of this study was to determine if trends - changes in the strearnflow - have
                                                     developed in the Edisto River Basin (Figure 3-1) during the period that streamflow data have
                                                     been collected in the Basin. If significant changes in strearnflow have occurred and cannot
                                                     be explained by changes in precipitation, then other factors such as stream channel
                                                     modifications and land use changes would have to be evaluated.







                                                HYDROLOGY ASSESSMENT


              Data Available
              Streamflow data have been collected continuously at four stations in the Edisto River Basin,
              dating from about 1939 to 1990, and for various periods at Stations in nearby basins that have
              geology and physiography similar to the Edisto Basin.
                       The strearnflow of the South Fork Edisto River near Denmark (Station No.
              02173000) and the North Fork Edisto River near Orangeburg (Station No. 021735000) were
              considered as indicative of the strearnflow in the upper Edisto River Basin. The strearnflow
              of the Edisto River near Givhans, South Carolina (Station No. 02175000) was considered as
              indicative of the lower Edisto River Basin.
                       Monthly mean streamflow data were adjusted for diversion for municipal water
              supply above the North Fork Edisto River at Orangeburg (Station No. 02173500) and the
              Edisto River station near Givhans (Station No. 01275000). Although the amount of diversion
              varies throughout the year, the strearnflow was adjusted by an average amount for the year.
              The diversions were small enough that deviations from the average diversion were consid-
              ered too small to substantially influence any analysis of trends in streamflow.


              ANALYZING STKAWLOW AND NECIPITA11ON

              The precipitation data were first evaluated to determine if there was a significant trend or
              difference in occurrence and amounts of precipitation among the various stations or if there
              was a trend (significant changes) in the amounts of precipitation for the period of time that
              data had been collected at the six precipitation stations.
                       The streamflow data for the three strearnflow stations were evaluated to determine if
              (1) there was a significant difference in duration and amount of strearnflow for the individual
              stations with respect to time, (2) trends in strearnflow differed with respect to upstream and
              downstream stations, (3) trends of strearnflow were related to concurrent trends in precipitation
              with respect to time and (4) trends in strearnflow identified in the Edisto River Basin were
              identifiable in nearby basins. The data collection stations ate described in Table 3-1.


              Techniques Used for Analysis
              Several techniques were used in analyzing the precipitation and strearnflow data: (1) single-
              mass analysis, (2) double-mass analysis, (3) the Kendall Tau Analysis, (4) the analysis of
              variance, (5) the analysis of covariance, (6) the box plot analysis, and (7) the regression
              analysis.
                       Single-mass analysis - A single mass analysis is a plot of accumulated values of
              precipitation or strearnflow over time. Deviations from a straight line (a break in slope)
              indicate changes in the strearnflow or precipitation with time but do not give any information
              as to the cause of the changes that have occurred.
                       Double-mass analysis - The theory of the double mass curve method to evaluate
              trends is based on the fact that a graphical accumulation of one quantity against the
              accumulation of another quantity during the same period Will plot as a straight line so long
              as the data changes are proportional. The break in slope of the double mass curve means that
              a change in the constant of proportionality between the two variables has occurred or that the
              proportionality is not a constant at all rates of accumulation. If the possibility of a variable
              ratio between the two quantities can be ignored, a break in slope indicates the time at which
              a change occurred in the relation between the two quantities (Searcy and Hardison 1960).
              When the double mass curve is used to study trends or possible breaks in precipitation-runoff
              relationships, the cumulative measured strearnflow should be plotted against the cumulative
              predicted streamflow taken from a precipitation -stre amflo W relation. A double mass curve
              of cumulative measured strearnflow and cumulative precipitation should not be used because
              the relationship between precipitation and strearnflow is seldom a constant ratio even during
              a period when there was no change in the relation.
                       Kendall Tau Analysis - The Kendall Tau method of detecting monotonic trends
              was used to examine several kinds of precipitation and strearnflow data. In the test, the first
              observation is compared to all subsequent observations with the assumption that the
              probability of the latter value being greater is equal to 0.5. The second observation is







                                                                             ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                      compared to all subsequent observations and so on. The pluses and minuses which represent
                                                      comparisons in which subsequent observations were greater than or less than preceding
                                                      observations, respectively, are then compared statistically to determine if one group is
                                                      significantly larger than the other. For a P-level of 0.05, the 5-percent level of significance
                                                      implies that if the data from the station are rejected from the analysis there is only a 5-percent
                                                      chance that it should not have been. Thus, a P-level less than 0.05 indicates that a trend in
                                                      the data most likely exists at that confidence level. The higher the P-level, the less likelihood
                                                      there is that a trend exists in the data set.
                                                                Several types of annual strearnflow data were retrieved for use in the Kendall Tau
                                                      test for monotonic trends. Annual peak discharges and 7-day average annual minimum
                                                      dischargeswere obtained from the U.S. Geological Survey, WATSTORE national database.
                                                      Additionally, the average mean monthly strearnflow for the period of record for each of the
                                                      three strearnflow stations was plotted in order to ascertain the months with the greatest and
                                                      smallest strearnflow amounts. Annual statistics may not reflect trends in seasonally affected
                                                      flows. For example, if the summer strearnflow amounts were increasing while the winter
                                                      strearnflow amounts were decreasing, it is possible that the trends could offset each other and
                                                      not be detected in the analysis of annual mean strearnflow.
                                                                Analysis of Variance - The analysis of variance is a statistical procedure that
                                                      analyzes data to determine if the variability associated with a particular time period is more
                                                      than the expected random error based on the general variability of the sample population. It
                                                      characterizes the means of two samples as significantly or not significantly different. In the
                                                      analysis of variance the F-ratio is used to test whether the means of two groups are
                                                      significantly different. This ratio compares the between-group variance with the residual
                                                      within-group variance. The term Pr is a probability level associated with the F-ratio. To
                                                      illustrate the interpretation of the Pr value for the F-ratio, assume an F-ratio of 10.5 and Pr
                                                      value of 0.0007 (or 0.07 percent) for two groups of annual precipitation values. This means
                                                      that if all the annual precipitation amounts for two sampling periods were about the same, an
                                                      F-ratio of 10.5 or larger would be found only 0.07 percent of the time. A large F-ratio, which
                                                      is a rare occurrence when the precipitations are about the same, means that the precipitations
                                                      are not alike.
                                                                Analysis of Covariance - The analysis of covariance was used in this study to test
                                                      for changes in slopes and/or intercepts of relations between two periods. This was
                                                      accomplished by creating qualitative variables to represent different time periods and then
                                                      testing their significance in the regression process.
                                                                Box Plot Analysis - A box plot summarizes a batch of data by indicating the
                                                      location of the median, the spread, the tails, and outlying data points. When a data set is
                                                      divided into groups representing different time periods, the box plots make it easier to
                                                      visualize the difference in subgroup midpoints and distributions. In order to determine if the
                                                      differences are significant, an ared (confidence interval) is defined around each median on
                                                      the basis of the hinge spread for that group and the standard deviation for the entire sample.
                                                      When these confidence intervals do not overlap, the medians of the different time periods are
                                                      significantly different at roughly the 5-percent level.
                                                                Regression Analysis - Regression analysis fits a linear equation to observed values
                                                      of multiple independent variables and a dependent variable. The statistical packages utilized
                                                      for this study included a forward-stepping algorithm in which independent variables are
                                                      added one at a time. The accuracy of the regressions can be expressed by two standard
                                                      statistical measures, the coefficient of determination (also noted as R') and the standard error
                                                      of regression. The coefficient of determination indicates the proportion of the total variation
                                                      of the dependent variable is explained by the independent variable. For instance, a coefficient
                                                      of determination value of 0.93 would indicate that 93 percent of the variation is accounted
                                                      for by the independent variables. The standard error of regression is, by definition, the
                                                      standard deviation of the residuals from the regression equation and contains about two-
                                                      thirds of the residuals within its range.







                                                           HYDROLOGY ASSESSMENT









                                                                   EDISTO RIVER BASIN
                                                                   SAMPLING STATIONS




                                                                               COL
                                           SALUDA
                                                                        LEXNGTON


                          EDGEFELD                                                               CALM

                                          Anp



                                           AKEN

                                                                 BLACKV


                                                     BARNWELL
                                                                                BAVIBERG

                                                                                                                                                  BERKELEY            CHARLESTON
                                                                                                                            4
                         AL Strearnflow Stations
                                  1. 02173000      near Denmark                                           0 WALTERBORO       DORCHESTER
                                  2. 02173500      at Orangeburg
                                  3.  02174000     near Branchville                                 COLLETON
                                  4.  02175000     near Givhans
                             Precipitation Stations



                    South Carolina Water Resources Commission
                    Natural Resources Decision Support System
                    Columbia, South Carorina













                Figure 3-1. Location of data collection stations for streamflow and precipitation in the Edisto River Basin, South Carolina.







                                                                           ASSESSING CHANGE IN THE EDISTo RIVER BASIN






          Table 3-1. Data collection stations in or near the Edisto River Basin.


                                                          Strearnflow Stations
                 Station                                            Drainage                     Years of          Period
                 number       Station name                         area (sq. miles)              Record            ofrecord

                 02173000     South Fork Edisto River                     720                      52              1931 to 1971
                              near Denmark, S.C.                                                                   1980 to 1990


                 02173500     North Fork Edisto River                     683                      53              1938 to 1990
                              at Orangeburg, S.C.

                 02174000     Edisto River near                         1720                       46              1945 to 1990
                              Branchville, S.C.


                 02175000     Edisto River near                         2730                       52              1939 to 1990
                              Givhans,S.C.



                 Strearnflow Stations - Other Basins


                 02136000     Black River at                            1252                       62              1929 to 1990
                              Kingstree, S.C.

                 02198000     Brier Creek at Millhaven,                   646                      54              1937 to 1990
                              Ga.


                 02202500     Ogeechee River near                       2650                       53              1938 to 1990
                              Eden, Ga.



                                                          Precipitation Stations
                                                                                                 Years of           Period of
                 Latitude       Longitude                 Station location                       record             record *

                 330 34'          810 44'                 Aiken, S.C.                              56              1935 to 1990


                 330 22'          810 19'                 Blackville, S.C.                         56              1935 to 1990

                 330 29'          800 52'                 Orangeburg, S.C.                         56              1935 to 1990

                 330 02'          800 12'                 Summerville, S.C.                        56              1935 to 1990

                 320 54'          800 40'                 Walterboro, S.C.                         54              1937 to 1990

                 330 56'          810 07'                 Columbia, S.C.                           66              1925 to 1990


                     *Note. -Actual record length for a station might be longer. Numbers and dates reflect only period
                              of record obtained for this study.







                                                   HYDROLOGY AsSESSMENT


              REsms OF THEANALYSES


              PreciplUirion
              A single-mass analysis was made by using annual precipitation totals from each of the six
              National Weather Service rainfall stations (Figure 3-2 presents the Orangeburg station). All
              six stations indicated a possible change of slope starting about 1958 to 1961. For four of the
              six stations, single-mass curves showed a possible second break in slope at about 1974 to 76.
              A visual inspection of the data indicated that the 16-year period from 1959 to 1975 appeared
              to be wetter than the 1939 to 1958 and the 1976 to 1990 Periods.
                        A box-plot analysis and an analysis of variance were made for the three periods
              1940 to 1958, 1959 to 1975, and 1976 to 1990 (Figure 3-3). The box plots indicate that the
              distribution and median of the mean annual precipitation for the 1959 to 1975 period were
              probably significantly different (wetter) from the other two periods. The analysis of variance
              also indicated that the mean annual precipitation for the 1ï¿½59 to 1975 period was probably
              significantly different from that of the other time periods.
                        A correlation matrix was computed for the six rainfall stations to determine if any of
              the data appeared to be anomalous (Table 3-2). This analysis did not indicate anomalies in the
              data. The Orangeburg station was most correlatable to the other stations. Orangeburg was used
              as an independent variable in the regression analysis to determine the predicted annual
              precipitation amounts for the other stations. These predicted amounts were then plotted against
              observed amounts in a double-mass analysis to check for consistency in the precipitation data
              for the other five precipitation stations. The results of this analysis indicated that the precipitation
              from one station was not predictable by the precipitation at another station. The coefficient of
              determination (RI) was about 0.50. All the rainfall stations were considered in determining the
              precipitation for the Basin for the individual strearnflow stations, using the Theissen polygon
              method. ne area weighting factors for precipitation in the drainage areas of the strearnflow
              stations in the Edisto Basin are presented tin Table 3-3.







                                                                         ASSESSING CHANGE IN THE EDISTo RIVER BASIN






           Table 3-2. Correlation matrix for rainfall stations in or near the Edisto Basin.


                              Aiken      Blackville      Columbia        Orangeburg         Summerville        Walterboro

               Aiken          1.0000        0.729            0.695             0.745             0.535             0.579

               Blackville      .729         1.000             .807             .694                 .628            .660

               Columbia        .695         .807             1.000             .699                                 .708

               Orangeburg      .745         .694              .699             1.000                .597            .622

               Summerville     .535         .628              .691             .597              1.000              .777

               Walterboro      .579         .660              .708             .622                 .777           1.000

                               4.283        4.518            4.357             4.600             4.228             4.346



           Table 3-3. Area weighting factors for precipitation in the drainage areas of the strearnflow stations in the Edisto Basin.


               Station Number: 02173000 at South Fork Edisto River, Denmark, S.C.

                   Aiken               Blackville       Columbia           Orangeburg         Summerville          Walterboro
                   0.57                  0.43

               Station Number: 02173500 at North Fork Edisto River, Orangeburg, S.C.

                   Aiken               Blackville       Columbia           Orangeburg         Summerville          Walterboro
                   0.15                  0.06                0.39              0.40           - - -                 - - -

               Station Number: 02175000 at Edisto River near Givhans, S.C.

                   Aiken               Blackville       Columbia           Orangeburg         Summerville          Walterboro

                   0.19                  0.16                0.10              0.38              0.10                  0.07




                                                       U
                                                       Cn
                                                          3,000


                                                          2,500


                                                          2,000


                                                          1,500


                                                          1,000


                                                             500


                                                       M
           Figure 3-2. Cumulative annual                         0
           precipitation for the Orangeburg, S.C.,
           weather station for the period              U         1936        1946        1956         1966       1976         1986
           1937 to 1990.                                                                    Water Year







                                           HYDROLOGY AsSESSMENT






                    Precipitation - South Fork Edisto River Drainage Area

                       I              - - - - - - - - - - -
                                           <1     +       >  I- - - - - - - -

                                       -----------
                       2)                         - - - - - - - - - - -
                                                        I <        +   > I - - - - - - - - - - - - -

                                                  -----------
                       3)                   ----------
                                                  I <    +         > I- - - - - - - - - - - - -

                                            ----------


                          32       36      40        44       48      52      56       60       64      68       72
                                                                         inches


                    Precipitation - North Fork Edisto River Drainage Area

                                           --------------
                         ----------               j<      +        >    I------------

                                           ---------------
                       2)                                 - - - - - - - - - - - - - - - - - - -
                                                                   I <       +          >      I- - - - - - - - -

                                                          -------------------
                       3)                         ------------
                                                     I    <        +   I> - - - - - - - - - - - - - -

                                                  -------------


                       30       33        36      39      42       45       48     51       54      57       60       63
                                                                         inches


                    Precipitation - Edisto River (main stem) Drainage Area
                       1)                   - - - - - - - - - - -
                        - - - - - - - - - - - -      I <           +   I> - - - - - - - - - - - -

                                            ------------
                       2)                                  - - --- - - - - - - - - - - - - -
                                           - - - - - - - - - -     I     <          +         >- - - - - - - - - - -

                                                           ------------------
                       3)                         - - - - - - - -- - -
                                                     I    <        +  1-> - - - - - - - - - - - - - -

                                                  ----------


                                33       36       39      42       45       48     51      54       57       60      63
                                                                         inches


                  Period 1) = 1940 to 1958                Hinges (25th and 75th percentile values, approximately)
                  Period 2) = 1959 to 1975             + = 50th percentile value (median)
                  Period 3) = 1976 to 1990             <> = 95-percent confidence limits for median value






           Figure 3-3. Box plots of precipitation for drainage areas of the South Fork near Denmark, S.C., North Fork near Orangeburg, S.C.,
           and Edisto River near Givhans, S.C. for three periods from 1937 to 1990.







                                                                             ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                      Streamflow


                                                      Kendall Tau Trends Analysis
                                                      The annual peak strearnflow, the 7-day streamflow, the high 3-month strearnflow, the low 3-
                                                      month strearnflow, the 90-day annual minimum streamflow, and the 1-day annual minimum
                                                      strearnflow for the South Fork Edisto River near Denmark, the North Fork Edisto River near
                                                      Orangeburg, and the Edisto River near Givhans were then tested for trends by using the
                                                      Kendall Tau method (Hirsch and others 1982). February, March, and April were selected as
                                                      the "high 3-month" strearnflow period, and September, October, and November were
                                                      selected as the "low 3-month" strearnflow period. The North Fork Edisto River at
                                                      Orangeburg, station number 02173500, had the lowest P-level. The 1 -day annual minimum
                                                      strearnflow at the North Fork Edisto River near Orangeburg, station number 02173500, also
                                                      indicated a possible trend (P-level 0.047) but the 90 day annual minimum flow at this station
                                                      did not indicate a trend in the discharge. No other indications of possible trends in stream
                                                      discharge were identified. The P-levels for the various groupings of strearnflow character-
                                                      istics are presented in Table 3-4.


                                                      Table 3-4. P-Levels resulting from Kendall Tau trends analysis for groupings of
                                                      strearnflow characteristics at strearnflow stations.


                                                                                                                Stations
                                                              Grouping                          South Fork North Fork            Edisto River at
                                                                                                                                 Givhans
                                                              Annual peak strearnflow              0.348          0.298           0.316

                                                              7-day low strearnflow                .597           .061             .783

                                                              high 3-month strearnflow             .807           .994             .389

                                                              low 3-month strearnflow              .679           .548             .434

                                                              1-day annual minimum flow            .754           .047             .689
                                                              90-day annual minimum flow           .639           .360             .986



                                                      Double Mass Trends Analysis
                                                      The Searcy and Hardison method for determining trends in strearnflow was used in the
                                                      analysis. The Searcy and Hardison method requires that the "effective precipitation" for the
                                                      drainage area of each station be determined. Searcy and Hardison (1960) in discussing
                                                      effective precipitation state that -

                                                              "The amount of precipitation that fell the previous year is one of the factors that
                                                                   affects the relationship between precipitation and runoff and causes the
                                                                   points on a graph of annual precipitation plotted against annual runoff to
                                                                   assume a 'shotgun' pattern. Generally the scatter of the points can be
                                                                   reduced by plotting an effective precipitation instead of an observed
                                                                   precipitation. Using an effective precipitation is one way of making
                                                                   allowance for the variable amount of water carried over from one year to
                                                                   another as groundwater storage in the Basin. The effective precipitation
                                                                   (Pe) commonly used is that proportion of the current year's precipitation
                                                                   (PO) and the proportion of the preceding year's precipitation (Pl) that
                                                                   furnishes the current year's runoff or Pe = aPO + bP1.
                                                              The sum of the coefficient (a and b) must equal unity. The coefficients of a and
                                                                   b can be determined by rank correlation..."







                                                HYDROLOGY AsSESSMENT




                 The coefficients computed for the three stations in the Edisto Basin were all similar in
             magnitude and are shown in Table 3-5.

             Table 3-5. Coefficients computed to determine effective 2recipitation

               South Fork Edisto River           Station Number: 02173000             a   0.75       b = 0.25
               near Denmark, S.C.


               North Fork Edisto River           Station Number: 02173500            a   0.77        b = 0.23
               at Orangeburg, S.C.

               Edisto River near                 Station Number: 02175000             a   0.78       b = 0.22
               Givhans,S.C.

                 a = the proportion of the current year's precipitation (130) and b      the proportion of
                 the preceding year's precipitation (PI). Together these furnish the current year's
                 runoff.


                      Using these equations, an effective precipitation was computed for each year of
             strearnflow for each station. Next, the least-squares multiple regression analyses were then
             performed to determine the relationship between the annual strearnflow (RO) in inches and
             effective precipitation (Pe). These annual strearnflow equations are shown in Table 3-6 with
             their standard error and coefficient of determination. The equations were then used to
             compute a predicted strearnflow amount for each year of record at each station. The double-
             mass curve (plot of cumulative observed and cumulative predicted annual runoff) was then
             plotted (South Fork station shown in Figure 3-4).

             Table 3-6. Annual strearnflow equations with standard error and coefficient of determination

             Station                                                                      Coefficient of
             number           Equation                          Standard error @TLyr)       detertnination(R2)
             02173000       RO = (0.533 * Pe) - 11.42                   2.72                      0.68
             02173500       RO = (0.534 * Pe) - 9.45                    2.28                     0.73
             02175000       RO = (0.655 * Pe) - 17.71                   2.40                      0.78

                      Minor breaks hidden by the smoothing of a double-mass curve were magnified for
             detailed study by using a residual-mass curve. The residbal-mass curve is computed by
             plotting cumulative residuals from the regression analysis against the year of occurrence.
             Using both the double-mass and residual-mass curves, a possible trend was observed in the
             South Fork data (station number 02173000) beginning about 1981 (see Figure 3-5). This was
             coincidental with the end of a period of no strearnflow data ( L 971 to 1980). A covariance test
             was performed to see if the relations described by the above equation for the South Fork
             varied by time period used. The result was that a statistically significant difference did exist
             between the two periods before and after 198 1. Other periods (at the same station) were tested
             (such as known wet and dry periods) and these also showed a statistically significant
             difference in the relations for these periods. The conclusion drawn from this portion of the
             analyses was that the strength of the relationship between Pe. and RO, as indicated by the low
             R' (0.68 to 0.78) made the double-mass analyses questionable.

             Streamflow Comparisons
             Next, a double-mass analysis was made to compare strearnflows at stations within the Edisto
             River Basin. A correlation matrix of flow data among the three strearnflow stations showed
             that the North Fork station was the most highly correlated to the other two. Another set of
             regression equations was developed for use in the double-mass analysis which used the North
             Fork (NF) flow to predict flow in the South Fork and Givhans stations. The regression
             equations are presented in Table 3-7.







                                                                           ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                     Table 3-7. Regression equations for use in the double-mass analysis which used the
                                                     North Fork (NF) flow to predict flow in the South Fork and Givhans stations.

                                                     Station                                                                    Coefficient of
                                                     number        Equation                         Standard error (in/yr)        determination

                                                     South Fork
                                                     02173000      RO = (1.027 - NF) - 0.962                  1.24                    0.94

                                                     Givhans
                                                     02175000      RO = (1.086 - NF) - 3.562                  1.60                    0.90

                                                              The double-mass curves show no breaks in either the relation for the South Fork
                                                     station or the Givhans station . Therefore, there does not appear to be any change in
                                                     strearnflow in the lower part of the Edisto Basin with respect to strearnflow in the upper part
                                                     of the Basin.
                                                              If all three Edisto subbasins experienced the same trend, however, the trend might
                                                     not be detected by the above analysis. Therefore, outside basins were used in a double-mass
                                                     analysis to detect possible trends in the Edisto River subbasins. A correlation matrix was
                                                     constructed to determine which station would be the most appropriate to use as the
                                                     explanatory variable in the regression analysis. Brier Creek (station number 021980) was the
                                                     most highly correlated, followed by Ogeechee River (station number 02202500). Both Brier
                                                     Creek and Ogeechee River gave comparable results. The coefficient of determination ranged
                                                     from above 0.75 to 0.85. All of the Edisto Basin strearnflow showed a break at about 1960
                                                     (plus or minus a few years). The breaks in these double-mass analyses coincided with the
                                                     beginning of an especially wet climatic period. The difference in response between the Edisto
                                                     and Brier Creek basins and the Edisto and Ogeechee River basins to climatic conditions may
                                                     not be accounted for in the regression equations used to estimate the runoff, as evidenced by
                                                     the low coefficients of determination (note that trends were not detected by the double-mass
                                                     comparisons using only the Edisto Basins where the coefficient of determinations were high,
                                                     that is, in the 0.90 to 0.94 range).
                                                              Finally, it was hoped that by using an outside index basin, along with some measure
                                                     of antecedent basin conditions (to reflect geologic relations of rainfall for recent years to
                                                     streamflow), that an improvement would be realized in the double-mass analysis. Brier
                                                     Creek (BC) was used in conjunction with the current year's precipitation (PO), and lags of
                                                     annual precipitation of from one (Pl) to two (P2) years in a regression analysis to estimate
                                                     strearnflow for each of the three Edisto subbasins. The equations, standard error, and
                                                     coefficient of determination are given in Table 3-8 for each regression.


                                                     Table 3-8. The equations, standard error, and coefficient of determination for regression
                                                     analyses to estimate strearnflow for each of three Edisto subbasins.

                                                     Station                                                 Standard            Coefficient of
                                                     number            Equation                              error (in/yr)       determination(R2)
                                                     South Fork
                                                     02173000      RO = (0.697 * 13C) + (.106 * PO)              1.53                 0.91
                                                                          + (.104 *P1) + (.064 *P2) - 7.45
                                                     North Fork
                                                     02173500      RO = (0.539 * BC) + (.167       PO)           1.22                 0.93
                                                                          + (.128 * Pl) + (.089    P2) - 9.63
                                                     Givhans
                                                     02175000      RO = (0,567     BC) + (.249    PO)            1.80                 0.88
                                                                          + (.102   Pl) - 10.85







                                              HYDROLOGY AsSESSMENT




                     The coefficients of determination were 0.88 - 0.91, and residual-mass plots indicated
            much smaller residuals than earlier equations used in the double-mass analysis. No trend was
            evident in the North Fork or in the South Fork strearnflow data. A small but perceptible change
            in streamflow at the Edisto River near Givhans began about '1968 (Figures 3-6 and 3-7).




                           700
                           600                                                         Z.
                                                                                       F


                           500
                           400                                         A
                                                                     or


                       4-
                           300


                        >0 200
                                                                                                           Figure 3-4. Cumulative observe an-
                        03
                           100                                                                             nual strearnflow and cumulative pre-
                                                                                                           dicted annual strearnflow based on
                                                                                                           effective precipitation (Searcy and
                       U
                               0                                                                           Hardison 1960) for the South Fork
                                                                                                           Edisto River near Denmark, S.C.,
                                 0      100       00     300 400           500      600 700                (02173000) for the period 1939 to
                                     Cumulative Observed Runoff (inches)                                   1990.


                         35

                         30                                         A


                         25


                         20
                      C3


                         15


                         10
                                         @-z
                                                                                                           Figure 3-5. Cumulative annual re-
                                                                                                           siduals from predicted annual
                      Uz   5                                                                               strearnflow based on effective pre-
                             : IV                                                                          cipitation (Searcy and Hardison
                           0    11111111111 In In III III in-n-ni-nil"ITIM797MI M                          1960) for the South Fork Edisto River
                                                                                                           near Denmark, S.C., (02173000) for
                            1937        1947        1957         1967        1977        1987              the period 1939 to 1990.,
                                                       Water Year







                                                                        ASSESSING CHANGE IN THE EDISTo RIVER 13ASIN














                                                                 700


                                                                 600--


                                                                 5 00

                                                              0

                                                              P4 4


                                                                 300---


          Figure 3-6. Cumulative observed                        200
          annual streamflow and cumulative
          predicted annual strearnflow for the
          Edisto River near Givhans, S.C.,                    E  100
          (02175000) based on cumulative ob-                  U
          served annual strearnflow for Brier
          Creek near Millhaven, Ga.,                                 0
          (02198000) for the period 1944 to                             0     100 200 300 400 500 600 700
          1990.                                                             Cumulative Observed Runoff (inches)



                                                                 25-

                                                            LID

                                                            Cd
                                                                 20-'


                                                                 15-


                                                                 10




          Figure 3-7. Cumulative annual re-                      0
          siduals from predicted annual
          strearnflow for the Edisto River near
                                                            E    -5
          Givhans, S.C., (02175000) based on
          cumulative      observed      annual              U                         NJ \JA\"_@
          strearnflow for Brier Creek near                       -10                1111111111 ITI I II I I I IM III I III I I I I rT
          Millhaven, Ga., (02198000) for the                      1943          1953         1963         1973         1983
          period 1944 to 1990.                                                              Water Year







                                                 HYDROLOGY AsSESSMENT


              SUMMARY OF FINDINGS

              Analysis of single-mass curves of precipitation and strearnflow indicates that changes in
              precipitation and streamflow occurred in the Edisto River Basin during the period 1939 to
              1990 and that changes in strearnflow are a result of changes in precipitation.
                        Box-plots and the analysis of variance indicate that mean annual precipitation was
              higher during the 1959 to 1975 period than during the 1940 to 1958 and 1976 to 1990 periods.
              Cross-correlations of precipitation measured at six stations in and near the Edisto Basin
              indicated no anomalies in the data for any station and that precipitation at the Orangeburg
              station was the most correlatable to precipitation at all other stations. The correlation
              analyses further indicated that precipitation at a station is not predictable from the precipi-
              tation at another station. The coefficient of determination was very low, about 0.50.
                        The Kendall Tau method did not indicate any trends in the annual peak streamflow,
              7-day annual low streamflows, high 3-month annual strearnflows, and low 3-month annual
              strearnflows; but it did indicate a possible trend (P-level 0.047) for the 1-day annual minimum
              streamflow in the North Fork Edisto River near Orangeburg. No trend was indicated,
              however, in the 90-day annual mean minimum flow for this station.
                        An analysis of double-mass curves and residual-mass curves of predicted strearnflow
              based on the effective -precipitation method of Searcy and Hardison (1960) was inconclusive
              because of the low coefficients of determination (0.68 and 0.78). Comparisons of double-
              mass curves of strearnflows for stations within the Edisto Basin indicate that strearnflows
              were highly correlatable with one another (coefficient of determination greater than 0.90) and
              indicate that strearnflow at any station had not significantly changed with respect to
              strearnflow at other stations in the Basin.
                        Comparisons of strearnflow at stations in other basins (Brier Creek and Ogeechee
              River) with stations in the Edisto Basin indicate that strearnflow at the Brier Creek station was
              the most correlatable to strearnflow at stations in the Edisto Basin (coefficient of determina-
              tion 0.85).
                        Regression estimates of strearnflow within the Edisto Basin using strearnflow at the
              Brier Creek station, and lags of mean annual precipitation of 1-2 years, indicate that the
              standard error ranged from about 1.22 to 1.80 inches a year. The coefficient of determination
              ranged from 0.88 to 0.91. Double-mass analyses using this estimating equation showed no
              detectable trends in the North and South Fork stations. A possible insignificant trend did
              show up for the Givhans station.
                        The combined analysis, including all methods, indicates that all changes in
              strearnflow were probably caused by changes in precipitation during the 1939 to 1990 period.
              Land use was not analyzed statistically with hydrology because long-term land use data for
              the hydrologically defined Edisto Basin are lacking, only county-based statistics of varying
              quality were available. However, the available data (presented in the land use chapter)
              suggest that land use and land cover conditions in the Edisto Basin have been fairly stable
              since 1950 and have probably supported the Basin's stable stream hydrology.


              REFERENCES

              Hirsch, R.M., J.R. Slack, and R.A. Smith. 1982. Techniques of trend analysis for monthly
                   water quality data. Water Resources Research 18 (1):107-121.

              Searcy, J.K. and C.H. Hardison. 1960. Double Mass Curves, in Manual ofHydrology: Part
                   I General Surface Water Techniques. U.S. Geological Survey Water Supply Paper No.
                   1541-B.


              Wharton, C.H., W.M. Kitchens, E.C. Pendleton, and T.W. Sipe. 1982. The Ecology of
                   Bottomland Hardwood Swamps of the Southeast: A Community Profile. U.S. Fish and
                   Wildlife Service, Biological Services Program, Washington, DC. FWS/OBS-81/37.

              Winner, M.D., Jr., and C.E. Simmons. 1977. Hydrology of the Creeping Swamp watershed,
                   North Carolina with reference to potential effects of stream channelization. U.S.
                   Geological Survey Water Resources Investigation 77-26.














































                                                                                                         M







                   Chapter 4
                   Water Quality

                   by:


                   Jeannie Pickett Eidson
                   South Carolina Department  of Health and
                   Environmental Control







                                                     WATER QUALITY


             INTRODucriON

             This chapter presents an analysis of the historical patterns of water quality in the Edisto River
             Basin and relates pollutant concentration patterns to changes in the hydrology and land use
             patterns. Particular emphasis is placed on phosphorus and total Kjeldahl nitrogen because
             of their importance to biological productivity in freshwater ecosystems.
                       Phosphorus, in comparison to other major nutrients required for biological pro-
             cesses, is the least abundant and commonly the first to limit freshwater primary productivity.
             Phosphorus is tightly bound to sediments; consequently, increased concentrations in streams
             and lakes are usually associated with accelerated rates of land erosion and runoff. In addition,
             phosphorus is a constituent of agricultural fertilizers, and all wastes derived from domestic
             sewage. Because of these characteristics and associations, the concentration of phosphorus
             in streams is an excellent index of cultural disturbance in developing watersheds.
                       Nitrogen rapidly cycles between sedimentary, aquatic, and atmospheric environ-
             ments and therefore creates problems in the analysis of long-term data sets. The constituents
             of total nitrogen in water include total Kjeldahl nitrogen (NH4+, dissolved organic N, and
             particulate organic N) and nitrate-ni trite. Because of the interconversions among these
             different forms, through nitrogen fixation, denitrification and atmospheric deposition, total
             Kjeldahl nitrogen is usually chosen to represent nitrogen dynamics in aquatic ecosystems.

             SITEDESCRIPTION

             The 3,120 square miles (800,000 hectares) of the Edisto Basin study area are drained by four
             major rivers, the North Fork Edisto River, South Fork Edisto River, Edisto River (main stem),
             and Four Hole Swamp.
                       The North Fork, formed by the confluence of Chinquapin and Lightwood Knot
             Creeks, flows southeasterly for 66 miles to Orangeburg, and then southward for 27 miles to
             its confluence with the South Fork. The South Fork flows southeasterly 91 miles to its
             junction with the North Fork near Branchville. Average annual strearnflow in these major
             tributary streams is 803 cfs (cubic feet per second) on the North Fork Edisto at Orangeburg
             and 797 cfs on the South Fork Edisto near Denmark. The main stem of the Edisto River,
             formed by the confluence of its north and south forks, flows southeasterly 48 miles to Givhans
             Ferry State Park, then southward 60 miles to the Atlantic Ocean. Average annual strearnflow
             on the Edisto River is 2,033 cfs near Branchville and 2,678 cfs near Givhans. The well-
             sustained flows are due primarily to discharge from groundwater reserves in the Upper
             Coastal Plain region in which more than half of the basin is located. The lower 38 miles of
             the river are tidally influenced, and saline waters extend approximately 20 miles inland.

             WATER QUALiTy DATA INTERPRETATION
             Water quality data were analyzed for I I stations located throughout the entire Basin (Figure
             4-1). Historical records of both hydrology and water quality were available for 7 of the 11
             stations, with the most extensive data base obtained from the Edisto River at the Givhans
             Ferry State Park site. Monthly water quality data were obtained from the South Carolina
             Department of Health and Environmental Control and discharge records were obtained from
             the U.S. Geological Survey's Benchmark and NASQAN (National Stream Quality Account-
             ing Network). Water quality characteristics of primary interest were total phosphorus (TP),
             total Kjeldahl nitrogen (TKN), nitrate-nitrite (N02-3), ammonia-ammonium nitrogen
             (NH3-4), turbidity (TURB) and total suspended solids (TSS). Fecal coliform, biochemical
             oxygen demand (BOD), dissolved oxygen (DO), and pH were also analyzed. Nutrients, TSS,
             BOD, and DO are in milligrams per liter (mg/1); turbidity is in units of NTU (nephilometic
             turbidity units); and fecal coliform is in number of bacteria per 100 milliliters. Analyses were
             based on monthly values, not monthly averages. Table 4-1 provides a descriptive location
             and stream classification for each site.
                       Water quality data from each station were analyzed for long-term trends by using







                                                                                         ASSESSING CHANGE IN THE EDISTo RIVER BASIN








                                                            EDISTO RIVER BASIN
                                                       MONITORING STATIONS








                                    SALUDA
                                                                LEXINGTON


                    EDGEFELD            E-0                                             CALHOUN


                                                                               E-W
                                    AKEN




                                              BAWNELL
                                                                       BAkffRG

                                                                                                                                     BEKLEY              CHRESTON
                                                                                                                 E-M


                                                                                                                  DORCFESTER

                        Frimary Water Quality Monitoring Stations                          COLLETON                             MD-195
                           used in Ka"s Tau TreM Analysis




                    South Carolina Wcter Resources Comn*sion
                    Natural Resources Decision Support System
                    Columbia, South Carolina











          Figure 4-1. Primary water quality monitoring stations in the Edisto River Basin used in Kendall's Tau trend analysis.







                                                     WATER QUALITY



             the Seasonal Kendall Tau test, which is intended for monthly water-quality time series with
             potentially large seasonal variability. The advantage of using this nonparametric test is that
             outliers, missing values, or values reported as being below detection limits (DL) are valid data
             points and present no computational or theoretical problems. The test statistic is a one-sided
             standard normal deviate, Z, with the sign of the Z score indicating the direction of the trend.
             A probability of 0.05 was used as a significance criterion. This is the functional equivalent
             of a two-sided test at a significance level of 0.10. Therefore, in 90 percent of the cases, a
             parameter trend or no trend status should have been correctly identified. In addition, a
             Seasonal Kendall Slope Estimator was calculated to indicate the magnitude of the trend and
             provide between-site comparisons. Values recorded at detection limits were omitted from the
             data set.
                       Water quality records were flow-adjusted prior to analysis to eliminate strearnflow
             variations as a potential cause. The flow-adjusted concentrations (FAQ were estimated
             through regression analysis, using the method of Smith and others (1982) and fitting the data
             to linear, log, hyperbolic, or inverse curves. The FAC was determined as the difference
             between the observed and predicted values from the best fit regression equation. Table 4-2
             lists the parameters that were adjusted by station, along with the functional form for
             transformation. All other regression relationships were poor (p > 0. 10) or had fewer than 24
             discharge values. In these cases, the FAC was the monthly concentration. In addition, a
             review of laboratory methods was conducted to identify changes in procedures that might
             result in trend artifacts.




             Table 4-1. Water quality station location descriptions and stream classifications.


                  Station          Description                               Stream            Watershed
                    ID                                                   Classification


                  E-091     North Fork Edisto River at S.C. 391                A               North Fork
                            5.5 miles south of Batesburg
                  E-099     North Fork Edisto River at S-38-74                 A               North Fork
                            Northwest of Orangeburg
                  E-008     North Fork Edisto River at S-38-9                  B               North Fork
                            West -southwest of Rowesville
                  E-090     South Fork Edisto River at US 1                    A, B            South Fork
                            12 miles northeast of Aiken
                  E-013     Edisto River at US 78                              A               Edisto
                            West of Branchville                                                (main stem)
                  E-015     Edisto River at S.C. 61,                           A               Edisto
                            Givhans Ferry State Park                                           (main stem)
                            (Corresponds with USGS station 02175000.)
                  E-059     Four Hole Swamp at S-38-50                         B*              Four Hole
                            5.3 miles southeast of Cameron                                     Swamp
                  E-100     Four Hole Swamp at US 78                           B*              Four Hole
                            East of Dorchester                                                 Swamp
                  MD- 119 Edisto River at US 17                                A, ORW**        Brackish/
                            12.5 miles northwest of Ravenel                                    Marine
                  MD-120 Dawhoo River at S.C. 174                              ORW             Brackish/
                            9 miles north of Edisto Beach                                      Marine
                  MD-195 Bohicket Creek at S.C. 700                            SFH***          Brackish/
                            I mile southwest of Cedar Springs                                  Marine


                    Site specific standard (DO not less than 4 mg/l, pH. 5-8.5)
                      ORWOutstanding Resource Waters
                     * SFHShellfish Harvesting Waters






                                                                               ASSESSING CHANGE IN THE EDISTo RIVER BASIN



                                                       Table 4-2. Functional forms of flow adjusted parameters, by station.

                                                            Station        Parameter           Form - f(Q)         R2               Probability

                                                            E-013          N02-3               I/Q                 0.29                0.0001
                                                            E-015          TURB                1/(l+BQ)*           0.12                0.0001
                                                                           N02-3               1/Q                 0.27                0.0001
                                                                           TOC                 1/(1+13Q)           0.36                0.0001
                                                            E-008          DO                  1/(l+BQ)            0.12                0.0001
                                                                           N02-3               1/Q                 0.27                0.0001
                                                                           TOC                 1/(1+13Q)           0.19                0.0001
                                                            E-090          TURB                1/(l+BQ)            0.10                0.0001
                                                                           DO                  In Q                0.15                0.0001
                                                            E-091          TURB                1/(1+8Q)            0.33                0.0001
                                                                           DO                  1/(I+BQ)            0.13                0.0001
                                                                           N02-3               In Q                0.24                0.0001
                                                                           TP                  1/(l+BQ)            0.49                0.0001
                                                            E-099          DO                  In Q                0.13                0.0001
                                                                           N02-3               1/(l+BQ)            0.18                0.0001


                                                                 *where 6 is a positive constant and Q is discharge.

                                                                 Simple linear regressions of concentration versus discharge were used to reveal the
                                                       controlling process for phosphorus stream input. In undisturbed forested watersheds, a
                                                       negative slope is indicative of the dilution of a constant phosphorus source. In disturbed
                                                       watersheds, a positive slope indicates that erosion processes and transport of total phosphorus
                                                       dominate the ecosystem.
                                                                 Box plots were used to show summary statistics for all parameters by station. The
                                                       horizontal mark in the box is the median value; the upper and lower hinges of the box
                                                       represent the interquartile range; the box width is a relative scale of sample size; and the notch
                                                       height represents the 95 percent confidence interval of the median value. Stations with
                                                       median values that fall within the notch area of one another are not significantly different.
                                                       The central vertical lines (whiskers) extend up to 1.5 interquartile ranges from the end of the
                                                       box. Values outside the whiskers are marked with an asterisk or a circle. An asterisk is used
                                                       if the value is between 1.5 and 3 interquartile ranges of the box, and a circle is used if the value
                                                       is farther away. Values that are far away from the rest of the data are outliers.
                                                                 Nutrient and total- suspended- solid fluxes were determined by using data from the
                                                       southernmost freshwater station on the Edisto River, located at Givhans Ferry State Park
                                                       (E-015). The drainage area for this station is approximately 2,730 square miles, incorporat-
                                                       ing the North Fork, the South Fork, and Four Hole Swamp, Three methods were used to
                                                       calculate mean annual loading, as described below.
                                                                 1. Daily fluxes of TP, TKN, N02-3, NH3-4, and TSS were computed as the product
                                                       of instantaneous daily discharge (cfs) and concentration (mg/1), and converted to kg/day.
                                                       Simple linear interpolation was used to determine nutrient and sediment fluxes in the
                                                       intervals between sampling events. The total load is the sum of the individual sample loads
                                                       during the time interval.
                                                                 2. The overall flux-weighted mean concentration of each parameter was multiplied
                                                       by the mean annual discharge observed at the station for the entire period of hydrological
                                                       record. Flux-weighted mean concentrations were calculated as follows:
                                                                                               C=(Ici qi ti) / (Eqi ti)
                                                       where ci = concentration of the ith sample; qi = instantaneous flow for the ith sample; and
                                                       ti = time multiplier for the i1h sample. A major assumption in this method is that the flux-
                                                       weighted mean concentrations, as based on the sampling period covered by the study, is
                                                       representative of the long-term flux-weighted concentrations characteristic of the station.
                                                                 3. The annual flux-weighted mean concentration of each parameter was multiplied
                                                       by the mean annual discharge observed at the station for the entire period of hydrological
                                                       record.






                                                     WATER QUALITY


              REsuLTS ANDDISCUSSION
              Trends Analysis
              Table 4-3 presents a summary of water quality trends at eleven stations in the Edisto Basin.
              Collectively, these stations provide a representative picture of overall water quality condi-
              tions. An increasing trend is designated by 'I'; a decreasing trend by 'D'; and data not
              available by 'DNA.' Blank cells are indicative of no significant trends. Temporal and spatial
              aspects of the data sets are listed in Table 4-4.

              Trends in Biochemical Oxygen Demand
              Five-day biochemical oxygen demand (BOD) is the amount of oxygen consumed by
              respiratory processes in the decomposition of carbonaceous and nitrogenous matter in the
              water. The BOD test indicates the amount of biologically oxidizable material present in
              wastewater or in natural water. Nationally, municipal and industrial BOD loads have
              decreased by 46 percent and 71 percent, respectively, in the decade after the passage of the
              Clean Water Act in 1972 (Smith and others 1982). One-third of the current point-source BOD
              is contributed by industrial sources. Since the federal expenditures for municipal facilities
              upgrading did not reach a maximum till 1980, it is probable that much of the declines in
              industrial loads took place slightly earlier than the decline in municipal loads (Smith and
              others 1987).
                        Concurrent with nationwide trends, decreasing trends in BOD were observed
              consistently across all stations within the Edisto Basin from the period 1975 to 1991.
              Summary statistics show the overall BOD mean decreased by 50 percent, from 3.05 mg/I in
              1975 to 1.52 mg/l in 1991 (Table 4-5). The highest percentage changes in mean concentra-
              tions were at Station E-008 (North Fork directly-below Orangeburg) and Station E-013
              (directly downstream from E-008, at the confluence of the North and South Forks). The
              average concentration at Station E-008 was 2.19 mg/I and the standard deviation was 1.237
              mg/l. The analysis indicates the existence of a decreasing, trend (p < 0.0001), and the slope
              estimate was -0.1 mg/I per year or -4.5 percent of the mean per year. At Station E-013, the
              mean concentration and standard deviation were 2. 11 and 2.57 mg/l, respectively. The slope
              estimate was -0.1 mg/l per year or -4.7 percent of the mean per year.
                        Although there are few permitted industrial and   'municipal facilities that discharge
              into the Edisto Basin, six of the eight major facilities in the entire basin discharge into the
              North Fork Edisto River and the Edisto River. Data collected from Stations E-008 and E-013
              are used to monitor the water quality in these areas. Consequently, with the reduced BOD
              loads from industries and municipalities, a higher percentage change in the elimination of
              BOD would be expected at these sites.

              Trends in Total Nitrate-Nitrite
              Trends for nitrate-nitrite (N02-3) concentrations were evenly divided between increases and
              decreases among stations. The North Fork Edisto River and the confluence stations exhibited
              an increase in N02-3 concentrations, while the coastal and Four Hole Swamp areas showed
              a decreasing trend.
                        Nationwide, changes in atmospheric deposition, municipal waste treatment, and
              fertilizer use have each been identified as a major cause of nitrate trends (Smith and others
              1987). In addition, increases in N02-3 have been associated with livestock population density
              and feedlot activity (Hem 1985). In comparing the observed N02-3 trends in the Edisto Basin
              with land use activity, increasing trends were found to be associated with urbanized
              watersheds. Station E-008 (directly below Orangeburg), with a mean of 0.238 mg/I and
              standard deviation of 0.194 mg/l, exhibited the maximum increase in mean change of 3.4
              percent per year (slope estimate = 0.002). With the concurrent decreasing trends in BOD and
              total phosphorus associated with waste treatment improvements at this site, drainage of
              nearby barnyards and septic tanks (sub-surface influences) may contribute more signifi-
              cantly to the N02-3 load.
                        Station E-091, located at the headwaters of the North Fork Edisto River, exhibited
              the highest mean N02-3 concentration. The average concentration for E-091 was 1.064 mg/
              1, an order of magnitude greater than all other stations. Concentrations over I mg/I usually
              are associated with waste inputs (Welch 1980), which may well be the case in this situation.







                                                                            ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                              A wastewater treatment facility, directly upstream from this site, discharges into a
                                                     small tributary to the North Fork Edisto River headwaters. The permit discharge limit is I
                                                     MGD (million gallons per day). Treatment modifications have decreased the BOD load
                                                     during normal operations; however, the detrimental effects of stormwater infiltration to the
                                                     plant were not adequately addressed until recently. Releases of partially treated wastewater
                                                     during storms have been a common occurrence. Currently, equalization ponds have been
                                                     established to handle the additional load, resulting in marked improvement in downstream
                                                     water quality. Confounding these conditions, the number of poultry farms and confined
                                                     livestock located near this site could also contribute significantly to the N02-3 load.
                                                              The lowest average concentrations were at Stations MD-120 and MD-195, at 0.09
                                                     and 0.06 mg/l, respectively. As mentioned previously, the coastal waters and Four Hole
                                                     Swamp experienced decreasing trends in'N02-3 concentrations. With relatively low
                                                     concentrations, interconversion of the different nitrogen species makes it difficult to interpret
                                                     results. A more detailed analysis of historical land-use changes may provide insight to
                                                     probable causes of trends.

                                                     Trends in TotalAmmonia
                                                     From the mid-reach of the North Fork Edisto River downstream to the confluence, and for
                                                     the entire South Fork Edisto River watershed, a decreasing trend in NH34 concentrations was
                                                     observed. The maximum decreases in mean changes averaged -2.25 percent per year at
                                                     Stations E-099 and E-091, with mean values of 0.118 mg/I and 0.146 mg/l, respectively.
                                                     Percentage changes decreased consistently with distance downstream for both the North
                                                     Fork and South Fork Edisto Rivers. On the North Fork Edisto River, this pattern coincides
                                                     with the increase in N02-3 concentrations. Again, the nonconservative nature of nitrogen
                                                     creates problems in data analysis if detailed information on individual processes is not
                                                     available. In such cases, total Kjeldahl nitrogen (TKN) is usually selected to represent the
                                                     overall nitrogen dynamics within the system.

                                                     Trends in Total Kjeldahl Nitrogen
                                                     As such, only 2 of the 11 stations exhibited decreasing trends in TKN concentrations. These
                                                     sites were limited, geographically, to the South Fork Edisto River (E-090) and the confluence
                                                     station (E-013). Both sites had an average TKN concentrations of 0.69 mg/I and slope
                                                     estimates of -0.016 mg/I or -2.3 percent of mean per year. Without major dischargers in the
                                                     South Fork watershed, improved modifications in agricultural practices may be associated
                                                     with the decrease in TKN concentrations.

                                                     Trends in Total Phosphorus
                                                     Total phosphorus concentrations decreased throughout the upper Edisto Basin and within
                                                     Four Hole Swamp. Minimal percentage mean change (less than 0. 1 percent) occurred at the
                                                     headwater reaches of the North and South Fork Edisto Rivers. Maximum percentage changes
                                                     were observed at Stations E-008 and E-100. Both sites are directly downstream from
                                                     municipal wastewater treatment facilities. Improvement in treatment methods may account
                                                     for the higher percentage mean change. As with N02-3, Station E-091 had the highest mean
                                                     phosphorus concentration of 0.56 mg/I (Table 4-5), five-fold higher than all other stations
                                                     examined. Partially treated wastewater discharged during storms may contribute signifi-
                                                     cantly to these high values. Annual mean concentrations ranged from 0.41 mg/I in 1976 to
                                                     0.09 mg/I in 1991 (Table 4-5).

                                                     Trends in pH
                                                     Decreasing trends were observed at three sites in the Edisto Basin: Four Hole Swamp (E-
                                                     100), Givhans Ferry (E-015), and South Edisto River (MD-119). Slope estimates ranged
                                                     from -0.05 to -0.10 standard units (s.u.) per year. It is not uncommon to find low pH values
                                                     in a cypress-tupelo swamp such as Four Hole Swamp, owing to the production of humic acids.
                                                     The increasing ratio of N113-4 to N02-3 percentage at Station E-100, in comparison to its
                                                     headwaters, is indicative of increased humic acid production. Consequently, the drainage of
                                                     this slightly acidic water appears to be exerting an effect on the downstream sites. Station
                                                     E-100 exhibited the most consistent decreasing trends across all the parameters analyzed,
                                                     including turbidity (TURB) and total suspended solids (TSS). No significant trends for
                                                     TURB or TSS were observed at any other sites.











                               Station                             TURB                      INS                    DO            FECAL                   BOD                               TP         TKN                       N02-3                  NH34                      PH
                                                                                   ................. -    ...                                                                                                                                    ..... ..
                                                              ........  ...............................................................   ................... ...... ................                                                      ............*..................
                                                                                                                                                                                                                                           ..............................                  .......
                                                                                ......................... ..............................
                                                                                                                           .......                                    ................ ....
                                                                                             ..........   ............................................                                                                                     ... .................................
                                                                                                                                                                      . .. ....... .........................................
                               E-091                                                         DNA                                                            D                               D*                                   1*
                                                                                                                                                          P<0.0001             P--0.007                                          P=0.035
                                                                                                                                                          [email protected]               [email protected]                                          S=0.001
                               E-099                                                         DNA                                                            D                               D                                    1*
                                                                                                                                                          P=0.038              P<0.0001                                          P=0.0006               P<0.0001
                                                                                                                                                          [email protected]              [email protected]                                           S=0.003                [email protected]
                               E-008                                                                                                                        D                               D                                    I*                        D
                                                                                                                                                          P<0.0001             P--0.0005                                         P<0.0001               P--0.01 13
                                                                                                                                                          [email protected]              [email protected]                                           S=0.008                [email protected]
                                                                                                                                                                                                                                           ............
                                                               .... ....   ....                                                                                  ...                        ...................... . ..............I...........         ......                           ..........
                                                                                                          ............................                    .......                                    ...... ..
                                                                    .............................         .......                                                                                               . .........                .....
                          S6tAh:::F      rk D in                   ""*."""'*".'...**'*"'.'*%".*.".***.*'* - * ** ** *.'.*.'*".* ... *.,..*.,.*..*.,**,.".*,*,*,*****",..,.****,..",**."%,*"...""",*..**'*',*"..",**.."",...,...""..,%"...""..""."*,..***""..*."*" *-..*-.-,.-..-.-.'-..-.-.".'*...'* -. . *** - '; : : .: ;: .... .: .::::: @' : ., .... ... ....
                                     ..0       ra                                                                              ........................   ............................................... ...........                      .... X......    .......
                                                                  .............                                                        .............................................. ........................................... .......... ........................... ..........
                                                                           ....................................                ...........                                                                                       ....................................................
                               E-090                                                         DNA                                                            D                               D              D                                               D
                                                                                                                                                          P<0.0001             P--0.0166             P--0.0052                                          P--0.001
                                                                                   I                                           I                          [email protected]              S--00001              IS---0.0145                                        [email protected]
                                                                                                             .............                                ................I..... .....      I.................
                                                                                                                                                                 . ..........  ..............................I..........................................
                                                                                                                                                                      ... ..... . . ...... ... ................. ... ......... ............             . . ....
                                                                                                                                                                                            ........                             ...
                                                                .......... .................. ..............            ................................................ X.                                                                                       ........ .
                                                                                                                                                                               ............... 11 .........         .........    .....                         ..... . ....           ..............
                               E-013                                                         DNA                                                            D                               D              D                     I*                        D
                                                                                                                                                          P<0.0001             P--0.0102             P<0.0001                    P--0.05                P--0.024
                                                                                                                                                          [email protected]               [email protected]               S=-0.01 8                   S=.002                 [email protected]
                               E-015                                                                                                                        D                                                                                                                       D
                                                                                                                                                          P<0.0001                                                                                                            P<0.0001
                                                                                                                                                          [email protected]                                                                                                                S=-0.05
                                                                         . ................................                                                                                                                                                                           . ......
                                                                         ... -- . ................... ..... ... . ..................................  ................................... ........... .......................................... .. .. . .. .........   .................................
                          Fdur.- H616 Swamp                                                  .................          ...
                                                                        ........................... ... .....................I .............................................
                                                       D                                ........................                                          ........ ........................................................  ............. ...... ............... ........  ....................................
                                                          rai       a  ...........    X'. *  .................
                                                                       .................................................................................................................................................................................................................... ....................................................
                                                                                                                                                          ................ ........... ....... -- ............................................................ ........................................  ...........................
                               E-059                                                         DNA                                                            D
                                                                                                                                                          P<0.0001
                                                                                                                                                          [email protected]
                               E-100                                   D                      D                                                             D                               D                                    D                         D                       D
                                                                   P=0.05                    P=0.0485                                                     P--0.004             P<0.0001                                          P=0.0031               P--0.008              P<0.0001
                                                                    S=41                     S=-0.04                                                      [email protected]               [email protected]                                           [email protected]                [email protected]               S=-0.025
                                                                                                                                              ........... I........................................................
                                                                                                                                                          ............... 1. ........................................ .......  .......
                          Brackish/                                                                                            ............                                                                         . .... ..
                                         . . . .........................................................................                                  ................I.........  ...................................
                                                         ................-...  .....................                                                      ..........  .......                        ...... .......              .......   ........... ................. .......... .........................
                               MD-1 19                                                       DNA                                                                                                                                 D                                                 D
                                                                                                                                                          P<0.0001                                                               P=0.004                                      P<0.0001
                                                                                                                                                          [email protected]                                                                S=-0.004                                       S=-0.10
                               MD-120                                                        DNA                                                            D                                                                    D
                                                                                                                                                          P<0.0001                                                               P<0.0001
                                                                                                                                                          [email protected]                                                                S=-0.003
                               MD-195                                                        DNA                                                            D                                                                    D
                                                                                                                                                          P<0.0001                                                               P<0.0001
                                                                                                                                                          [email protected]                                                                 S=-0.0012


                          Blank Cells indicate no trend                            P=One-sided significance level
                          D=SigMficant declining trend                             DNA=Data not available
                          1--Significant increasing trend                                    Flow adjusted concentrations




                      Table 4-3. Summary of the Seasonal Kendall Tau trend assessment for the Edisto Basin.






                     Table 4-4. Temporal range and sample number for water quality constituents, by site.


                  Station                           TURB                   TSS                   DO                FECAL                   BOD                   TP                 TKN                 N02-3                 NF13-4                  PH
                                                                                                                                                                                                                                ...................
                                                                                                                                                                                    ................                                                          rx:
               14 0A6
                                                     . . .....                                                                                                               ................                                                                X@X'X'
                  F,091                               126                  DNA                   126                      136              195                   122                  176                   121                  184                  142
                                                  1975-199                                   1975-1991             1980-1991           1975-1991             1975-1991              1975-1991           1975-1991             1975-1991           1980-1991

                  E-099                               135                  DNA                   122                      132              133                   138                  131                   126                  135                  138
                                                  1980-1991                                  1980-1991             1980-1991           19MI991               1980-1991              1980-1991           1980-1991             1980-1991           1980-1991

                  F,008                               181                  139                   127                      140              184                   172                  163                   127                  167                  168
                                                  1975-1991            1975-1992             1975-1991             1980-1991           1975-1991             1977-1991              1975-1991           1975-1991             1975-1991           1980-1991

                                                                                                                                                                                                                                                  ....... ...........
                                                                                                                                                                                                                                                X.:          .......
                                                      ..............
                                                                                                                                                             ....     ..... .....   ......
                                                                                                              ..........
                                                                                                                                                                 . .... .....
                                                                                                                                                                                                                                     ..... ...... . .... ....
                  F,090                               120                  DNA                   119                      13@              193                   173                  171                   180                  175                  139
                                                  1975-1991                                  1975-1991             1980-      1        1975-1991             1975-1991              1975-1991           1975-1991             1975-1991           1980-1991

                                             ............                                       ..........                                                          ... ..                              .............
                                                                                                                                                                                                 . . . . . . . . . ..
                                                                                                                                                                                    .......... . .
                                                    . . . ... ... ... . ...                                                                                  .......... :::z;,:
                                                                                                                              .................... . ............
                  E-013                               187                  DNA                   192                      137              193                   167                  164                   113                  169                  142
                                                  1975-1991                                  1975-1991             1980-1991           1975-1991             1975-1991              1975-1991           1975-1991             1975-1991           1980-1991

                  F-015                               ill                  134                   221                      139              192                   169                  171                   107                  173                  155
                                                  1975-1991            1975-1991             1975-1991             1980-1991           1975-1991             1975-1991              1975-1991           1975-1991             1975-1991           1980-1991

                                                                                                                              ------- -------------------           ................                                     ........              ......
                                                                                                                                                                                                                            Xwo
                                                                                                                                                                                                                          .......                             ....
                50
                                                                                                         ..........
                                                                                        ...            ............. ...... .                                                       .....           ..... .......
                  F,059                               186                  DNA                   197                      138              193                   175                  171                   188                  183                  139
                                                  1975-1991                                  1975-1991             1980-1991,          1975-1991             1975-1991              1975-1991           1975-1991             1975-1991           1980-1991

                  E-100                               130                  129                   156                      135              135                   129                  125                   128                  127                  146
                                                  1980-1991            1980-1991             19MI991               1980-1991           1980-1991             1980-1991              1980-1991           1980-1991             1980-1991           1980-1991


                                                                                                                                . .. ....... ..
                                                                                                                   xx:@xx                                                                 .. . ... ...      ........  ......
                                                                                                                   ....... :.:.,: ......                     ...... ... -.. . ::;,    .. . .....     ............  ......
                  MD- 119                             186                  DNA                   193                      68               188                   172                  152                   177                  173                  132
                                                  1975-1991                                  1975-1991             1980-1991           1975-1991             1975-1991              1975-1991           1975-1991             1975-1991           1980-1991

                  MD-120                              181                  DNA                   203                      7                193                   161                  166                   169                  161                  133
                                                  1975-1991                                  1975-1991             1980-1991           1975-1991             1975-1991              1975-1991           1975-1991             1975-1991           1980-1991

                  MD-195                              195                  DNA                   217                      11               198                   172                  166                   180                  174                  140
                                                  1975-1991                                  1975-1991             1980-1991           1975-1991             1975-1991              1975-1991           1975-1991             1975-1991           1980-1991











                                                                                                                                                                                           . . . ..................
                                                                                                                  . .... ......
                                                                                                                  -:::,
                                                                                                                                                                                                          06
                                                                                                   Mu
                Overall       Mean       4.44          6.67              163         1,027         7.04           7.41           2.28        0.17           0.80       0.31             1.11              0.16      9.62                12.17
                Mean      I SD           4.16                            172         L511          737            2.18           1.47        0.26           0.55       039              0.:               013       5.47                10.01

                                                                                                                                                                                 ............ .... ...... X
                terSjjW:r:
                              .......... ........................................................................... ............................................ ..... ........                          ...
                              .. ..........                                    ...........%....................                                   ...........-............                                ....
                              --   ..... -* .......*. ................ ...... .......*..... .                                                '     'X: "x-,'% '", , ,",::
                              . ........................................................................................................... ........
                              ......... ..............................I........................  ............................................................   ..... .x.:
                                             ....... .... .............. ...... ........................ .............................................                                         .............
            Wa                                    ........................... .........................%........  ....................................
                                                                                                                                                                                        . ........ .....                                    x
                                                                                                                        ....................... .. -
                North         Mean       5.30          6.24              218         432           6.42           7.88           2.19        0.22           0.76       0.51             1.28              0.29      7.57                9.04
                Fork          SD         4-50                            207         392           7.40           2.14           1.63        0.38           0.59       056              0.87              0.38      4.22                7.56
                South         Mean                     6.67              165         52            8.52           8.77           2.05        0.15           0.69       0.45             1.15              0.10      6.46                17.20
                Fork          SD                                         128         43            12.20          1.94           157         0.18           0.61       0.24             0.67              0.10      8.70                13.01
                Edisto        Mean       4.42          6.53              93          2,208         4.74           7.48           2.08        0.16           0.76       0.20             0.95              0.11      10.51               11.52
                              SD         3.45                            113         IJ938         5.04           1.98           2.06        0.41           0.59       0.19             0.62              0.09      9.06                8-52
                Four          Mean       3.06          6.68              189         376           5.90           6.82           2.24        0.17           0.95       0.34             1.27              0.11      14.21               16.32
                Hole          SD         2.65                            171         563           5.47           2.21           1.08        0.27           0.59       0.32             0.65              0.12      8.98                10.97
                Bracldshl     Mean                     7.20              70                        9.68           6.83           2.65        0.16           0.83       0.11             0.96              0.10      11.14               12.03
                Marine        SD                                         100                       8.73           2.12           1.27        0.26           0.52       0.24             0.69              0.07      9.92                14-57

                Stations
                                                               ............. .........X                                      .............................................. ........    .........         ............I...... ........
                                                                                                                                                                            .     :::   .. ..................................  .............I......
                                                                                                                  ........       ........................                                                 .......... ....
                                             ...... .. .... ...... ........                                                                                          .........                                  ..........................
                                                                                                                                                                                                                            .......... ............
                                                             ................             ..................                                                                                                                            ...........
                                                             ...........                                                                                                                   .............................. ...........
                                                             ..............                                                                                                                                                 .......  .... ... ....
                                                 ............... '' ......... ......-..........................   .... .......                                                             ...........    I...............     ......   ...............
                E-091         Mean       3.50          6.56              431         16            9.20           8.60           2.63        0.29           0.92       1.06             2*0 1             0.56      7.21                7.64
                              SD         2.12                            221         14            9.03           2.10           1.45        0.39           0.64       0-59             OB4               0.50      3.60                7.65
                E-099         Mean                     5.75              129         587           3.68           7.85           1.52        0.12           0.56       0.14             0.69              0.09      6.21                11.64
                              SD                                         112         269           4.17           2.16           0.87        0.14           0.52       0.07             0-53              0.09      3.12                7.78
                E-008         Mean       5.35          6.37              134         682           5.66           T.23           2,07        0.19           034        0.24             0.97              0.17      8.15                8.01
                              SD         4-53                            126         359           6.47           1.95           1.11        0.27           0.53       0.15             0-54              0.13      4.69                5-55
            Soutti;                                                                  ...........  .............................,......            .....     ...........                       ..........  I.................. .
                                                  ........................................................ .      .....................................  ...... ....... ...             . .. . . . . . . . . . . . . . . . . . . . . . ..............................
                                                                   .......................                        ..... ....................................                            ....................
                                                                                                                                 .........................................................                                              ........
                                                                                                                                         .................... ........ .........................  ........  ... ...................... ...  ...................
                                                                                                                                 ....................................................
                                                                                                                                                  ...................                                           .............I....... .......................
                                                                                                                  ...........                                                           ..................................
                                                                               ........................  ................. 1. ........ ...                                                 .......        I-- ......
                E-090         Mean                                       165         52            7.38           8.77           2.05        0.15    1      0.69       0.45             1 14              0.10      5.54                17.20
                                                                         128         43            925            1.94           1.57        0.18           0.61       0.24             65                0.10      3.11                13.01
                              SD                                                                                  1                                                                     0'
                                             ............  ............  .....       . .. ......   .. ..........  ...-... . .............       ...............                 .. ....                                                 . ..............
                                         ............................ ................................. ......................... ............... ............ .:X .... .. ................................                             . ......... ...
                                                                                                                                                                                               .. .. ... .... . .
            EdIstd..                                                                                                                           ................                         ........ .... . . .                 . ..... ... . .........
                                                                                                                                          ...........
                                                                                                                                          .. . ........ . .                                                                             .........
                                                                                                                                                                                                                    ................... .... ... ............
                                     ............................................  ...................... ............................ ............. ........                                                       ...............I... ....... ...
                E-013         Mean                     6.31              102         1,664         5.30           7.71           2.11        0.15           0.69       0.21             0.89              0.12      8.88                106
                              SD                                         99          1.133         656            1.98           2.57        0.19           0.38       0.19             0.42              0.11      4.10                7.99
                E-015         Mean       4.44          6.74              84          2,487         4.18           7.28           2.04        0.13           0.78       0.19             0.96              0.10      10.00               12.55
                              SD         3.45                            126         2,192         2.68           1.96           1.38        0.26           0.53       0.19             0-53              0.06      4.66                8.84
                                                                                             ............         ......
                                                                                     ............................... ................... .. ......
            fot*              MPA katin                                                                                                                     X X
                                                                                                                                                                     .................
                                                                                          ..........................................                                         ............................................................ ....................... .................... ..... ..
                                                                                     .........                                                                                          .................................. ... .. .
                                                             . ........ ......... ......... ...................                      .........................  ........... , " ':                        - - - - - -. .............
                                                             ... ................... ..... ........ ........          ...        .......................................         .........I................
                E-059         Mean                     6.56              260                       7.50           6.88           2.34        0.16           088        0.50             1.37              0.13      10.06               16.69
                              SD                                         181                       6.33           2.22           1.11        0.20           0.'56      0-31             0                 0.15      4.79                12.01
                E-100         Mean       302           6.80              117         376           3.62           6.74           2.07        0.18           1'03       0.11             1.13              0.09      15.55               15.84
                                           63                            125         563           2-58           2.20           0.87        035            0.63       0.11             062               0.07      6.64                9.47
                              SD         2.*
                                                                         ................................  ...........
                                                                  ............ ..............I......  ...................................                               ...............
                                                             ............ .    ...................... ... ........................                                   ........................... ...............................        .........
                                                       ..........              ......           .....                 .......    ........                                               .............................
                                                                                                                           ................
            Orack1s;                                             ........                                                                                                                                 ............ ...................
                                                                               .........................
                                       .....      .. . ..........                                                     ......... .... .......  ......                                                                .. .....
                MD-119        Mean                     6.79              67                        4.17           7.31           2.26        0.13           0.80       0.19             0.97              0.10      11.52               12.44
                              SD                                         93                        4.26           2.04           1.26        0.27           0.49       0.29             0-53              0.06                          9.60
                              Mean                     7.31              147                       16.42          6.67           2.64        0.17           0.84       0.09             0.99              0.11      10.65               11.42
                              SD                                         197                       1033           2.06           1.20        0.25           0.44       0.28             OB4               0.08      4-59                12.21
                              Mean                     7.48              43                        8.78           6.56           3.04        0.18           0.84       0.06             0.89              0.10      8.67                10.74
                                                                                                                                                                                                          0.06
                              SD                                         37                        5.70           2.19           1.23        0.26           0.55       0.09             0-56                        4.61                7.91
                                                                                                                                                                                                                                                         ?Z

            *Represents median value



                  Table 4-5. Summary statistics for the Edisto Basin by watershed and station.







                   Table 4-5 continued. Summary statistics for the Edisto Basin by year.




                      Annual
                                                                                                                                                    BOD,::::                                                                             @NWRATJO-
                                   .................. .......
                                                                                                                                                                    .. ...........
                                                                                                                                                                                                                            ........... ...... .-........
                          1975          Mean                                                                        7.12            7.58            3.00            0.08            0.72           0.42           0.06          9.33           23.99
                                        SD                                                                          6-59            2.15            1.11            0.05            0.44           -0.64          0.04          4.25           15.38
                          1976          Mean                                                                        7.51            7.54            3.61            0.17            1.05           0.41           0.15          10.43          17.14
                                        SD                                                                          7.48            1.80            1.72            024             0.50           0.33           0.16          5.07           10.41
                          1977          Mean                                                                        8.69            7.26            3.21            0.14            0.94           0.31           0.12          9.49           i6.62
                                        SD                                                                          9.87            1.86            3.65            0.11            0.52           033            0.13          5.37           15.60
                          1978          Mean                                                                        9.40            7.71            3.06            0.10            0.82           0.24           0.11          9.32           16.78
                                        SD                                                                          11.34           221             1.95            0.11            0.43           023            0.14          4.03           11.95
                          1979          Mean                                                                        9.81            7.35            2-54            0.10            0.60           0.35           0.15          8.51           12.52
                                        SD                                                                          9.19            226             1.23            0.17            0.42           030            0.19          5.02           13.65
                          1980          Mean         7.02            6.57            161             1,140          7.10            6.97            2-17            14.33           0.15           0.38           0.33          0.15           10.10
                                        SD           5.49                            153             1,729          5.20            233             1.23            0.26            0-52           036            0.22          4.37     1     13.47
                          1981          Mean         4.70            6.53            138             579            7.86            6.74            2.57            0.40            1.10           0.30           0.25          8.79           8.31
                                        SD           3.68                            160             637            10.21           2.62            1.52            0.47            1.03           0.41           0.28          6.32           5.97
                          1982          Mean         3.49            6.67            158             771            6.01            7.12            2.18            0.40            1.09           0.22           0.28          10.52          5.98
                                        SD           3.11                            165             845            8.73            1.74            0.97            0-52            0.81           024            0.19          5.04           5.00
                          1983          Mean         3.71            6.84            162             1,122          5.68            7.97            2-27            0.17            0.81           0.28           0.19          8.15           11.15
                                        SD           2.90                            171             1,715          6.08            2-55            1.03            024             0-57           031            0.25          335            13.49
                          1984          Mean         3.34            6.81            164             964            4.88            8.02            1.90            0.16            0.75           0.29           0.14          7.88           10.39
                                        SD           2.33                            190             1,241          4.81            221             0.74            0.20            0.35           0.40           0.16          3,80           6.29
                          1985          Mean         3.57            6.86            186             829            6.17            7.67            2-44            0.19            0.80           0.27           0.14          9.25           13.14
                                        SD           3.78                            211             1,101          6.91            232             1.11            0-28            0.43           036            0.25          6.37           7.23
                          1986          Mean         6.13            6.74            151             649            7.21            7.47            1.83            0.15            0.73           0.35           0.18          8.89           11.46
                                        SD           6.90                            151             877            7.28            1.93            0.96            0.15            0.32           0.49           0.39          628            6.87
                          1987          Mean         4.57            6.57            173             789            6.84            7.36            1.88            0.12            0.76           0.32           0.17          10.12          11.29
                                        SD           3.88                            188             1,014          7.84            1.87            0.98            0.10            0.48           0.40           0.31          630            6.88
                          1988          Me@tn        4.03            6.75            164             550            5.70            7.83            1.73            0.12            0.68           0.31           0.13          9.25           12.24
                                        SD           4.39                            179             616            5.63            1.96            0.72            0.14            0.41           0.41           0.20          6.63           8.94
                          1989          Mean         3.89            6.43            181             982            6.36            6.89            1.90            0.12            0.75           0.25           0.10          11.54          12.30
                                        SD           3.99                            174             1,254          5.29            2-57            1.36            0.17            0.30           036            0.09          4.62           7.05
                          1990          Mean         4.39            6.52            145             538            7.12            7.55            1.78            0.08            0.62           0.34           0.10          11.36          15.05
                                        SD           2.96                            156             847            7.05            1.76            0.86            0.04            0.22           0.40           0.14          6.08           9.67
                          1991          Mean         4.83            6.55            183             4,831          9.37            6.86            1.52            0.09            0.72           0.27           0.09          13.69          14.59
                                        SD           2.54                            146             3,907          6.75            2.03            0.63            0.08            0.30           033            0.07          4.64           11.19

                     *Represents median value







                                                   WATER QUALITY


             Water Quality Standards
             The presence of a significant trend indicates improvement or degradation of a water resource
             over time. However, information regarding compliance of water quality conditions to
             acceptable standards is not provided. To determine if watersheds met stream use classifica-
             tion requirements, individual values were compared to state water quality standards or
             federal water quality criteria. Excursions are values higher than standards or criteria.
             Excursions due to natural conditions are not considered standard violations.

             Dissolved Oxygen Excursions
             Oxygen depletion rates are primarily a function of temperature and the availability of organic
             substances for microbial respiration. Stream classifications A and B require that the average
             daily dissolved oxygen (DO) should be no less than 5.0 mg/I and individual DO readings
             should never be less than 4.0 mg/l.
                      The Four Hole Swamp and coastal stations exhibited the highest percentage
             excursions of DO standards, averaging 4.8 percent beyond the 4.0 mg/I standard, and 17.5
             percent beyond the 5.0 mg/l standard (Table 4-6). The natural occurrence of low DO values
             in these areas can be attributed to the abundance of organic material in both watersheds and
             limited water exchange at tidal nodes at the coast.
                      With the exception of Four Hole Swamp, mean DO values at freshwater stations
             decreased with distance downstream (Figure 4-2), concurrent with increasing total organic
             nitrogen and carbon (Figures 4-3 and 4-4). All sites in the North Fork Edisto River were
             significantly different from one another. Basinwide, excursions occurred 2.9 percent of the
             time from 1975 to 1991. There were no significant trends in DO values at any of the stations
             examined.

             Fecal Coliform Excursions
             The South Carolina Class A water quality standards for fecal coliform bacteria state that the
             waters shall not exceed a geometric mean of 200 per 100 ml, based on five consecutive
             samples during a 30-day period, nor shall more than 10 percent of all samples during any 30-
             day period exceed 400 per 100 mi. For Class B waters, the waters shall not exceed a geometric
             mean of 1,000 per 100 mi, nor shall more than 20 percent of all samples exceed 2,000 per 100
             ml for the above-mentioned intervals.
                      Percentage excursions from fecal-coliform standards ranged from 0.0 percent to
             50.0 percent over the entire basin. As with other contraventions, Station E-091 exhibited the
             highest percentage of excursions (48 percent) (Table 4-6). The maximum number of
             excursions observed at this site occurred during the early to mid 1980s. The high percentages
             at Stations MD-120 and MD-195 reflected the limited number of samples.
                      The highest levels of fecal coliform counts were exhibited in the headwaters of the
             North Fork, South Fork, and Four Hole Swamp (Figure 4-2). These sites were significantly
             different from one another, as well as from all other stations. In contrast to the decreasing
             BOD levels, there were no significant trends in fecal coliform counts. The discrepancy in
             trends may be at *tributed to an additional source of fecal coliform bacteria associated with
             nonpoint sources, such as livestock wastes and feedlot activity.

             pHExcursions
             The pH standard for Class A waters is between 6 and 8 standard units (s.u.). For Class B
             waters, the standard is between 6 and 8.5 s.u. As is characteristic of blackwater rivers, the
             majority of the Edisto Basin had slightly acidic waters, associated with the production of
             humic acids. The colloidal humic substances contribute to the tea-colored or "blackwater"
             appearance.
                      Maximum excursion percentage was observed on the North Fork Edisto River at
             Station E-099. Physical characteristics of this site are dramatically different from upstream
             and downstream sites. The width of the river increases from approximately 20 feet to 115
             feet and the sediment/water interface is covered with organic debris. Turbidity values also
             decrease significantly (Figure 4-4). Close examination of the excursions revealed that
             although the pH values were less than 6 s.u., the majority were greater than 5 s.u. In
             association with the above-mentioned factors, the increase in acidity may be attributed to the
             increased production of humic acids at this site.







                                                                           ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                              Basinwide, pH excursions occurred 14 percent of the time during 1975 to 1991. As
                                                     with Station E-099, the majority of the excursions were less than 6 sm. but greater than 5 s.u.
                                                     and could be attributed to natural conditions.

                                                     Total Phosphorus Excursions
                                                     The absolute concentration of total phosphorus is an indication of a watershed's eutrophica-
                                                     tion state. Although there are no official standards for phosphorus, the USEPA's recom-
                                                     mended criterion to prevent accelerated eutrophication is 0.10 mg/l. This standard applies
                                                     only to running streams that do not flow into impoundments.
                                                              Maximum percentage excursions of 87 percent (Station E-091) and 65 percent
                                                     (Station E-008) were observed in the North Fork Edisto River (Table 4-6). On an annual
                                                     basis, from 1975 to 1991, the number of excursions at Station E-091 were evenly distributed
                                                     through time. The average concentration at this site was 0.56 mg/I (Table 4-5). A slight
                                                     decreasing trend in total phosphorus concentrations was detected at E-091, with a minimum
                                                     mean change of 0.01 percent per year. Conversely, the majority of excursions at Station E-
                                                     008 occurred in the early 1980s. The average total phosphorus concentration at this site was
                                                     0. 17 mg/l. Station E-008 exhibited the maximum mean change (3.0 percent per year) of all
                                                     the stations examined.
                                                              Median concentrations at both stations were significantly different from each other
                                                     and from all other stations (Figure 4-2). With the significant decrease in average concentra-
                                                     tions, from 0.56 to 0.09 mg/I between Station E-091 and E-099, the North Fork Edisto River
                                                     appears to assimilate the incoming flux of phosphorus.
                                                              The only other significant difference observed between sites was in Four Hole
                                                     Swamp. Total phosphorus concentrations decreased from an average of 0.13 mg/I in the
                                                     headwaters to 0.09 mg/I near the confluence with the Edisto River, possibly indicating the
                                                     swamp is functioning as a sink for phosphorus.
                                                              Basinwide, the EPA-recommended concentration of 0.10 mg/I was exceeded 39
                                                     percent of the time. If the North Fork Edisto River excursions were removed from the data
                                                     base, the percentage would drop to 30 percent. For the majority of the stations, period-of-
                                                     record mean phosphorus concentrations were approximately 0. 10 mg/l, although the median
                                                     values were usually below the EPA criterion. In 1991, the mean annual phosphorus
                                                     concentration for all the stations was 0.09 mg/l, exceeding the criterion only 14 percent of
                                                     the year.







                                                                        WATER QUALITY










                                                                                                                     ............... ............
                                                                                                                                                                                          ... . . . . .......
                                                                                                                                                                                 ....... . ......
                                                                                                                      ...........                                         . ........
                                                                                                                     ......  .......................
                                                                                                                                                      `6 14 011:0
                                                                                   d,"O'X   ..............
                                                                              bNo '*0
                                                                                 .............. ............ .....         ......
                                 ...........
                                                                                                                                             o    . .........
                                                      .......... .:: :: " .. ": (:'::4 ... ...    @                           ..... ... ..     I   .
                                                                                  .............                                                                                          ...................
                                                                       ................                                       ......

                                                              ............
                                                                      ....  :4-@ ....  ..... gq
                                              .............. ..........
                                 .................


                                 North Fork Drainage                                                                          156/178                                51/107              11/139
                                         E-091             #Exc./N*           1/199                      4/199
                                       (1975-1991)**           % -            0.50%                      2.01%                87.64%                                 47.66%              7.91%
                                         E-099             #Exc./N            3/136                      4/136                33/138                                 4/129               93/136
                                       (1980-1991)             %              2.21%                      2.94%                23.91%                                                     -6813@8@%-
                                                                                                                                                                                         4'.
                                                                                                                                                                                         33/159
                                         E-008             #Exc./N            3/211                      51/211               109/167                                0/134
                                       (1975-1991)             %              1.42%                      1%                   65.27%             1                   0.00%     1         20-75%
                                       Watershed               %              1.00%                      3.40%                62.00%                                 14.80%              31.60%


                                 South Fork Drains!
                                         E-Coo             #Exc./N            01194                      1/194                47/173                                 9/131               20/136
                                       (1975-1991)             %              0.00%                      0-52%                27.17%                                 6.87%               14.71%
                                       Watershed               910            0.00%                      0.52%                27-17%                                 6.87%               14.71%


                                 Edisto - Main Stem
                                         E-013             #Exc./N            2/192                      5/192                61/167                                 1/136               28/139
                                       (1975                   %              1.04%                      2.60%                36.53%                                 0.74%               20.14%
                                         E-015             #EXC./N            6/219                      21/219               48/169                                 5/136               15/152
                                       (19;                    %              2.74%                      9.59%                28.40%                                 3.68%               9.87%
                                       Watershed               %              2.00%                      6.00%                32.00%                                 2.00%               14.00%


                                                                                                                                                      ..................
                                                                                                                                                      -.200offoUrn
                                 Four Hole Swamp           rainage                                                                                                   q
                                         E-059             #Exc,./N           10/197                     31/197               58/175                                 0/134               1/139
                                       (1975-1991)             %              5.08%                      15.74%               33.14%                                 0.00%               0.72%
                                         E-100             #Exc./N            9/153                      33/153               37/129                                 0/134               1/144
                                       (1980-,                 %              5.88%                      21-57%               28.68%                                 0.00%               0.69%
                                       Watershed               %              5.0017b                    I&M                  31.00%                                 0.00%               0.70%


                                                                                                                                                                     .................   .........I........
                                 Brackish/Marine                                                                                                                     01
                                       MD.-I 19            #Exc./N            4/193                      12/193               53/171                                 2/67                12/130
                                       (1975.,                 %              2.07%                      622%                 30.99%                                 2.99%               923%
                                       MD-120)             #Exc./N            8/201                      45/201               58/161                                 1/6                 6/132
                                       (1975-1991              %              3.98%                      2239%                36.02%                  .......        46.67..%....... ...... .... -4 :. -5.5 %MY
                                                                                                                                                                     t.1,0.
                                 Shellfish Harvest
                                                                                                  --     @- -F                45/169                                 5110                3/136
                                       MD-195              #Exc./N            16/205                     49 /201
                                       (1975-1991)             %              7.80%                      23. %                26.63%                                 50.00%              2.21%
                                       Watershed               %              4.60%                      17.00%               31-00%                                 4.10%               5.00%



                                                                                                                                                                     6.49%               14.009@'
                                       BASINWIDE               %              2.909o                     1040%                39.00%


                                       # Exc.=Number of excursions         N=Number of samples
                                       Dates shown are for all parameters except fecal coliforni and pH which were analyzed from 1980-1991.
                                       Includes shellfish harvest and brackish/marine sites.






                  Table 4-6. Summary of DO, TP concentrations, and bacteria counts exceeding State Standards or USEPA recommendations within
                  the Edisto River Basin.






         Figure 4-2. Fecal coliform, pH, total phosphorus, and dissolved oxygen levels1for the Edisto Basin water quality stations.





         9.0              CD    43-
                                   0                            700-

         8.o                                                    600-     0   0               0

                                                                500-
         7.0

                                                           E
                                                                400-
         6.0                                     CD        0
                                                                300 -
                                                           0
                                                           0                          910
                                                           (a   200-
         5.0
         4.0                                               LL   100
                                                                0
                      CO  C) CO LO 0)  0   0) C) LO
                      9   9)           0   -                             0'  00 C3 CY) U) 0) C:) 0)0
                Lb           7  -  T         C\j 0)                      (3) 0  0')          0  -  C\j 0)
                   UJ W   LU LU W  LU  7     7   -                   L;j           -  7   T
                                       W                                 Lb  L6 LL L@ W W    7     7  7
                                                                                             W


           15                                                   0.9 -

                                                                0.8-                      CP
                                                                             CD
       CD                                  r                                              0
       E                                                        0.7-
           10                                               Q)  0.6-
                                                            E
                                                                             0
                                                            CL  0.5-
       X
       0
       @O                                                       0.4-                  0   8  0 0  0
       CD   5
       0                                                        0.3-
       (n
       An                                                       0.2-

                                                                0.1-
            0
                                                                0.0
                   0) CO  0  CV) U) 0)0  0) CD  LO                              C) m  LO  0)   0) 0
                dj 9) 9   9  7  7  T  5  -  cm  a)                    L;j    9  9  7  7   9    -  N   0)
                   W  W   W  W  W  W  -, 7  7   7                        W LLJ  LLI W W W    7 7  7   7
                                      W  0  C)  0                                            W C) 0   0








                                0.7-                                                              @m                                    go                                                                                                                                                                      I
                                                                     0         8        a                                               10                                                   30
                                                                                                            0                   0
                                0.6-                                                                                            8                                                            25
                                                                               0                                                0
                                0.5-
                                                                                        Cb        C31                 8                                                                      20
                  E             0.4-                                                                                                                                          IL
                                                                                                                                                                              z
                                                                                                                                                                                             15
                                                                                                                                                                              cz
                 6              0.3-                                                                                                                                          0
                  r
                 z              0.2-                                                                                                                                                         10    -

                                0.1                                                                                                                                                               5-

                                0.0                                                                                                                                                               0            A
                                                                                        co        -         a)        C>      0)        0        U)                                                                      a)       co        C)       cr)       U*)       0)        0       !@2         0        LO
                                                            0)       CDP       0)       7         7         u?                                                                                                           q)       9         9        7         7                   C)
                                                   Lb       Lb       Lb        Lb       LU        LIJ       W                                                                                                 LU         W-       LLJ
                                                                                                                                        6        6                                                                                          LU       W         LLJ       W



                            2.00


                                                                                                                                                                                                                                            0
                            1.50                                                                                                                                                             1.2
                   E                                                                                                                                                                         1.0
                                                                                                                                                                              E
                                                                                                                                                                              t@)            0.8
                  z         1.00                                                                                                                                              C@
                                                                                                                                                                              0              0.6
                                                                                                                                                                              z
                            0.50                                                                                                                                                             0.4
                                                                                                                                                                                             0.2                                                                                                   1
                            0.00                                                                                                                                                             0.0
                                                            0)       OD        0        CI)       U)        0)        0       (3)       C)       LO                                                                               00        0        C)        LO        0)       0       0)        0          LO
                                                                     0         0)       7         7         T         c)      7         @2       !@!                                                                              C)        0)                           L9       0       -         N         0)
                                                                     L@        U@       W         LLJ       W         7       CS        6        6                                                                       W        LL        L;j      7
                                                                                                                      W                                                                                                                              LU        W         W        7
                                                                                                                                                                                                                                                                                  W




                         Figure 4-3. Total Kjeldahl nitrogen (TKN), NH34 levels, and NP ratios for the Edisto Basin water quality stations.







           Figure 4-4. Total organic carbon, turbidity, BOD, and discharge levels for the Edisto Basin water quality stations.




            30                                                                      25 -
                                                                                                                   0
            25                                                                                       CP
                                                                                    20 -                           0
                     0
        0)
        E   20   -                                                                                             0
                                                                               z    15                                         CP
                                                                                                 0
        0   15   -
                                 0
            10   -                                                             -2

               5                                                                      5-

               0
                                                                                     0
                              CO 0                 0 CD   0    LO                                CD  cC)  0            0)   0       C)   LO
                          q) cD  cn   @2                                                         0)  0    0)   @2  7        3
                     LU                    7                                                                                        !@! Cn
                          W L@j  dj   L;j  W   W                                                 L;j di   di   L@  W   LU   7
                                                                                                                            LU


               6                                                                  3000-                             0

               5 -                                  0                             2500-

                          CO
               4 -                                                           Z    2000-         0

                                                                             0)
         E
               3 -                                                           CO   1500-

         0                                                                   .0
         CO    2 -                                                                1000-


               1                                                                    500-


               0
                     Z;;  CD  CD  0    CO  U)   0)   0  0)   0   Ln                             M    CO 0   CO  LO  C>
                     L@   q)  9   T    7   7    L9   0  -    C\j 0)                             T    9  (7) -   -   C@'
                          LU  W   W    W   W    W    -, 7                                  di   W    Lu L@  dj  L@  7
                                                     W                                                              W







                                                     WATER QUALITY


             Discharge Relationships
             It has been well documented that in many streams, total phosphorus concentrations are
             related to stream discharge (Smith and others 1982). Depending on the relative importance
             of dilution and erosion processes, the slope of the discharge/phosphorus relationship can be
             negative or positive. In undisturbed forested watersheds, sediments and nutrients are
             conserved, minimizing the effects of erosion. A regression of concentration on discharge
             results in a negative slope, as nutrients and sediment loads are often diluted by increases in
             stream volume. Conversely, in a disturbed or cleared watershed, discharge and concentra-
             tions are positively related, characterized by nutrient additions and erosion during periods of
             high discharge.
                       For the period of study, the regression slopes of total phosphorus versus discharge
             were negative for the North Fork Edisto River and the Edisto River, indicative of a dilution-
             dominated relation (Figure 4-5). In these regressions, discharge explained 24 percent of the
             variability in TP concentrations in the North Fork and 4 percent of the variability in the Edisto
             River (Table 4-7). In addition, turbidity and stream discharge in the North Fork Edisto also
             exhibited a negative relationship (r2 = 0.06, P < 0.0001). Considering both upland forest and
             wetland forest, 56 percent of the North Fork and 60 percent of the Edisto River (main stem)
             subbasins were forested. On the basis of forest cover, the negative relationships between
             concentrations and discharge were expected.
                       There were no significant relationships between discharge and TP concentrations
             at any of the other watersheds. However, a positive relationship between turbidity and
             discharge was observed at both the South Fork Edisto River and Four Hole Swamp, with r2
             values of 0.09 and 0.13, respectively. Discharge obviously explains little of the variability
             associated with the turbidity values; however, it may be indicative of some degree of
             disturbance within these watersheds. It should be noted that turbidity values were quite low
             in the Edisto Basin, with a mean of 7.0 nephilometric turbidity units (NTU) and minimum
             and maximum values of 0.5 and 77.0 NTIJ, respectively. The extremely high turbidity values
             were observed in the Atlantic Intracoastal Waterway, not within the freshwater subbasins.
             The South Fork Edisto River and Four Hole Swamp watersheds, both associated with high
             agricultural land use, exhibited the highest freshwater turbidity values. The positive slope
             of turbidity as a function of stream discharge in the South Fork Edisto River may indicate that
             erosion processes are exerting an influence on the water quality and eutrophication of this
             stream. The increasing turbidity with discharge exhibited in the Four Hole Swamp probably
             is also related to the resuspension of bottom materials during flooding events rather than to
             a flux of incoming sediment.
                       For the freshwater subbasins, a multisource regression was performed on turbidity
             and total phosphorus with stream discharge (Table 4-8). As expected in a basin where 60
             percent of the area is forested or in natural cover, results showed a significant negative
             relationship between discharge and both constituents. Stream discharge explained approxi-
             mately 5 percent of the variability in total phosphorus and 6 percent of the variability in
             turbidity values.
                       Omernik (1977) showed that a watershed that is more than 50 percent forested has
             typical stream total phosphorus and nitrogen concentrations of 0.036 and 0.839 mg/l,
             respectively. The total phosphorus concentration for the Edisto Basin was as high as 2.8 mg/
             1, with a mean of 0.156 mg/l. The total nitrogen concentrations averaged 1.11 mg/l and
             ranged from 0.13 to 9.36 mg/l. Thus, on the basis of forest cover, both total phosphorus and
             nitrogen levels were much higher than would be suggested by Omernik's research. Omernik's
             study was conducted nationwide, incorporating many streams in colder climates associated
             with granite and/or other hard-rock substrates. Concurrent with the findings of Gosselink and
             Lee (1989), the higher nutrient levels found in the Edisto Basin may simply be characteristic
             of southern coastal plain sedimentary environments.


             Nitrogen / Phosphorus Ratios
             Nitrogen / phosphorus (N/P) ratios are used to determine which nutrient is limiting to aquatic
             primary productivity. The N/P ratio varies with trophic state and decreases with increased
             eutrophication (Welch 1980). Stricter control of loading on the limiting nutrient is often
             justified, as it indicates which nutrient poses the greatest threat of cultural eutrophication.







                                                                           ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                     Based on the N/P ratio of living plant tissue, a molar ratio of 10 to 15 reflects a balanced
                                                     ecosystem (Hecky and Kilhan 1988). In freshwater systems, phosphorus is considered the
                                                     limiting nutrient at N/P ratios above 15, and nitrogen is limiting below the ratio of 10.
                                                              The headwaters stations of each watershed exhibited the largest deviations in N/P
                                                     ratios. The lowest total N/P ratio of 7.6 was observed at Station E-091 in the North Fork,
                                                     indicating that N and not P may be the critical nutrient for water quality control at this site
                                                     (Figure 4-6). Within the past five years, the eutrophic state of the North Fork River has shown
                                                     improvement, with an N/P ratio increasing from 3.55 to 14.39. The South Fork Edisto River
                                                     exhibited the highest N/P ratios, ranging from 7.38 to 28.88 with an average of 17.20. Four
                                                     Hole Swamp exhibited an increasing trend in N/P ratios over time, with the system becoming
                                                     more phosphorus limited. N/P ratios at the Edisto River were the most reflective of a balanced
                                                     ecosystem, with an average ratio of 12.5.
                                                              From 1975 to 1991, the lowest N/P ratios observed, for all stations examined,
                                                     occurred in the early 1980s. Stream discharge and rainfall significantly decreased during this
                                                     period; subsequently, high phosphorus concentrations lowered the N/P ratios. Basinwide,
                                                     for the period of record the molar N/P ratio averaged 12.2 (with a range of 8.31 to 23.99).
                                                     Since 1983 the annual mean ratio has been between 10 and 15, indicative of a balanced
                                                     ecosystem.


                                                     Nutrient Fluxes
                                                     Fluxes of nutrients and sediments from the Edisto Basin were determined by using data from
                                                     the southernmost freshwater monitoring station, E-015, at Givhans Ferry State Park. The
                                                     drainage basin for Station E-015 encompasses the North Fork, South Fork, Edisto River, and
                                                     Four Hole Swamp watersheds. Of all the stations examined, this site perhaps best represents
                                                     overall water quality conditions for the basin. Discharge is typically four or more times the
                                                     discharge measured in the North and South Fork Edisto Rivers. Strong seasonal peaks in
                                                     discharge coincide with storm events (Figure 4-7).
                                                              The total mass flux of nutrients and suspended sediments, as the sum of daily fluxes,
                                                     is summarized in Table 4-9. Annual flux-weighted loading estimates were approximately
                                                     19.5 percent higher than interpolated loading estimates for nutrients and 18 percent higher
                                                     for total suspended solids. The use of annual flux-weighted values in the calculation of annual
                                                     loads maximizes the weight of episodic events, such as the high nutrient concentrations
                                                     observed in the early 1980s (Figure 4-7). Conversely, by the nature of the process,
                                                     interpolations smooth the data set, often underestimating extreme values. The second
                                                     methodology used the period-of-record flux-weighted mean (identical to the flow-adjusted
                                                     load value) to estimate total annual loads. A major assumption in this method is that the flux-
                                                     weighted mean concentrations, as based on the sampling period covered by the study, is
                                                     representative of the long-term flux-weighted concentrations characteristic of the station.
                                                     This method produced mid-range loading estimates for total phosphorus and total suspended
                                                     solids and the lowest estimates for total Kjeldahl nitrogen.
                                                              For the period of study, the regression slopes of nutrient and sediment loads versus
                                                     time were negative, indicating a decreasing trend (Table 4-7). High annual loads were
                                                     primarily associated with increased stream discharge (the increased loadings were associated
                                                     with the rains following Hurricane Hugo in 1989 (Figure 4-7) and an increase in discharge
                                                     during 1991). An exception to this phenomenon occurred in the early 1980s. Following a
                                                     long period of high stream volume, discharge decreased significantly in 1981. Although an
                                                     increase in phosphorus and nitrogen inputs to the system was unlikely at this time, high
                                                     concentrations were observed because the dilution process had been significantly hindered
                                                     (Figure 4-8).
                                                              Flow-adjusted loads average 0.08 g/m3 for total phosphorus (Table 4-9) and is well
                                                     within the permissible level of less than 0.12 g/M3 recommended by Gosselink and Lee
                                                     (1989). Point and nonpoint source contribution of 55 percent and 45 percent, respectively,
                                                     were determined by using the loading coefficients associated with land use to estimate
                                                     nonpoint-source flow-adjusted values. Nationwide, nonpoint-source pollution accounts for
                                                     53 percent of the total phosphorus load (Cooley 1976). Percentages from this study for
                                                     nonpoint-source contributions were slightly lower than the national average.













                                          South Fork Edisto River                                                                  North Fork Edisto River
                                                      (E-090)                                                                                  (E-091)

                      0.6-                                                                                    3-


                      0.5-

                  a   0.4-                                                                                 'M 2-
                  E                                                                                        E
                      0.3-                                                                                      -

                 M                                                                                        CL
                      0.2                                                                                     1

                      0.1
                      0.0                                                                                     04
                           0           50           100           150          2;0           250                0          10         20          30          40         50          60

                                                        CFS                                                                                    CFS



                                               Four Hole Swamp                                                                             Edisto River
                                                      (E-100)                                                                                   (E-015)
                      0.5-                                                                                  0.4-

                      0.4                                                                                   0.3-

                      0.3-
                                                                                                      IM
                 E
                                                                                                      E     0.2-
                      0.2

                 M
                                                                                                      CL
                      0.1                                                                                   0.1-

                                                                      b

                      0.0                                                                                   0.0
                           0              500             1000              1;00            2000                0       2500         5000        7500       10000       12500       15000
                                                           CFS                                                                                  CFS




              Figure 4-5. Total phosphorus and discharge relationships for selected watersheds within the Edisto Basin.







                                                                                                                                        ASSESSING CHANGE IN THE EDISTo RIVER BASIN






                                          Four Hole S amp                                                                                           North Fork Edisto River
                                          DEPENDENT INDEP. SLOPE                                   PROB               R2                N           DEPENDENT             INDEP. SLOP4                    PROB             R2       I N
                                          PHOS                      TKN                   +        0.0001             0.74              284         PHOS                  TKN                    +        0.0001           0.064         453
                                          PHOS                      TSS                   +        0.004              0.67              122         PHOS                  TURB                   +        0.013            0.014         446
                                          PHOS                      NE4                   +        0.0001             0.049             :F98        PHOS                  NI-14                  +        0.0001           0.053         467
                                          PHOS                      N02                   +        0.028              0.016             298         PHOS                  N02                    +        0.0001           0.417         474
                                          PHOS                      DATE                           0.058              0.012             304         PHOS                  DATE                            0.016            0.012         482
                                                                                          ......                      ....
                                                                                                                                                    HOS                   CFS                             0.0001           0.242         373
                                                                                  .... ....... .. .                                     ........
                                                                                                                                                                                                                           . . . . . ......
                                                                                                                                                                                                                           .........
                                          TKN                       NH4                   +        0.0001             0.294             289                                               ELL:                             -.... .
                                                                                                                                                    TKN                   TURB                   +        0.0001           0.102         429
                                                       ......       ..........      ............
                                                       .......      .. .....        ............ .. .............
                                                                                                                                        ..............
                                          TURB                      TSS                   +        0.001              0.091             120         TKN                   N114                   +        0.0001           0.388         456
                                          TURB                      N02                   +        0.0001             0.114             290         TKN                   N02                    +        0.003            0.02          458
                                          TURB                      CFS                   +        -0.0001            0.138             87          TKN                   DATE                            0.001            0.026    -463
                                                                                                                                        .. ...........
                                                                                    .... ........
                                                                                                                                                                                                          0.0001           0.039         357
                                          ................                                                            ............... ...
                                                                                                                      ..............                TKN                   CFS
                                                                                                   ...................... ................ ..............
                                          TSS                       N02                   +        0.0001             0.114             120                                                                                         77M
                                          TSS                       DATE                           0.005              0.061             128         TURB                  TSS                    +        0.0001           0.104         131
                                                                    7=77M7          . . . .....
                                                                                                                                        Mmg         TURB                  NI-14                  +        0.0001           0.024
                                                       ....  ..... ..........                                                                                                                                                            445
                                                                                                   ................
                                                                                                   ................
                                          NH4                       DATE                           0.008              0.023             310         TURB                  N02                    +        0.0001           0.026         461
                                                                                                                      . ........
                                                                                  . . ........ . . ....                                 ..... ............
                                                                                  ::%...++ -+--.-.-.-.-.-.-.-.-.-.-,.......................,.:::::::::::::::............                                                   0.014         498
                                                                                                                                        ............ TURB                 DATE                            0.008
                                          :::X'. ..x                .......                        ............                         :+
                                                                                                                                        ............
                                          N02                       DATE                           0.0001             0.06              315         TURB                  CFS                             0.0001           0.062         375
                                                                                                                                        ............. ............... ...  :.::           ----
                                                       ... ..... .                ....... ....                                                      .......... .....                   . . . ......
                                                                                                                                                    ............. . .I.
                                                                                                                                                    ............... .. .
                                                                                  .. . ............                                     ................
                                          :                                                                                                         ...............
                                                                                                                                                    ...............
                                                                                          ........ .......                              . ....      ...............                               . . .......
                                                                                                                                        ....        ...............
                                                                                  . ...................... .
                                          FA-PHOS                   FA-TKN                +        0.0001             0.384             83          NH4                   N02                    +        0.016            0.012         476
                                          FA-PHOS                   DATE                           0.0001             0.181             86          NE4                   DATE                            0.002            0.02     1    481
                                                                                                                                        ..............
                                                                                                                                                    NE4                   CFS                             0.0001           0.037         371
                                                                                                                      ..........        ......
                                          FA-TURB                   FA-TSS                +        0.023              0.065             79
                                          FA-TURB                   DATE                           0.05               0.04              87          N02                   CFS                             0.0001           0.408         374
                                                                                                                                        ....           .......
                                                                                    ......                                                                                                                                 77M
                                          FA-TSS                    DATE                           0.004              0,094             85 1        DATE                  CFS                             0.036            0.011         392
                                                                                                                                                                          .................                                         ..............
                                          Edisto River                                                                                              FA-PHOS               FA-TKN                 +        0.0001           0.054         356
                                          PHOS                      TKN                   +        0.002              0.03              311         FA-PHOS               DATE                            0.0001           0.044         373

                                                                                                                                                                          1:X:  .............
                                          PHOS                      NI-14                 +        0.0001             0.046             321                                               =                                E= EM
                                          PHOS                      DATE                           0.013              0.018             334         FA-TKN                FA-TURB                +        0.0001           0.104         345
                                          PHOS                      CFS                            0.002              0.035             280         FA-TKN                DATE                            0.003            0.025         357
                                                           ......   ............                                                                                                                      ......
                                                                                  :xx:::           ...............
                                                                                  ......           .. ..........                        77=                                                                                         7=
                                                                                                                                                                                                                   . ............
                                          TKN                       N114                  +        0.0001             0.132             322         19A - T 'U'R'*'B* .... .FA-TSS               +        0.0001           0.113
                                          TKN                       DATE                           0.001              0.032             334
                                          TKN                       CFS                            0.03               0.017             278
                                                                                                                                                    South Fork Edisto River
                                          TURB                      TSS                   +        0.007              0.058             126
                                          TURB                      DATE                           0.005              0.021             372         DEPENDENT INDEP. 3LOPI                                PROB             R2            N
                                                       .....                                                                                        PHOS                  TKN                    +        0.0001           0.099         162
                                                       ......                                                                           .....
                                          N02                       DATE                           0.006              0.021             360         PHOS                  N114                   +    -0.0001              0.123         168
                                                                                                                                                    PHOS                  N02                    +        0,0001           0.087         168
                                          FA-PHOS                   FA-TKN                         0.0001             0.045             265                               77777.='K*@ 7M                                   77M77M
                                          FA-PHOS                   DATE                           0.007              0.025             280         TKN                   TURB                   +        0.003            0.06          149
                                                                                                                                                    TKN                                          +        0
                                                                                    . . . . . . . .........                             .. . . ....                                                       .0001            0.318         166
                                                                                                                                                                          N114
                                          FA-TURB                   FA-TSS                +        0.001              0.085             126         TKN                   DATE                            0.015            0.035         170
                                                                                                                      .........                                                                                            ....
                                                                                                   .........
                                                                    ............                   . ........
                                                           ...                                     ........
                                                                                                                                                    777777M 7777                                                                    7M
                                                                                          ..... .                                       ..............
                                          TPLOAD                    DATE                           0.0001             0.012             6210        TURB                  CFS                    +        0.001            0.097         119
                                                                                                                                                                                          777=                             777=
                                          TKNLOAD                   DATE                           0.0001             0.008             @21 0
                                          TSS LOAD                  DATE                           0.0001             0.01              6210        NH4                   DATE                            0.02             0.031         174

                                                                                                                                                                                                                                 . ........ .
                                          Bracktsh/Marine Watersheds                                                                                FA-PHOS               FA-TKN                 +        0.0001           0.624         110
                                          PHOS                      JTKN                  +        0.0001             0.103             451         TA-PHOS               FA-TURB                +        0.0001           0.155         110
                                          PHOS                      TURB                  +        0.003              0.018             466         FA-PHOS               DATE                            0.0001           0.104         115
                                                                                                                                                                            .. ..... .. . . . . . . .
                                          PHOS                      N114                  +        0.001              0.022
                                                                                    .........                                           LEM         A-TKN                 FA-TURB                +        0.0001           0.907         110
                                                                                  . ............
                                                           . .........            :-:
                                          TKN                       TURB                  +        0.03               0.11              441         A-TKN                 DATE                            0.009            0.061         Ill
                                                                                                                                                                                                      .. .........
                                          TKN
                                                                                                                                        462
                                                                    NI-14                 +        0.0001             0.245
                                                           ...... ....                                                                                                    DATE
                                          .....                                   ..                                                                FA-TURB
                                                                                                                      ....... ...... .
                                                                                                                                        ............
                                          TURB                      N02                            0.012              0.013             480


                                          N02                       DATE                           0.0001             0.041             524


                Table 4-7. Listing of regressions for highly significant relationships, by watersheds, from 1975 to 1991.







                                                                                                 WATER QUALITY






                                                FRESHWATER WATERSHEDS

                                                DEPENDENT                        INDEPENDENT                                 SLOPE                                 PROB                             R2                               N
                                                PHOS                             TKN                                             +                                 0.0001                           0.048                            926
                                                PHOS                             TURB                                            +                                 0.003                            0.009                            910
                                                PHOS                             NH4                                             +                                 0.0001                           0.059                            956
                                                PHOS                             N02                                                                               0.0001                           0.385                            974
                                                PHOS                             CFS                                                                               0.0001                           0.05                             765
                                                                                                                                                    . .......................
                                                                                                                                                                   ......................
                                                                                                        ................ ....................       ......... ...........                                      ......
                                                                                     .................................. ......... ..
                                                                                           .......................                                                                   . . . .......
                                                ... ... ...............                                                                             ........................................ ......................
                                                TKN                              TURB                                            +                                 0.0001                           0.054                            883
                                                TKN                              NH4                                             +                                 0.0001                           0.29                             945
                                                TKN                              N02                                                                               0.005                            0.008                            954
                                                TKN                              DATE                                                                              0.0001                           0.027                            967
                                                                                                                                                                                         .............................. .
                                                                                                                                                                                          ...............................
                                                                                           .............................                                                                                         .... ...
                                                ...................... ........                              ..... .................................. ... ......
                                                                                                                    ............. . ....                                               . . .... ....... ...
                                                                                                                             ................................
                                                                                                                                                                   .................
                                                                                                 ................ W-Www&.W.Wwww........W......................................:.:.:.:.:.:.:.,............W................................@...."............. . ............ ..
                                                TURB                             TSS                                             +,                                0.0001                           0.95                             258
                                                TURB                             NH4                                             +                                 0.0001                           0.013                            908
                                                TURB                             N02                                             +                                 0.0001                           0.018                            946
                                                TURB                             DATE                                                                              0.002                            0.009                            1045
                                                TURB                             CFS                                                                               0.02                             0.06                             795


                                                TSS                              CFS                                                                               0.064                            0.014                            253
                                                                                           .... ........                                              ...          ......
                                                                                                        ............... ......... ........          ...............                                                      ........... .
                                                                                                                                                                                                                         .. .... .....
                                                                                                                                                    ..... .......

                                                N'H4                             N02                                             +                                 0.0001                           0.013                            984
                                                NH4                              DATE                                                                              0.001                            0.012                            996
                                                NH4                              CFS                                                                               0.001                            0.015                            767
                                                                       ...       . ............................................
                                                                                           ........................... .                                           ...........
                                                                       ....                                                                                                                                              ........
                                                  ... ......                     . .........                                                                                                                                              .......
                                                                       ........                                                                                                                                          ........
                                                                                 ..........
                                                            ..............       ...W ............... %%..%....%..%..%-.-.-.-.-.-.-.-. ............................................. .............. ........
                                                            4............        ........                                    ............
                                                .... .                                                                                              ... . ....... ......................
                                                                                                                    ................................                                                @77777                                ........... .
                                                                                 ................................... ......................................                          ... . .
                                                N02                              CFS                                                                               0.0001                           0.103                            782
                                                            ... ..                                                                                  ..... ...................... .....                ......                 ...............
                                                                       -.'4-..'-..'-..'-.'.....@..@..'.".:.:.:.:.::"::":":W".w .............. ::::,4 .........*.......... .......... ............ ..... ..........................
                                                                                                                                 .....              .....                                                                    ................
                                                                                                        ............ . ......................       :.X.:.X.
                                                                                                                             ......                 ........... ................. ......                                     ......
                                                                                                                                                    .................................
                                                                                                                                                                                     ..............
                                                DATE                             CFS                                                                               0.0001                           0.057                            866
                                                                       .........
                                                                       ...... .. ........                                                                                    ........
                                                                                                                    .................... ............. ... .
                                                                       ...........
                                                                                                        ....        ..................
                                                                                 . ..........................                                                                                             . ..           :           ..............................
                                                                                                                                                                                                    .......... ...           ...........
                                                FA-PHOS                          FA-TKN                                          +                                 0.0001                           0.065                            731
                                                FA-PHOS                          FA-TURB                                         +                                 0.002                            0.013                            733
                                                FA-PHOS                          DATE                                                                              0.001                            0.013                            768
                                                                                                                                                                          .. ........
                                                                                                                                                    .......        ......... ....                                                         ......
                                                                                                        :: ................ ........... ........    .... ............
                                                FA-TKN                           FA-TURB                                         +                                 0.0001                           0.076                            711
                                                FA-TKN                           DATE                                                                              0.0001                           0.019                            746
                                                                                                                                                    . ... .........................  ...            ..........           ..................
                                                                                                                                                    .... ....................................                                  ..........
                                                ............                                                                                                                                                             .. ........... .
                                                                                                                                                                                                    .................
                                                                                                        ........             .......................
                                                                       ........... ..............                            ......................
                                                IFA-TURB                         FA-TSS                                          +                  1              0.0001            1              0.083                            244
                                                IFA-TURB                         DATE                                                                              0.034                            0.006                            795
                                                FA represents flow-adjusted concentrations.
                                                BRACKISH/MARINE WATERSHEPS
                                                DEPENDENT                        INDEP.                                      SLOPE                                 PROB                             R2                               N
                                                PHOS                             TKN                                             +                                 0.0001                           0.103                            451
                                                PHOS                             TURB                                            +                                 0.003                            0.018                            466
                                                PHOS                             NE4                                             +                                 0.001                            0.022                            480
                                                            .............                                                                                                                                                    ----------
                                                                                                                                                                                                                         . . .........
                                                ............. ........
                                                            ..........                     ... . ......
                                                                                                 ..................... . ...                                       ...........
                                                                                                                                                    .....                                                                .....
                                                                       ...                                                                          ...........
                                                ...................                  .............................. .......                                                                                              .................
                                                TKN                              TURB                                            +                                 0.03                             0.11                             441
                                                TKN                              NE4                                             +,                                0.0001                           0.245                            462
                                                    . .......................... .................................... .......................             . ....                                               .......   ........ .
                                                ............
                                                ............                                                 ...... ................
                                                                                                                                                                                                                         .........
                                                                                                           -------                                                              ....
                                                TURB                             N02                                                                               0.012                            0.013                            480
                                                                                 ........... ....                                ....               ..............
                                                ..............................
                                                ............                                                        ..........                                                  .....                             ....
                                                                                                                    . .........                     . .....
                                                            ........      .......          ... . .. .
                                                    ........................................ ...........
                                                            ..................             ............. .
                                                                       ...............
                                                                                                 ....... .......... ...........                     ....................
                                                                                 JDATE                              1                                              0.0001            1              0.041                1           524




                        Table 4-8. Listing of regression statistics for highly significant relationships for the period
                        from 1975 to 1991.






             Figure 4-6. Molar nitrogen to phosphorus ratios for freshwater watersheds within the Edisto Basin.




                                      South Fork Edisto River                                                            North Fork Edisto River
                                                  (E-090)                                                                            (E-091)
              30                                                                                  30-



        .9     20-                                                                                20-

        W
        CL                                                                                  Ir
        z                                                                                   CL
               10-                                                                          z     10



                0                                                                                  0
                    75      77      79      81      83       85      87       89      91              75      77      79      81       83      85       87      89      91



                                         Four Hole Swamp                                                                         Edisto River
                                                (E-100)                                                                              (E-015)

                30                                                                                30-



          .9    20                                                                           0    20
          15
          cc                                                                                 W
          a.                                                                                 a-
                10                                                                           z    10-


                01                                                                                  0
                   75       77      79      81      83       85      87      89       91              75       77     79       81      83       85      87      89       91

                                                   YEAR                                                                               YEAR















              400000-                                                                   4000000.




              300000.                                                                   3000000-


        tm                                                                         m
        :@@   200000.                                                              :@@  200OU00-
        CL                                                                         z


              100000.                                                                   1000000-



                     0                                                                         0.
                       75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91                        75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91






                 5000.
                                                                                      30000000 -


                 4000.

                                                                                  V
                                                                                      26000000-
                 3000 -                                                           CD



                 2000.
                                                                                  U)
                                                                                      10000000 -
           B     1000


                     0                                                                       0
                       75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91                        75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91
                                                                                                                     d1h























            Figure 4-7. Annual fluxes of total phosphorus (TP), total Kjeldahl nitrogen (TKN), total suspended solids (TSS), and discharge in the
            Edisto River at Givhans Ferry State Park.







                                                            ASSESSING CHANGE IN THE EDISTo RIVER BASIN







                          4-                                                                             4
                                                                                    TKN                 -3
                                                                                    TOTN
                  E                                                                                          E
                                                                                                         2

                                                                                                             z

                                                                                                             0



                          0                                                                              0

                        0.



                  E     0.2-



                  0     0.1



                        0.0  .....................              . . . . ...........

                        10                                                                               20
                          8-             TSS                                                            -15
                                         TURB
                  tM
                  E       6-

                          4-

                                                                                                         5
                          2-


                          0-     ........                                                                0


                        6

                  .E
                  .E    4
                  cc
                  Cr
                        2


                      800


                      6000-


                      4000-



                  2
                      2000-


                          0
                           ....................... .             ........................
                           75       77       79       81      83        85      87       89        91

                                                              YEAR







        Figure 4-8. Physical and chemical characteristics of Station E-015 (Givhans Ferry State Park).







                                                    WATER QUALITY


            Table 4-9. Estimated loadings and flow-adjusted loads, Station E-015,
            Givhans Ferry State Park


                 Estimated load           TP (kg/yr)         TKN (kg/yr)         TSS (kg/yr)

                 METH. 1                  161,744            1,613,466           7,099,246
                 METH. 2                  188,400            1,380,667           8,550,415
                 METH. 3                  200,979            1,986,901           9,929,338
                 Flow-adjusted load*      TP (g/m3)          TKN (g/m3)          TSS (g/m3)

                 METH. 1                  0.07               0.72                3.16
                 METH. 2                  0.08               0.60                3.72
                 METH. 3                  0.09               0.86                4.32


                 * Flow-adjusted load = total load (g/yr) / discharge (m3/yr)

            SUMMARY

            Although the analyses of historical water quality records for the years from 1975 to 1991
            indicate that certain areas in the basin reflect disturbance, the overall assessment of the Edisto
            Basin is positive. The combined analysis of all freshwater stations showed highly significant
            and negative relationships of total phosphorus (TP), total suspended solids, and turbidity to
            stream discharge. This concurrent decrease in concentration with increase in stream volume
            suggests a dilution phenomenon characteristic of undisturbed, forested watersheds. The low
            turbidity and total suspended solid concentrations observed throughout the Basin also
            indicate that erosion loading during storm events is minimal.
                      Of the Edisto basin watersheds, 56 percent is upland and wetland forest, and only
            34 percent is agricultural. According to Omernik's 1977 study of the relationship of land use
            to water quality, typical stream concentrations of TP and total nitrogen should have been
            around 0.034 mg/I phosphorus and 0.839 mg/I nitrogen. On the basis of forest cover, total
            nitrogen levels were slightly higher than those predicted, ranging from 0.96 mg/I in the
            coastal region to 1.28 mg/I in the North Fork Edisto River. As with nitrogen, TPconcentrations
            averaging 0.16 mg/l, were much higher than the predicted values based on land use.
            However, the TP mean concentration of 0.09 mg/I from this study in 1991 was similar to the
            TP mean concentration of 0.08 mg/I observed in the Pearl River, a relatively undisturbed
            forested watershed in Louisiana (Gosselink and others 1990).
                      Overall, the watershed is maintaining acceptable water quality based on a 0.1 mg/
            I TP criterion derived by the USEPA (1976). The North Fork subbasin exhibited the highest
            TP concentration of 0.29 mg/l. All other basins had remarkably similar TP mean concentra-
            tions of 0.10 mg/l, with a range of less than 0.01 mg/I for mean values. Basin-wide, the
            recommended concentration was exceeded 39 percent of the time. If the excursions within
            the headwaters of the North Fork Edisto River are removed from the data base, the percentage
            decreases to 30 percent. Median values for the majority of the stations were usually below
            the criterion. In 1991, the mean annual phosphorus concentration for all the stations was 0.09
            mg/l, exceeding the criterion only 14 percent of the year.
                      From 1975 to 1991. the basinwide molar N/P (nitrogen / phosphorus) ratio averaged
            12.2 (with an annual range of 8.31 to 23.99). The extreme fluctuations in N/P ratios occurred
            prior to 1983. Since then the annual mean ratio has been between 10 and 15, indicative of
            a balanced ecosystem. The North Fork water quality stations exhibited the lowest N/P ratios,
            owing to unequal nutrient enrichment (P > N) attributed primarily to point-soutce discharges.
                      During the period from 1975 to 1991, the most consistent trends observed were
            declining concentrations of TP and declining BOD loads. The decreases in these constituents
            are concurrent with the large reductions in BOD loads and phosphorus concentrations
            observed nationwide (Smith and others 1982, Smith 1987). Because both municipal and
            industrial sources were the object of pollution control efforts during the 1970s and 1980s, it







                                                                         ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                    will be interesting to see if the decreasing BOD and TP trends persist without the implemen-
                                                    tation of nonpoint-source controls.
                                                             Basin-wide, excursions of State Standards for dissolved oxygen, pH, and fecal
                                                    coliform were primarily attributed to natural conditions and, therefore, were not considered
                                                    violations. The exception was the North Fork Edisto River, which violated the fecal coliform
                                                    standard 48 percent of the time. Upstream point-source dischargers contributed significantly
                                                    to the high fecal coliform counts in this subbasin.
                                                             Although the Basin's water quality is acceptable and appears to be improving, it is
                                                    important to acknowledge the disturbance reflected in certain areas (such as the North Fork)
                                                    and to address this in the goal-setting and management phases of the cumulative impact
                                                    assessment. In addition, certain management practices must be encouraged. Forest
                                                    management practices that would maintain and improve water quality in this area include
                                                    protection of existing forested corridors along streams and establishment of strearnside
                                                    buffer zones in developing areas. Implementation of nonpoint source controls in farming,
                                                    such as no-till farming and fertilizer injection techniques would also enhance the water
                                                    quality conditions.


                                                    REFERENCES


                                                    Childers, D.L., and J.G. Gosselink. 1990. Assessment of cumulative impacts to water quality
                                                        in a forest wetland landscape. Journal of Environmental Quality 19:454-463.

                                                    Gosselink, J.G., and L.C. Lee. 1989. Cumulative impact assessment in bottomland
                                                        hardwood forests. Wetlands 9:83-174.


                                                    Gosselink, J.G., G.P. Shaffer, L.C. Lee, D.M. Burdick, D.L. Childers, N.C. Leibowitz, S.C.
                                                        Hamilton, R. Boumans, D. Cushman, S. Fields, M.Koch, and J.M. Visser.1990.
                                                        Landscape conservation in a forested wetland watershed: can we manage cumulative
                                                        impacts? Bioscience 40 (9) No. 8.

                                                    Hecky, R. E., and P. Kilham. 1988. Nutrient limitations of phytoplankton in freshwater and
                                                        marine environments: A review of recent evidence on the effects of environment.
                                                        Limnology and Oceanography 33(4.2):796-822.

                                                    Hem, J.D. 1986. Study and interpretation of the chemical characteristics of natural water.
                                                        Water Supply Paper 2254. U.S. Geological Survey, Washington, D.C. 264 pp.

                                                    Hirsch, R.M., J.R. Slack, and R.A. Smith. 1982. Techniques of trend analysis for monthly
                                                        water quality data. Water Resources Research 18 (1):107-121.

                                                    Omernik, J.M. 1977. Nonpoint source-stream nutrient level relationships: a nationwide
                                                        study. Corvallis Environmental Research Laboratory, Office of Research and Develop-
                                                        ment, U.S. Environmental Protection Agency, Corvallis, Oreg. EPA-600/3-77-105.

                                                    Smith, R.A., R.M. Hirsch, and J.R. Slack. 1982. A study of trends in total phosphorus
                                                        measurements atNASQANstations. Water Supply Paper 2190. U.S. Geological Survey,
                                                        Washington, D.C. 256 pp.

                                                    Smith, R.A., R.B. Alexander, and M.Gordon Wolman. 1987. Water-quality trends in the
                                                        nation's rivers. Science 235:1607-1615.


                                                    Welch, E.B. 1980. Ecological effects of wastewater. Cambridge University Press.















                              Chapter 5
                              Biological Diversity

                              by:

                              William D. Marshall
                              South Carolina Water Resources Commission



























                                                                                  X








                                                                                         P,


                                                                                       AI.Ar-
                                                                                                       71







                                                 BIOLOGICAL DIVERSITY


             INTRODUcriON

             This study was designed to evaluate the ecological components of the landscape resource at
             a large scale rather than at a site-specific scale. The purpose is to assess the ecological
             conditions of the landscape and the changes in those conditions through time for the purpose
             of enabling land managers to make more informed decisions relative to conservation and
             development.
                       Biological diversity is an important indicator of ecological integrity, but it is
             difficult to assess at a landscape scale. The primary problems are that (1) long-term data for
             trend analyses are limited and interpretation can be very complex; and (2) it is difficult to
             devise indices that measure biological diversity over large areas (Gosselink and others 1990).
             Several indices of biological diversity at landscape scales were recommended by Gosselink
             and Lee (1989): extent and distribution of old growth stands of forest, presence of endangered
             and threatened species, presence of indicator species (such as top carnivores), and historical
             changes in species richness. These and other indicators of I andscape condition were used to
             assess biological diversity in the Edisto River Basin. Information regarding old-growth
             forests, as well as relatively undisturbed natural communities, was derived from a natural-
             area inventory conducted by The Nature Conservancy and South Carolina Water Resources
             Commission. For historical changes in species richness, birds were evaluated because the
             U.S. Fish and Wildlife Service's Breeding-Bird Surveys were the only consistent, long-term
             data available. Other, and more general, information is presented to describe the relative
             abundance and diversity of freshwater fisheries, waterfowl, and mammals in the area.
                       In Chapter III of The History of Orangeburg County, A.S. Sally (1898) provided a
             description of this region of South Carolina from about 1750 to 1840. Section 1 of the chapter
             is called "Pioneer Life in Orangeburgh. Or, Roughing it on the Edisto." Excerpts from this
             book provide some description of the wildlife found in the Edisto Basin by Europeans who
             first settled the area.


                     Having cleared a piece of land, we planted, and found the soil to be exceedingly
                          fertile in the river swamp, producing abundant crops. The country was
                          literally infested with wild beasts, which were annoying to the inhabitants
                             killing stock and destroying the crops - and were so bold, daring, and
                          ravenous, that they would come into our yards and before our doors take
                          our sheep and poultry. Indeed, it was dangerous to venture out at night
                          beyond the precincts of our yards unarmed. We used every device to
                          exterminate them, and ultimately effected our object by setting traps and
                          poisoned bait.
                     The forest abounded with all kinds of game, particularly deer and turkeys - the
                          former were almost as gentle as cattle. I have seen fifty together, in a days
                          ride in the woods. The latter were innumerable, and so very fat that I have
                          often run them down on horseback.
                                                              - Memoirs from Tarleton Brown


                       Sally's historical account, originally published in 1898, describes a land with
             buffaloes, wild horses, beaver, wolves, and bears. His book provides an account of the
             techniques used for trapping wolves. He describes "the killing of the last wolf ... in this
             section" which reportedly occurred about 1839 or 1840. It was killed by William Robinson
             on the plantation of his father, Joseph Robinson, on a place called Limestone. "Bear were
             also plentiful in this section in the days of the pioneer, and occasionally one is to be met with
             today in the Edisto river swamp" (Sally 1898).
                       In 1992, wild turkey, reintroduced from other parts of the State, and deer continue
             to abound in the Edisto River Basin. Buffaloes, wild horses, and wolves no longer inhabit
             the region, but possibly bear and certainly beaver can be found.







                                                                              ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                       METHODS
                                                       Analyzing Changes In Bird Species Richness
                                                       The Breeding-Bird Survey (BBS), jointly conducted by the U.S. Fish and Wildlife Service
                                                       and the Canadian Wildlife Service, is the most comprehensive survey of non-game wildlife
                                                       on the continent. Begun in 1966, the BBS now includes survey routes over the entire
                                                       continent and data for more than 500 bird species (Droege 1990). These data are valuable
                                                       as indicators of wildlife populations and landscape-level changes and trends. BBS routes
                                                       consist of 50 stops 1/2 mile apart and are run along a standardized route, about 25 miles in
                                                       length, one morning in June at the height of the breeding season. For three minutes at each
                                                       stop, all birds seen or heard are recorded and counted.
                                                                 Six BBS routes in or adjacent to the Edisto River Basin were analyzed for this study:
                                                       Johns Island, Holly Hill, New Holland, Wagener, Walterboro, and Adams Run (see map,
                                                       Figure 5-1). The routes were analyzed for species abundance and richness changes over time
                                                       and for changes in species preferring either water, field and forest edge, or forest habitats.
                                                       Results of these analyses were compared with changes in land use and land cover over the
                                                       survey period in order to provide an indication of changes in habitat structure and floristic
                                                       components that could have affected bird species richness and composition. Also, relevant
                                                       information from other regional BBS data analyses, as well as information on waterfowl
                                                       population trends, is presented in the "Results" section of this chapter.
                                                                 The BBS data were analyzed in two ways. First, counts for each species for each
                                                       route were regressed over time (linear regression) to detect significant (P<0.10) trends in
                                                       population changes. This follows the methods of Gosselink and others (1990) for the Pearl
                                                       River Basin and is similar to the analyses performed on the BBS data for the entire continent
                                                       (Droege 1990, Droege and Sauer 1990).
                                                                 Second, the preferred habitat was determined for each species by using Bent (1963),
                                                       Ehrlich and others (1988) and Gosselink and others (1990), and species were grouped into
                                                       habitat categories. Habitat preferences were: open water, marsh, swamp, field, forest edge,
                                                       forest with open canopy, forest with closed canopy, and forest in general. For analyses, these
                                                       habitats were grouped into general categories of water (water + marsh + swamp), field and
                                                       edge (field + forest edge), or forest (forest with open canopy + forest with closed canopy +
                                                       forest in general). Then the number of species significantly increasing, decreasing, or
                                                       showing no change in each of these categories was determined.
                                                                 Temporal change in bird species richness by habitat was compared to change in land
                                                       cover for five of the six routes. The Adams Run route was excluded because bird data were
                                                       only available from 1988 to 1991. The land cover data were derived by delineating a 0.25-
                                                       mile corridor on either side of each BBS route on available sources of spatial data. Where
                                                       digital data were available and applicable to the BBS period of record, routes were digitized
                                                       and acreage summaries were automated. Where digital data were not available, the routes
                                                       were delineated on aerial photographs, general land cover classes were interpreted, and acres
                                                       were tabulated manually. Data sources for each route are described in Table 5-1. The results
                                                       of land cover change for each route are in Table 5-2.
                                                                 For all routes, species that were counted fewer than six times over the entire survey
                                                       period were eliminated. The four years of data for the Adams Run route were analyzed but
                                                       are of little use in showing trends; however, they are useful for indicating species richness
                                                       of the area of the Adams Run route. Although several routes had more than one observer
                                                       throughout the entire survey period, all routes were treated the same in the analyses;
                                                       differences in observers may, in fact, be reflected in variations in the quality of these surveys.







                                                                   BIOLOGICAL DIVERSITY








                                             BREEDING BIRD SURVEY ROUTES
                                                        IN THE EDISTO RIVER BASIN








                                             SALUDA
                                                                             LEXNGTCN


                            EDGEFELD                                                                     CALHOLN
                                                                         0



                                                             008
                                             AIKEN




                                                                LL
                                                                                      BAIBERG

                                                                                                                                                              BERKELEY              aRESTON

                                       BBS Routes                                                                                      DORMTER
                                    001  John's Island                                                   COLLETON          0 13           101
                                    005  Holly Hill
                                    008  New Holland                                                                                                     001
                                    009  Wagener
                                    013  Walterboro
                                    101  Adams Run





                      South Cardho Water Resources Commission
                      Natural Resources Decision &ffort System
                      Cokrnbick South Coroino









                  Figure 5-1. Breeding-Bird Survey routes in or adjacent to the Edisto River Basin.
                  Source: U.S. Fish and Wildlife Service.







                                                                          ASSESSING CHANGE IN THE EDISTo RIVER BASIN




                                                    Table 5-1. Data sources for land cover change along Breeding-Bird Survey
                                                    routes in the Edisto River Basin.


                                                      Route                  Survey Period               Data Sources for Land Cover Change

                                                     001 - Johns Island       1966-79                    1966 - Photointerpreted from 1966
                                                                                                                1:20,000 scale and 1:4,800 scale
                                                                                                                aerial photography.
                                                                                                         1977 - Digitized from 1977 LUDA data.

                                                     101 - Adams Run          1988-91                    1989 - Digitized from 1989 SCWRC
                                                                                                                land use data.


                                                     005 - Holly Hill         1972-81, 86-88, 90         1977 - Digitized from 1977 LUDA data.
                                                                                                         1989   - Digitized from 1989 SCWRC
                                                                                                                land use data.


                                                     008 - New Holland        1967-81, 83-91             1966   - Photointerpreted from 1966
                                                                                                                1:20,000 scale aerial photography.
                                                                                                         1989   - Digitized from 1989 SCWRC
                                                                                                                land use data.


                                                     009 - Wagener            1966-68, 77-81, 83-91      1966-71 - Photointerpreted from 1966
                                                                                                                and 19711:20,000 scale aerial pho-
                                                                                                                tography.
                                                                                                         1989 - Digitized from 1989 SCWRC
                                                                                                                land use data.


                                                     013 - Walterboro         1970-81, 86-88, 90-91      1977 - Digitized from 1977 LUDA data.
                                                                                                         1989 - Photointerpreted from 1989
                                                                                                                1:40,000 scale NAPP photogra-
                                                                                                                phy (route was outside 1989 digi-
                                                                                                                tal data coverage).







                                                  BIOLOGICAL DIVERSITY




              Table 5-2. Land cover change in areas of Breeding-Bird Survey
              routes in the Edisto River Basin.


                  Shown as percentage of route corridor areas (each were approximately 8,000 acres)
                  digitized and photointerpreted from sources specified in Table 5-1.



                                                         Land             Percent of Area Percent of Area
              Route                      Subbasin        Cover            Early in Survey Late in Survey
                                                                                  1966            1977
              001 - Johns Island         Edisto          agriculturea             45%             66%
                                         (main stem)     forestb                  45%             19%
                                                         waterc                   5%                9%


                                                                                  1989
              101 - Adams Run            Edisto          agriculture              5%              (only 1989
                                         (main stem)     forest                   92%             source is
                                                         water                    <1%             available)


                                                                                  1977            1989
              005 - Holly Hill           Four Hole       agriculture              60%             57%
                                         Swamp           forest                   36%             37%
                                                         water                    -               <1%


                                                                                  1966            1989
              008 - New Holland          South Fork      agriculture              57%             50%
                                                         forest                   42%             47%
                                                         water                    -               <1%


                                                                                  1966            1989
              009 - Wagener              South Fork      agriculture              56%             41%
                                         North Fork      forest                   38%             49%
                                                         water                    -               <1%


                                                                                  1977            1989
              013 - Walterboro           Just west of    agriculture              44%             35%
                                         main stem       forest                   55%             64%
                                                         water                    <1%


                  a Includes agricultural lands and grasslands.
                  b includes all upland forest types and wetland forest types
                  and associated scrub/shrub types.
                  c includes all open water and nonforested wetland types







                                                                            ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                     Assessing Threatened and Endangered Species,
                                                     Indicators, and Other Wildlife
                                                     Additional information on native wildlife was sought in reference to the presence of
                                                     threatened and endangered species, indicator species (species that indicate high ecological
                                                     integrity because of habitat requirements), and historical changes in species richness of
                                                     animals other than birds. Personal contacts and references from the South Carolina Wildlife
                                                     and Marine Resources Department and the U.S. Fish and Wildlife Service were used to gather
                                                     this information.


                                                     Natural Area Inventory
                                                     The Natural Area Inventory entailed a systematic survey for sites with relatively undisturbed,
                                                     high-quality natural communities in the Edisto River Basin. This effort was conducted as a
                                                     cooperative arrangement between the South Carolina Water Resources Commission and The
                                                     Nature Conservancy's Southeast Regional Office. The inventory was conducted in two
                                                     phases. Phase I was a detailed survey of 1:40,000-scale, color infrared photography from the
                                                     National Aerial Photography Program. Phase 11 was an aerial survey from a small airplane
                                                     and selected on-site field visits to further examine and document the sites that qualified from
                                                     the photo survey. The work began in the spring of 1991 and was completed in the winter of
                                                     1993.

                                                     Phase I: Aerial Photography Survey
                                                     The first phase involved several steps. First, a list of survey features was developed that
                                                     named and defined the types of high-quality natural communities and relatively undisturbed
                                                     areas (survey sites) to be sought. The Nature Conservancy's Southeastern Regional
                                                     Ecological Community Classification System was the primary source for defining the survey
                                                     features.
                                                               Second, the selection standards for the survey features were developed. Selection
                                                     and screening criteria were used to determine what kind of sites would be "candidate sites"
                                                     and what kind of sites would be "qualifying sites." Based on White and Aulbach-Smith
                                                     (1993), the criteria and their application are specified as follows:
                                                               The selection and screening criteria were based primarily on acreage and quality
                                                          (degree of unnatural disturbance). These standards vary among the different ecological
                                                          communities to allow the largest and least disturbed examples of each community to be
                                                          identified, where possible. For example, communities that characteristically occur in
                                                          very small, localized patches were given lower acreage standards than communities that
                                                          occupy extensive areas. Furthermore, ecological communities that have suffered
                                                          wholesale degradation warrant lower quality standards than communities that still have
                                                          many high-quality examples.
                                                               It was decided that these standards should not be too stringent, lest qualifying sites
                                                          be overlooked or rejected. At each stage of the inventory, the selection and screening
                                                          process was kept liberal enough so that no site would be eliminated that would have been
                                                          found to qualify if it had later been examined more closely. Because it was decided that
                                                          the screening process should not be too stringent, many of the candidate sites that were
                                                          carried from one stage to the next stage were eventually be found to be nonqualifying.
                                                               Acreage. A minimum acreage for selecting examples of the survey feature was
                                                          defined. After a minimum acreage was selected and some surveying completed,
                                                          standards were refined where necessary. For example, if an inordinate number of sites
                                                          were selected, then the standards were raised. If seemingly significant sites were
                                                          rejected because they did not meet the minimum acreage, then these sites were added by
                                                          lowering the standards and re-examining maps and photos that had already been
                                                          screened.
                                                               Quality. The degree of allowable unnatural disturbance or degradation in a survey
                                                          site was described. Examples of entries under this heading are as follows: "The forest
                                                          canopy should be mature, with little or no evidence of recent logging" or "When viewed
                                                          on aerial photography, the forest should show no evidence of damage by grazing







                                                  BIOLOGICAL DIVERSITY


                  livestock" or "The presence of drainage ditches does not necessarily disqualify a
                  candidate site unless the hydrology has been significantly altered." For some survey
                  features, it was desirable to combine acreage standards with quality standards. For
                  example, a candidate survey site might be defined as 100 acres of undisturbed forest with
                  a mature canopy or 20 acres of undisturbed forest with an obviously old (overmature)
                  canopy.
                       Additional Criteria. Other factors, in addition to acreage and quality, that were used
                  to choose survey sites were described. For example, if a particular survey feature is
                  almost always associated with certain ecological communities, then it could be decided
                  that an occurrence of the survey feature is not likely to be viable unless it co-occurs with
                  the other ecological communities. In such cases, the co-occurrence of the other
                  ecological communities could be made a part of the selection and screening criteria.
                       Adding many factors to the selection and screening criteria was discouraged. A
                  great number of factors (for example, the number of ecological communities, the
                  presence of special species, and the potential for educational use) could have been used
                  to assign relative priorities among sites; however, it was deemed that such consider-
                  ations should not be part of the initial selection and screening of survey features.
                       The third step in phase one was to develop search images for survey sites. These
              search images included descriptions of how the survey features appear on maps and aerial
              photography. Development of the search images required field reconnaissance of reference
              sites, which are known high quality examples of survey features.
                       The fourth step involved detailing the inventory methods for applying the selection
              standards and search images to identify survey sites. Detailing the inventory methods
              involved the following: gathering and reviewing available information (studying back-
              ground material, contacting persons and agencies, and reviewing literature) and examining
              maps and aerial photographs.
                       Finally, the inventory was conducted by the methods described above. Survey sites
              were identified and documented on maps, photos, and survey site screening forms.
              Phase II: Aerial Reconnaissance and Field Verification
              The aerial reconnaissance was conducted for the following purposes:               (1) to screen
              previously selected survey sites in the study area for potential significance; (2) to determine
              if these sites were still intact; and (3) to find additional sites not previously determined with
              map and aerial photograph interpretation. Each additional survey site that was discovered
              during aerial reconnaissance was documented in the same manner as the sites from phase one.
                       The photo survey and aerial reconnaissance did not finish screening every site to
              resolve its significance; therefore, the sites were categorized as follows:

                     ï¿½ Qualifying Survey Site - meets selection criteria.
                     ï¿½ Candidate Survey Site - significance is yet to be determined. The site's
                          potential significance and probability of qualifying was listed as:
                                 High Potential, Medium Potential, or Low Potential.
                     ï¿½ Nonqualifying Survey Site - does not meet selection standards.

                       Field verification began after the aerial reconnaissance and documentation of
              survey sites were completed. Initially, a subset of potential and qualifying sites was selected
              for field verification. This subset (1) gave preference to sites that had the highest potential
              significance for which there is no known existing information and (2) represented the range
              of community types and covered the geographic extent of the study area. On-site field
              verification was conducted to collect and record information for the selected survey sites to
              verify their community components, quality, and condition. The Nature Conservancy's
              Southeastern Regional Ecological Community Classification was used to name natural
              communities. Standard Heritage site and element occurrence data forms were prepared for
              each site visited. In addition, the information gathered was entered into the South Carolina
              Heritage data base.







                                                                            ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                     RESULTS
                                                     Changes In Bird Species Richness

                                                     Trends in Population Change
                                                     Ninety-eight species of birds were seen six or more times on at least one survey route in the
                                                     Edisto Basin. Appendix 11 shows trends for each individual species on each route. Increasing
                                                     or decreasing trends at both 0.10 and 0.05 significance levels are given. Very few species
                                                     show consistency in the direction or strength of change. Many species (Cattle Egret, Yellow-
                                                     Billed Cuckoo, Downy Woodpecker) show a highly significant (P<0.05) change for one
                                                     route but no significant change on any other route. Others (American Crow, Orchard Oriole,
                                                     Carolina Wren) show significant increases and decreases on different routes. Of the 98
                                                     species analyzed, 24 species have populations that appear to be increasing, 37 species have
                                                     populations that appear to be decreasing, and 37 species have populations that appear to be
                                                     stable or unchanged.
                                                               A few species do show consistent population trends over most of the routes where
                                                     they were found. On the basis of the BBS data, the following 10 species seem to be
                                                     experiencing definite population declines in the Edisto Basin:

                                                            Little Blue Heron               Northern Bobwhite            Blue Jay
                                                            Red-winged Blackbird            Eastern Meadowlark           Rufous-sided Towhee
                                                            Northern Cardinal               Painted Bunting              Northern Parula
                                                            Common Yellowthroat


                                                          Each of these 10 species is declining statewide or throughout their continental range
                                                     (Droege and Sauer 1990) and should be monitored closely in the future (see "Regional Trends
                                                     for Breeding Birds," below). Interestingly these declining species represent all three
                                                     categories of habitat preference: water, forest, and field/forest edge. Barn Swallow,
                                                     American Robin, and Eastern Bluebird are the three species apparently experiencing general
                                                     population increases. These species all utilize the field/forest edge interface. The Barn
                                                     Swallow has benefited from improved nesting sites available under road overpasses (Cely
                                                     1992).

                                                     Trends for Birds Relative to Habitats
                                                     Table 5-3 summarizes results of the regression analysis at each route for all birds, and for
                                                     categories of birds based on habitat preferences. Route 1 (Johns Island), being adjacent to
                                                     the coast, had by far the most water species (15). Of these, one, the Laughing Gull, increased
                                                     in numbers while four - the Ring-billed Gull, Great Blue Heron, Little Blue Heron, and
                                                     Marsh Wren - decreased. The herons and the Marsh Wren all utilize vegetated marshes for
                                                     nesting and feeding habitat, while the gulls are more closely tied to open waters. Land cover
                                                     changes, however, do not show a corresponding decrease in marsh habitat at the Johns Island
                                                     route. Only one of these species, the Little Blue Heron, is known to be in decline statewide
                                                     (Cely 1992) and throughout its range (Droege and Sauer 1990).
                                                               Routes 8 (New Holland) and 9 (Wagener) were the only routes where more species
                                                     were significantly increasing than decreasing. Both routes had more forest species showing
                                                     significant increases than decreases. The other four routes all showed many more forest
                                                     species decreasing than increasing. These findings for forest species correspond with the
                                                     land cover changes along the New Holland and the Wagener routes, as both showed increases
                                                     in forest cover over the survey period.
                                                               The Johns Island route showed the greatest losses, with 51.6 percent of the forest
                                                     species decreasing in population. Several species preferring forest with closed canopy or
                                                     forest in general, such as Red-eyed Vireo, Summer Tanager, and Carolina Chickadee, were
         M@wm@

















                                                     responsible for this. Corresponding to the decline in forest species, the Johns Island route also
                                                     showed the greatest losses in forest cover (from 45 to 19 percent). For Route 13 (Walterboro),
                                                     the data showed that 28.6 percent of the forest species decreased significantly; however, the
                                                     change in land cover showed increases in forest land. Interestingly, the Johns Island and
                                                     Walterboro routes do not show increases in field/forest edge species (Table 5-3); rather a
                                                     substantial percentage of these species are decreasing in population. In particular, Blue Jay,







                                                   BIOLOGICAL DIVERSITY


             Red-winged Blackbird, Eastern Meadowlark, Orchard Oriole, and Painted Bunting are all
             decreasing significantly at these sites.
                        Johns Island and Walterboro are the only routes to have more bird species decreasing
             than increasing in all three categories. Overall, the population of 42.4 percent of the bird species
             found at Johns Island and 31.4 percent at Walterboro are decreasing significantly. This may
             indicate that the most serious habitat alteration has been occurring in the area of these two routes.
             The major forest cover losses that occurred at the Johns Island route support this hypothesis. At
             Walterboro, land cover changes and habitat alterations were not simply structural changes (such
             as forest to field) but rather changes in forest species composition from mixed upland forest types
             to a monoculture of loblolly pine forest. 1989 NAPP photography of this area shows that most
             of the forest cover along the route is planted pine.

             Regional Trends for Breeding Birds
             Droege and Sauer (1990) reported continental trends since 1966 for 88 of the same 98 species
             analyzed in the Edisto Basin; 50 percent of these species showed increasing populations and
             50 percent showed decreasing populations. Comparing results from both the Edisto Basin
             and the continental analyses, only 38 species showed a consistent direction of population
             change for both areas; of these, 25 species showed decreases in populations and 13 showed
             increases.
                        A statewide analysis of the BBS data for South Carolina (includes 22 BBS routes)
             from 1966 through 1989 showed declines for most of the bird species found to be declining
             in the Edisto Basin (previously noted as species "experiencing definite population declines
             in the Edisto Basin"). The exception was the Common Yellowthroat; this bird is decreasing
             in numbers statewide, but the trends are not statistically significant at this time (Cely 1992).
             Three species in decline statewide but showing relative stability in the Edisto Basin are
             Prairie Warbler, Loggerhead Shrike, and Woodthrush. The limited sample size from the
             Edisto Basin may explain the inconsistency for these three species. Declining species in the
             Edisto Basin that are of statewide concern and should be given special attention in the future
             are: Little Blue Heron, Eastern Meadowlark, Northern Parula, Northern Bobwhite, Common
             Yellowthroat, and Painted Bunting (Cely 1992).
                        Cely (1992) identified bird species (with their preferred habitats) found in the Edisto
             Basin and known to be in decline throughout much of their breeding range:

                Field Species -                            Loggerhead Shrike, Bobwhite, Meadowlark,
                                                                Barn Owl.
                Forest Edge/Shrub Species -                Prairie Warbler, Painted Bunting.
                Forest Species -                           Wood Thrush, Swainson's Warbler.
                Longleaf Pine Species -                    Red-cockaded Woodpecker, Bachman's Sparrow.
                Maritime Forest Species -                  Ground Dove, Yellow-throated Warbler.
                Beach/Dune Species -                       Wilson's Plover, Least Tern, Piping Plover.







                                                                                 ASSESSING CHANGE IN THE EDISTo RIVER BASIN






           Table 5-3. Summary of numbers of birds regressed over time.


                Species Summary                                                                     Routes
                                                                   RI          R101           R5            R8            R9           R13
                                                                Johns         Adams          Holly        New         Wagener        Walter-
                                                                Island         Run            Hill        Holland                      boro,
                Total no. species                                  66            48           68            72            76            70
                No. species increased*                                2           1           10            17            15             7
                % species increased                                   3           2.1         14.7          23.6          19.7          10
                No. species decreased*                             28             5           13            8             11            22
                % species decreased                                42.4          10.4         19.1          11.1          14.5          31.4
                No. species showing no trend                       37            42           45            47            50            41
                % species showing no trend                         56.1          87.5         66.2          65.3          65.8          58.6

                Categorized by Habitat
                Total no. water species                            15             0                 4          1            3            5
                % of total that are water species                  22.7           0                 5.9        1.4          3.9          7.1
                No. water species increased                           1           0                 0          0            0            1
                % water species increased                             6.7         0                 0          0            0           20
                No. water species decreased                           4           0                 1          0            1            1
                % water species decreased                          26.7           0           25               0          33.3           1.4
                No. water species showing no trend                 10             0                 3          1            2            3
                % water species showing no trend                   66.7           0           75          100             66.7          60

                Total no. forest species                           31            36           40            43            45            42
                % of total that are forest species                 47            75           58.8          59.7          59.2          60
                No. forest species increased                          0           0                 4          9          11             5
                % forest species increased                            0           0           to            20.9          24.4          11.9
                No. forest species  -decreased                     16             5                 7          1            5           12
                % forest species decreased                         51.6          13.9         17.5             2.3        11.1          28.6
                No. forest species showing no trend                15            31           29            33            29            25
                % forest species showing no trend                  48.4          86.1         72.5          76.7          64.4          59.5

                Total no. field / forest edge species              21            12           24            28            28            23
                % of total that are field species                  31.8          25           35.3          38.9          36.8          32.9
                No. field species increased                           1           1                 6          8            4            1
                % field species increased                             4.8         8.3         25            28.6          14.3           4.3
                No. field species decreased                           8           0                 5          7            5            9
                % field species decreased                          38.1           0           20.8          25            17.9          39.1
                No. field species showing no trend                 12            11           13            13            19            13
                % field species showing no trend                   57.1          91.7         54.2          46.4          67.9          56.5


                * All numbers given are for species showing a trend significant at P< 0.10.
                Water species = water + marsh + swamp preferences.
                Forest species = forest in general + forest with open canopy + forest with closed canopy preferences.
                Field/Forest Edge species = field + forest edge preferences.







                                                 BIOLOGICAL DIVERSITY


                      The Neotropical Migratory Landbird Conservation Program, also known as the
            Partners in Flight Program, has compiled data on neotropical migrant bird populations for the
            southeastern United States in an attempt to prioritize species for protection. Three species
            which are in apparent decline in the Edisto Basin are also on the priority list of the Partners
            in Flight Program. These priority species include the Painted Bunting, Common Yet-
            lowthroat, and the Northern Parula; species experiencing significant widespread population
            declines.

            Waterfowl
            Information provided by Strange (1990) for midwinter surveys of waterfowl of the Atlantic
            Flyway indicate that populations of ducks have decreased dramatically since 1964. The
            steepest declines were in the late 1960s and early 1970s, andpopulations seem tohave leveled
            out somewhat since that time. The midwinter surveys indicate that South Carolina has
            experienced a greater decline than the Flyway. South Carolina has had a 60 percent decrease
            in ducks since 1964, while the Flyway has experienced less than a 40 percent decrease in
            ducks. The surveys indicate a much more unfavorable comparison for geese. South
            Carolina's goose populations have decreased more than 90 percent since 1964, while
            populations of the Flyway have increased more than 60 percent.
                      Strange provided harvest records for the State's waterfowl management areas and
            these data indicate that the impoundment systems in the coastal areas of the Edisto Basin,
            specifically in the vicinity of Bear Island Wildlife Management Area, provide very favorable
            habitat for waterfowl. Harvest trends at Bear Island are similar to overall trends for waterfowl
            management areas throughout the State. However, the average annual harvest (birds per gun
            per day) at Bear Island has been consistently higher than the rest of the state since 1969
            (beginning of record). As mentioned above, Bear Island is part of the region known as the
            ACE Basin, an area identified as one of the highest priorities for protection under the North
            American Waterfowl Management Plan and has been classified as a nationally significant
            wildlife ecosystem by the U.S. Fish and Wildlife Service.
                      In other portions of the Basin, waterfowl use is considered moderate in the marshes
            and bottomiands along the Edisto River from the coast up through Orangeburg County
            (winter populations are estimated at roughly 100 to 200 ducks per 1000 acres in these areas)
            as compared to high waterfowl use (greater than 200 ducks per 1,000 acres) attributed to the
            wetland impoundments of the ACE Basin (USDA 1982).


            Changes in Other Wildlife Species Richness

            Anadromous Fish
            Anadromous fish species known to spawn in the Edisto River include the American Shad,
            Hickory Shad, Blueback Herring, Striped Bass, Atlantic Sturgeon, and Shortnosed Sturgeon.
            A survey conducted by the U.S. Fish and Wildlife Service reports that the recent status of each
            of these species in the Edisto River, except for the American Shad and Shortnosed Sturgeon,
            was judged to be stable (Rulifson and others 1982). The Shortnosed Sturgeon is an
            endangered species, and census and harvest data have indicated declines in American Shad.
            The shad fishery of the Edisto has traditionally been important to residents of the region.
            Ulrich and others (undated) stated that the recreational shad fishery for South Carolina
            centers on the Edisto River in the Jacksonboro area. Reports on commercial catches for Shad
            in the Edisto date back to 1880.
                      There have been a few efforts to assess the Shad fishery of the Edisto River. Major
            declines in commercial landings have been noted, but few comparable sources of data provide
            estimates of catch per unit of effort (CPUE). A summary of American Shad landed in South
            Carolina shows a decrease of approximately 85 percent over the period from 1896 to 1977
                                                                                                                             r
                                                                                                                 lmmq@

















            (Ulrich and others undated). On the Edisto River historical catches of Shad are reported as
            follows:
                 30,000 were estimated for 1880 and 28,273 in 1899 (from Walburg 1956);
                 11,011 in 1955 - about 1,500 of these by recreational fishermen (Walburg 1956);
                 14,259 in 1971 - 2,582 from creel census and 11,677 reported at fish houses (Wade 1971);
                 4,132 in 1975 - limited to creel census (Crochet 1975).







                                                                               ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                                  The Edisto Shad fishery was reported to extend from Willtown Bluff to Branchville in
                                                        1978, but Shad are known to ascend the river as far as Orangeburg on the North Fork and Norway
                                                        on the South Fork (Ulrich and others undated). Unpublished data from a 1938 study by L.E.
                                                        Cable indicated that the major Shad spawning grounds were between Westbank Landing and
                                                        Givhans Ferry. Similarly, Wade reported in 1971 that 92 percent of the spawning activity of the
                                                        American Shad on the Edisto River occurred between Westbank Landing and Jellico Landing
                                                        just south of Givhans Ferry State Park. Another 7 percent occurred between Jellico Landing and
                                                        Givhans Ferry.
                                                                  Generally, the U.S. Fish and Wildlife Service biologists at the Orangeburg National
                                                        Fish Hatchery believe that there has been a steady decline in the population of anadromous fish
                                                        species that use the Edisto River. They believe that the species that do enter, do not venture or
                                                        spawn as far inland as in the past.

                                                        Freshwater Fish
                                                             The South Carolina Wildlife and Marine Resources Department (SCWMRD) has sampled
                                                        the Edisto River for freshwater fish species at more than 160 locations. However, at this time,
                                                        none of the sampling has been repeated at these locations and changes in species composition
                                                        and abundance cannot be assessed. Sampling was conducted in 1989 and 1990 using rotenone
                                                        and electrofishing methods. A tot   'al of 71 species of fish. were collected. Spotted Sucker was
                                                        the most abundant species. Other dominant species (by weight) included Bowfin, Creek
                                                        Chubsucker, Largemouth Bass, Common Carp, Longnose Gar, Striped Mullet, and American
                                                        Eel. Redbreast Sunfish, an important recreational species, contributed 6 percent to the total
                                                        biomass of the rotenone sampling.
                                                                  A 1989 to 1990 creel census for the Edisto River to determine the user and harvest
                                                        characteristics of the sport fishery was conducted by SCWMRD. These data indicate that the
                                                        Redbreast Sunfish is by far the most sought species in terms of the percentage of fishermen and
                                                        hours of directed effort (65 percent of total directed effort). Redbreast was the dominant species
                                                        harvested in terms of numbers (45 percent) and pounds (32 percent) of fish caught. Results
                                                        indicated that Flat Bullhead and Channel Catfish followed the Redbreast in being sought after
                                                        and in total catch. The catch per unit of effort was much greater for the Bullhead and Catfish.
                                                        Census results show that the Edisto freshwater sport fishery may be characterized as a winter
                                                        Bullhead and Catfish fishery and a late spring - early summer redbreast fishery with low fishing
                                                        pressure in the late summer and autumn.

                                                        Other Wildlife
                                                        There are very few wildlife species for which long-term data are available on species
                                                        composition and population levels other than for birds. However, the Basin does support a
                                                        diversity of wildlife populations that seem to be maintained at healthy levels. Large game
                                                        animals that are sought after by hunters include the white-tailed deer, which is widely distributed,
                                                        and the eastern wild turkey.
                                                                  The bottomlarids of the Edisto River, particularly along the main stem, are believed to
                                                        support a high population density of deer (greater than 5 deer per 100 acres) relative to the rest
                                                        of the state. Portions of Calhoun, Orangeburg, Dorchester, and Charleston Counties support
                                                        medium densities of deer (3 to 5 deer per 100 acres). Turkey populations in the Basin arebelieved
                                                        to be increasing along the Edisto River in Bamberg and Orangeburg Counties and in Four Hole
                                                        Swamp (USDA 1982). SCWMRD staff members believe that previous declines in the turkey
                                                        populations were probably brought about by illegal hunting activities and, to a lesser degree,
                                                        habitat degradation (Bauman 1992). Restocking efforts begun in Bamberg and surrounding
                                                        counties in 1981 have proven highly successful.


                                                        Presence of Indicator Species
                                                             Indicator species can be defined as top carnivores or species with large ranges whose
                                                        presence or absence is an index of landscape integrity (Gosselink and Lee 1989). Species that
                                                        could possibly serve as "indicators" of landscape integrity in this region are the Red Wolf, Black
                                                        Bear, and Eastern Cougar. A recent occurrence of the Black Bear in Aiken County is recorded
                                                        in the South Carolina Heritage data base; however, the State's wildlife biologists believe all of
                                                        these have been extirpated from the Edisto River Basin. "Extirpated" means that the species is
                                                        completely gone from a specific portion of its former range. Other species suggested as






                                                  bIOLOGICAL DIVERSITY


             indicators of landscape ecological integrity include raptors. Carnivores with smaller range
             requirements may also serve as indicators of ecological integrity.
                       Generally, there are no time series data available for population changes for indicator
             species; however, there is some knowledge of apparent trends in the population of raptors. The
             population of American Bald Eagle, for example, is known to be increasing in the lower basin
             at the coast. This region, known as the ACE Basin (coastal region of the Ashepoo-Combahee-
             Edisto Basin) presently supports 40 percent of South Carolina's nesting eagles, representing the
             most important Southern Bald Eagle nesting region in the State. It is estimated that there are 24
             active nesting territories in this region. Raptors known to occur in the Basin are listed in Table
             5-4. Populations for most of the raptors found in the Edisto River Basin are believed to be either
             increasing or stable within the region.
                       Bobcats and River Otters are known to inhabit the Edisto Basin and seem to have stable
             populations. These animals have smaller range requirements than the wolves, bears, and cougars
             but their presence may indicate good ecological conditions in the areas where they are found.


             Presence of Threatened and Endangered Species
             The U.S. Fish and Wildlife Service defines endangered species as those in danger of extinction
             throughout all or a significant portion of their range. Threatened species are those likely to
             become endangered within the foreseeable future. Table 5-5 shows the listed threatened or
             endangered animal species that are native to the Edisto River Basin.
                       The Florida Manatee is a periodic summer visitor to the coastal waters in the Basin. The
             Edisto Basin is within the historical range of the Bachman's Warbler, Eskimo Curlew, and Ivory-
             billed Woodpecker, but there are no records of occurrence for these species in the region. Bald
             Eagles, as mentioned above, are nesting in increasing numbers in the coastal areas of the Basin.
             The Red-cockaded Woodpecker is known to be nesting in several locations within the Basin.
             Wood Storks are known to be nesting near the Edisto River and American Swallow-tailed Mtes
             have been seen carrying nesting materials near Cottageville, so they are probably nesting as well.
             The Peregrine Falcon is a fall and winter visitor to the coast.
                       Figure 5-2 is a map of the distribution of sensitive species and communities found in
             the Edisto Basin and associated counties derived from the South Carolina Heritage data base.
             This data base includes the known locations of threatened and endangered species. Several
             species listed in Table 5-5 are not shown in Figure 5-2 because exact locations are not known
             or have not been recorded in the Heritage data base. The distribution and density of the sensitive
             features shown in Figure 5-2 reflect the gaps that are common for biological data. In this case,
             the location is known for many more sensitive features around the heavily developed areas
             outside of the Basin. Much less is known of what exists in the remote areas within the Basin -
             areas where a greater density of sensitive species and communities would be expected.
                       As mentioned above wolves, bears, and cougars, which once inhabited this region, are
             believed to have been extirpated. Of these, only the Eastern Cougar is listed as endangered by
             the State of South Carolina; however, this species is known to exist only in southern Florida.
                       Several species are believed to have been extirpated from the region of the Edisto
             Basin. Some of these species are likely to be extinct. Others appear on the national list of
             threatened or endangered species; still others maintain stable populations in other regions of the
             United States. These extirpated species include the following:

                  Ivory-billed Woodpecker (extirpated, possibly extinct);
                  Eskimo Curlew (extirpated, possibly extinct);
                  Bachman's Warbler (extirpated, possibly extinct);
                  Whooping Crane (extirpated);
                  Bison (extirpated from area before end of 18th century);
                  Elk (extirpated from area before end of 18th century);
                  Eastern cougar (extirpated from area);
                  American Black Bear (extirpated from area);
                  Red Wolf (extirpated from area in early to middle 19th century);
                  Gopher Tortoise (extirpated from area, now found in South Carolina only in Jasper and
                       Hampton Counties;
                  Eastern indigo snake (extirpated from area, may occur in Hampton and Jasper Counties,
                       South Carolina).







                                                                            ASSESSING CHANGE IN THE EDISTo RIVER BASIN





          Table 5-4. Raptors known to frequent the Edisto River Basin.


               Species                                                                Occurrence a                          Population
                                                                                     & (Residency)                             Trend b


               Bald Eagle (Haliaeetus leucocephalus) -                               U&L (resident of Edisto estuary)              I
               Golden Eagle (Aquila chrysaetos) -                                    R     (winter visitor)                        I
               American Swallow-tailed Kite (Elanoides forficatus) -                 U     (breeder)                               S
               Mississippi Kite (Ictinia mississippiensis) -                         L     (breeder)                               I
               Cooper's Hawk (Accipiter cooperii) -                                  FC    (winter visitor)                        I
                   11      11                                                        R to U (breeder)
               Sharp-shinned Hawk (Accipiter striatus) -                             FC (migrant & winter visitor)                 S
               Red-tailed Hawk (Buteo jamaicensis) -                                 C     (resident)                              S
               Red-shouldered Hawk (Buteo lineatus) -                                FC    (resident)                              S
               Broad-winged Hawk (Buteo platypterus) -                               CS    (breeder)                               S
               Northern Harrier / Marsh hawk (Circus cyaneus) -                      FC&L (winter visitor)                         D
               American Kestrel / Sparrow hawk (Falco sparverius) -                  FC (winter visitor)                           U
                   Ic        11                                                      U     (breeder)
               Merlin / Pigeon Hawk (Falco columbarius) -                            U (winter visitor)                            U
               American Peregrine Falcon (Falco peregrinus anatum)                   U     (winter visitor)                        I
               Osprey (Pandion haliaetus) -                                          L (breeder)                                   I
               Great Horned Owl (Bubo virginianus) -                                 FC (resident)                                 S
               Barred Owl (Strix varia) -                                            C     (resident)                              S
               Barn Owl (Tyto alba) -                                                U&L (resident)                                D
               Eastern Screech Owl (Otus asio) -                                     C     (resident)                              S
               Turkey Vulture (Cathartes aura) -                                     C     (resident)                              S
               Black Vulture (Coragyps atratus)                                      C     (resident)                              S

               a Occurrence: Irregular Occurrence - species is not recorded annually; Regular Occurrence - reported at least
               once a year (adapted from Post and Gauthreaux 1989, and Cely 1992).
               Species of irregular occurrence: CS = Casual, 2-6 records exist

               Species of regular occurrence:                   R = Rare, 1-6 individuals per season
                                                                U = Uncommon, 1-6 individuals per day per locality
                                                                L = Localized distribution; could be common or fairly
                                                                       common in appropriate location
                                                                FC = Fairly Common - more widespread than localized,
                                                                       7-20 individuals per day per locality
                                                                C = Common, 21-50 individuals per day per locality
               b Population Trends: S = Stable, U = Unknown, I = Increasing, D = Decreasing







                                               BIOLOGICAL DIVERSITY





            Table 5-5. Threatened and endangered species of the Edisto River Basin.a

            Species                                                      State Status   Federal Status b

            Mammals
            Eastern Cougar (Felis concolor cougar)                           LE             LE
            Florida Manatee (Trichechus manatus)                             LE             LE
            Rafinesque's Big-eared Bat (Plecotus rafinesquii)                LE


            Birds
            Bachman's Warbler (Vermivora bachmanii)                          LE             LE
            Eskimo Curlew (Numenius borealis)                                LE             LE
            Ivory-billed Woodpecker (Campephilus principalis)                LE             LE
            Southern Bald Eagle (Haliaeetus leucocephalus)                   LE             LE
            Red-cockaded Woodpecker (Picoides borealis)                      LE             LE
            American Peregrine Falcon (Falco peregrinus anatum)              LE             LE
            Wood Stork (Mycteria americana)                                  LE             LE
            American Swallow-tailed Kite (Elanoides forficatus)              LE
            Piping Plover (Charadrius melodus)                               LT             LT
            Common Ground Dove (Columbiana passerina)                        LT
            Glossy Ibis (Plegadis falcinellus)                               LT
            Least Tern (Sterna antillarum)                                   LT
            Wilson's Plover (Charadrius wilsonia)                            LT

            Fish and Reptiles
            Shortnose Sturgeon (Acipenser brevirostrum)                      LE             LE
            Loggerhead Turtle (Caretta caretta)                              LT             LT
            Gopher Tortoise (Gopherus polyphemus)                            LE
            Flatwoods Salamander (Ambystoma cingulaturn)                     LE
            Eastern Indigo Snake (Drymarchon corais couperi)                 LE             LT


                a Known to have occurred in the Edisto Basin, or occurrence is strongly suggested by
                geographic range.
                b LE = listed endangered, LT = listed threatened.
                                                                                                                         r







                                                                                                ASSESSING CHANGE IN THE EDISTO RIVER BASIN










                               SENSITIVE SPECIES AND COMMUNITIES
                                                   IN THE EDISTO RIVER BASIN





                                                                                                                                                           W-








                                                                                A





                                                                                                              N

                                                                                  ATLE

                                                                                             [31CPAWFISHFACKI
                                                                                            Mw7U
                                                                                                     0
                                                                                                              WOODPECKER           WARBLER

                                                                                                                                        4
                                                                                              Mew MOLE                                                 r     A
                       0 ANIMALS                                                           SPOTTED TURTLE


                       ,n, PLANTS


                       El COMMUNITIES



                           OUTSIDEOFBASIN




                                                                                                                                  LOGGER-HEACTURTLE
                   South Corolim Water Resources Cormnission                                                                    LOGGER-HEAD TURTLE
                   Natural Resources Decision &Wort System                                                                   LOGGER-HEAD TURTLE
                   Columbia, South COrOrM











            Figure 5-2. Locations of sensitive species and communities in the Edisto River Basin and outside the basin in associated counties.
            Source: Nongame and Heritage Trust Section of the South Carolina Wildlife and Marine Resources Department.







                                                BIOLOGICAL DIVERSITY


            Natural Areas
            The Natural Area Inventory was a systematic survey for sites with relatively undisturbed,
            high quality natural communities. Aerial photo examination, aerial reconnaissance, and
            selected on-the-ground field verification identified and assessed more than 400 sites within
            the Edisto River Basin. Working through the selection and screening criteria (see "Meth-
            ods") resulted in the identification of 301 qualifying and candidate sites. Figure 5-3 shows
            a map of these sites identified in the Natural Area Inventory. One hundred and forty-nine sites
            were found to be qualifying natural areas, and 152 sites were candidates (60 candidate sites
            had high potential for qualifying, 19 had medium potential, and 73 had low potential). Many
            other sites were found to be nonqualifying. The sites were categorized according to the
            complex of communities found on the sites. Nine community complexes were determined
            for the 94 natural communities believed to exist in the Edisto River Basin (upland and wetland
            communities were included but aquatic communities were excluded). Figures 5-4 through
            5-7 show the sites by natural community type for each subbasin. Table 5-6 and Appendix III
            list community groups and specific natural communities of the Basin and summarize findings
            of the Natural Area Inventory.
                      In rather large areas of the Edisto Basin, few qualifying sites were found. The flat
            interstream areas were generally devoid of natural areas. Little remained intact except for
            an occasional wet depression or drainageway that had escaped recent disturbance. Ninety-
            five percent of the qualifying sites and 85 percent of the sites with high potential were
            wetland communities.
                      Most of the sites for high quality natural areas in the Edisto Basin were found in the
            coastal region; the inland areas had very few sites. Over 50 percent of the Edisto Basin's
            qualifying sites were found in the coastal region of the Edisto (main stem) subbasin, primarily
            estuarine wetlands. Twenty-eight qualifying sites were found in the upper portions of the
            main stem; most were bottomland hardwood and Carolina bay communities. The North Fork
            had 11 qualifying sites and the South Fork had 10. Most of these were palustrine wetland
            communities associated with the streams. Only six qualifying sites were found in Four Hole
            Swamp - all were bottomland hardwood communities. Two of the sites in Four Hole
            Swamp were the largest of the qualifying natural areas; one was about 5,000 acres and the
            other, 7,000 acres.
                      It-was rare to find a portion of the landscape where a sizable block of high-quality
            natural area encompassed both lowlands and uplands. There were many intact areas in wet
            lowlands, and a few areas on the ruggedly dissected uplands. Usually the uplands were
            cleared (or once were cleared and are now in pines) to the edge of the swampy bottomland.
            There was only one area where a large block of intact bottomland adjoined a large block of
            intactupland; thiswas northwest of Pringletown where several hundreds of acresof unfarmed
            upland borders Four Hole Swamp and supports significant flatwoods. Other than this site,
            there are no large potential preserves that span the full local range of natural diversity from
            the drainage divides to the streamside.
                      The Basin has extensive tracts of bottomland forest and swamp along the length of
            the Edisto River and its tributaries. Much of the forest is mature (40 to 80 years old). Few
            stands of old trees were identified in the survey. The condition of most of the forest is the
            result of a long history of timbering disturbances; much of the cutting was selective in the
            past, but now it is predominantly clearcutting.
                      On the uplands, few high-quality xeric and subxeric pine forests were found owing
            to a long history of fire suppression.
                      During the survey, no thorough examination was given to the aquatic habitats of the
            streams other than to look at the water and the aquatic plants. The overall impression was
            that the Edisto and its tributaries generally had good water quality. Black Creek, a tributary
            of the North Fork Edisto River in Lexington County, in particular seemed to have a unique
            aquatic habitat with very clear water and an abundance and diversity of aquatic macrophytes.







                                                                                     ASSESSING CHANGE IN THE EDISTo RIVER BASIN





                                                  EDISTO RIVER BASIN
                                     NATURAL AREA INVENTORY





                                  "'j -4"













                                                                                                               x"


                                                  Current Status

                                                          Qualifying

                                                          Candidate









                South Carolina Water Resources Comrnission
                Natural Resources Decision Support System
                Cokrrbkk South Carolina









          Figure 5-3. Locations of natural areas found in the Edisto River Basin, 1992.







                                                BIOLOGICAL DIVERSITY










                                                        Natural Area luventory


                                                                       North Fork Sub-Basin

























                                  COMMUNITY TYPE
                                  BOTTOMLAND HARDWOODS

                                  SANDHILLS PALUSTRINE COMPLEX

                                  ISOLATED FRESHWATER WETLANDS

                                  CAROLINA BAY COMPLEX

                                  DRY SANDHILL SCRUB














                           c    -1 @ c.













             Figure 5-4. Locations of natural areas, by community type, found in the North Fork subbasin of the Edisto River Basin, 1992.







                                                                              ASSESSING CHANGE IN THE EDISTo RIVER BASIN










                                                         Natural Area Inventory


                                                                       South Fork Sub-Basin


























                   COMMUNITY TYPE
                   BoTroMLAND HARDWOODS

                   SANDHILLS PALUSTRINE COMPLEX

                   ISOLATED FRESHWATER WETLANDS

                   CAROLINA BAY COMPLEX

                   DRY SANDHILL SCRUB











              1@ c.l.".. .1.1 .....















         Figure 5-5. Locations of natural areas, by community type, found in the South Fork subbasin of the Edisto River Basin, 1992.







                                                                                BIOLOGICAL DIVERSITY



                                                                                                                                                                                                                     7






                                                                      NATURAL AREA INVENTORY


                                                                                                                                       Four Hole Sub-Basin





                                                                                                                                                                                         F- Hd, S,b B,,,,

























                                                      COMMUNITY TYPE

                                                      BO'I7TOMLAND HARDWOODS

                                                      PINE FLATWOODS COMPLEX

                                                      ISOLATED FRESHWATER WETLANDS

                                                      CAROLINA BAY COMPLEX















                                              N.t  .1 R1-1 11, D11. 1, 1. S.pp., t Sy@t
                                              C.1 - 1, S11t h C11 11 1 11













                    Figure 5-6. Locations of natural areas, by community type, found in the Four Hole Swamp subbasin of the Edisto River Basin, 1992.






                                                                                            ASSESSING CHANGE IN THE EDISTo RIVER BASIN










                                                                NATURAL AREA INVENTORY



                                                                                   Main Stem Sub-Basin

































                                                COMMUNITYTYPE
                                                MARITIME COMPLEX
                                                130'"01111AND HARDWOODS
                                                SANDMILLS PALUSTRINE COMPLEX
                                            F-1 PINE FLATWOODS COMPLEX
                                                ISOLATEDFRESH ATERWETLANDS
                                                CAROLINA BAY COMPLEX
                                                DRY SANDHILL SC UB
                                            r_1 MISCELLANEOUS
                                                                                                                  4@1



















            Figure 5-7. Locations of natural areas, by community type, found in the main stem subbasin of the Edisto River Basin, 1992.







                                                 BIOLOGICAL DIVERSITY


            Table 5-6. Qualifying and candidate sites of the Natural Area Inventory by community
            complexes, frequency, and total acreage.


            Community Complex                                   Frequency                  Acreage

                      Bottomland Hardwoods                          41                     61,166
                      Carolina Bay Complex                          39                     4,992
                      Dry Sandhill Scrub                            13                     2,202
                      Isolated Freshwater Wetlands                  17                     1,064
                      Maritime Complex                              89                     47,393
                      Miscellaneous                                 15                     1,322
                      Pine Flatwoods Complex                        43                     26,057
                      Sandhills Palustrine Complex                  44                     31,850
                      Total                                         301                    176,045


            Significant Discoveries
            The following review is not comprehensive but mentions the most notable finds of the survey.
                      Bottomland hardwoods and swamp forests - The Edisto (both forks, Four Hole
            Swamp, and the main stem) has thousands of acres of bottomland forests that appear to be
            relatively undisturbed and in good condition. Most of it probably is not exceptional in terms
            of its age and degree of past disturbance, but some stretches of river and swamp appear to have
            exceptional forests. As seen from the air, some sites have many giant old bald cypresses.
            These big cypress trees are probably hollow culls, so they may have been passed over when
            the stands were logged long ago. If this is so, then the forest surrounding the big cypresses
            is probably second-growth.
                      Most of the natural areas in forested bottomlands are adjacent to the streams;
            however, one site on the St. George SW Quadrangle stands out because it is a greater distance
            from the riparian zone. It was an obvious choice on the NAPP photos, and when the area was
            field checked it stood out as a high-quality site.
                      There are not many tracts of obviously old forest; perhaps they are very scarce.
            Some extensive old forests may exist, perhaps in parts of Four Hole Swamp, but this should
            be confirmed through on-site visits or consultations with people. Much of the bottomland
            forest and swamp appears basically uniform, and the forests seen on the ground are not
            especially old; consequently, most of the similar looking forest is similarly mature rather than
            old.
                      Longleaf pine savannas and flatwoods - Several sites seemed to have high
            potential as natural areas. One of the most promising in appearance on NAPP photography
            was just behind the Harleyville High School; later it was learned that it had been clearcut
            within the past several months. It also had heavy invasion by young trees, but it might be
            recoverable over the long term. All examples of such communities should not be dismissed
            simply because no sites could be found in good condition. Another site seen from the air was
            intact longleaf pine managed with fire.
                      Atlantic white cedar swamps - There are extensive white cedar (Chamaecyparis)
            swamps in the Black Creek and South Fork Edisto drainage (southern Lexington County).
            Some of them extend for more than a mile and cover more than 100 acres.
                      Granitic flatrocks - Three flatrocks were found at the extreme northwest end of
            the survey region. These Piedmont communities are actually outside the Edisto drainage
            but are in the quadrangle-based survey region, which extends beyond the Edisto watershed.
                      Hitchcock Woods - This is a large, old, outstanding forest in the sandhills in Aiken
            County just outside of the Edisto drainage. It has been protected for decades. Hitchcock
            Woods was not visited on the ground but was flown over. Nothing else in the sandhills
            compared with it. Such an outstanding natural area helped to put into perspective the many
            marginal areas that were encountered in the survey.
                      Streamhead and Streamsidepocosins - Many pocosins are found along both forks







                                                                             ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                      of the Edisto and in small tributary valleys. The strearnhead pocosins are found at the very
                                                      headwaters of small sandhill streams on seepage slopes. However, other large pocosins are
                                                      found that stretch for a mile or more on slightly elevated flats in floodplains of streams in the
                                                      sandhills; they contain loblolly bay (Gordonia lasianthus) and are floristically similar to bay
                                                      forests (which are not associated with rivers but rather peatland interstrearn flats); therefore,
                                                      these areas are tentatively called strearnside pocosins. The differences between these
                                                      pocosins is unclear but the community is locally common in the sandhills.
                                                                InlandMaritime Shrub Swamps - This was another new community discovered in
                                                      the estuarine areas. It occurs between salt or brackish marshes and uplands or on slightly
                                                      elevated areas within brackish marshes. This community is dominated by red bay (Persea
                                                      palustris), wax myrtle (Myrica cerifera), and marsh cordgrass (Spartina bakeri).
                                                                Pond cypress ponds - Many of these are found in Carolina bays, particularly in
                                                      bays south of Orangeburg. Many appear to be in good condition. They are beautiful and
                                                      exhibit quite a diversity in structure (dwarfed, open stands; tall, dense, productive stands;
                                                      open, grassy areas). These areas have potential for much preservation work and scientific
                                                      study.
                                                                Depression meadows - Many depression meadows are found near the coast,
                                                      including two on the Adams Run Quadrangle that were particularly unique owing to their
                                                      size. Many of the depressions are round and less than an acre, but some are linear and several
                                                      acres. These are not always apparent on the NAPP photos but are easy to spot from a plane.
                                                      There are many more depression meadows than originally anticipated. Another intriguing
                                                      type of depressional wetland was found in the study area. The largest one (a few acres) is
                                                      dominated by Xyris (a graminoid known as yellow-eyed grass) and quite a variety of true
                                                      grasses.
                                                                Other isolated wetlands - The most distinctive of this group are known as "high
                                                      ponds." These probably are the same as any Carolina bay except that they are in the very
                                                      headwaters, they are small, and they often are herb-dominated. There are few high ponds,
                                                      and most have suffered from direct disturbances or degradation from surrounding farming
                                                      practices. Heritage Trust had previously inventoried high ponds. Several found in this survey
                                                      appear to be high-quality sites. A few sites are distinct from typical Carolina bays and high
                                                      ponds because they consist of irregularly shaped depressions or clusters of depressions. The
                                                      most interesting looking site that seems well qualified for preservation is south of Denmark.
                                                                Old cypress stands - Several stands of old cypress were found; one stand has 300-
                                                      year-old bald cypresses. These are located along the Edisto River in the fresh tidewater areas.
                                                                Coastal islands - Otter Island and several of its neighboring islands are outstand-
                                                      ing complexes of maritime communities.

                                                      Recent Land Conversion
                                                      When this survey was conducted (1992) there was less destruction of survey sites than was
                                                      anticipated, since the NAPP photos were taken in 1989. For the most part, the potential natural
                                                      areas had survived this 3 year period. A reason for the high survival rate could be that most of
                                                      the destructible areas were destroyed years ago. Sites that had survived until 1992 were likely
                                                      already deliberately protected or it had not been economically feasible to exploit them.
                                                                Suburban sprawl (mobile homes) was claiming some sandhills sites, especially near
                                                      Columbia; similar sprawl was occurring near Charleston from expensive homesites.
                                                                Some survey sites have suffered severe damage (such as clearing) or minor
                                                      intrusions (such as a new homesite). However, these disturbances have not always eliminated
                                                      an entire survey site. Furthermore, recent disturbance was not necessarily evidence that a
                                                      high-quality natural area had been damaged, because most of the survey sites turned out not
                                                      to meet final qualification standards. Consequently, most of the recent disturbances have
                                                      been to areas that were not especially significant even before the most recent disturbance.
                                                                One of the greatest causes of recent logging was Hurricane Hugo. Many of the
                                                      potential sites suffered heavy blowdown followed by salvage logging. In many instances it
                                                      appeared that people opted to clearcut areas that were wind damaged rather than limiting their
                                                      activities to salvaging windthrows. Almost all of the forested survey sites south of Lake
                                                      Marion were either wiped out by post-hurricane logging or were so badly broken over by the
                                                      storm that they no longer met the survey standards. Other areas with much wind damage







                                                 BIOLOGICAL DIVERSITY


              included Four Hole Swamp and other bottomland areas on the Sandridge, Wadboo Swamp,
              Holly Hill, Harleyville, Ridgeville and Pringletown Quadrangles. The extreme southeast
              part of the survey region (Wadmalaw Island and Johns Island) also received much wind
              damage. If a site was salvage logged, it was judged nonqualifying. If the site looked good
              on the photos and was not salvage logged, it was assessed as high potential or qualifying.
                        One of the most significant land conversions was not necessarily a new one:
              impoundment of headwater streams. The many small, deep., springfed valleys in the sandhills
              are ideal sites for ponds and small lakes. It was rare to find a headwaters stream that had no
              dam, and most have several dams. According to a fisheries biologist at the South Carolina
              Wildlife Department this was having a big impact on the aquatic animals that depend on this
              habitat.
                        Areas logged years ago recovered fairly well. Areas clearcut in recent years were
              removed from consideration as potential natural areas due to the extent of damage,
              particularly soil disturbance in wetland areas, done by the equipment that is now used. Where
              feasible, clearcut areas are often being converted to planted pine forest.


              DISCUSSION AND CONCLUSIONS

              There is a lack of data to support an analysis of trends in species richness and composition
              for the Edisto Basin. The only long-term, systematic data available are for birds - the
              Breeding-Bird Surveys (BBS). The BBS data are available for six routes at intermittent
              periods of time since 1966 and represent birds that may be seen or heard from a road in early
              June. These data show trends for many species that coincide with changes in land use and
              land cover. Other very limited data for fisheries and waterfowl are available and provide
              some informative facts for a better perspective of the Basin. Indicators of biological diversity
              show that much has been lost in the Basin since European settlement; however, substantial
              remnants of high-quality habitat and many rare or sensitive species remain.


              Changes Affecting Bird Species
              Analysis of the Breeding-Bird Surveys suggests that the habitat structure of the Edisto River
              Basin, based on avian habitat preferences, is undergoing change. However, there does not
              appear to be consistent change from forest to field or vice-versa. In some areas, forest-
              dwelling species are increasing, while in other areas they are decreasing. The same trend
              exists for the field-dwelling species, although fewer field species appear to be increasing than
              decreasing. This variability was similarly found by Gosselink and others (1990) in the Pearl
              River Basin. These patterns may indicate that some land is being allowed to grow into forest
              while other land is being cleared.
                        Analysis of land-use data and vegetation cover showed a fair degree of correlation
              with bird trends. The Wagener and New Holland routes had more significant increases in the
              populations of forest species than the other routes; this was consistent with increased forest
              along these routes. The Johns Island route showed the greatest losses in forest species and
              these losses corresponded with the greatest losses in forest cover. The Walterboro route had
              a large number of forest species that decreased significantly; however, the ratio of forest to
              cleared land along the route appeared to be about the same at the beginning and at the end of
              the survey period (1970 to 1991). Declines in forest species at Walterboro may be related to
              the conversion of land from natural forest to the monoculture pine plantation forests that
              currently dominate land cover along this route. These findings are consistent with opinions
              of biologists at the South Carolina Wildlife and Marine Resources Department who believe
              that the greatest threats to bird diversity in the Edisto region are the loss of longleaf pine
              forests; loss of hedgerows and edges from small agricultural fields; replacement of natural
              forests with pine plantations; and short timber rotations and excessive- clearcutting in
              bottomlands (Cely 1992). Studies in Louisiana and Florida found bird species abundance and
              diversity to be significantly less in stands of even-aged pine monoculture forest compared to
              natural forest stands (Harris and others 1974, Noble and Hamilton 1975).
                        Wagener and New Holland were the only routes where more species were signifi-
              cantly increasing rather than decreasing; elsewhere the overall numbers of species declined.







                                                                           ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                     Johns Island and Walterboro showed the greatest losses in the numbers of species, with more
                                                     losses than increases for each of the three categories of habitat preference. No species had
                                                     plummeting populations or appeared threatened with local extinction. However, those listed
                                                     previously (in "Results") as experiencing definite population declines should be paid extra
                                                     attention. As additional years of BBS data are collected, general trends will become even
                                                     more evident. A reasonable strategy may be to perform regression analyses and look for
                                                     trends on all data every five years.
                                                              Nearly half (43 percent) of the bird species examined in the Edisto Basin BBS
                                                     analysis are neotropical migrants, meaning they breed in North America but migrate to
                                                     regions south of the United States in the winter. Populations for many of these species have
                                                     experienced continued declines, and in some cases severe declines, throughout North
                                                     America since the late 1940s (Finch 1991). Two factors are believed to be causing population
                                                     declines for neotropical migrants: forest fragmentation on their breeding grounds in North
                                                     America; and deforestation of their wintering habitats in Central and South America (Finch
                                                     1991). Overall, the neotropical migrant species analyzed in Edisto Basin show no consistent
                                                     pattern or direction of change. These migrant species were evenly distributed among three
                                                     broad groupings - those with populations that appear to be increasing, decreasing, or
                                                     remaining relatively unchanged. Four of the 10 species that show definite population
                                                     declines in the Edisto Basin are neotropical migrants.
                                                              The analysis of bird trends affected by land use changes discussed in this section
                                                     represents possible explanations for changing trends in bird species richness; however, many
                                                     factors may be affecting these changes. Note that the bird data analyzed for the Edisto Basin
                                                     are limited. A greater number of survey routes (a larger sample) is needed to make definitive
                                                     statements relating bird trends with land cover change. One problem with the BBS data for
                                                     the Edisto Basin is years of missing data. For example, the Wagener route has an 8-year gap
                                                     in data. Because populations tend to show wide year-to-year fluctuations, such a gap
                                                     weakens the ability to analyze general trends. Those routes with the longest unbroken data
                                                     sets are therefore the most reliable. The inevitable year-to-year variation may be due to
                                                     factors such as weather or breeding status of the birds (Droege 1990).
                                                              A further problem with BBS data arises with flocking and colonial birds (Droege
                                                     1990). Some of the species showing the most variation in this analysis (White Ibis, Little Blue
                                                     Heron, Turkey Vulture) tend to occur in groups, and if a group is not near a survey point, no
                                                     birds will be counted there. Additional years of data will significantly help in deciphering
                                                     fluctuations in trends for these species. Also, the BBS data represent birds that may be seen
                                                     or heard from a road in the spring; birds that prefer forest-interior habitats were not sampled
                                                     as effectively as those that prefer edges.
                                                              Birds are just one class of organisms sensitive to changes in land use and habitat
                                                     quality. They do not reflect all aspects of ecological change. Ideally, other measures of
                                                     species abundance and diversity, for other vertebrates, invertebrates, and plants, should be
                                                     used in land management decisions. However, more species populations are decreasing than
                                                     increasing at four of the six BBS routes analyzed. Two routes are showing declines for 30
                                                     to 40 percent of the species over the last 20 years, which is markedly different compared to
                                                     the average of 14 percent among the other four routes. The population declines in these two
                                                     areas may indicate ecological instability, specifically in the Edisto (main stem) and Four Hole
                                                     Swamp subbasins (the lower half of the Basin).


                                                     Indicator Species and Threatened and Endangered Species
                                                     The large, wide-ranging mammals native to the Edisto River Basin - bears, cougars, and
                                                     wolves - have been extirpated. There was recently a documented sighting of a bear in Aiken
                                                     County, but no viable population exists in the Basin. This sighting may indicate that habitat
                                                     within the Edisto Basin is capable of supporting the Black Bear. Stable populations of
          WMWM@

















                                                     medium-sized carnivores with smaller range requirements, such as bobcats and river otters,
                                                     are found in the Edisto Basin, and the apparent trends of increasing and stable populations
                                                     for most of the raptors in the Basin are evidence that the region provides stable food web
                                                     support for these top-level carnivores.
                                                              The presence of nationally threatened and endangered species in the Edisto River
                                                     Basin can be a positive sign of ecological integrity - showing that certain areas serve as a







                                                 BIOLOGICAL DIVERSITY


            refuge for sensitive or specialized species. The few Red-cockaded Woodpeckers found in
            the Basin require mature pine forest for nesting habitat. Generally, these birds have declined
            due to the loss of mature pine stands resulting in part from more intensive planted-pine forest
            management with shorter rotations for harvests. Populations of the Southern Bald Eagle in
            the ACE Basin survived the effects of widespread chlorinated pesticide use during the 1950s
            and 1960s.     Biologists believe that the remote character and extensive system of tidal
            impoundments in this area protected the eagle nesting and feeding habitats from disturbance
            and contamination. The Loggerhead Turtle has continued to nest on the Basin's coastal
            beaches because of their relatively undeveloped character. The Shortnosed Sturgeon, which
            is believed to be a very sensitive species - unable to adapt well if its habitat is destroyed or
            polluted, has maintained a spawning population in the Edisto River. During spring floods,
            Shortnosed Sturgeon are believed to swim as far upstream as Orangeburg to spawn among
            the roots and tree trunks of swamps and oxbow lakes. This suggests that the aquatic habitat
            of the Edisto River is relatively intact and uncontaminated.


            Natural Areas in the I.Andscape
            The Natural Area Inventory revealed that the relatively undisturbed, high quality natural
            communities that remained in the Edisto River Basin were almost all wetlands, and the major
            portion of these were found in the coastal region. Most of the Edisto landscape has a long
            history of intensive land management for agriculture and forest products; therefore, very few
            upland communities of any size remained intact.
                      Much of the Basin's bottomland forests were mature (40 to 80 years old), but not
            old. Very few areas of old forest were found in the Basin, with the exception of a few old
            cypress stands in the main stem and one in Four Hole Swamp subbasin. Most of the natural
            areas in bottomlands were found along the streams. Intensive land use activities, particularly
            agriculture and pine plantations, have encroached on much of the bottomlands in the Basin
            and narrowed their natural extent. Despite these activities the largest natural areas of the
            Edisto Basin were found in the wetland communities of the bottomlands. Most of these areas
            were part of the Basin's larger forest patches, the cores of which were primarily forested
            wetland. Owing to the wide extent of intensively managed uplands, these wetland natural
            areas are likely to be very critical for maintaining wildlife diversity throughout much of the
            Edisto Basin.
                      Forest stands with older, larger trees are thought to support more wildlife species
            than those with younger and smaller trees (O'Neil and others 1991). The reasons for this are
            increased surface area of bole, branches, and foliage; increased production of leaves, twigs,
            branches, fruits, and seeds; and increased probability of decay leading to cavities and, further,
            to cavities of different sizes. Because much of the upland forests were intensely managed
            planted pine, the overall age of the Basin's forests was relatively young. Most (over 70
            percent) of the Basin's older forest stands (stands greater than 80 years old) were bottomland
            hardwoods, according to the U.S. Forest Service (1991) Forest Survey data for the Edisto
            Basin. These stands, however, amounted to only about 4 percent of all the forestland in the
            Basin (about 32,000 acres). Twenty-four percent of all forestland in the Basin had mature
            stands (stands from 40 to 80 years old). More than half (54 percent) of these mature stands
            were bottomland hardwoods. These data promote the relative importance of the Basin's
            bottornland hardwood forests, particularly the associated natural areas, for the maintenance
                                                                                                                  IMIWM















            of species diversity in the Edisto Basin.
                      The greatest number and diversity of qualifying sites was concentrated in the main
            stem subbasin, which spans the most ecologically diverse portion of the Basin. The main
            stem had nearly 80 percent of the qualifying sites, sites that represented flatwoods, Carolina
            bays, bottomland hardwoods, a full array of intertidal wetlands, and barrier island commu-
            nities. Far fewer qualifying sites and fewer community types were found in the more inland
            subbasins.







                                                                                ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                        Ecological Integrity Based on Indicators of
                                                        Biological Diversity
                                                        Several indices of biotic diversity that can be used to assess the ecological integrity of a region
                                                        like the Edisto River Basin were suggested by Gosselink and Lee (1989), and have been
                                                        addressed in this chapter. Indices of biotic diversity have included the extent and distribution
                                                        of old-growth stands of forest, and in this study, high-quality natural areas; the presence of
                                                        threatened and endangered species; the presence of indicator species (such as top carnivores);
                                                        and historical changes in species richness, in this study primarily for birds. Ecological
                                                        integrity, as it relates to the quality of an area for biota (animals and plants), also depends upon
                                                        the structure of the landscape; that is, the mix and pattern of land uses and land cover types
                                                        affecting the quality of natural habitats of the region.
                                                                  The structure of the landscape, in terms of the remaining natural cover - its
                                                        distribution and pattern - is important for maintaining populations of indigenous wildlife
                                                        species. Discussion of landscape structural characteristics is therefore brought forward from
                                                        Chapter 2 which addresses land use and land cover in the Edisto River Basin. Reductions in
                                                        area of forest and natural cover lead to reductions in the number of species. Forest pattern
                                                        - the sizes of forest patches and the connections between patches in a landscape - is
                                                        considered a key index in the "island" (or isolation) affect of biogeography (Gosselink and
                                                        Lee 1989). As a forested landscape becomes fragmented, species richness often increases
                                                        due to the invasion of alien and opportunistic species; but this usually occurs to the detriment
                                                        of native species that require large forest reserves. To support favorable habitats for many
                                                        indigenous species, large interconnected forest patches should be maintained in a landscape.
                                                                  This discussion emphasizes "forests" because it is in reference, generally, to rapidly
                                                        diminishing natural forested landscapes. However, it is important to note that maintenance
                                                        of a variety of natural habitats, particularly unique or rare natural communities, is also
                                                        necessary to support many native species. Pine savannas and flatwoods, shrub pocosins, and
                                                        a variety of marshlands, meadows, and grasslands are natural habitats of the Edisto Basin and
                                                        should also be maintained in the landscape. Conserving landscape ecological integrity
                                                        involves maintaining and restoring a mix of natural communities in a regional pattern that can
                                                        support viable indigenous plant and animal populations in the context of traditional land uses.
                                                        Hunter (1990) suggests that the interspersion or juxtaposition of different ecosystems and
                                                        forest stands of varying sizes, ages, and species compositions will provide the greatest
                                                        biological diversity in a forested landscape; and because some of the most threatened species
                                                        require very large forested habitats, further forest fragmentation should be avoided.
                                                                  In summary, based on the indices of biotic diversity and the landscape structural
                                                        characteristics that relate to maintenance and support of wildlife species, the Edisto River
                                                        Basin could be judged to have a moderate level of ecological integrity. No native far-ranging
                                                        animals, such as bears or cougars, still inhabit the Basin; but bobcats and otters are resident,
                                                        and most of the region's raptor populations are stable or increasing. The Breeding-Bird
                                                        Surveys indicate that several species of birds have declining populations and that the total
                                                        number of species is declining in several areas. In terms of landscape structure, the Edisto
                                                        River Basin is mostly forested, about 56 percent, with an additional 6 percent in nonforested
                                                        wetlands. The remaining areas are primarily agricultural with very little urban or built-up
                                                        land. Most of the Basin's stream-edge habitats, or riparian zones, are intact with natural
                                                        vegetative cover on 75 to 85 percent of these areas. Healthy riparian ecosystems are key
                                                        components in maintaining the wildlife diversity of forested landscapes (Hunter 1990).
                                                                  About 70 percent of the Basin's total forest is in large patches (patches greater than
                                                        50,000 acres). These forest patches tend to be linear and extend through most of the landscape
                                                        via the bottomlands of the streams connecting most of the upland and wetland forests into a
                                                        continuous, irregular, and dendritic (branching) pattern of forested corridors. Large forest
                                                        patches distributed in an irregular linear pattern often do not provide an abundance of isolated
                                                        interior-forest habitat that is required by a number of sensitive species (O'Neil and others
                                                        1991). In addition, many roads and utility corridors crisscross the forest patches creating
                                                        more fragmentation than is demonstrated by the patch analysis (presented in Chapter 2).
                                                        Nevertheless, the Basin's forest pattern of extensive regional connectivity and interspersion
                                                        of different habitat types is probably very supportive of many indigenous wildlife species,
                                                        though isolated interior-forest habitats are rare.







                                                 BIOLOGICAL DIVERSITY


                      As discussed in Chapter 2, where maintaining biological diversity is a goal,
             silviculture practices must enrich forest structure (Sharitz and others 1992). At the scale of
             individual forest stands, important features of forest structure include the presence of native
             herbaceous and shrub plants, complex vertical structure in the forest canopy, some large
             living trees, standing dead snags, and large downed woody debris (Van Lear 1991, Seymour
             and Hunter 1992). Pine plantations, which represent one-third of the Basin's forests,
             typically lack the multilayered canopy, diverse tree sizes, abundant snags and fallen trees, and
             the high species diversity that exists in natural communities (Van Lear 1991). After canopy
             closure, dense pine plantations may furnish little for wildlife other than escape or thermal
             cover (Thill 1990). Plantation forests, however, can be established and maintained in ways
             that will improve their diversity. They can support a variety of plant and animal species
             depending upon how the stands are managed. Different management schemes for harvesting,
             site preparation, planting, and intermediate stand treatments will each have different effects
             on the quality of wildlife habitats in pine plantation stands.
                      The landscape scale, as suggested by Hunter (1990), remains the level at which the
             fate of wildlife species is ultimately determined and the interspersion of various types of
             forest habitats and ecosystems will provide the greatest biological diversity in a forested
             landscape. Thill (1990) recommends that the habitats which are lacking in the pine
             plantations may best be provided through retention and management of native riparian forests
             or upland hardwoods interspersed within the plantations. In the Edisto Basin landscape,
             some pine plantation stands are quite extensive but generally they remain interspersed with
             other types of habitats - primarily upland and wetland forests and agricultural lands.
             Therefore, existing habitat conditions at the landscape scale are probably favorable for most
             species with the exception of those requiring isolated forest interiors, and old forest habitats,
             as noted previously.
                       As discussed in Chapter 2, the hydric soils analysis indicates that a great potential
             exists throughout the Basin for restoration of many sights to native wetland forest commu-
             nities. The restoration of such sights is one option for providing increased dispersion of
             habitats within and adjacent to the existing plantations. Also discussed in Chapter 2 was the
             age structure of the Basin's forests. On balance, the forests are relatively young in age and,
             therefore, provide limited habitat for species that require late successional forests. Longer
             rotations for timber harvests, particularly in the non-plantation forests, could balance the
             forest age distribution and enhance the potential for increased biological diversity in the
             landscape of the Edisto Basin. Forest management principles that enhance biological
             diversity in forest stands and in forested landscapes that support intensive silvicultural
             activities - landscapes such as the Edisto River Basin - are discussed by Hunter (1990),
             Thill (1990), Seymour and Hunter (1992), Sharitz and others (1992), and Van Lear (1991).







                                                                          ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                    REFERENCES


                                                    Bauman, David. 1992. Personal Communication. South Carolina Wildlife And Marine
                                                         Resources Department.

                                                    Bent, A.C. 1963. LifeHistories offorthAmerican Wood Warblers. Dover Publications, Inc.
                                                         New York. 734 p.

                                                    Cely, John. 1992. Personal Communication. South Carolina Wildlife and Marine Resources
                                                         Department.

                                                    Crochet, D.W. 1975. Commercial and anadromousfishery, Waccamaw and Pee Dee Rivers.
                                                         Annual Progress Report, AFC-5-2, for period July 1, 1974 - June 30, 1975. South
                                                         Carolina Wildlife and Marine Resources Department.

                                                    Droege, S. and J.R. Sauer. 1990. North American Breeding-Bird Survey Annual Summary,
                                                         1989. U.S. Fish and Wildlife Service, Biological Report 90(8). 22 p.

                                                    Droege, S. 1990. The North American Breeding-Bird Survey. In: Sauer, J.R., and S. Droege,
                                                         eds. Survey designs andstatisticalmethodsfor the estimation ofavianpopulation trends.
                                                         U.S. Fish and Wildlife Service, Biological Report 90(l). 166 p.

                                                    Ehrlich, P.R., D.S. Dobkin, and D. Wheye. 1988. The Birder's Handbook: A Field Guide to
                                                         the Natural History offorth American Birds. Simon and Schuster, Inc. New York.

                                                    Finch, D.M. 1991. Population ecology, habitat requirements, and conservation ofneotropical
                                                         migratory birds. Gen. Tech. Rep. RM-205. U.S. Department of Agricultur6, Forest
                                                         Service, Rocky Mountain Forest and Range Experiment Station, Ft. Collins, Colorado.

                                                    Gosselink, J.G. and L.C. Lee. 1989. Cumulative impact assessment in bottomland hardwood
                                                         forests. Wetlands: TheJournal ofthe Society of WetlandScientists, Vol. 9, Special Issue.

                                                    Gosselink, J.G., C.E. Sasser, L.A. Creasman, S.C. Hamilton, E.M. Swenson, and G.P.
                                                         Shaffer.1990. Cumulative ImpactAssessment in the PearlRiverBasin, Mississippi and
                                                         Louisiana. U.S. Environmental Protection Agency Report 90(3).

                                                    Harris, L.D., L.D. White, J.E. Johnson, and D.G. Milchunas. 1974. Impact of forest
                                                         plantations on north Florida wildlife and habitat. In: Proceedings of the 28th Annual
                                                         Southeastern Association of Game and Fish Commissions 28:659-657.

                                                    Hunter, M.L., Jr. 1990. Wildlife, forests, and forestry: principles of managing forests for
                                                         biological diversity. Regents/Prentice Hall, Englewood Cliffs, New Jersey. 370 p.

                                                    Langley, A.K. Jr. and D.J. Shure. 1980. The effects of loblolly pine plantations on small
                                                         mammal populations. American Midland Naturalist Vol. 103 (1): 59-65.

                                                    Noble, R.E. and R.B. Hamilton. 1975. Bird populations in even-aged loblolly pine forests
                                                         of southeastern Louisiana. In: Proceedings ofthe 29thAnnualSoutheasternAssociation
                                                         of Game and Fish Commissions 29: 441-450.

                                                    O'Neil, L. J., T.M. Pullen, Jr., R.L. Schroeder. 1991. A wildlife community habitat evaluation
                                                         model for bottomland hardwood forests in the southeastern United States, Draft
                                                         Biological Report dated 6/17/91. U.S. Department of the Interior, Fish and Wildlife
                                                         Service, Research and Development, Washington D.C.

                                                    Post, W., and S.A. Gauthreaux. 1989. Status and Distribution ofSouth Carolina Birds. The
                                                         Charleston Museum, Charleston, S.C.






                                                                                                                       F.
                                              BIOLOGICAL DIVERSITY




            Rulifson, R.A. 1982. Status of Anadromous Fishes in the Southeastern U.S. Estuaries. In:
                Estuarine Comparisons: Proceedings of the Sixth Biennial International Estuarine
                Research Conference, Gleneden Beach, Oregon, November 1-6, 198 1. Academic Press
                Inc. New York.


            Sally, A.S. 1898. The History of Orangeburg County South Carolina, from its First
                Settlement to the Close of the Revolutionary War. Revised in 1969 by Regional
                Publishing Company. Baltimore, Md.

            Seymour, R.S. and M.L. Hunter, Jr. 1992. New forestry in eastern spruce-fir forests:
                principles and applications to Maine. Miscellaneous Publication 716, Maine Agricul-
                tural Experiment Station, University of Maine, Orono.

            Sharitz, R.A., L.R. Boring, D.H. Van Lear, and J.E. Pinder 111. 1992. Integrating ecological
                concepts with natural resource mangement of southern forests. EcologicalApplications
                2(3): 226-237.

            Strange, T. 1990. Waterfowl Status Report 1988-1989. South Carolina Wildlife and Marine
                Resources Department.

            Thill, R.E. 1990. Manageing southern pine plantations for wildlife. Proceedings oftheXIXth
                IUFRO World Congress, Vol. 1: 58-68.

            Ulrich, G., N. Chipley, J.W. McCord, and D. Cupka. Undated -1978. Development offishery
                management plans for selected anadromous fishes in South Carolina and Georgia.
                Special Scientific Report Number 14. South Carolina Wildlife and Marine Resources
                Department and Contribution Number 31 of the Coastal Resources Division, Georgia
                Department of Natural Resources.

            U.S. Department of Agriculture. 1982. Fish and Wildlife Resources of South Carolina.
                Published as part of a South Carolina Statewide Cooperative River Basin Study.

            U.S. Forest Service. 1991. Forest Survey statistics for the Edisto River Basin from the 6th
                forest survey. Prepared by: Southeastern Forest Experiment Station, Forest Inventory
                and Analysis, Asheville, N.C.

            Van Lear, D.H. 1991. Integrating structural, compositional, and functi  'onal considerations
                into forest ecosystem management. In: Ecosystem Management in a Dynamic Society,
                Proceedings of a conference held by the Department offorestry and Natural Resources,
                Purdue University, West Lafayette, Indiana.

            Wade, W.C. 1971. Commercial Anadromous Fishery, Edisto River, South Carolina. South
                Carolina Wildlife Resources Department.

            Walburg, C.H. 1956. Commercial and Sport Shad Fisheries of the Edisto River South
                Carolina, 1955. U.S. Department of the Interior, Fish and Wildlife Service. Special
                Scientific Report - Fisheries No. 187.

            White, J. and C. Aulbach-Smith. 1993. Edisto RiverBasin NaturalArea Inventory: Survey
                Standards and Guidelines. Report for the Natural Resources Decision Support System
                Project prepared by the Nature Conservancy, Chapel Hill, N.C. and by the South
                Carolina Water Resources Commission, Columbia, South Carolina, May 1993 edition.
                110 P.







                                                                         ASSESSING CHANGE IN THE EDISTo RIVER BASIN




           APPENDIX I

               Hydric soils* used to assess changes in native wetland vegetation of the Edisto River Basin.
               Source: U.S. Soil Conservation Service, County Hydric Soils Lists.


               Argent loam                            Bayboro sandy clay loam                     Bayboro loam
               Bayboro clay loam                      Beaches                                     Bethera clay loam
               Bethera loam                           Bibb sandy loam                             Bibb loamy sand
               Bladen fine sandy loam                 Bohicket association                        Brookman clay loam
               Byars loam                             Cape Fear loam                              Capers silty clay loam
               Capers association                     Chastain association                        Chastain soils
               Chenneby silty clay loam               Chenneby soils                              Coxville fine sandy loam
               Coxville loam                          Coxville sandy loam                         Daleville silt loam
               Dasher mucky peat                      Dawhoo-Rutlege loamy fine sand              Dunbar sandy loam
               Dunbar fine sandy loam                 Elloree loamy fine sand                     Elloree loamy sand
               Enoree soils                           Grady loam                                  Grady loam, thin surface
               Grady sandy loam                       Grifton fine sandy loam                     Handsboro muck
               Haplaquents, loamy                     Hobcaw fine sandy loam                      Johnston sandy loam
               Johnston soils                         Johnston mucky loam                         Leaf clay loam, thin surface
               Leaf loamy sand, sandy substratum      Leon sand                                   Leon fine sand
               Levy mucky silty clay loam             Lumbee loamy sand                           Lumbee fine sandy loam
               Lumbee sandy loam                      Lynn Haven loamy sand                       Lynn Haven fine sand
               McColl loam                            McColl sandy loam                           Meggett loam
               Meggett clay loam                      Mixed wet alluvial land                     Mixed alluvial land
               Mouzon fine sandy loam                 Myatt sandy loam                            Myatt loam
               Myatt loamy sand                       Nakina fine sandy loam                      Ogeechee loamy fine sand
               Ogeechee sandy loam                    Ogeechee fine sandy loam                    Okenee loam
               Osier loamy fine sand                  Osier loamy sand                            Osier fine sand
               Paleaquults, sandy                     Pamlico muck                                Pantego sandy loam
               Pantego fine sandy loam                Paxville fine sandy loam                    Pelham loamy sand
               Pelham sand                            Pickney loamy fine sand                     Pickney loamy sand
               Plummer loamy sand                     Plummer loamy fine sand                     Plummer-Rutlege loamy sand
               Portsmouth fine sandy loam             Portsmouth loam                             Portsmouth sandy loam
               Pungo muck                             Rains fine sandy loam                       Rains loamy sand
               Rains sandy loam                       Rembert loam                                Rutlege loamy sand
               Rutlege loamy fine sand                Rutlege-Pamlico complex                     Santee clay loam
               Santee loam                            St. Johns fine sand                         Stono fine sandy loam
               Swamp                                  Tawcaw association                          Tidal marsh, soft
               Tidal marsh, firm                      Torhunta-Osier association                  Wadmalaw fine sandy loam
               Wadmalaw variant loamy sand            Wehadkee silt loam                          Williman loamy fine sand
               Williman sand                          Yonges loamy fine sand

                 This list was derived from 1989 Hydric Soils Lists for the 12 counties of the Edisto Basin and includes only the soil "map unit
                 names" determined to have a "hydric soil component" for the "whole map unit."







                                                 APPENDICES




            APPENDIX 11

                    Bird species, preferred habitat, and results of regression over time for six Breeding-Bird Survey routes, Edisto River Basin,
                    South Carolina.


                AOU
                No.      SPECIES                                HABITAT         R1        R101    R5       R8      R9       R13

                  540    RING-BILLED GULL                       W
                  580    LAUGHING GULL                          W               +
                  650    ROYALTERN                              W               NS
                1260     BROWN PELICAN                          W               NS
                1440     WOOD DUCK                              W                                 NS       NS
                1840     WHITE IBIS                             W/FE            NS                NS                        NS
                1860     GLOSSY IBIS                            W               NS
                1880     WOOD STORK                             W/FE            NS                                          +
                1940     GREAT BLUE HERON                       W                                                           NS
                1960     GREAT EGRET                            W               NS                NS               NS       NS
                1970     SNOWY EGRET                            W               NS
                1990     TRICOLORED HERON                       W               NS
                2000     LITTLE BLUE HERON                      W                                                           NS
                2001     CATTLE EGRET                           FD/W            NS        NS      NS               NS       NS
                2010     GREEN-BACKED HERON                     W               NS                +*               NS
                2110     CLAPPER RAIL                           M               NS
                2730     KILLDEER                               FD/M                              NS       NS      NS       +
                2890     NORTHERN BOBWHITE                      FD              NS        NS               NS
                3131     ROCK DOVE                              FD              NS                +                NS       NS
                3160     MOURNING DOVE                          FEjFD           NS        NS      NS       NS      NS       NS
                3200     COMMON GROUND DOVE                     FE/FD
                3250     TURKEY VULTURE                         FE/FD                     NS      NS       NS      NS       NS
                3260     BLACK VULTURE                          F/FOC                     NS                       NS
                3370     RED-TAILED HAWK                        FE/FD                                      NS      NS       NS
                3390     RED-SHOULDERED HAWK                    S/F                                                         NS
                3680     BARRED OWL                             FCC                       NS      NS                        NS
                3870     YELLOW-BILLED CUCKOO                   FCC             NS        NS               NS      NS       NS
                3930     HAIRY WOODPECKER                       F                                 NS               NS       NS
                3940     DOWNY WOODPECKER                       F                         NS      NS       NS      NS       +*
                4050     PILEATED WOODPECKER                    FCC             NS        NS      NS       NS      NS       NS
                4060     RED-HEADED WOODPECKER                  FOC                               NS       NS               NS
                4090     RED-BELLIED WOODPECKER                 FOC                       NS      NS       NS               NS
                4120     YELLOW-SHAFTED FLICKER                 FE/FD           NS        +       NS       NS      NS       -
                4160     CHUCK-WILL'S WIDOW                     FCC             NS                NS       +*      NS       -
                4170     WHIP-POOR-WILL                         FOC                                                +
                4200     COMMON NIGHTHAWK                       FOC/FE          NS                         NS      NS       -
                4230     CHIMNEY SWIFT                          F               NS        -       NS       NS      NS       -
                4280     RUBY-THROATED HUMMINGBIRD              FOC                       NS      NS       NS      NS       NS
                4440     EASTERN KINGBIRD                       FE/FD                             NS       +*      +*       NS
                4520     GREAT-CRESTED FLYCATCHER               FOC                       NS      +        NS      NS       NS
                4560     EASTERN PHOEBE                         FE/F                                       NS      NS
                4610     EASTERN WOOD-PEWEE                     FOC                       NS      NS       +*      +*       NS
                4650     ACADIAN FLYCATCHER                     FCC                       NS      NS       NS      NS       NS
                4740     HORNED LARK                            FD                                         NS
                4770     BLUEJAY                                F/FE                      NS               NS
                4880     AMERICAN CROW                          F/FE                      NS      NS       +*      NS       NS
                4900     FISH CROW                              F/FE            NS        NS      NS       NS      +        NS
                4930     EUROPEAN STARLING                      FOC/F/FD        NS                NS                        NS
                4950     BROWN-HEADED COWBIRD                   FOC/FE/FD       NS        NS      NS       +*      +        NS
                4980     RED-WINGED BLACKBIRD                   FD/FOC/S
                5010     EASTERN MEADOWLARK                     FD                                                 NS
                5060     ORCHARD ORIOLE                         FOC/FE                    NS      +*       NS      NS
                5110     COMMON GRACKLE                         FOC/FE/FD       NS        NS      NS       +*







                                                                 ASSESSING CHANGE IN THE EDISTo RIVER BASIN






            AOU
            No.      SPECIES                              HABITAT          Rl     R101    R5        R8        R9     R13


            5130     BOAT-TAILED GRACKLE                  FD/M             NS
            5290     AMERICAN GOLDFINCH                   FD/FOC                                    NS        NS
            5500     SEASIDE SPARROW                      M                NS
            5600     CHIPPING SPARROW                     FD/FE/FOC        NS      NS       NS      +         NS
            5630     FIELD SPARROW                        FD                                        +         NS
            5750     BACHMAN'S SPARROW                    FD                       NS               +         +
            5870     RUFOUS-SIDED TOWHEE                  FOC/FE                            NS      -         NS     NS
            5930     NORTHERN CARDINAL                    FE/FOC/FC                NS               NS        NS
            5970     BLUE GROSBEAK                        FD/FE                             NS      +*        NS     NS
            5980     INDIGO BUNTING                       FD/FE                    NS       NS      NS        NS     NS
            6010     PAINTED BUNTING                      FD/FE
            6100     SUMMER TANAGER                       F                        NS       NS      NS        +      +
            6110     PURPLE MARTIN                        FOC/FD                            NS      NS        -      NS
            6130     BARN SWALLOW                         FD/FE            NS               +*      +*        +*
            6140     TREE SWALLOW                         FD/FE            +
            6170     NORTHERN ROUGH-WINGED
                       SWALLOW                                             FD                                 NS     NS
            6220     LOGGERHEAD SHRIKE                    FE/FD            NS               NS      NS        NS     NS
            6240     RED-EYED VIREO                       FCC                      NS       NS      NS        NS     -
            6280     YELLOW-THROATED VIREO                FOC                      NS               NS        NS     NS
            6310     WHITE-EYED VIREO                     FOC              NS      NS       NS      NS        NS     +*
            6360     BLACK-AND-WHITE WARBLER              FCC                                       NS
            6370     PROTHONOTARY WARBLER                 F/S                               NS      NS        NS     NS
            6480     NORTHERN PARULA                      FOC              NS      -                NS
            6630     YELLOW-THROATED WARBLER              FE               NS      NS       NS      NS        NS
            6710     PINE WARBLER                         FOC              NS      NS       NS      NS        +*     +*
            6730     PRAIRIE WARBLER                      FOC/FE                                    NS        NS     NS
            6760     LOUISIANA WATERTHRUSH                F                                                   NS
            6770     KENTUCKY WARBLER                     FOC                      NS               NS        NS     NS
            6810     COMMON YELLOWTHROAT                  FOC/FE/M                 NS               NS        NS
            6830     YELLOW-BREASTED CHAT                 FOC/FD           NS      NS       NS      +*        NS     NS
            6840     HOODED WARBLER                       FOC                               NS      NS        NS     +*
            6882     HOUSE SPARROW                        FD/FE            +*               +*
            7030     NORTHERN MOCKINGBIRD                 FE                       NS       NS                NS     NS
            7040     GRAY CATBIRD                         FOC                      NS               NS        NS
            7050     BROWN THRASHER                       F                        NS       NS      NS        NS     -
            7180     CAROLINA WREN                        F                        NS       +       +         +*     NS
            7250     MARSH WREN                           M
            7270     WHITE-BREASTED NUTHATCH              F                                         NS               NS
            7290     BROWN-HEADED NUTHATCH                F                        NS       NS      NS        NS     NS
            7310     EASTERN TUFTED TITMOUSE              F                NS      NS       NS      +*        +*     NS
            7360     CAROLINA CHICKAGEE                   F                        NS       NS      NS        +      NS
            7510     BLUE-GRAY GNATCATCHER                F                NS               NS      +*        +*     NS
            7550     WOOD THRUSH                          F                NS      NS               NS        NS
            7610     AMERICAN ROBIN                       FOC/FE/FD                         +*      +*        +*
            7660     EASTERN BLUEBRID                     FE                       NS       +       +*        +      +




            APPENDIX 11: PREFERRED HABITAT CODES:
                 W   WATER;                                                M  MARSH;
                 F   FOREST IN GENERAL;                                    FD = FIELD;
                 FE = FOREST EDGE;                                         FOC = FOREST WITH OPEN CANOPY;
                 FCC = FOREST WITH CLOSED CANOPY;                          S = SWAMP


                 NS=NO SIGNIFICANT TREND
                 - = POPULATION DECREASING, P<0.10
                 + = POPULATION INCREASING, P<0.10
                 -* = POPULATION DECREASING, P<0.05
                 +* =POPULATION INCREASING, P<0.05








                                                  APPENDICES




           APPENDIX III

                Community groups of the Edisto River Basin, communities found during the Natural
           Area Inventory, and communities probably present in the Basin.

                         Sandhills Palustrine Complex
                                      Atlantic White Cedar Swamp Forest
                                      Coastal Plain Small Stream Swamp Forest
                                      Strearnside Pocosin / Bay Forest
                                      Strearnhead Pocosin


                         Sandhill and Coastal Plain Scrub

                                      Southeastern Coastal Plain Xeric Sandhill
                                      Southeastern Coastal Plain Turkey Oak Barrens
                                      Southeastern Coastal Plain Subxeric Pine-Scrub Oak Sandhill
                                      Atlantic Coastal Plain Mesic Longleaf Pine Forest a, b
                                      Longleaf Pine Seep
                                      Coastal Plain Seepage Shrub Slope a
                                      Strearnhead Pocosin
                                      Small Depression Pocosin a
                                      Coastal Plain Hillside Herbaceous Seepage Bog a
                                      Atlantic Coastal Plain Depression Meadow
                            ??        Pond Pine Seep a
                                      Slash Pine Seep c

                         Pine Flatwoods Complex
                                      Atlantic Coastal Plain Mesic Longleaf Pine Forest a,b
                                      Wet Longleaf Pine Flatwoods
                                      Wet Longleaf Pine - Slash Pine Flatwoods b, c
                                      Longleaf Pine Savanna
                                      Pond Cypress Savanna
                                      Atlantic Coastal Plain Depression Meadow
                                      Swamp Tupelo Pond Forest
                                      Pond Cypress Pond Forest
                                      Pond Pine Woodland
                                      Pond Pine Seep a, b
                                      Strearnhead Pocosin
                                      Non-Riverine Wet Hardwood Forest
                                      Non-Riverine Swamp Forest
                                      Coastal Plain Small Stream Swamp Forest
                                      Slash Pine Flatwoods C


                         Isolated Freshwater Wetlands
                                      Atlantic Coastal Plain Depression Meadow
                                      Non-Riverine Swamp Forest
                                      Non-Riverine Wet Hardwood Forest
                                      Coastal Plain Small Depression Pond Complex
                                      Pond Cypress Pond Forest
                                      Swamp Tupelo Pond Forest
                            ??        Pond Cypress Dome and Swamp Forest
                                      Pond Pine Woodland
                                      Low Pocosin c
                                      High Pocosin
                                      Bay Forest







                                                                  ASSESSING CHANGE IN THE EDISTo RIVER BASIN


                                                                        Coastal Plain Hillside Herbaceous Seepage Bog a
                                                                        Limesink Pond Complex a
                                                                        Small Depression Pocosin a
                                                                        Interior Freshwater Marsh C
                                                                        Natural Impoundment Pond

                                                           Bottomland Forests
                                                               ??       Bald Cypress Swamp
                                                                        Bald Cypress - Water Tupelo Swamp
                                                                        Bald Cypress - Swamp Black Gum Swamp
                                                               ??       Tupelo Swamp
                                                                        Bald Cypress - Hardwood Forest
                                                                        Overcup Oak - Water Hickory Bottomland Forest
                                                                        Willow Oak Forest
                                                                        Sweetgum - Mixed Bottomland Oak Forest
                                                                        Sycamore - Sweetgum - American Elm Bottornland Forest
                                                                        Swamp Chestnut Oak - Cherrybark Oak Bottomland Forest
                                                                        Black Willow Riverfront Forest
                                                               9?       River Birch - Sycamore Riverfront Forest
                                                                        Eastern Cottonwood - Willow Riverfront Forest
                                                                        Coastal Plain River Edge Shrub Wetland
                                                                        Riverside Shoal and Stream Bar Complex
                                                                        Coastal Plain Small Stream Swamp Forest
                                                                        Beech - Magnolia Forest
                                                                        Forested Canebrake a
                                                                        Lowland Pine - Oak Forest a, c
                                                                        Deciduous Forested Coastal Plain Seep a
                                                                        Wet Marl Forest a
                                                                        Flood Plain pool a
                                                                        Coastal Plain Lakeshore Complex
                                                                        Interior Freshwater Marsh c


                                                           Upland Forests - Miscellaneous
                                                                        Interior Upland Dry-Mesic Oak-Hickory Forest
                                                                        Coastal Plain Calcareous Mesic Forest a
                                                                        Southern Mixed Hardwood Forest
                                                                        Spruce Pine - Mixed Hardwood Forest
                                                                        Beech - Magnolia Forest
                                                                        Upland Slash Pine Forest C
                                                                        Interior Calcareous Oak-Hickory Forest C
                                                                        Coastal Plain Limestone Sinkhole pit a
                                                                        Atlantic/Gulf Coastal Plain Marl/Shell Bluff
                                                                        Piedmont/Coastal Plain Heath Bluff a
                                                                        Coastal Plain Acidic Cliff a
                                                                        Wet Acidic Cliff a, c


                                                           Maritime Complex
                                                                        South Atlantic Inland Maritime Forest
                                                                        South Atlantic Barrier Island Forest
                                                               ??       Barrier Island Depression Forest
                                                                        Temperate Shell Midden Woodland
                                                               ??       Barrier Island Dune Scrub Woodland
                                                                        Palm - Live Oak Hammock C
                                                                        Maritime Dune Shrub Thicket
                                                                        Atlantic Maritime Dry Grassland
                                                                        Atlantic Dune Grassland
                                                                        Estuarine Fringe Loblolly Pine Forest c







                                                     APPENDICES


                                        Maritime Shrub Swamp
                                        Maritime Wet Grassland
                                        Barrier Island Pond Complex
                                        Salt Shrub Thicket
                                        Salt Marsh
                                        Brackish Marsh
                                        Salt Flat
                                        Estuarine Intertidal Mud Flat
                                        Estuarine Intertidal Sand Flat
                                        Tidal Pool
                                        Mollusk Reef
                              ??        Seagrass Bed
                              ??        Intertidal Algal Bed
                              ??        Submergent Algal Bed
                              ??        Subtropical Sponge Bed
                              ??        Subtropical Worm Reef

                          Tidal Freshwater Complex
                                        Freshwater Tidal Bald Cypress - Tupelo Swamp
                                        Tidal River Edge Shrub Wetland
                                        Tidal Freshwater Marsh
                                        Estuarine Intertidal Mud Flat
                                        Estuarine Intertidal Sand Flat


                           Carolina Bay Complex
                                        Non-Riverine Swamp Forest
                                        Atlantic Coastal Plain Depression Meadow
                                        Pond Cypress Pond Forest
                                        Pond Cypress Savannah
                                        Bay Forest
                              ??        Pocosin
                                        Pond Pine Woodland
                                        Natural Impoundment Pond

                       Found; ?? = Probably present;      a = Difficult search image;
                  b   Possibly extirpated;  c = Probably not present in the basin.














































                                                                                                                                                                r































                                                          Assessing Change in the Edisto River Basin

                                                          Total copies:                    1500
                                                          Total cost:               $10,975.00
                                                          Cost per copy:                    7.32
                                                          Date:                           11-93


                                                          S.C. Water Resources Commission


























































                                  South Carolina Water Resources Commission
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                                                (803) 737-0800






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