[From the U.S. Government Printing Office, www.gpo.gov]






                                          NA170ZO497-01


                                              TASK 20




                              FUTURE SEA LEVEL RISE IMPACTS
                          MARYLAND'S ATLANTIC COASTAL BAYS





                                            Prepared by

                                         Claudio R. Volont6
                                       Stephen P. Leatherman

                                   Laboratory for Coastal Research
                                      Department of Geography
                                       University of Maryland
                                            College Park


                                                for


                             Maryland Department of Natural Resources
                              Coastal and Watershed Resources Division
                                        Annapolis, Maryland








                                          November, 1992











           GB
           459.4
           N65
           1992













                              FUTURE SEA LEVEL RISE IMPACTS
                          MARYLAND'S ATLANTIC COASTAL BAYS





                                             Prepared by

                                          Claudio R. Volont6
                                        Stephen P. Leatherman

                                   Laboratory for Coastal Research
                                      Department of Geography
                                        University of Maryland
                                             College Park


                                                 for


                              Maryland Department of Natural Resources
                              Coastal and Watershed Resources Division
                                         Annapolis, Maryland

                                      US Department of Commerce
                                 XOAA Coastal Services Center Library
                                       2234 South Hobson Avenue
                                       Charlestont SC 29405-2413



                                          November, 1992

















































             Funding for this project was provided by the Coastal and Watershed Resources
             Division, Maryland Department of Natural Resources, through grant No. NA1 70ZO497-
             01 provided by the Coastal Zone Management Act of 1972, as amended,
             administrated by the Office of Ocean and Coastal Resource Management, National
             Oceanic and Atmospheric Administration. The views expressed herein are those of the
             author(s) and do not necessarily reflect the views of NOAA or any of its subagencies
             and the Department of Natural Resources. We would like to thank Vincent Pito, Jr.
             of the Coastal and Watershed Resources Division, Maryland Department of Natural
             Resources for his extensive editorial comments.










                                                 TABLE OF CONTENTS


              Chapter One: Introduction       ...................................                           1

                      1. Project Objectives    ...................................                          1
                      11. Global Warming and Sea Level Rise        .......................                  1
                      Ill. Impacts of Sea Level Rise     .............................                      5
                      IV. Sea Level Rise Scenarios       .............................                      5



              Chapter Two: Maryland's Atlantic Coastal Bays           .....................                 7

                      1. Physical Characteristics    .................................                      8
                      11. Description of Zones    .........................                 I ........     14
                      111. Human Use and Population       ............................                     .17


              Chapter Three: Present Rates of Shoreline Change            ..................               21


              Chapter Four: Projection of Future Shoreline Position         .................              38

                      1. Erosion/Inundation Model      ..............................                      38
                      11. Future Shoreline Positions     .............................                     43
                      Ill. Quantification of Land at Risk    ..........................                    75



              Chapter Five: Impacts      ......................................                            80

                      1. Land at Risk   .......................................                            80
                      11. Economic and Infrastructure at Risk       ......................                 81
                      Ill. Wetland Loss     .....................................                          82
                      IV. 100-year Flood    .....................................                          85


              Chapter Six: Strategies for Management           .........................                   87


                      1. Retreat   ..........................................                              88
                      11. Accommodation     ....................................                           90
                      Ill. Protection  ........................................                            90


              References     .............................................                                 94


              Appendix      ..............................................                                 97









                                                                  LIST OF FIGURES


                   Figure 1.     Sea level rise scenarios           ...............................                                       4
                   Figure 2.     Global Coastal Problems: A Collision Course                       ................                       4
                   Figure 3.     Study area zonation            .................................                                         9
                   Figure 4.     Ancient barriers in the study area               .........................                            10
                   Figure    5.  Erosion at the edge of the marsh (transect 13, Figure 14)                            .......          12
                   Figure    6.  Inundation of marsh has caused upland vegetation to die
                              (transect 55, Figure 14)            ...............................                                      12
                   Figure    7. Salt marsh zonation            . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       13
                   Figure 8. Aerial view of Turville Creek and downstream
                              section of Herring Creek            . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .        15
                   Figure 9. Aerial view of the left bank (north bank) of St. Martin River                                .....        15
                   Figure    10. Aerial view of the eastern half of Isle of Wright                      .............                  16
                   Figure    11. Aerial view of Ocean Pines right bank
                               (south bank) of St. Martin River                ........                                    ....        19
                   Figure    12.  Stabilization of shorelines with bulkhead                   ..................                       19
                   Figure    13.  Land use categories in study area                 . . . . . . . . . . . . . . . . . . .  . . .       20
                   Figure    14.  Location of transects           . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .        25
                   Figure    15.  Location of survey profiles along the study shoreline                        ..........              41
                   Figure    16.  Representative profile and erosion/inundation model                         ..........               42
                   Figure    17.  Zone     1 : Estimated      shoreline positions for the year 2020                 .......            46
                   Figure    18.  Zone     1 : Estimated      shoreline positions for the year 2050                 .......            47
                   Figure    19.  Zone     1 : Estimated      shoreline positions for the year 2100                 ...   * * '   "    48
                   Figure 20.     Zone     2:  Estimated      shoreline positions for the year 2020                 .......            49
                   Figure 21.     Zone     2:  Estimated      shoreline positions for the year 2050                 .......            50
                   Figure    22.  Zone     2:  Estimated      shoreline positions for the year 2100                 .......            51
                   Figure    23.  Zone     3:  Estimated      shoreline positions for the year 2020                 .......            52
                   Figure    24.  Zone     3:  Estimated      shoreline positions for the year 2050                 .......            53
                   Figure 25.     Zone 3:      Estimated      shoreline positions for the year 2100                 . . . . . . .      54
                   Figure 26.     Zone 4:      Estimated      shoreline positions for the year 2020                 .......            55
                   Figure 27.     Zone 4:      Estimated shoreline positions for the year 2050                      .......            56
                   Figure    28.  Zone 4:      Estimated      shoreline positions for the year 2100                 .......            57
                   Figure    29.  Zone 5:      Estimated      shoreline positions for the year 2020                 .......            58
                   Figure 30.     Zone 5:      Estimated      shoreline positions for the year 2050                 .......            59
                   Figure 31.     Zone 5:      Estimated      shoreline positions for the year 2100                 .......            60
                   Figure 32.     Aerial view of St       . Martin Neck          ........................                              61
                   Figure 33.     Zone     6:  Estimated      shoreline positions for the year 2020                 .......            62
                   Figure 34.     Zone     6:  Estimated      shoreline positions for the year 2050                 .......            63
                   Figure 35.     Zone     6:  Estimated      shoreline positions for the year 2100                 .......            64
                   Figure 36.     Zone     7:  Estimated      shoreline positions for the year 2020                 .......            65
                   Figure 37.     Zone     7:  Estimated      shoreline positions for the year 2050                 .......            66
                   Figure 38.     Zone     7:  Estimated      shoreline positions for the year 2100                 .......            67
                   Figure 39.     Zone     8:  Estimated      shoreline positions for the year 2020                 .......            68
                   Figure 40.     Zone     8:  Estimated      shoreline positions for the year 2050                 .......            69
                   Figure 41.     Zone     8:  Estimated      shoreline positions for the year 2100                 .......            70








                  Figure 42.      Zone 9: Estimated shoreline positions for the year 2020                          . . . . . . .      71
                  Figure 43.      Zone 9: Estimated shoreline positions for the year 2050                          . . . . . . .      72
                  Figure 44.      Zone 9: Estimated shoreline positions for the year 2100                          . . . . . . .      73
                  Figure 45.      Ponding causing wetlands destruction in.the Isle of Wight                           ......          74
                  Figure 46.      Total land at risk vs. sea level rise scenarios                 ................                    76
                  Figure 47.      Mash at risk vs. sea level rise scenarios                 . . . . . . . . . . . . . . . . . .       83
                  Figure 48.      Comparison of setbacks              . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       91
                  Figure 49.      Proper location of bulkheads               ..........................                               91









                                                LIST OF TABLES


            Table 1.  Sea level rise scenarios for study area   .....................                6
            Table 2.  Rates of shoreline change: Zone 1    .......................                26
            Table 3.  Rates  of shoreline change: Zone 2   (south bank)   ................        27
            Table 4.  Rates  of shoreline change:  Zone   2(north bank)    ..............         28
            Table  5. Rates  of shoreline change:  Zone   3(east bank)   ...............          29
            Table 6.  Rates of shoreline change: Zone 3    (west bank)  ................          30
            Table 7.  Rates of shoreline change: Zone 4 (south bank)       ..............         31
            Table 8.  Rates of shoreline change: Zone 4 (south bank)       ...............        3  1
            Table 9.  Rates of shoreline change: Zone 5    (south bank)    ..............         32
            Table  10. Rates of shoreline change: Zone    5  (north bank)  ..............         33
            Table  11. Rates of shoreline change: Zone 6     (south bank)   ..............        34
            Table  12. Rates of shoreline change: Zone    6  (north bank)  ..............         34
            Table  13. Rates of shoreline change: Zone 7     ......................               35
            Table  14. Rates of shoreline change: Zone    8  ......................               36
            Table  15. Rates of shoreline change: Zone    9  .......................              37
            Table  16. Example of erosion rate estimates     ......................               39
            Table  17. Land at risk   ......................................                      75
            Table  18. Land at risk by zone    ................................                   78
            Table  19. Land at risk by land use    ...............................                80
            Table  20. Mash loss and deficit from existing marsh      .................           84










                                                 CHAPTER ONE
                                                 INTRODUCTION
             1. PROJECT OBJECTIVES


                    Maryland's Atlantic coastal bays are valuable because of their coastal location
             which attracts development, and because they support abundant natural resources,
             including tidal wetlands. Accelerated sea-level rise projected for the next century will
             have severe impacts on both development and natural resources. In order to
             responsibly manage land use in this region, the impact of sea level rise must be
             a*ddressed. This study has three major aims:

                    (1)    Predict future wetland and upland losses around the
                           northern portion of Maryland's Atlantic coast bays (namely
                           Assawoman Bay, and Isle of Wight Bay) to the years 2020,
                           2050 and 2100 for eight realistic scenarios of sea-level
                           rise: 0.4 ft and 0.5 ft (2020), 0.8 ft and 1.5 ft (2050) and
                           1.4 ft, 1.7 ft, 3 ft and 4.4 ft (2100);


                    (2)    Analyze the impacts of the land losses predicted by each
                           sea-level rise scenario with respect to present development
                           patterns and likely future development, including net
                           wetland losses, real estate upland losses and enhanced risk
                           of flooding; and

                    (3)    Examine and develop strategies that would be useful at the
                           state and local level to mitigate these impacts such as
                           retreat, accommodation, and protection.

             11. GLOBAL. WARMING AND SEA-LEVEL RISE


                    It has long been theorized that an increase in   atmospheric concentrations of
             carbon dioxide, primarily due to fossil fuel combustion, would cause a gradual rise in
             global temperatures. The amount of carbon dioxide (C02) in the atmosphere, now 340
             parts per million (ppm), has ranged from several thousand to as low as 200 ppm.
             These changes, however, have occurred on geological time scales (over thousands
             and millions of years) and have been primarily due to natural phenomenon. Now C02
             and other trace gases (methane, nitrous oxide, and chlorofluorocarbons) are
             accumulating in the atmosphere at an unprecedented rate with effects that will be
             measured in decades. Atmospheric measurements show that concentrations of C02
             have increased 20 percent since 1960 and are continuing to rise (Shands and Wel       IS
             1987).

                    While it is still being debated if global warming has begun, it is clear that sea
             level has been rising as indicated by tide gauge data from around the world's coasts,


                                                         1








             including those in Maryland (Douglas, 1991). Although some government officials,
             scientists and the general public are unaware of or have largely ignored these
             warnings, the evidence for global change and its impacts is mounting. The relevant
             facts include the following:

                    1.     The concentrations of carbon dioxide and other greenhouse gases are
                           rapidly increasing in the atmosphere. The amount Of C02 in the
                           atmosphere is now more than 340 pprn (Shands and Wells, 1987).

                    2.     World temperatures are rising (about 0.51C in the last 100 years). The
                           1980's was the warmest decade on record (IPCC, 1990a).

                           Regardless of future emission policy, further global warming is inevitable
                           due to the' greenhouse gasses already emitted (i.e. there is a
                            commitment" to global warming).

                    4.     Water expands when heated; thermal expansion of near surface ocean
                           waters as well as melting of land-based glacial ice will increase sea level.

                    5.     Most mid-latitude glaciers have retreated during the 20th century
                           (releasing their ice-locked water to the ocean) (IPPC, 1990a).

                    6.     Relative sea levels have risen at most tide gauges in the last century; the
                           eustatic (worldwide) contribution is estimated to be about 0. 18 rn during
                           the last century (Douglas, 1991).

                    7.     Sea-level rise and shoreline recession are directly linked as shown by
                           laboratory experiments and erosion in the Great Lakes region during
                           periods of high water levels (Bruun, 1962; Hands, 1983).

                    8.     Shorelines are retreating on a global basis; approximately 70% of the
                           sandy beaches worldwide are presently eroding (Bird, 1985). In the U.S.
                           best estimates are that 90% of sandy beaches are eroding (Leatherman,
                           1988).


                    9.     Coastal wetlands are lost when sea-level rise exceeds sedimentation
                           rates; Louisiana is losing about 130 square kilometers of wetlands
                           annually (DeLaune, et al., 1983). Wetland loss in Louisiana largely due
                           to land subsidence but provides an example of the fate of other coastal
                           wetlands in response to accelerated sea level rise.







                                                         2








                     10.    Global warming will most likely increase the intensity of hurricanes
                            (Emanuel, 1987), which have the greatest impact on low-lying coastal
                            landforms and the area's inhabitants by inducing massive erosion and
                            flooding.

                     11.    There is a worldwide trend of coastal urbanization at more than twice
                            the inland rate (NOAA, 1990). These coastal areas contain a
                            disproportionate share of the nation's economic wealth. In addition,
                            beach front property is some of the most expensive real estate in the
                            U.S. (Leatherman, 1988).


                     12.    Sea-level is predicted to rise worldwide by as much as 1. 10 meters by
                            the year 2100 (Figure 1); best estimates are for a 0.66 meter rise with
                            at least a 0.31 meter global or eustatic increase within the next century
                            (IPCC, 1990a).


                     13.    Global environmental problems are intensified in the coastal zone; sea-
                            level rise is pushing the shore landward at the same time that population
                            growth and coastal urbanization are rapidly increasing (Figure 2).

                     Of all the potential impacts of human-induced climate change, a global rise in
              sea level appears to be the most certain. Over the next few decades we can anticipate
              that sea-level will continue to rise at a rate similar to or slightly exceeding the recent
              experience. By the middle of the next century, sea level can be expected to rise by a
              factor of 2 to 3, and it may ultimately rise 1.10 meters during the next 100 years
              (Figure 1).























                                                           3









                                                                                                         Projected Rise from IPCG 1990             Scenario A
                                                        Historic Sea Level Rise                                         ("Business As Usual")

                                                                                                                                                                 110


                                                                                                   100-


                                                                                                                                                            High
                                                                                                                                                   171


                                                                                                                                                                 66



                                                                                                                                                   '44      Best
                                                                                                   so -
                                                                                                                                                        estimate
                                                                                                                           '29                                   31
                                    W                                                                                       I          I           I
                                                                                                                      1     118        132         21
                                                                                                                                                            Lov@

                                                                                                                             8
                                                                                                                          5



                                     -8
                                     16
                                       1880      1900        1920       1940       1960       1980 1990  2000          2025          2050          2075          2100
                                                                                                    Year

                                  So urc e s: T.P. B a rn e ti, "G lob a I S e a Leve I Cha ng a,' N OAA, 1988; 1 PCC, Climate Ch a nge: The I P CC S cientific As ses sm ent, 1990.


                                        Figure 1 .                Sea-level rise scenarios.



                                                                     G LO BAL C OASTAL PRO 8 LE M S
                                                                             A Collision Course




                                                  Greenhouse Gases





                                                 Earth Temperatures


                                                     Fsea Level


                                                    Beach Erosion                                             Coastal Populati
                                                    Wetlands Loss'                                                                   on




                                                                     GLOBAL ENVIRONMENTAL PROBLEMS


                                           Figure 2.                 Global Coastal Problems: A Collision Course



                                                                                                      4
                                                                                                                                                            H



                                                                                                                                                                 66



                                                                                                                                                   @44
                                                                                                                            289










             Ill. IMPACTS OF SEA-LEVEL RISE
                    Scientists commonly cite five physical impacts due to sea level rise
             (Leatherman, 1983):

                    (1) beach and upland erosion;
                    (2) inundation of low-lying lands and wetlands;
                    (3) salt-water intrusion into aquifers and surface waters;
                    (4) higher water tables; and
                    (5) increased flooding and storm damage.

                    Erosion and inundation in the coastal zone are accelerated by higher water
             levels, the impact of which will   be accentuated in the future if low-lying areas are
             developed. Sea-level rise would increase the severity of storm-related flooding. The
             higher base for storm surges would be an additional threat in regions where hurricanes
             are common. Higher water levels in the low-lying coastal zone may reduce drainage
             of adjacent land areas, which could damage roads, buildings and agricultural land.
             Salt-water intrusion into fresh water aquifers would tontaminate drinking water.
             Wetlands are particularly at risk from sea level rise because they are directly
             dependent on water levels.


             IV. SEA LEVEL RISE SCENARIOS


                    The relative sea level rise scenarios used in this analysis were obtained by
             adding the two components that are responsible for relative sea level change at any
             one coastline. These two components are:

                    (i)    global or eustatic sea-level change; and
                    00     vertical land movement.

                    Eustatic sea-level change values for the years 2020, 2050 and 2100 were
             obtained from predictions made by the Intergovernmental Panel on Climate Change
             Working Group 1 (1 990a; Figure 1). The IPCC predictions assume an acceleration of
             the rate of sea level rise based on predictions of global warming due to the
             11 greenhouse effect." For the years 2020 and 2050 we examined only two scenarios
             of eustatic sea level: (1) Present Trend (no acceleration in eustatic sea level) and (2)
             Most Likely Trend in sea level (values obtained from the best estimate curve of Figure
             1, middle curve). For the year 2100, we used the three IPCC sea level rise scenarios
             (Low, Best, and High) plus the present sea level trend (no acceleration). Thus, a total
             of eight scenarios were investigated.

                    Land subsidence values for the study area were obtained by subtracting
             eustatic sea level rise from relative sea level rise. This latter value was obtained from
             tide gauge data at Lewes, Delaware --the nearest long-term record (Lyles, Hickman
             and Debaugh, 1988). The tide gauge data indicate a relative rise in sea level of 0.39


                                                         5








             m (1.3 ft) per century from 1919 to 1986. Eustatic sea level rise for the same period
             was estimated at 0.18 m (0.6ft) (Douglas, 1990). Hence, the subsidence component
             is 0.21 m (0.68 ft) per century, or 0.23 rn (0.7 ft) by the year 2100.

                    These two components were then added to determine the total relative sea
             level rise at the study area. The following table (Table 1) presents these sea level rise
             scenarios that will be used in this study (the base year is 1989):





                  Table 1. Sea Level Rise Scenarios for Study Area.

                  Year                        Eustatic            Subsidence           Total
                  Scenario                    (feet)              (feet)               Sea Level
                                                                                       Rise
                                                                                       (feet)
                  2020
                  Present Trend               0.18                0.22                 0.4
                  Best Estimate               0.28                0.22                 0.5


                  2050
                  Present Trend               0.37                0.43                 0.8
                  Best Estimate               1.05                0.43                 1.5


                  2100
                  Present Trend               0.67                0.7                  1.4
                  Low                         1.02                0.7                  1.7
                  Best Estimate               2.17                0.7                  3
                  High                        3.7                 0.7                  4.4

















                                                        6










                                                  CHAPTER TWO
                                   MARYLAND'S ATLANTIC COASTAL BAYS


                     Maryland's Atlantic coastal bays are a significant resource to the peop  le of the
              state (see figure 3, pg 9). They present a microcosm of the global pressures on the
              coastal zone already described (Figure 2). Coastal land loss in this region is already a
              major issue as'More and more people move closer to the water's edge. Rapid coastal
              changes are taking place, for instance at northern Assateague Island the shore is
              moving landward at an average rate of -9.1 meters/year. The island is likely to be
              breached near the Ocean City Airport before the year 2020 exposing the mainland
              shore to the Atlantic waves (Leatherman et aL, 1987).

                     As the shoreline changes, it is projected that by the year 2100, the coastal
              population of Maryland will have increased by more than 66 percent above 1960
              levels (NOAA, 1990). Development pressures in the coastal bays are increasing
              because Ocean City has approached saturation and as a result new shore front
              property has become scarce. This makes the relatively undeveloped coastal bays
              increasingly attractive for development (Maryland's Forgotten Bays, 1990).

                     The problems of the Atlantic coastal bays, especially development pressures,
              have been brought to' the forefront by a recent conference held at Ocean City
              (Maryland's Forgotten Bays, 1990). A number of issues of relevance to this study
              were identified:


                     0     Local land use plans need to recognize the impacts of sea-level rise and
                           help to protect the resources of the coastal bays;

                     0     The Chesapeake Bay Critical Area Program places setbacks and
                           restrictions on development along the Chesapeake Bay and its tributaries,
                           but there are no state or county laws or regulations requiring setbacks
                           on the coastal bays;

                     0     Present development proposals frequently do not take into account
                           future coastal recession. The proposed marina at Ocean City Airport,
                           opposite the point where Assateague Island is likely to breach, illustrates
                           that some coastal developers are either not aware of or are unconcerned
                           with scientific predictions;

                     0     Wetland and other habitat losses would greatly reduce the commercial
                           fisheries and ecological value of the bays; and

                     0     Considerable local concern about these issues exists (e.g.; Baltimore
                           Sun, May 14/15, 1990).



                                                         7











             1. PHYSICAL CHARACTERISTICS


                    The study area is located on the northeastern corner of Worcester County,
             Maryland. It includes the outer bays lying between the mainland of Worcester County
             and the barrier island of Fenwick (Ocean City). The study area shoreline extends about
             41 miles from just south of Route 50 (before it crosses to Ocean City) to the area of
             Back,Creek on Assawoman Bay just south of the border between Maryland and
             Delaware (Figure 3). The study area consists of a series of "necks" (Sinepuxent,
             Turville, Jenkins, and St. Martin) separated by creeks (Turville, Manklin and St. Martin,
             River).

                    A recent morphological study (Demarest and Leatherman, 1985) determined that
             the present mainland shores of the Delmarva Peninsula, including the study area,
             developed over the last million years. These researchers found three ancient barrier
             islands in the study area that were dated to the Pleistocene. These barrier islands are
             located sub-parallel to the present shore and are referred to as the Bethany, Cedar
             Neck and White Neck barriers, dated at 0.06, 0.6 and 1.0 million years respectively
             (Figure 4). The pre-existing topography plays an important role in the morphologic
             development of these coastal areas. For example, the steep slopes on some parts of
             the study area can be traced back to the Pleistocene shoreface (scarp) of the ancient
             barriers.


                    The topography of the study area is relatively low, not exceeding 10 feet. The
             bays shorelines are generally gentle compared to that of the banks of the creeks. A
             typical cross-section of the shores show the presence of a scarp between the 1 and
             3 feet contour lines, while for contours higher than 4 feet the slopes become gentler
             (see fig 16 on pg 50).




















                                                        8







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                    Figure 3.              Study area and zonation                               9
















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                                          Figure 4.           Ancient barriers in the study                  area (Dernarest
                                                              and Leatherman, 1985)





                                                                                    10








                    According to 1989 aerial photography, about 58       percent or 24 miles of the
              entire shoreline of the study area (41 miles) contain wetlands. The width of these
              wetlands vary along the shoreline, from a minimum of 40 feet (on the Turville Creek)
              to a maximum of about 1000 feet (Assawoman Ba y*). The most extensive wetlands
              occur on the north bank of the St. Martin River and the shores of the Assawoman
              Bay. It was estimated that presently wetlands cover about 1500 acres in the study
              area. Most of these wetlands have suffered extensive erosion (Figures 5 and 6) and
              drowning since 1850.

                    Coastal wetlands are subject to flooding by brackish or salty..,water and are
              composed of salt-tolerant plants. Because of the changing relative influence of various
              governing factors, such as tidal range and slope, there is a gradation in plant species
              from the lowest elevation of the wetlands to the upper. boundary. Generally, one can
              easily distinguish between the lower wetlands (vegetated tidelands) and the upper
              wetlands (Figure 7).

                    It has been recognized that coastal wetlands are vital areas because they play
              a valuable and critical role in the functioning of coastal ecosystems. The benefits of
              wetlands are: habitat for many important estuarine species, shore stabilization, flood
              control, water purification and recreation (Clark, 1983). Wetland vegetation plays an
              important role in converting inorganic compounds (nutrients) and sunlight into stored
              energy. When the dead leaves and stems of the wetland plants enter the water and
              are broken down by bacteria, they are transformed into small particles of organic
              detritus, which is food for fiddler crabs, worms, snails, mussels and the myriads of
              larval stages of fish and shellfish of estuarine waters. This rich environment provides
              food and habitat necessary for the protection and survival of various species; many
              of which are commercially important.

                    Wetland vegetation also removes toxic materials and excess nutrients from
              estuarine waters. In addition, sediment and other inert suspended materials are
              mechanically and chemically removed from the water and deposited in the marsh,
              reducing the sedimentation of navigation channels and shellfish beds. Wetlands serve
              not only to stabilize the shoreline and prevent erosion but actually can extend the
              land's edge by trapping sediments and building seaward.

                    Wetlands provide storm protection for urbanized areas in several ways. The
              marshes create surface friction for both tidal surges and winds. The result is that
              marshes help reduce tidal surge levels and wind velocities of storms. Wetlands have
              also recreational value as they are used for fishing, hunting, photography, and boating.


















                                                          OMSUIZ-7












                     Figure 5.    Erosion at the edge of the marsh



















                                J




                     Figure 6.    Inundation of marsh has caused upland vegetation to die



                                                  12




































                                                                                                                                                                              SPRING HIGH TIDE
                                           Wax Myrtle              Common           Black or                                                                                            HIGH TIDE
                                                                      Reedgr.sa       Needle Rush                      Salt Marsh Cordgrass
                                           Marsh Elder             Cattails                                            Spike G,a.s
                                           S:a Myrtle                                                                                                                           MEAN SEA LEVEL
                                           P ison I                                                                                             Salt Meadow
                                                   vy                                                                                               C.rdgrass                                     LOIW
                                                                                                                                                                                                 TIDE




                                          SHRUB BORDER             REEDGRASS                             HIGH MARSH                                LOW MARSH
                                                                     MARSH
                                        Figure 7.                  Salt marsh zonation (from Leatherman, 1988)





















                                                                                                            13









              11. DESCRIPTION OF ZONES


                    In order to easily describe the study area it was divided into 9 zones according
              to the type of environment and geography (Figure 3). Zone 1 encompasses 4.66
              miles of the study area and includes the shores of the Isle of Wight Bay from Route
              50 north to Keyser Point. Urban developments such as West Ocean City, Bay Shores
              Acres, Captain Hills and Cape Isle of Wight are located in this zone. Zone 2 encircles
              the banks of Turville Creek, a tributary of Isle of Wight Bay and is abo'ut 8.63 miles.
              Herrings Creek, a tributary of Turville Creek, is Zone 3 with a shoreline length of about
              4.5 miles (Figure 8). The banks of Manklin Creek, about 4.75 miles, is Zone 4, a
              tributary of Isle of Wight Bay, including the development Ocean Pines. Zone 5
              encompasses the banks of Saint Martin River, about 7.17 miles (Figure 9). The banks
              of Shingle Landing Prong (3.52 miles) and Bishopville Prong (2.66 miles) are part of
              the St. Martin river system and are Zone 6 and 7, respectively. The Isle of Wight was
              assigned Zone 8, about 2.54 miles (Figure 10). Finally, all of the shores of
              Assawoman Bay that lay within, the study area, about 4.56 miles has been assigned
              Zone 9.







































                                                        14




























                                                               4-














                        Figure 8.     Aerial view of Turville Creek (diagonally) and
                                      downstream section of Herring Creek (left to
                                      right)























                                                         IF @'P777









                        Figure 9.    Aerial view of the left bank of St. Martin River
                          I ri



                                                       15





























                        Figur;e 10.  Aerial view of t,h,e:e:astern half,of Isle,of Wight
                                     (Zone 8)















                                                     16









              Ill. HUMAN USE AND POPULATION


                    In the last three decades Worcester County has undergone significant change,
              especially in the northeastern sector where the study area is located. Easy access
              from two large metropolitan cities (Washington, DC and Baltimore) and beautiful
              coastal natural resources have resulted in the creation of a major recreation and
              tourism industry in this area. Today, recreation surpasses agriculture in terms of its
              overall contribution to the economy of the County. The shores of the study area are
              under development pressure because of their proximity to Ocean City. It is anticipated
              that as land in Ocean City becomes more expensive and scarce, the bay shorelines
              will receive spillover growth. It has been projected that this part of the County will
              witness a 25 percent increase in population by the year 2005 (CDP, 1989).

                    Today, about 7.5 miles or 17 percent of the 41 miles of the study area has
              been intensely developed (Figure 11). Canals have been created in some of the
              residential areas which allow residents water access to the bay. Most of these
              developed shorelines have been stabilized with bulkheads (Figure 12). The most
              developed shores of the study area are located along the shores of Isle of Wight Bay,
              the north bank of Turville Creek and Manklin Creek and the west bank of Herring
              Creek. The Worcester County Comprehensive Development Plan (CDP, 1989) indicates
              that there are 6 land use types in the study area; Commercial Centers, Suburban,
              Agriculture, Suburban Residential, Rural Estate, and Conservation (Figure 13)).
              Commercial Centers are areas reserved for retail, service and office development. The
              only Commercial land use in the study area is located along Herring Creek, on both
              sides of Route 50, and accounts for 3.5 percent of the study area shoreline.
              Suburban land use accounts for only 1.5 percent of the study shoreline and is located
              on the east bank of Herring Creek. The suburban land use type was designed to
              anticipate the growth of Ocean City and permits the highest development densities.
              Agriculture land use is located along only 1 percent of the shoreline in the study area.

                    Most of the study shoreline (58 percent) falls under the Suburban Residential
              land use category. It accommodates a large portion of the county's population but
              development occurs at a lower density than the Suburban land use category (four
              units maximum per acre compared to six dwelling units per acre). Rural Estate land
              use also occurs along a large portion of the study area shoreline (30 percent).
              Residential development in this area is limited to lot sizes larger than one unit per two
              acres, which is larger than Suburban and Suburban Residential land use densities.
              Finally, the Conservation land use type comprises the Isle  of Wight, about 6% of the
              total study shoreline. This land use category is reserved for areas which pos6
              constraints to development and where development could have a significant adverse
              effect on the environment.




                                                        17














                                                  SUMMARY


                         0 Rapid coastal changes are   taking place today, and erosion
                         and submergence at various rates are evident throughout the
                         study area.

                         0 Development pressures are increasing as Ocean City
                         approaches saturation and new waterfront property becomes
                         scarce.


                         0 The steep slopes on some parts of the study area can be
                         traced back to the Pleistocene shoreface (scarp) of ancient
                         barrier islands.


                         0 About 58 percent or 24 miles of the study area shoreline are
                         wetlands based on the 1989 aerial photography.

                         0 About 25 percent or 10 miles of the study area shoreline is
                         sandy beaches or small bluffs, and non-marshy coasts.

                         0 Today about 7.5 miles or 17 percent of the 41 miles of the
                         study area is developed, most of it intense residential
                         development.

                         0 The most developed shores of the study area are the Isle of
                         Wight Bay, the north bank of Turville Creek and Manklin Creek
                         and the west bank of Herring Creek.
















                                                       18































                       Figure 11    Aerial view of Ocean Pines, on  the right bank
                                    of St. Martin River








                            eA















                                                     -1W




                       Figure 12.   Stabilization of shorelines with bulkhead



                                                     19








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                                                 CHAPTER THREE
                                   PRESENT RATES OF SHORELINE CHANGE


                    To determine rates of shoreline change, we employed our in-house Geographic
             Information System called Metric Mapping. Metric Mapping is capable of calculating
             shoreline change by comparing the spatial and temporal components of two or more
             shorelines. We began our analysis by digitizing shorelines off of NOAA-NOS T sheets
             (accurate historical maps), scale-corrected vertical aerial photographs, U.S.G.S.
             topographic sheets and other pertinent maps covering six historical dates: 1850,
             1908, 1934, 1962, 1977 and 1989.

                    Metric Mapping requires that we digitize perpendicular lines to the shoreline,
             called transects. Metric Mapping intersects the transects with the different dated
             shorelines and estimates the horizontal distance between these shorelines. The
             distance is then divided by the time period between the two shorelines and a shoreline
             change rate is assigned to the particular transect. To cover the 41 miles of the study
             area shoreline, 215 transects were equally spaced approximately 1000 feet apart
             (Figure 14).

                    In same cases, the rate of shoreline change was estimated by considering the
             geomorphology, topography and human activities in each transect in addition to the
             shoreline change values generated by Metric Mapping. For example, if an area has
             been developed (i.e., construction of bulkheads or marinas), we considered the
             shoreline change rate to correspond to the human modification of the shore, which
             is stable. Also, on those shores that were occupied by marshes according to 1850
             maps, but were later destroyed, shoreline change rates were estimated for the present
             shoreline type and not for the historic marsh. All negative shoreline change values
             correspond to movement of the shoreline towards the land and is called erosion. All
             positive shoreline change values correspond to movement of the shoreline away from
             the land is called accretion.


             Zone 1: Isle of Wight Bay Shores

                    Metric Mapping data showed that the rates of shoreline change for Zone 1
             range from -3 ft/yrl to stable (Table 2)2 . The erosion rate is high in this zone because
             most of the transects (70 percent)    'were calculated along marshy shorelines which
             seem to erode quicker than other shorelines. Erosion rates at marshy shorelines
             average -1.3 ft/yr in this zone (note marsh average, Table 2). A maximum erosion
             trend of -3 ft/yr in the area of Horn Island (transect 4, Table 2). Two' communities,
             Cape Isle of Wight and Captains Hill, have armored their shoreline and thus, no



                 Negative number. indicate erosional trends, while positive numbers represent accretion


                 Tables 2 through 15 are located at the end of this chapter.


                                                        21








             significant shoreline change has been observed in this area since -1962 (transects 10-
             12 and 18, Table 2).


             Zone 2: Turville Creek shores
                    In Zone 2, along the north and south banks of Turville Creek, shoreline change
             rates remained consistent between the two banks (Tables 3 and 4). Along the south
             bank, half of the transects were calculated along marshy areas. These transects
             exhibited erosion rates that average -0.6 ft/yr (transects 24-26 and 29, 55-58, Table
             3). The trend diminishes upstream. Shoreline change continues even though the
             shoreline has been stabilized at a small area of development near the mouth of Herring
             Creek (transects 27, Table 3). Along the shoreline.at the upper part of the Creek,
             where there exists three race tracks, erosion rates vary from -0.5 ft/yr to stability
             (transect 61-67, Table 3).

                    The shoreline on the upper part of the north bank of Turville Creek has been
             armored with bulkheads and small seawalls as indicated by maps from 1962. As a
             result no significant shoreline change has been observed since this time (transects 68-
             77, Table 4). Marshes dominate the shoreline along the mouth of the north bank of
             the Creek (transects 78 to 85, Table 4). Erosion rates increase downstream in this
             area and average -0.8 ft/yr, with a maximum of -1.8 ft/yr.

             Zone 3: Herring Creek shores


                    Herring Creek, Zone 3, is a tributary of Turville Creek and is geomorphologically
             similar. The mouth of the Creek is fringed by marshes, while the middle section is
             occupied by development. Along the shores of the upper part of the Creek there exists
             agricultural fields and no marsh development.

                    The shoreline of the east bank of the Creek is eroding at rates from -2 ft/yr to -
             1.1 ft/yr and decreases upstream (transects 30 to 42, Table 5). The developed
             shoreline of the middle part of the Creek is eroding at rates ranging from -0.5 to -0.2
             ft/yr (transects 38 and 39, Table 5).

                    The west bank of the Creek is eroding at an average rate of -0.3 ft/yr, less than
             the east bank of the Creek (Table 6). The middle part of this bank has been developed
             and has not changed significantly since 1934. The marshy shores (transects 49 to 54,
             Table 6) near the mouth of the Creek have eroded at a rate ranging from -0.9 to -0.2
             in the last 139 years (1850-1989).

             Zone 4: Manklin Creek shores
                    Zone 4, Manklin Creek, extends from trans'ect 86 to 100 (Tables 7 and 8). The
             south bank is occupied by marshes and a few areas of development. The shoreline at
             the mouth of the Creek, near Isle of Wight Bay, is eroding at rates ranging from -1.5


                                                        22








              ft/yr to -0.5 ft/yr (transects 86-93, Table 7). Erosion rates diminish upstream
              especially where marshes are small and narrow because of steeply sloped banks.

                     The mouth of the north bank of Manklin Creek (Table 8) has been armored
              because of extensive residential development including many access canals. The
              shoreline at the upper part of the Creek is steeply sloped with narrow coastal marshes
              and is eroding at rates of -1.5 ft/yr (transect 97, Table 8).

              Zone 5: St. Martin River shores


                     The south shores of the Saint Martin River are relatively stable although some
              areas are accreting (transects 101-107, 125-126, 132-133, Table 9). Only a small
              portion of the south bank of the Saint Martin River contains marshy shores, the rest
              has been developed into residential marinas with hard shoreline stabilization structures
              (Ocean Pines, between transect 103 and 104, Table 9). The marshy shores at the
              source of the River have been accreting or are stable as is evident from historical
              maps (transects 106-107, 125-126, 132-133, Table 9).

                     On the other hand, the north bank of the Saint Martin River has less
              development and more marshy shorelines. All transects here (from 150 to 165, Table
              10) indicate erosion at rates higher than - 1 ft/yr, with the exception of three transects
              (1150, 151 and 164, Table 10) which show erosion rates of -0. 5 ft/yr.

              Zone 6: Shingle Landing Prong shores

                     Shingle Landing Prong is located on the upper part of the Saint Martin River.
              The steep slopes of the @shores of this prong reduce the possibility for wetland
              expansion to upland areas as sea level rises. Transects at the mouth of the south bank
              of the prong (transects 108-111, Table 11) indicate erosional trends of about -0.5
              ft/yr. At the upper part of the prong, accretional trends vary between 1.4 and 0.4
              ft/yr (transects 112, 116-118, Table 11). The north bank of the prong (transects 119-
              124, Table 12) has steep slopes and small areas of marshes that are presently eroding
              at an average rate of -0.5 ft/yr.

              Zone 7: Bishor)ville Prong shores


                     Bishopville Prong, Zone 7 (Table 13), is also part of the Saint Martin River
              basin. Its banks consist of steep slopes and a small marshy shoreline at the mouth of
              the prong. Transects on the west bank indicate a stable shoreline since 1934
              (transects 134-139, Table 13). The east bank of the prong has been slightly eroding
              north of Daye Road but in general this bank is stable (transects 140-147, Table 13).





                                                          23









              Zone 8: Isle of Wi-ght

                    The Isle of Wight shoreline, Zone 8, is predominantly occupied by marshes
              except for the southern shore of the island. Erosion rates range from -0.4 to -2.5 ft/yr
              around the island (Table 14). The more exposed southern part of the island is
              experiencing the greatest erosion rates (transects 175-179, Table 14).

              Zone 9: Assawoman Bay shores

                    Zone 9 encompasses the south shores of Assawoman Bay (Ta             'ble 15). The
              slope of the coastline is gentle, very indented and fringed with marshes. The 5-foot
              contour lies about 4000 feet from the shore. Marshes are being lost due to erosion
              and submergence. More than 50 percent of the transects indicate erosion rates
              between -0.5 and -1.5 ft/yr for records between 1850 to 1989 (transects 186-188,
              193-196, 202-203, 208-209, 211-214, Table 15). The lack of historical shoreline
              data for the northern section of the shoreline did not allow for a reliable estimate of
              long term shoreline change in this area.





                                                    SUMMARY


                         The mouth. of the north bank of Saint Martin River appears to be the
                  area where marshes are eroding most rapidly. Marshes are also eroding at
                  the south shores of the Isle of Wight Bay, the west bank of the middle part
                  of Herring Creek, the north bank of Manklin Creek, and the Isle of Wight.




















                                                        24






                                                       1320000                                             1328000                                             1336000                                             1344000




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                                  Figure 14.                     Location of transects                                                            25



















                      Table 2.        Rates of Shoreline Change (feet/year)
                                      Zone 1: Isle of Wight Bay Shores


                      TRANSECT        DESCRIPTION            RATE            DATES                   YEARS


                      1               Trees                  -2              1908-1989               81
                      2               No Marsh               -1              1908-1989               81
                      3               Marsh                  -1.0            1850-1989               139
                      4               Marsh                  -3              1850-1989               139
                      6.              Marsh                  -3              1850-1989               139
                      7               Sandy beach            -0.6            1850-1989               139
                      8               Marsh                  -0.8            1850-1989               139
                      9               Marsh                  -1.2            1850-1989               139
                      10              Development            0               1962-1989               27
                      11              Development            0               1962-1989               27
                      12              Development            0               1962-1989               27
                      13              Marsh                  -1.3            1850-1989               139
                      14              Marsh                  0               1934-1989               55
                      15              Marsh                  -1.6            1850-1989               139
                      16              Marsh                  -0.9            1850-1989               139
                      17              Marsh                  -0.6            1850-1989               139
                      18              Development            0               1962-1989               27
                      19              Marsh                  -0.9            1850-1989               139
                      21              Marsh                  -0.3            1850-1989               139
                      22              Marsh                  -1.5            1850-1989               139
                      23              Marsh                  -2.2            1850-1989               139


                      Overall Average -1.0
                      Marsh Average -1.3


                      Notes:
                      DATES refers to the dates of the information sources
                      YEARS refers to the time period between two sources













                                                                  26





















                      Table 3.        Rates of Shoreline Change (feet/year)
                                      Zone 2: Turville Creek (South Bank)


                      TRANSECT        DESCRIPTION             RATE             DATES                   YEARS


                      24              Marsh                   -0.6             1850-1989               139
                      25              Marsh                   -1.0             1850-1989               139
                      26              Marsh                   -1.2             1850-1989               139
                      27              Development             -1.0             1934-1989               55
                      28              Development             0                1934-1989               55
                      29              Marsh                   -0.8             1850-1989               139
                      55              Marsh                   0                1850-1989               139
                      56              Marsh                   0                1934-1989               55
                      57              Marsh                   -0.8             1934-1989               55
                      58              Marsh                   -0.7             1934-1989               55
                      61              Filling,NM              -0.3             1934-1989               55
                      62              Filling,NM              -0.5             1934-1989               55
                      63              Trees,NM                0                1934-1989               55
                      65              Filling                 -0.3             1934-1989               55
                      66              Filling                 0                1934-1989               55
                      67              Filling                 0                1934-1989               55

                      Overall Average -0.5
                      Marsh Average -0.6


                      Note:
                      NM: No Marsh
                      DATES refers to the dates of the information sources
                      YEARS refers to the time period between two sources
















                                                                   27


















                      Table 4.        Rates of Shoreline Change (feet/year)
                                      Zone 2: Turville Creek (North Bank)


                      TRANSECT        DESCRIPTION            RATE             DATES                  YEARS.


                      68              Development            0                1962-1989              27
                      69              Development            0                1962-1989              27
                      70              Development            0                1934-1989              55
                      71              Development            0                1962-1989              27
                      72              Development            0                1962-1989              27
                      73              Trees                  -0.8             1934-1989              55
                      74              Development            0                1934-1989              55
                      75              Marsh                  -0.6             1934-1989              55
                      76              Marsh                  -0.5             1934-1989              55
                      77              Development            -0.7             1850-1989              139
                      78              Marsh                  -1.5             1850-1989              139
                      79              Marsh                  -1               1850-1989              139
                      80              Marsh                  -1.8             1850-1989              139
                      81              Marsh                  -0.3             1934-1989              55
                      82              Sandy                  -0.2             1850-1989              139
                      83              Sandy                  -0.9             1850-1989              139
                      84              Marsh                  -0.9             1850-1989              139
                      85              Marsh                  0                1850-1989              139


                      Overall Average -0.5
                      Marsh Average -0.8

                      OVERALL AVERAGE -0.5
                      MARSH AVERAGE -0.7


                      Notes:
                      DATES refers to the dates of the information sources
                      YEARS refers to the time period between two sources














                                                                  28




















                       Table 5.           Rates of Shoreline Change (feetlyear)
                                          Zone 3: Herring Creek (East Bank)

                       TRANSECT           DESCRIPTION               RATE              DATES                      YEARS


                       30                 Marsh                     -1.6              1850-1989                  139
                       31                 Marsh                     -2.0              1850-1989                  139
                       32                 Marsh                     -1.4              1850-1989                  139
                       33                 Marsh                     -1.1              1850-1989                  139
                       37                 Trees,NM                  0.2               1850-1989                  139
                       38                 Field                     -0.2              1850-1989                  139
                       39                 Field                     -0.5              1850-1989                  139
                       40                 Field                     -0.2              1934-1989                  55
                       41                 Trees                     0.9               1934-1989                  55
                       42                 Marsh                     -0.3              1934-1989                  55


                       Overall Average -0.6
                       Marsh Average -1.3


                       Notes:
                       DATES refers to the dates of the information sources
                       YEARS refers to the time period between two sources
























                                                                         29

















                      Table 6.        Rates of Shoreline Change (feet/year)
                                      Zone 3: Herring Creek (West Bank)

                      TRANSECT        DESCRIPTION            RATE            DATES                   YEARS


                      43              Fringe Marsh           1.0             1934-1989               55
                      44              Trees                  -0.4            1934-1989               55
                      45              Development            0               1934-1989               55
                      46              Development            0               1934-1989               55
                      47              Development            0               1934-1989               55
                      48              Development            -0.5            1934-1989               55
                      49              Marsh                  -0.7            1850-1989               139
                      50              Marsh                  -0.9            1850-1989               139
                      51              Marsh                  -0.2            1850-1989               139
                      52              Marsh                  -0.4            1850-1989               139
                      53              Marsh                  -0.5            1850-1989               139
                      54              Marsh                  -0,4            1850-1989               139


                      Overall Average -0.3
                      Marsh Average -0.3

                      OVERALL AVERAGE -0.4
                      MARSH AVERAGE -0.7


                      Notes:
                      DATES refers to the dates of the information sources
                      YEARS refers to the time period between two sources






















                                                                 30














                     Table 7.        Rates of Shoreline Change (feet/year)
                                     Zone 4: Manklin Creek (South Bank)


                     TRANSECT        DESCRIPTION            RATE            DATES                   YEARS


                     86              Marsh                  -1.5            1850-1989               139
                     87              Marsh                  -1.5            1934-1989               55
                     88              Fringe Marsh           -0.5            1850-1989               139
                     89              Marsh                  -0.5            1934-1989               55
                     90              Fringe Marsh           -0.6            1934-1989               55
                     92              Marsh                  0.3             1934-1989               55
                     93              Fringe Marsh           -0.5            1934-1989               55
                     94              Fringe Marsh           0               1934-1989               55
                     95              Fringe Marsh           0               1934-1989               55
                     96              Fringe Marsh           0               1934-1989               55

                     Overall Average -0.5
                     Marsh Average -0.5


                     Notes:
                     DATES refers to the dates of the information sources
                     YEARS refers to the time period between two sources




                     Table 8.        Rates of Shoreline Change (feet/year)
                                     Zone 4: Manklin Creek (North Bank)


                     TRANSECT        DESCRIPTION            RATE            DATES                   YEARS


                     97              Marsh                  -1,5            1934-1989               55
                     98              Marsh                  -1.4            1934-1989               55
                     99              Development            -1.3            1934-1989               55
                     100             Development            0               1934-1989               55

                     Overall Average -1.1
                     Marsh Average -1.5


                     OVERALL AVERAGE -0.6
                     MARSH AVERAGE -0.6


                     Notes:
                     DATES refers to the dates of the information sources
                     YEARS refers to the time period between two sources





                                                                31



















                     Table 9.        Rates of Shoreline Change (feet/year)
                                     Zone 5: St. Martin River.(South Bank)


                     TRANSECT        DESCRIPTION            RATE            DATES                   YEARS


                     101             Marsh                  -03             1934-1989               55
                     102             Sandy                  0               1850-1962               112
                     103             Sandy                  -1              1850-1962               112
                     104             Fringe Marsh           0               1934-1989               55
                     105             Marsh                  -0.6            1850-1989               139
                     106             Marsh                  0               1850-1989               139
                     107             Fringe Marsh           0.2             1850-1989               139
                     125             Fringe Marsh           0.8             1934-1989               55
                     126             Sandy                  0.9             1934-1989               55
                     132             Trees                  0               1934-1989               55
                     133             Trees                  0.8             1934-1989               55


                     Overall Average 0.03
                     Marsh Average -0.06


                     Notes:
                     DATES refers to the dates of the information sources
                     YEARS refers to the time period between two sources

























                                                                32


















                        Table 10.        Rates of Shoreline Change (feet/year)
                                         Zone 5: St. Martin River (North Bank)


                        TRANSECT         DESCRIPTION               RATE             DATES                     YEARS


                        148              Development               -1.4             1934-1989                 55
                        150              Fringe Marsh              -0.6             1934-1989                 55
                        151              Fringe Marsh              -0.5             1934-1989                 55
                        152              Fringe Marsh              -1.3             1934-1989                 55
                        153              Marsh                     -2.2             1850-1989                 139
                        154              Marsh                     -3.2             1850-1989                 139
                        155              Marsh                     -3.1             1850-1989                 139
                        156              Marsh                     -2.9             1850-1989                 139
                        157              Marsh                     -1.3             1850-1989                 139
                        158              Marsh                     -3.3             1850-1989                 139
                        159,             Marsh                     -1.3             1850-1989                 139
                        160              Marsh                     -1.6             1850-1989                 139
                        161              Marsh                     -2.2             1850-1989                 139
                        162              Marsh                     -1.6             1850-1989                 139
                        163              Marsh                     -1.4             1850-1989                 139
                        164              Marsh                     -0.7             1850-1989                 139
                        165              Marsh                     -1.7             1850-1989                 139


                        Overall Average -1.8
                        Marsh Average -1.8


                        OVERALL AVERAGE -1.1
                        MARSH AVERAGE -1.3


                        Notes:
                        DATES refers to the dates of the information sources
                        YEARS refers to the time period between two sources















                                                                       33














                        Table 11.        Rates of Shoreline Change (feet/year)
                                         Zone 6: Shingle Landing Prong (South       Bank)

                        TRANSECT         DESCRIPTION               RATE             DATES                     YEARS


                        108              Development               -0.5             1934-1989                 55
                        109              Narrow Marsh              -0.7             1934-1989                 55
                        110              Trees                     -1               1934-1989                 55
                        ill              Trees                     0                1934-1989                 55
                        112              Sandy                     0                1934-1989                 55
                        116              Trees                     1.4              1934-1989                 55
                        117              Filling                   0.4              1934-1989                 55
                        118              Trees                     0.6              1934-1989                 55


                        Overall Average 0.02
                        Marsh Average -0.7


                        Notes:
                        DATES refers to the dates of the information sources
                        YEARS refers to the time period between two sources






                        Table 12.        Rates of Shoreline Change (feet/year)
                                         Zone 6: Shingle Landing Prong (North       Bank)


                        TRANSECT         DESCRIPTION               RATE             DATES                     YEARS


                        119              Marsh                     -0.6             1934-1989                 55
                        120              Trees                     0.3              1934-1989                 55
                        121              Trees                     -1.1             1934-1989                 55
                        122              Marsh                     -0.5             1934-1989                 55
                        123              Trees                     0                1934-1989                 55
                        124              Fringe Marsh              -1.3             1934-1989                 55

                        Overall Average -0.5
                        Marsh Average -0.8

                        OVERALL AVERAGE -0.2
                        MARSH AVERAGE -0.8


                        Notes:
                        DATES refers to the dates of the information sources
                        YEARS refers to the time period between two sources




                                                                       34















                      Table 13.       Rates of Shoreline Change (feet/year)
                                      Zone 7: Bishopville Prong (West Bank)


                      TRANSECT        DESCRIPTION             RATE            DATES                  YEARS


                      134             Trees                   0               1934-1962              28
                      135             Trees                   0               1934-1962              28
                      136             Trees                   0               1934-1962              28
                      137             Trees                   0               1934-1962              28
                      139             Development             0               1934-1962              28

                      Overall Average 0
                      Marsh Average 0

                      Bishopville Prong (East Bank)

                      140             Trees                   0               1934-1962              28
                      141             Trees                   -1.3            1934-1962              28
                      142             Trees                   -1.5            1934-1962              28
                      143             Trees                   0               1934-1962              28
                      144             Trees                   0               1934-1962              28
                      145             Trees                   0               1934-1962              28
                      146             Marsh                   -0.6            1934-1989              55
                      147             Narrow Marsh            0               1934-1962              28


                      Overall Average -0.4
                      Marsh Average -0.3


                      OVERALL AVERAGE -0.3
                      MARSH AVERAGE -0.3


                      Notes:
                      DATES refers to the dates of the information sources
                      YEARS refers to the time period between two sources
















                                                                  35















                        Table 14.        Rates of Shoreline Change (feet/year)
                                         Zone 8: Isle of Wight

                        TRANSECT         DESCRIPTION               RATE             DATES                     YEARS


                        170              Marsh                     -1.4             1850-1989                 139
                        171              Marsh                     -1.2             1850-1989                 139
                        172              Fringe Marsh              0                1850-1989                 139
                        173              Fringe Marsh              -0.7             1850-1989                 139
                        174              Sandy beach               -1.7             1850-1989                 139
                        175              Marsh                     -1.7             1850-1989                 139
                        176              Fringe Marsh              -2.5             1850-1989                 139
                        177              Sandy beach               -1.8             1850-1989                 139
                        178              Sandy beach               -1.9             1850-1989                 139
                        179              Sandy beach               -1.4             1850-1989                 139
                        180              Sandy beach               0.3              1850-1989                 139
                        181              Sandy beach               -1.1             1850-1989                 139
                        182              Marsh                     -1.0             1850-1989                 139
                        183              Marsh                     -0.4             1850-1989                 139
                        184              Marsh                     -0.5             1850-1989                 139


                        OVERALL AVERAGE -1 .1
                        MARSH AVERAGE -1.0


                        Notes:
                        DATES refers to the dates of the information sources
                        YEARS refers to the time period between two sources























                                                                       36


















                              Table 15.            Rates of Shoreline Change (feet/year):    Zone 9


                              TRANSECT             LOCATION             DESCRIPTION          RATE       DATES                YEARS


                              185       Isle of Wight (NE)              Road                 -0.4       1850-1989            139
                              186       St. Martin Neck                 Marsh                -1.1       1850-1989            139
                              187@      St. Martin Neck                 Marsh                -0.8       1850-1989            139
                              188       St. Martin Neck                 Marsh                -0.9       1850-1989            139
                              189       St. Martin Neck/Drum Pt.        Marsh                0          1850-1989            139
                              190       St. Martin Neck/Drum Pt.        Fringe Marsh         0          1934-1989            55
                              191       St. Martin Neck                 Fringe Marsh         0.5        1934-1989            55
                              192       St. Martin Neck                 Marsh                0          1934-1989            55
                              193       Assawoman Bay                   Marsh                -1.7       1850-1989            139
                              194       Assawoman Bay                   Marsh                -0.7       1850-1989            139
                              195       Assawoman Bay                   Marsh                -0.5       1850-1989            139
                              196       Assawoman Bay                   Marsh                -1.5       1850-1989            139
                              197       Goose Pond                      Marsh                -0.4       1850-1989            139
                              198       Goose Pond                      Marsh                0          1850-1989            139
                              199       Goose Pond                      Marsh                -0.2       1934-1989            55
                              200       Goose Pond                      Marsh                -0.2       1850-1989            139
                              201       Goose Pond                      Marsh                0          1850-1989            139
                              202       Goose Pond                      Marsh                -0.5       1934-1989            55
                              203       Goose Pond                      Marsh                -0.6       1850-1989            139
                              205       Goose Pond                      Marsh                -0.4       1850-1989            139
                              206       Goose Pond                      Marsh                -0.3       1850-1989            139
                              207       Goose Pond                      Marsh                -0.4       1850-1989            139
                              208       Goose Pond                      Marsh                -0.7       1850-1989            139
                              209       Goose Pond                      Road                 -0.6       1850-1989            139
                              210       Assawoman Say                   Sandy                4.4        1962-1989            27
                              211       Hills Island                    Marsh                -0.5       1850-1989            139
                              212       Brady Island                    Marsh                -1.7       1850-1989            139
                              213       Assawoman Bay                   Marsh                -1.4       1962-1989            27
                              214       Peeks Creek                     Marsh                -0.7       1962-1989            27
                              215       Peeks Creek                     Marsh                -3.5       1962-1989            27


                              OVERALL AVERAGE -0.5
                              MARSH AVERAGE -0.7


                              Notes:
                              DATES refers to the dates of the information sources
                              YEARS refers to the time period between two sources



















                                                                                         37










                                                  CHAPTER FOUR
                                PROJECTION OF FUTURE SHORELINE POSITION


                     In the previous section we described the rate of shoreline change in the study
              area. In this section we will estimate the future position of the shorelines based upon
              the past rate of change, topography, landform type, and projected sea level rise
              scenarios. Even though Maryland's Atlantic coastal bay region would be subject to all
              of the impacts associated with accelerated sea level rise (erosion, inundation, salt
              water intrusion, higher water tables, and increasing flooding and storm damage), this
              section considers potential increases in erosional trends and inundation impacts only.

              1. EROSIONANUNDATION MODEL


                     Because erosion and inundation are complex processes, their contribution to
              coastal retreat as sea level rises is not entirely understood. To simplify these complex
              processes we assumed a simultaneous occurrence of both processes due to sea level
              rise for each scenario.


                     As we discussed in the last chapter, shoreline change rates for the study area
              were obtained through a comparison of historical maps and past sea level rise (please
              see tables 2-15). We assumed that one of the major factors causing erosion was sea
              level rise occurring during the historical period studied. Shoreline change rates can be
              projected into the future by first establishing a rule of thumb between shoreline
              change and sea level rise* ' For example, if a shoreline has eroded -200 feet in 100
              years, as indicated by a historical maps, then the erosion rate for this shoreline is -2
              ft/yr. At the same time, if during this same time period relative sea level rose by 1.3
              ft, then for every 0.013 ft of sea level rise, the shore eroded by -2 feet. These
              values (0.013 ft/yr of sea level rise = -2 ft/yr of shoreline retreat) were then used as
              a rule of thumb to determine the future shoreline position in our study area. Relative
              sea level rise was obtained by adding eustatic or global sea level rise (0.6 ft) with the
              local rate of subsidence (0.7 ft). Erosion rates for the various sea level rise scenarios
              were calculated and are shown in Table 16 (the base year was 1989).
















                                                         38














                        Table 16. Erosion Rate Estimates


                        Year          Relative Sea Level Rise             Erosion Rate
                                                     (ft)                        (ft/yr)

                        Last 100 years               1.3                         -2.0

                        2020                         0.4                         -2.0
                                                     0.5                         -2.5


                        2050                         0.8                         -2.0
                                                     1.5                         -3.8


                        2100                         1.4                         -1.9*
                                                     1.7                         -2.4
                                                     3.0                         -4.2
                                                     4.4                         -6.1


                          Erosion rates for 2100 are based on 111 years. The baseline is
                        1989.



                     We drew shoreline prof iles at several locations (Figure 15). @.ppendix A contains
              all of the profiles. These profiles were used to estimate inundation potential. The sea
              level rise scenario (y axis) was drawn on the profile and the inundated area was
              estimated (x axis). The study area shoreline is predominantly occupied by wetlands,
              but sandy shores are also present. Thus, it was necessary to establish two types of
              erosion rates: (1) for wetlands and (2) for sandy shores. Shorelines stabilized with
              engineering structures were assumed to remain stable as sea level rises. When
              projecting the position of a marshy shoreline, we discovered that erosion and
              inundation would destroy the marsh for sea level rise scenarios greater than 1.4 feet.
              Therefore, it was necessary to apply erosion rates for sandy shores obtained from
              nearby representative areas. A sea level rise of 1.4 feet is higher than the high mid-
              tidal range 0.1 feet) that determines the upland limit of today's marshes. This is
              discussed below.


                     A sample shoreline profile is provided as an example of how the erosion and
              inundation potential at wetland shorelines was determined (Figure 16). The profile was
              divided into three sections based on its elevation. A combination of erosion rates and
              inundation were used in each section to determine the future position of the


                                                          39








            shorelines. Sector A represents the lower part of the shoreline profile where wetlands
            are generally located. In this sector, the hypothetical shoreline position was estimated
            by adding inundation and shoreline regression due to erosion as determined by
            historical erosional trends. Sector B represents a steeper slope where wetlands will
            not be able to form, except as a narrow fringe marsh, as sea level rises. In this sector,
            the new shoreline position was estimated by adding inundation plus erosion rates
            calculated for sandy shores in nearby areas. We used erosion rates for sandy shores
            because we assumed that all marshes will be lost at this elevation and as a result, the
            shoreline will be sandy. Sector C represents the upland areas of the profile. If the
            slope was found to be gentle enough for new wetlands to form, erosion rates for the
            original marshy shore were used to determine the hypothetical shoreline position. If
            the slope was not gentle enough for wetland formation, no wetlands were allowed to
            form and erosion rates were applied from sandy shores of other nearby areas.




































                                                       40




                                                                                    g.-1111@.':@:-:'. od






                                                    1320000                                             1328000                                             1336000                                             1344000




           CD

           0                                                 +                                                   +                                                    +                                                  +
           '7
           C:)



           CU
           CU






                                                                0
                                                                                                                                                                                                                         ASSAWOMAN
           CD                                                           3                                                                                                                                                        BAY
           CD
           CD                                                +
           LID                                                                   30                                                                                   +


                                                                                                                                                                                                                    41
                                                          28                           27
                                             Shingle Landing
                                                 Prong                                                                                                                      39


                                                                                                                                                                                                         Isle
           CD                                                                                                                                                                           41.5             of
           0                                                                                                                                                                                             Wight
           cc[:))                                           +                                                                                                         +
           CD




                                                                                                                                4-1
                                                                                                                                  e/)


           CD                                                                                                                        18
           C)
           C)                                               +                                                   +                                                     +
           CD                                                                                                                                                                                                           +
           0
                                                                                                                                                                                                                               ISLE
                                                                                                                                                                                                                               OF
                                                                                                                                                                                                                               WIGHT
                                                                                                                                         Cv.                                    8.5                                            BAY
                                                                                                                                                                                                                         4
                                                                                                                                                                         8.

                                                                                                                                        12
           C:)
           0
           CD
           CU                                              +                                                   +                                                                                                       +
           Cn                                                                                                                                                                                                                           3

                                                                                                                                                                                                                   1.5





                              Scale

                               1: 72000                                           0                                                         Feet                                                       21000
                             Figure 15.                     Location              of survey profiles along the study
                                                            shoreline                                                  41





















                                  10-


                                   9  . ..... .................. ............ --- - ------ - --------------- -------------- ---- ---- ---- - ---------- - --------- - ----


                                   8  . ....................... ........ . ..... . ... .... . .. . ................ - - - - -------------- - ----------- --------- -


                                   7  . ....... . .. . ..... ................ . .. ...... - - ------ - ------------ - ------ - ----- ------------------------------------


                                   6  . .............. ............... . ..... . ......... . .........


                                   5  . ............. . ........ . .. . ....... . .. .................... - --------- . ............ .......... . ..


                                   4  - -- - --------------------- - ---- -       - ----------




                                   2  - -------- -----------

                                   1  . ....... . ...                   . . .... Upper limft marsh]
                                   0)
                                      0              26o            .400               660               86o             1600              1 @00
                                              Sector A            Sector B             Feet          Secto Ir C
                                      Figure 1. 6.      Representative p          rofile and erosion/inundation
                                                        model


















                                                                                   42










             Il. FUTURE SHORELINE POSITIONS


                   We derived the hypothetical shoreline position for the various sea level rise
             scenarios by incorporating the historical shoreline change (erosion x the # of years
             from 1989) and the inundation potential derived from the topography of the shoreline
             for each transect. The shoreline position between the transects was interpolated. It
             was assumed that areas where development is presently located will maintain and
             upgrade their protection as sea level rises and therefore, no estimates for shoreline
             change were measured in these areas. Because interpolation and representative
             profiles were used, the position of hypothetical shorelines are not to be considered
             final but an estimation of the extent of shoreline retreat. A series of maps (Figures 17
             through 44)3  depicting the possible position of the shoreline, by zone, under different
             scenarios of sea level rise are included in this analysis.

             Zone 1: Isle of Wight Bay shores (Figures 17, 18 and 19). Shoreline retreat in this
             zone averages between 100 and 150 feet, depending on the transect, for the year
             2020; 250 to 400 feet for year 2050; and 400 to 780 feet for the year 2100.
             Shorelines adjacent to transect 4 and 19 (Figure 14) had the highest coastal retreat.
             The area of Bay Shore Acres (transect 7, Figure 14) showed the lowest retreat rate
             because of its steep shoreline profile.

             Zone 2: Turville Creek shores (Figures 20, @11 and 22). Shoreline retreat on this Creek
             diminishes in a upstream direction because of steep slopes and a decrease in
             wetlands. Shoreline retreat rates are lower on the south bank of the Creek. On
             average, shoreline retreat varies from 35 to 200 feet for the year 2020, 60 to 500
             feet for the year 2050 and 100 to 700 feet for the year 2100. Shoreline retreat was
             least along Gum Point Road and at the Ocean Downs Raceway. Wetland areas near
             the mouth of Herring Creek and the western end of Turville Creek had the highest
             shoreline retreat.


             Zone 3: Herring Creek shores (Figures 23, 24 and 25). The most severe shoreline
             regression is possible near the mouth adjacent to Turville Creek. Shoreline regression
             in this region averages 150 to 200 feet for the year 2020, 350 to 500 feet for the
             year 2050, and 480 to 600 feet for the year 2100. The shores along the source of
             the Creek are protected, mainly around Route 50 and, therefore, the banks were
             assumed stable and no projections were made.

             Zone 4: Manklin Creek shores (Figures 26, 27 and 28). More than 75 percent of the
             north bank of this Creek is developed and protected by engineering structures and
             therefore, no projections were made along this section. The south bank may retreat
             between 70 and 85 feet for the year 2020, 120 and 200 feet for the year 2050, and
             180 to 660 feet for the year 2100.



                These figures are located at the end of this section


                                                       43








              Zone 5: St. Martin River shores (Figures 29, 30 and 31). The urban development of
              Ocean Pines, on the south bank of this river, accounts for more than 50 percent of
              this shoreline. No shoreline projections were estimated here because of the existence
              of hard structures. Wetlands on this bank exist only from transect 104 to 107 (Figure
              14). Historical shoreline analysis indicates very low rates of coastal erosion. The north
              bank of the river starting on transect 150 (Figure 14) and continuing downstream is
              occupied by one of the        most extensive wetlands in the study area. Aerial
              photography and field surveys indicate the presence of inland ponding. This area,
              together with zone 9, can expect a significant amount of shoreline retreat as sea level
              rises. Average shoreline retreat may run between 350 and 450 feet for the year 2020,
              560 to 850 feet for the year 2050 and 840 to 1600 feet for the year 2100.
              According to the analysis, the western end of St. Martin Neck, where Isle of Wight
              Road (golf course) is located, could be breached and as a result the area could be
              converted into an island. The highest point is about 5 feet above present sea level
              along the road. Figure 32 shows an aerial photograph of St. Martin Neck.

              Zone 6: Shingle Landing Prong shores (Figures 33, 34 and 35). The shores of Shingle
              Landing Prong have steep slopes and small areas of fringe marsh. The model projected
              small changes in the position of its present shoreline. On average the shoreline could
              retreat between 20 to 50 feet for the year 2020, 40 to 80 feet for the year 2050 and
              50 to 150 feet for the year 2100.

              Zone 7: Bishopville Prong shores (Figures 36, 37 and 38). Bishopville Prong has banks
              with steep slopes and some low-lying areas. Shoreline retreat projections were made
              only for the lower part of the east bank of the prong (transects 146 and 147, Figure
              14). Here, the shoreline may retreat between 30 to 50 feet for the year 2020, 70 to
              130 feet for the year 2050 and 130 to 200 feet for the year 2100.

              Zone 8: Isle of Wight Island (Figures 39, 40 and 41). Shoreline retreat on this island
              will be greatest on the western shore, but shoreline retreat will also occur on the east
              and northwest shores. The southern shores of the island are expected to retreat the
              least because they consist of'steep slopes. The highest point of the island barely
              exceeds 10 feet above present sea level and because most of the shores have very
              gentle slopes the island is vulnerable to even low levels of inundation. On average, the
              projected shoreline retreat for the island varies between 130 and 160 feet for the year
              2020, 250 and 420 feet for the year 2050 and 380 and 840 feet for the year 2100.

              Zone 9: Assawoman Bay shores (Figures 42, 43 and 44). The shores of this bay
              contain extensive wetlands with very gentle slopes that decrease northward along the
              shore. Wetland ponding is already occurring as shown by aerial photography (Figure
              45). Sea level rise could have catastrophic consequences in this area because of the
              shore's low elevation and high rates of erosion. Average shoreline retreat projections
              vary from 300 to 400 feet for the year 2020, 600 to 1000 feet for the year 2050 and
              900 to 1400 feet for the year 2100.


                                                        44








             Legend clarification for the following maps (fig 17-31, 33-44).

             The shoreline position for each map is based on the hypothetical sea level rise value,
             historical shore erosion and inundation.


                    For the year 2020

                    Present Trend       = 0.4 ft. of sea level rise (SLR)
                    Most Likely         = 0.5 ft SLR

                    For the year 2050

                    Present Trend       = 0.8 ft SLR
                    Most Likely         = 1.5 ft SLR

                    For the year 2100

                    Present Trend       = 1.4 ft SLR
                    Low Scenario        = 1.7 ft SLR
                    Most Likely         = 3 ft SLR
                    High Scenario       = 3.7 ft SLR

                    Present Protection/Future Protection     for all maps the hypothetical shoreline
             position was not calculated in these areas because these areas are protected by
             structural shoreline protection. The authors assumed that these structures will be
             upgraded to accommodate higher water levels.





















                                                       45















                                                                       Keyser
                                                                      -Pt                           I S L E                       0 F                        I G              T



                                                                                                        6
                                                                                                                                   B A Y

                                              4
                                                                                                                              LEGEND
                                                                                                                                            Present Trend
                                                                                                                                            Most Likely
                                                                   -7                                                                       Present Protection
                                                                                                                                            Future Protection


                                                                                                                                  3




                                                                                     Q
                                                                                                                                       Dog and Sitch
                                                                                                                                            Islands
                                                                                                       Wight
                                                                                      ape   JAI 6
                                                                                                                     '4v


                                                                   6
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                                                                                        C
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                                                                                                 Ocerin City                     A


                                                                         9
                                                                                                                                                                7



                                                                                                                                               r
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                                                                                                                                                  3
                                                                                               12



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                                                                                          Park'
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                                                                                                                   est
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                                                             i
                                                            ORE                        4       10
                                                                                                                                8
                                                 s ,_@!Tlm       E                          At,                                                           Coast/a

                                                                                                                                                          @4
                                                   1000            0        1000        2000         3000         4000        5000          6000       7000 FEET
                                                     - -        F--
                                                Figure         17.       Zone       1      Estimated          Shoreline positions                  for the
                                                                         year      2020

                                                                                                           46















                                                                           lKeyser                                                                     tb
                                                                                                        IT S L E                       (0 F                 w I G H T




                                                                                                                                         B      A Y

                                                4

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                                                                                                                                                Win Likely
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                                                    FiguTe I B.                Zone 1c Estimated slhare$ine positti                                   ns if ar the
                                                                                         2050
                                                                                                             47















                                                                  Keyser
                                                     4         -..-Pt
                                                                                             I S L E                     0 F               W I G H T



                                                         7.1
                                                                                                                          B A Y


                                                                                                                         LEGEND
                                                                                                                                     Present Trend
                                                 lizle-                                                                              Low Scenario
                                                                        3                                                            Most Likely
                                                                                                                                     High Scenario
                                                  x                                                                                  Present Protection
                                                                                                                                     Future Protection


                                                                                                  3



                                                                                                                             Dog and Bitch
                                                                                                                                  Islands
                                                                                 ipe          Wight

                                                                                                     0


                                                                 N.



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                                                                    9
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                                                                                                                                              Coast/G

                                                                                                                                  is

                                               1000         0         1000        2000        3000       4000         5000       6000       7000 FEET
                                               Figure 19.             Zone 1: Estimated                 shoreline positions                for the
                                                                      year 2100
                                                                                                 48











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                                                                                                                          19
                                                                                                                                   1000        0         1000       2000      3000
                                                                                                                      rp
                          Figure 20.            Zone 2: Estimated shoreline                    positions for the
                                                year 2020













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                                                                                                                                              1000         0         1000        2000        3000
                           Figure 21.             Zone 2:          Estimated         shoreline        positions for the
                                                  year 2050




















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                               Figure 22.               Zone 2: Estimated shoreline positions for the
                                                        year 2100









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                                                                                                            V
                                                                                                                        V                   LEGEND
                                                                                                          z
                                                                                                                                             -           Present Trend
                                                                                                                                            -            Most Likely
                                                                                                                                                         Present Protection
                                                                                                                                                         Future Protection



                                                                                                     2000                       4000         5000          6000          7000 F@EET
                                                            Figure 23.                 Zone        3@ EStimated Shorekne positions for the
                                                                                       year       2020              52




























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                                                   113
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                                                                                                    it                                   Low Scenario
                                                                                                    ff
                                                                                                                                         Most Likely
                                                                                                   If                                    High Scenario
                                                                                                                                         Present Protection
                                                                                                                                         Future Protection


                                                  1000         0           1000     2000        30.00      40         5000        6000        70100 FEET
                                                   Figure 25.              Zone     3:  ESt!Mated shoreline positions for the
                                                                           year    2100
                                                                                                  54















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                                                                                                                                                                                                4
                                                                                                                                                                                      0



                                                                               1000         o                     2000       3000        4000        5000       6000        7000   FEET
                                               Figure       26.       Zone       4    Estimated shoreline position                      s for the
                                                                       year 2020
























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                                                                                                                                                                                       4
                                                                                                                                                                             10

                                                                            1000         0        1000       2000       3WO        4000       5000       6000       70W FEET
                                              Figure      27.       Zone 4:       Estimated shoreline                positions for         the
                                                                    year 2050












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                                                                                                                                                                                    ag




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                                                                                                                                                                                   0
                                                                                                                                        c


                                                                              1000         0         looo       2000        30DO       4000        5000       6000        70100 FEET

                                               Figure 28.            Zone 4:        Estimated shoreline                 positions for the
                                                                     year 2100










                                                                                       ft
                                                                -C@                    11 C_-       M )A            I         N E C K%,
                                                                                         S


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                                                                                                                                                            6



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                                                                                   0

                                                                                                                                  oo.     90


              LEGEND
                       Present Trend
                       Most Likely
              -.000500 Present Protection                                                           Q@
                       Future Protectio(I                                                                       N E                                          Jenki
                                                      00                        60"00        0 R
              1000      0        1000     2000                         5000
                                                                                                    Figure     29..    Zone 5:      Estimated        shoreline
                                                                                                                       year 2020





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                                                                                                                     M )A               I                E
                                                                                                                       A'
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                                                                                                                                                                                       6
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                                                                                                                                U



                   LEGEND
                             Present Trend
                             Most Likely
                              Present Protection
                              Future Protection                                                                                     N E
                                                                                                                                                                                       .'Jen
                   1000,       o'        i dob'       0*
                                                                                                                         S.,
                                                               3000       40         500        6000       70 0 FftT                                                           -z'
                                                                                                                         Figure 30.           Zone 5: Estimated shorelin
                                                                                                                                              year 2050





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                                                                                                Po'                                      ----Saltgr.a


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                                                                                                                                                                 6
                                                                                                                                                  5


                                                                                     3olf Course





                LEGEND
                           Press t Tr
                                     end
                           Low Scenario
                           Most Likely
                           High Scenario
                4*MWMPW-   Present Protection
                                    otection
                           Future Pr                                                                                N E

                                                                           00
                                             2000      3                   W                                0                                                 1
                1000       0'      1000                   0       0       500       6000      7000 EET
                                                                                                       Figure 31.          Zone 5: Estimated shoreline
                                                                                                                           year 2100

































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                                                                                                            Ch
                                                                                                                   21          -
                                                                                                                              589
                                   LEGEND
                                                  Present Trend
                                                  Most Likely
                                                  Present Protec                                                                                          2
                                                  Future Protection
                                                                                                          1000           0            1000          2000           3000          4000           5000           6000           7000 FEET
                                                                                                            F=1  F=A-- Fzq                             -
                                    Figure 33.                   Zone         6:    Estimated shoreline positions for                                          the
                                                                 year         2020














                                                                                                                                7-



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                                                                                 rt S.@;
                                                                                         22

                           LEGEND
                                      Present Trend
                                      Most Likely
                                      Present Protection
                                      Future Protection
                                                                                 1000        0         1000       2000       3000       4000        500                   7000 FEET

                            Figure 34.             Zone      6:   Estimated shoreline positions for                        the
                                                   year     2050








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                     '71











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                                                                                                                                                     -rong
                                                                                             A'                        Shingle      Lauding        P                  Eagi
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                                                                                                         Landing
                                           24


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                                                                          en?
                      LEGEND
                                ?iesenll Trend
                                @Low Scenario
                                Most Likely
                                High Scenurio
                                pfe%eC@*, PlOtOCtiOn
                                F,m.,,vle Pfatectie"
                                                                       low                  I"        2WO       3000       4WO       5000      bow       7000 FEET
                                                                                                                  L
                      Figuve 35,           Zone     6: Estimated shoreline positions for the
                                           'year   2100






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                                LEGEND
                                           Present Trend                                      Shingle        Landing         Prong               'Eagle
                                           Most Likely                         Shingle,
                                                                                                                                                  Island
                                                                           J'  Landing
                                           Present Protection
                                                                                                                                                   s\
                                           Future Protection
                                                                        I @)                      4000        $000        6000       7000 FEET
                                         1000         C         1000       2000        3000
                                 Figure 36.             Zone 7: Estimated                Shoreline positions for the
                                                        year 2020
                                                                                               65





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                                           Most Likely                      Shingle.                                                           s a n
                                           Present Protec                                                                                     I I    d
                                                           tion              Lan,ding

                                                                             00
                                           Future Protection                                                                               N-Ns
                                         10          0          10,00     2000       3000       4000       5000       6000       7000 FEET
                                 Figure     37,       Zone      7 :  Estimated         Shoreiine positions for the
                                                            @ @,i@






                                                      year     2050                             66











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                                          Low Scenario
                                          Most Likely
                                                                                             ShingLe          Landing Prong                    'Eagle
                                          High Scenario                      Shingle.
                                                                                                              Ir
                                          Present Protection      111        Landing                                                            Iland
                                          Future Protection
                                                                       I ;                                                         700o FEET
                                         1000        0         1000       2000        3000       4000         5000     6000
                              Figure 38.            Zone       7:  Estimated          shoreline       positions for the
                                                     year 2100                          -      67









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                                                          1000                0               1000             2000              3000              4000              5000              6000
                                                             F=r-T=F--F::q
                                      Figure      39.        Zone 8: Estimated                 shoreline        positions        for   the
                                                             year     2020









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                                                                                                     3



                                                                                                                 LEGEND


                        @@Jenkins     Point:@,-,

                                      1000        0        1000       2000       3000       4000       5000       6000
                          Figure 40,    Zone  8: Estimated   shoreline positions for  the
                                        year  2050








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                                                    0        1000        2000       3000       4000       5000        6000
                                       loob
                          Figure  41.    Zone 8:  Estimated   shoreline  positions  for the
                                         year 2100











                                                                                Tidal Flat
                                              'r                                                            I    nd

                                                                                                                                               South
                          CL
                                                                                                                                         I     Hammacks








                                                                                                           6

                                                                                                                                              Present Trend
                                                                                               Hills
                                                                                              Island                                          Most Likely
                                                                                                                                  LEGEND


                         SA
                                                                                                                                              Present Protection
                                                                                                 Brady                                        Future Protection
                                                                                                 [Sland                                                           3
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                                                                    1000           0       1000        2000       3000        4000       5000       6000        7000 FEET
                @@Jenkins Point                e_                     -         -                                                                                 I
                                                                     Figure 42.              Zone     9: Estimated           shoreline positions for the
                                                                                             year    2020

                                                                                                 71











                                                                                   Tidal Flat
                                             CreeN                                                              i's 1,
                                                                                                                                                    South
                         13 0,                                                                                                                      Hammocks


                                                                                                                                                                     4q


                                                            Q)                                                 6                        LEGEND      Present Trend
                                                               oo
                                                                                                     and
                                                                                                     lls
                                            ..7                                                   I's                                               Most Likely
                                                                                                                                                    Present Protection
                                                                                                                                                    Future Protection
                                                                                                   QBrady
                                                                    0                                Island



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                                                                       1000         0          1000        2000       3000         4000        5000       6000        7000 FEET
                 @@Jenkins Point
                                                                        Figure 43.               Zone      9: Estimated shoreline positions for the
                                                                                                 year    2050


                                                                                                   72











                                                                                Tidal Flat
                                            C'r P e
                                                                                                                                                @)outh
                         13 c6                                                                                                                  Hammocks

                                                                                  5
                                                                                                                                                                QQ



                                                               e                                            6
                                                                                                                                        LEGEND
                                                                                                                                                   Present Trend
                                                              oo                               Hills                                               Low Scenario
                                                                                          @>.lsland                                                Most Likely
                                                                                                                                                   High Scenario
                                                                                           o    Q Brady
                                                                 0                                                                                 Present Protection
                                                                  0                              Island                                            Future Protection


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                                                                                                                                                  0
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                                                                       Figure      44.         Zone     9: Estimated Shoreline positions for the
                                                                                               year    2100

                                                                                                73




















































                                                                                              ddwddmL















                                                          ,V'4







                                  Figure 45.         Ponding causing          wetlands       destruction in the
                                                     Isle of Wight















                                                                              74









              Ill. QUANTIFICATION OF LAND AT RISK


                     After calculating the hypothetical shoreline positions for the various sea level
              rise scenarios, we were able to estimate the amount of land that could be at risk from
              erosion and permanent inundation. These estimates were obtained by assuming that
              existing shoreline protection will be maintained, and that no additional shoreline
              protection would occur. It was estimated that in 1989 there were about 1500 acres
              of wetlands in the study area. We estimated that the total existing wetlands could be
              submerged and eroded by the year 2050 if sea level reaches 1.5 feet above present
              levels. By the year 2100, all existing wetlands would be destroyed for all sea level rise
              scenarios.


                     Table 17 provides quantitative values for the estimates of upland and wetland
              areas at risk (in acres) for different scenarios of sea level rise. Figure 46 shows a
              graph of total land at risk under the various sea level rise scenarios. It should be noted
              that in accordance with the model, present wetlands were not allowed to accrete and,
              therefore, once they are destroyed, those areas are treated as sandy shores. In a later
              section we will discuss the possibility of new wetland formation as sea level rises.








                        Table 17. Land at Risk (acres)

                        Year Scenario (ft)          Marsh         Other*        Total


                        2020          0.4           431           22            454
                                      0.5           552           30            582


                        2050          0.8           889           44            933
                                      1.5           1059          334           1393


                        2100          1.4           1059          290           1349
                                      1.7           1059          367           1426
                                      3.0           1059          673           1732
                                      4.4           1059          1404          2463


                         Other category includes    upland areas other than marsh areas.






                                                         75



















                              250




                              2000    - --- ------- - ----------------- ... ........................ ... ... . . ...... . ..... . ... ........ ......... . ... . ..... - --------- -------------- - --------------------- ------ - -





                              1500    . ............ . ...... . . ..... . ............. ..................... ......... . ........ . ...... . ..... ----------- ---- ---------- --------- --------------- ------------ . ............





                              1 000____-  ... . ............. ................... .I........ . ........... ... . . . .... . .. . ........ ........... . ................ . .................. . . . . ............................................... ... . .............I................... . .......... ------------------- --






                                                     .. . ........................ - --------- - --- - --------------I------------------ - -- -- .... . ........................... .... . .......... ....... . ....... . .................... .... ........ . . . ............ ...... . ..........







                                     0
                                            0.4           0.5            0.8           1.4           1.5           1.7                         4'.4
                                                                               SLR SCENARIOS (ft)
                                      Figure 46.            Total land at risk vs. sea-level rise scenarios
















                                                                                         76








                    In Table 18 we estimated the total acreage of land within each zone at risk
             from the various sea level rise scenarios. Note that zones 5NI3 and 9 (Table 18) could
             have the greatest amount of land at risk due to. sea level rise (50 percent of the total
             land at risk in the study area). These two areas have the most extensive areas of
             wetlands and the highest historical rates of shore erosion in the study area. As sea
             level increases, more areas will become vulnerable to inundation and erosion Zone 8
             and 2NB (Table 18) show extensive land at risk for sea level rise scenarios higher than
             1.4 feet.


                    The vulnerability of some of the marsh islands such as Horn, Drum, Dog and
             Bitch, Horse, Hills and Brady should also be of concern. They all are located on the
             open waters of both bays and are barely above sea level. Small increases in sea levels
             could cause them to ultimately disappear. Other islands inside creeks, such as Eagle
             and Piney Islands could also be reduced significantly. Other geographic features at risk
             include points, which are remains of some of the older wetland areas such as Keyser,
             Jenkins, Cedar, and Drum. In addition, tidal flats and shoals, the main sediment supply
             for the shores of the bays, are at risk due to sea level rise.

































                                                        77















                         Table 18. Land at Risk by Zone (Total Acreage)

                                                          YEARS
                                         2020          2050                2100
                                                Sea Level Rise Scenarios (ft)
                         Zone            0.4  0.5    0.8    1.5    1.4     1.7    3.0    4.4


                         1               48   66     103    168    165     182    223    283


                         2SB             28   37     58     91     88      93     105    148


                         2NB             31   39     64     96     95      101    120    189


                         3EB             21   27     44     61     59      62     68     79


                         3WB             17   22     .34    57     55      57     62     70


                         4SB             16   19     31     46     44      45     64     160


                         4NB             4    5'     7      7      6       6      8      16


                         5SB             7    8      12     20     18      20     33     45


                         5NB             120  144    228    282    278     286    324    548


                         6SB             7    8      10     14     14      16     29     40


                         6NB             3    3      5      9      9       11     23     32


                         7WB             0    0      0      0      0       0      0      0


                         7EB             1    5      8      15     14      16     25     37


                         8               41   50     80     131    120     131    172    260


                         9               111  149    250    396    385     401    475    557


                         TOTAL         .454   582    933    1393   1349    1426   1732   2463


                         Notes:
                         NB: North Bank of Zone
                         SB: South Bank of Zone
                         EB: East Bank of Zone
                         WB: West Bank of Zone





                                                            78














                                                   SUMMARY


                         0 Inundation is about 60 to 80 percent of the total future
                         shoreline recession in our study area, and is a much more
                         important problem than erosion.

                         0 Wetlands are more vulnerable to sea level rise than sandy
                         shores and creek banks because of their low-lying elevation.

                         0 Creeks banks will experience the greatest shoreline retreat
                         at their mouths.


                         0 St. Martin Neck could be breached by sea level rise
                         scenarios greater than 1.4 feet, forming an island north of Isle
                         of Wight.

                            Shingle Landing and Bishopville Prong are the least
                         vulnerable to erosion and inundation mainly because of their
                         steep slopes and absence of wetlands.

                             Many of the present natural shoreline features are
                         threatened by erosion and inundation and could disappear,
                         including islands, points, and tidal flats.

                         0 The north bank of St. Martin River and the shores of the
                         Assawoman Bay are the most vulnerable shorelines and have
                         the greatest amount of land at risk for all sea level rise
                         scenarios. For the higher scenarios (1.4 feet and greater),
                         Turville Creek (north bank) and Isle of Wight are most
                         vulnerable.


                           About 50% of the total land of Isle of Wight is at risk of
                         erosion and permanent inundation.










                                                        79










                                                        CHAPTER FIVE
                                                           IMPACTS


              1. LAND AT RISK


                      According to the Worcester County Comprehensive Development Plan, six land
              use types exist in the study area (Figure 13). In this section we compare the land use
              categories at risk from the various sea level rise scenarios. Table 19 summarizes the
              total land at risk for each land use type under future sea level rise scenarios.

                      We measured the 1989 shoreline for each of the land use types and found that
              58 percent of the study shoreline has been designated Suburban Residential land use.
              We also found that between 60 and 70 percent of the total upland at risk in this study
              area is the Suburban Residential land use type. Suburban residential land use exists
              in the entire study area except in Zones 6, 7 and 8 (Figure 3). According to the
              Worcester County Comprehensive Development Plan (CDP, 1989), this category of
              land use has been designated to accommodate a large portion of the future growth
              of the county's population. We believe that the inundation of low-lying areas will
              cause a greater impact on the study area shorelines than shore erosion alone.





                    Table 19.       Land at Risk by Land Use (Acres)
                                                               YEAR
                                             2020             2050                  2100
                                                          Sea Level Rise
                                            0.4     0.5    0.8      1.5    1.4      1.7    3.0     4.4
                    LAND USE


                    Commercial              7       10     17       29     28       31     40      53


                    Suburban Residential    268     354    576      890    873      920    1093    1460


                    Suburban                0       0      0        0      0        0      1       1


                    Estate                  137     166    259      318    315      323    366     405


                    Agriculture             0       0      0        0      0        1      1       1

                    Conservation            41      50     80       131    120      131    172     260


                    TOTAL                   454     581    933      1368   1337     1405   1673    2180







                                                                80








                    The Rural Estate land use comprises between 20 and 30 percent of the total
             land at risk in our study area (Figure 13). Low density residential homes with large
             open spaces and environmentally sensitive areas occur in this land use type. Rural
             Estate land use occurs in zones 5, 6 and 7 (Figure 3 and 13) predominantly on the
             north bank of the St. Martin River, where the greatest shoreline recession is projected.

                    The Commercial land use type occurs in zones 1 and 3 along Route 50 (Figure
             3 and 13). This land use type accounts for only 3.5 percent of the entire shoreline
             under study. The amount of land at risk under this type ranges from 7 to 53 acres.

                    Only a small portion of Suburban and agricultural land use types are located on
             the study area (banks of Herring Creek, zone 3, Figure 3 and 13). The amount of land
             at risk under these two categories ranges from 0.2 to 1.4 acres.

                    Finally, the Isle of Wight is classified under the conservation land use type
             (Figure 13). Close to 50 percent of the entire island or 260 acres, could be at risk
             under the highest sea level rise scenario of 4.4 feet.

             11. ECONOMIC AND INFRASTRUCTURE AT RISK


                    Presently, the recreational and resort-related industries employ about 61 percent
             of the residents of Worcester County (CDP, 1989). The. primary tourist attraction in
             the county is the Atlantic Ocean shoreline. However, the back bays also attract many
             tourists. Sea level rise could impact the economy of the County in this area by eroding
             and inundating land areas.

                    One of the possible strategies to protect the ,economic activities and
             infrastructure of the area is to invest in engineering structures, such as stone,
             breakwaters or bulkheads. However, these structures are expensive and can be
             detrimental to the environment. Wetland creation and beach nourishment are less
             costly engineering options and are not normally detrimental to the environment. '

                    Routes 50 and 90 are the major transportation links between Ocean City and
             the mainland. Both routes are at risk from sea level rise, through; (1) erosion which
             can undermine foundations of bridges or shoulders of the roads and; (2) flooding
             which affects low-lying areas. Route 60 is most vulnerable at Herring Creek and near
             West Ocean City. Route 90 could be impacted near Ocean Pines and on Isle of Wight.
             The entire length of Route 90 on the Isle of Wight is located on grounds under 5 feet
             above present sea level. It was projected that the southern shore of the island would
             retreat as much as 600 feet in response to a 4.4 feet sea level rise.






                                                       81










              Ill. WETLAND LOSS


                     Land loss in most marshes results from a combination of two mechanisms;
              shore erosion and inundation (Leatherman, 1989; Gehrels and Leatherman, 1989;
              Orson et al., 1985). Shore erosion at the seaward,-^edge of the marsh is the most
              obvious process and will accelerate with increased water levels. However, as
              described previously, erosion accounts for only a small percentage of all marsh losses
              annually. The comparative resistance of marshy shorelines to wave attack suggests
              that with rapidly rising sea levels, most marshes will be inundated before extensive
              shoreline erosion occurs.


                     A more probable catastrophic mechanism of marsh loss with a large increase
              in sea level will be the formation of extensive interior ponds. The rapid enlargement
              and coalescence of interior ponds in marshes subject to rapid coastal submergence
              have been amply documented in the Mississippi delta (Delaune et al., 1983) and at
              the Blackwater Wildlife Refuge,Maryland (Stevenson et al., 1986). The physiological
              mechanism behind the development of interior ponds is believed to be anoxia and
              ultimate death of marsh plants as sea levels outpace the ability of the marsh to
              maintain elevation.


                     As we discussed in previous sections of this study, wetlands have been
              decreasing since the 1 850's. The rates of retreat along marshy shorelines were found
              to be up to 3 feet per year in the most extreme cases. We attempted to determine
              how erosion and inundation at a marshy shoreline would reduce wetlands with
              accelerated sea level rise. We also estimated the area of land that could be converted
              into wetlands due to higher water levels.

                     Our analysis of existing wetlands in the study area indicates that the entire
              1500 acres could disappear completely in response to a sea level rise of 1.4 feet or
              greater. This sea level scenario is the Best Estimate scenario for the year 2050 and
              the low scenario for the year 2100 (Table 1). Figure 47 shows a graph of marsh loss
              vs. sea level rise in our study area. When we compare existing wetlands areas with
              losses that could occur in the future due to sea level rise, we observe that for the year
              2020, 40 to 50 percent of wetlands could be lost. For the year 2050 the losses could
              range from 84 to 100 percent of today's wetlands. The high water levels projected
              for the year 2100 could destroyed all existing wetlands for all scenarios. The basis for
              these results is due to the shore topography of the study area. The slope of these
              shores is too steep between the 1 and 3 feet elevation contours for the wetlands to
              migrate upland or for new ones to form as sea level rises.








                                                         82


















                                                 1100-



                                                  1000      . ......... . ....... . ........................ .......... ... .... ..... . ..... ........... .... ......... ...... .. . ................. .... . ............. ................. . ............................. . ......... . ........ .. .................. . ...



                                                    900     . ......... ..... . .................................. . ........................ ... . ... ...... ....... ......................... ... .... ....... . ... . .............. . ............... ............... . ...-........... . ......................... ..........................



                                                    800     . ...... ..-. ..........................I........ ......... ........ ....I. . . . ........................... .. . ...... . ...... . .......... . .- - --- - --- --------- - ------- ----- - ------ - ------ ................. .. . ......... ............ .................................


                                         0

                                                    700     . ...... ........ ...... ............................................... . . . .......... ..... .... . .. ..... .............................. . .. ... - -- - - -------------------- -........................... .......... . ..... . . ...... . ............... . .. ........ ...............

                                        <


                                                    600     . ..... . ....................... .... ........I......... .. ............................... ................ ..I................. --------------- - ----- - - ---- ------------------- . ....... ................... .. ...... . .I............. ... .. ..........I.. ...............



                                                    500     . ........ .... ... . ..........I.. ........  -1 ........ .......... . ...... ..  _- .... ....... . ...................... ... .......... . ... .. - - - --- - ----- - -- - -------------------------------- - ------------ - --- - ----------------- ----------------------------



                                                    40r'
                                                                    0.4                0.5                  0.8               1   4               1.5                1.7                                   4'4
                                                                                                                   SLR SCENARIOS (ft)
                                                              Figure 47.                    Marsh at risk vs. sea-level rise scenarios














                                                                                                                           83








                    Even though the topography of the study shoreline does not allow for extensive
             wetlands migration, higher sea levels will affect dry upland areas. The various sea
             level scenarios were superimposed on the representative shoreline profiles to estimate
             how much land could be regularly flooding in the future. In this way we determined
             the acreage of new marshes that could be formed. Table 20 presents a comparison
             of existing marshes, marsh loss, and the area flooded by higher water levels. It also
             shows the difference between existing marshes and new marshes, estimating the
             possible deficit of marshes in the future compared to 1989 acreage.




                    Table 20. Marsh Loss and Deficit from Existing Marsh
                               (Acres)


                    YEAR       EXISTING MARSH OTHER       TOTAL    NEW     DEFICIT
                    SCENARIO   MARSH    LOSS     LOSS*    LOSS     MARSH   FROM 1989-


                    2020
                    0.4        1059     431      22       454      609     450
                    0.5        1059     552      30       582      508     552


                    2050
                    0.8        1059     889      44       933      245     815
                    1.5        1059     1059     290      1349     10      1050


                    2100
                    1.4        1059     1059     333      1393     0       1059
                    1.7        1059     1059     366      1426     0       1059
                    3          1059     1059     672      1732     70      990
                    4.4        1059     1059     1404     2463     700     359


                    OTHER LOSS is uplands and sandy shorelines.
                    DEFICIT FROM 1989 = existing marsh - new marsh.





                    It was observed that because of the topography of the study area, new
             marshes' could be formed if sea level were to rise up to 1.4 feet. Between 431 and
             552 acres of existing wetlands could be lost by the year 2020 (40 to 50 percent), for
             0.4 and 0.5 feet sea level rise scenarios, respectively. Between 508 and 609 acres
             of marshes could be formed or survived by the year 2020, creating a deficit of 450
             to 552 acres (40 to 50 percent) from existing wetlands. By the year 2050, sea level
             rise could cause the destruction of almost all existing marshes (889 and 1059 acres
             or 84 to 100 percent) for the two sea level rise scenarios, 0.8 and 1.5 feet. Under
             these sea level rise scenarios only a small amount of land would be available for marsh
             formation (245 acres for sea level rise of 0.8 feet). For the 1.5 feet sea level rise


                                                    84








            scenario, all marshes would be destroyed and no new land would be available for new
            marshes to form.


                   The situation could become even more drastic by the year 2100 with respect
            to existing marshes. All existing marshes will be affected by sea level rise by the year
            2100. For sea level rise scenarios of 3 feet or higher some dry land areas could
            become flooded (in general, the topography of the study area becomes flatter above
            the 4 feet contour). We estimated that between 70 and 700 acres of land (3 and 4.4
            feet.scenarios, respectively) could be available for the formation of new wetlands.
            This still leaves a enormous deficit, between 93 and 32 percent, from existing
            wetlands. All of these estimates assume existing levels of development, and that no
            action is taken to mitigate or preserve wetlands.

                   The model projects that the wetlands of Zone 1 (Figure 3) would be most
            affected by sea level rise. For the year 2020, between 40 and 60 percent of the
            existing marshes could be destroyed (47 to 65 acres). When we compare these losses
            with the possible formation of new marshes, this area has the greatest deficits,
            between 63 and 75 percent by the year 2020. Moreover, the model did not project
            the formation of any new marshes for the highest sea level rise scenario. On the other
            hand, extensive new marshes could be formed on the north bank of the St. Martin
            River, Isle of Wight and the shores of Assawoman Bay for the highest sea level rise
            scenarios.


            IV. 100-YEAR FLOOD


                   The National Flood Insurance Program (NFIP) of FEMA generates Flood
            Insurance Rate Maps (FIRM) to delineate areas subject to various degrees of flooding.
            We examined the impact of sea level rise on the 1 00-year flood zone (A-Zone) in our
            study area. The A-zone delineates an area that has a one percent chance of being
            flooded any given year. According to the FIRM's, the A-zone incorporates all areas
            between sea level and 6 feet above sea level in our study area. The exception occurs
            in Zone 1 (the shores of Isle of Wight Bay) where the A-Zone boundary varies
            between 6 and 8 feet above sea level.


                   We added the present A-zone boundary elevation with the various sea level rise
            scenarios to obtain hypothetical A-zone boundaries. The entire shoreline of the study
            area lies within the A-zone boundary. As sea level rises the probability for flooding
            along the shoreline and in previously unaffected upland areas will increase. As a
            result, human and natural resources will become under increasing pressure from
            flooding and its associated affects. The NFIP should revise their FIRMS as sea level
            rises because more residential, commercial and industrial structures will be affected
            by flooding (FEMA, 1991). These new areas would then be required to satisfy building
            codes for structures in A-zone boundaries (i.e., raise their structures).



                                                      85














                                                    SUMMARY


                   0 60 to 70 percent of the land at risk in our study area is classified as
                   Suburban Residential land use.


                   0 Most of the developed areas lie belo   w the 5-foot contour.

                   0 About 50 percent of the Isle of Wight is at risk of being eroded or
                   permanently inundated for 4.4 feet of sea level rise.

                   0 No major agricultural land would be at risk of erosion and inundation.

                   0 The economy of the county would be affected by sea level rise because
                   degradation of coastal resources and their associated benefits is probable.

                   0 The analysis shows that all the existing wetlands in the study area (about
                   1500 acres) could disappear completely with sea level rise scenarios of 1.4
                   feet or greater.

                   0 For sea level rise scenarios between 1.4 and 3 feet, marsh migration to
                   upland areas is not possible or feasible. This is due to the presence of steep
                   slopes between the 1 and 3 foot contours.

                   0 For sea level rise scenarios of 3 and 4.4 feet, wetland migration to upland
                   areas is possible because the topography of the study area at this elevation
                   is gentler. We predict that between 70 and 700 acres of wetlands could
                   form as a result of this scenario.


                   0 The wetlands of Zone 1 will experience the most losses due to sea level
                   rise because of their low elevation and because there exists many
                   restrictions to their possible upland migration (i.e., steep slopes and
                   development).

                   0 The north bank of the St. Martin River, Isle of Wight and the shores of
                   Assawoman Bay are the areas where most of the wetland migration to
                   upland areas is possible.







                                                        86










                                                    CHAPTER SIX
                                         STRATEGIES FOR MANAGEMENT


                     As land for dev 'elopment in the barrier islands of Maryland becomes scarce, the
              shores of the back bays will become increasingly attractive for new development.
              These lands are extremely vulnerable to any acceleration of sea level and its
              associated effect of increased erosion, inundation, flooding and saltwater intrusion.
              From an economic, safety and environmental point of view, we believe that strategies
              that diminish the possible damages and losses due to sea level rise must be
              established. These strategies can be propagated by the state's coastal zone
              management program.
                     Coastal zone management' does not necessar       .ily require restrictions on coastal
              development. It recognizes that coastal zones are attractive areas for development,
              but that a comprehensive plan to preserve natural resources and to allow certain
              forms of development is possible. The main objective of coastal zone management is
              to direct development to areas least susceptible to natural hazards. To do this
              effectively, it is necessary to incorporate sound scientific knowledge into development
              strategies.

                     A management plan for the coastal zone should take into account future sea
              level rise. It is essential that all parties involved in coastal development be active
              participants in the decision-making process. After scientific studies identify a potential
              problem, all of the affected parties should be educated about the results and possible
              strategies to mitigate any problems. Participants should include developers,
              environmental advocates, public officials, scientists and other citizen groups.
              Strategies that are made with formal and informal public participation have greater
              public acceptance and political support.

                     The issue of sea level rise has been widely publicized in the last couple of years.
              Despite this publicity many people do not know about the causes, mechanisms and
              consequences of sea level rise. Public education, at the national and state level,
              through media coverage, brochures, and meetings can improve peoples understanding
              and acceptance of the issues and the means to mitigate any problems.

                     It is important to recognize that any attempt to make coastal zone management
              more effective is labor intensive. The most serious impacts of sea level rise in the
              back bays of Maryland would be experienced under the higher sea level rise scenarios.
              These are projected to occur in the middle of the next century. This gives coastal
              communities some time to implement effective strategies. Coastal zone management
              plans can evolve with time. This does not mean that we should not start the planning
              process today. Coastal resources are undergoing serious degradation. Coastal zone
              management may enhance the chances of preserving natural resources in the coastal
              zone, regardless of the accuracy of predictions regarding accelerated sea level rise.


                                                          87








              Planning for the future needs to start today, and public education is a good first step.

                     Coastal zone management plans must remain flexible as new scientific
              knowledge is attained. Scientific research in matters related to future sea level rise,
              such as magnitude and timing of occurrence, is critical. Equally important, but
              sometimes overlooked, is the need for applied research to determine which options
              are warranted, given current information. Finally, other climate change impacts, such
              as precipitation changes in coastal watersheds and changes in storm frequency and
              intensity should also  be examined.

                     The principal objectives of coastal zone management in relationship to future
              sea level rise are to:


                     1      Avoid development in areas that are vulnerable to inundation and
                            erosion;


                     2)     Ensure that critical natural systems continue to function; and

                     3)     Protect human lives, essential properties and economic activities from
                            the sea.


                     We discuss three strategies available for coastal zone management to reduce
              the impacts of sea level rise: retreat, accommodation, and protection (IPCC Working
              Group 111, 1990). In our study area the implementation of these strategies should be
              made on a site-specific manner. The retreat option or strategy involves no effort to
              protect the land from the sea. The accommodation strategy includes elevating
              buildings on piles or allowing arable land to become rougher pasture, etc. The
              protection strategy involves the placement of hard structures such as bulkheads and
              dikes, or soft solutions such as beach nourishment or artificial wetlands which protect
              existingJand uses.


              LRETREAT


                     As sea level rises, coastal communities can abandon the area (or shore) and
              allow the sea to advance unobstructed. Existing development could be relocated
              inland. In addition, development setback standards could be established to reduce
              future development in hazardous areas. Although under this strategy the economic
              use of the land will be lost, it would prevent human and economic losses in the future.
              From an environmental point of view, a retreat strategy may increase the survival
              ability of wetlands.

                     Unfortunately, politicians will probably find the retreat strategy to be politically
              unfavorable. It is unrealistic to expect residents of coastal areas such as Ocean Pines
              or Cape of Isle of Wight to abandon their hom     es because of the possibility of future


                                                          88








              sea level rise. Three different approaches can be implemented to introduce a retreat
              strategy on existing development: (a) restrict reconstruction of buildings and
              protective devices after major storms and as sea level rises; M presumed mobility
              (Titus, 1991); and (c) remove subsidies or increase incentives to guide development
              away from the coast.

                    Several states have already implemented restrictions on rebuilding existing
              buildings and shoreline protection structures after they have been damaged from
              storms. In some cases, if a structure is more than 50 percent damaged, it cannot be
              rebuilt. As sea level rises, damage to most buildings in the coastal zone will increase.

                    Titus 0 990) introduced the idea of presumed mobility. It involves incorporating
              sea level rise into the deeds of coastal property, and thus to the market economy.
              Presumed mobility does not interfere with the property rights of coastal home owners.
              Rather, it's similar to a long-term lease which for example, would expire after 99
              years, or whenever the sea rises enough to inundate a property. As existing properties
              are sold and transferred the deed would still remain in effect.


                    The third approach is to provide direct financial incentive (i.e., tax reduction)
              for property owners to remove or relocate structures that are in highly hazardous
              areas or are in danger of imminent collapse due to erosion or flooding.

                    Retreat strategies for new development could include an array of policy
              alternatives Karin et al., 1990). The aim of these alternatives is to preserve existing
              wetlands and open spaces to allow wetlands to migrate to upland areas as sea level
              rises. We have found that in our study area there are limited areas where wetlands
              could form by migration to upland areas.

                    Setbacks either fixed or dynamic can be established to provide a buffer zone
              around wetlands. They should be established from the wetland/upland interface and
              not from the shoreline to account for seasonal and episodic variation in the spatial
              extent of the wetlands (Figure 48). Conditional use permits could be established to
              allow some temporary or restricted use of the land adjacent to wetlands. Special
              zoning regulations could be established to restrict structures or reduce their size and
              density within the coastal zone. Environmental Impact Assessments can incorporate
              potential sea level rise for proposed projects that would border wetlands and may lead
              to policies to protect them. Finally, reduce funding for infrastructure and other
              services that promote and direct new development in coastal zones.

                    We recommend that Worcester County investigates the utility of the strategies
              discussed above in order to reduce possible losses to human and natural resources
              due to sea level rise. According to the Worcester County Comprehensive Development
              Plan, Zones 1, 2, 3, 4, the lower areas of 5, and 9 (Figure 3) are those areas where
              development will most likely occur. Special attention should be directed to reducing


                                                        89








             coastal hazards at these areas and to plan for wetland migration to upland areas
             where possible. These areas include the north bank of the St. Martin River, the shores
             of Assawoman Bay and both banks at the mouth of Herring Creek (Figure 3).

             11. ACCOMMODATION


                    The accommodation strategy assumes that occupation of vulnerable coastal
             areas will continue even under the risk of increased flooding and erosion due to sea
             level rise. Physically raising buildings is one of the most commonly suggested
             accommodation strategies. The National Flood Insurance Program's building standards
             attempt a similar strategy in flood prone areas. The life span of the structure is
             estimated and the height of the piling, for example, is calculated. The height of the
             base of the structures, estimated by the NFIP should include the 1 00-year flood level
             plus any projected future sea level rise values. The addition of 1 or 2 feet to the
             height of a support piling might save the structure in the future without adding much
             to the initial capital investment required to build the structure.

                    Open spaces where wetland migration is possible should be preserved. In areas
             with steep slopes, development could be allowed, while gentle sloping areas could be
             preserved for future wetland migration.

             111. PROTECTION


                    Under the protection strategy, valuable real estate and existing structures are
             not abandoned as water levels rise. Most of the existing development areas along the
             shores in our study area will need protection. However, as sea level rises, protection
             measures are just a temporary solution. At one point in the future, protection will
             become either too costly or technically impossible.

                    Hard structures such as bulkheads are commonly used on the bay shores of
             Maryland. Some of the major environmental concerns and problems resulting from the
             construction of such structures are: (1) coastal marsh and other vital habitat areas are
             lost, (2) interruption of sand supply to adjacent shorelines. The adverse impacts are
             greatest when the outer periphery of a coastal marsh is bulkheaded in order to extend
             property lines and to provide boat landings.

                    Permits for the construction of new bulkheads should be closely regulated
             (Clark, 1983). A primary rule is that bulkheads in general should be discouraged in all
             cases, primarily where wetlands exist. Whenever possible, the existing shoreline
             should be preserved with natural protection measures such as marsh grasses.
             Bulkheads should be located landward of annual flooding, which marks the upland
             limit of the coastal wetland (Figure 49). They should be constructed so they do not
             disrupt the outward flow of ground water or runoff. This could be accomplished by
             constructing perforations ("seepholes" backed with screens) along the structure.


                                                       90















                                                 7@7






                                                                   7 "-Z@
                                                                    7









                          Figure 48.    Comparison of setbacks: new development
                                        (center) setback from the shore, maintaining
                                        existing   wetlands    in  contrast to      older
                                        development (left)    where   wetlands     where
                                        destroyed











                                               ,;age        41II&W



                                                                            7777777





                                   7, 1



                         Figure 49.    Proper  location of bulkheads: behind    the line
                                       of annual flooding, which marks, the inner
                                       edge of the coastal vvetland.

                                                          91








            Rprap is often an easier and a less costly technique for protection and it has a higher
            permeability than other methods.

                   A more desirable protection measure, which should be encouraged on the
            shores of the study area is the planting of wetland vegetation. This is the most
            effective method of preserving wetlands on these shores. Marsh planting is most
            useful where erosion rates and wave action are low. The artificial marsh has the
            benefit of creating a more biologically productive shoreline, as well as being
            aesthetically appealing. Methods for marsh creation and restoration are outlined in
            several papers (Woodhouse, 1979; Knutson and Woodhouse, 1983; Lewis, 1982;
            Zedler, 1984). Most marsh creation projects are only possible in the upper third of an
            intertidal area. Mechanical grading may be necessary to form a lower slope angle (this
            has the added advantage of offsetting the chances of destructive wave action by
            creating a more dissipative shoaling zone). It has been estimated that a minimum of
            6 rn (20 feet) of new planted marsh are needed for the success of a new marsh.
            Marsh vegetation may be propagated by seed or by transplants. Placing a temporary
            breakwater along the seaward margin may be recommended to diminish erosion or
            overwash.






































                                                      92













                                          Summary of Strategies


                       Retreat
                       Existing Development:
                             - Restrict reconstruction of buildings and protection.
                             - Presumed mobility
                             - Subsidies and incentives to relocate
                       New Development:
                             - Setbacks
                             - Conditional use permits
                             - Zoning
                             - Environmental reviews
                             - Mitigation


                       Accommodation
                       - Building code standards: rising buildings
                       - Open space requirements for new developments
                       - Land use change: changing crops to more salt tolerant ones


                       Protection
                       - Natural protection: planted marsh grasses
                       - Bulkheads behind the line of annual flooding
                       - Ripraps




















                                                   93










                                                REFERENCES


            Bird, E.C.F., 1985. Coastline Changes - A Global View. J. Wiley-Interscience,
            Chichester, England. 219 pp.

            Bruun, P., 1962. Sea-level rise as a cause of shore erosion. Journal Waterways and
            Harbours Division, American Society of Civil Engineers, 88: 117-130.

            Clark, J.R. Coastal Ecosystem Management. A Technical Manual for the Conservation
            of Coastal Zone Resources. Krieger Publishing Company, Malabar, Florida. 928 pp.

            Comprehensive Development Plan, Worcester County Maryland, 1989. Prepared by
            Redman/Johnston Associates, Ltd., Easton, Md.

            DeLaune, R.D., Baumann, R.H., and Gosselink, J.G., 1983. Relationships among
            vertical accretion, coastal submergence, and erosion in a Louisiana Gulf Coast marsh.
            Journal of Sedimentary Petrology, 53: 147-157.

            Demarest, J.M. and Leatherman, S.P., 1985. Mainland influence on coastal
            transgression: Delmarva Peninsula. In: G.F. Oertel and S.P. Leatherman (Editors),
            Barrier Islands. Marine Geology, 63: 19-33.

            Douglas, B.C., 1991. Global Sea Level Rise. In: Journal of Geophysical Research. Vol.
            96, No.C4, pg 6981-6992, April 15, 1991. Washington, D.C.

            Emanuel, K.A., 1987. The dependency of hurricane intensity on climate. Nature
            (London), 326: 483-485.

            Federal Emergency Management Agency (FEMA), 1991. Projected Impact of Relative
            Sea Level Rise on the National Flood Insurance Program. FEMA/Federal Insurance
            Administration, Washington, D.C.

            Intergovernmental Panel for Climate Change (IPCC), Working Group 1, 1990. Scientific
            Assessment of Climate Change. Report prepared for IPCC by Working Group 1.

            Intergovernmental Panel for Climate Change OPCC), Working Group 111, 1990.
            Formulation of Response Strategies, Report prepared for IPCC by Working Group Ill.
            257 pp.

            Gehrels, R. and Leatherman, S.P., 1989. Sea-level rise: Animator and Terminator of
            coastal marshes, Vance Bibliography, Monticello, Illinois, 39 pp.

            Hands, E.B., 1983. The Great Lakes as a test model for profile responses to sea level
            changes. In: Komar, P.D. ed., Handbook of Coastal Processes and Erosion, Boca


                                                     94








            Raton, Florida, CRC Press, pp. 167-189.

            Klarin, P.N., Branch, K.M., Hershman, M.J., and Grant, T.F., 1990. Sea Level rise
            Policy Alternatives Study: Volume 2. An Analytical Review of State and Federal
            Coastal Management Systems and Policy Responses to Sea Level Rise. Battelle
            Human Affairs Research Centers, Seatle Washington, No. 90-40.

            Knutson, P.L, and Woodhouse, W.W., 1983. "Shoreline Stabilization with Salt Marsh
            Vegetation," SR-4, CERC, US Army Corps of Eng., Fort Belvoir, Va.

            Leatherman, S. P., 1983. Coastal Geomorphic Responses to Sea Level Rise: Galveston
            Bay, Texas. In Greenhouse Effect and-Sea Level Rise. A Challenge for this Generation,
            Barth, M.C. and Titus, J.G., eds. New York: Van Nostrand Reinhold Company.

                   1988. Impact of climate-induced sea-level rise on coastal areas. Statement
            -p-r-e--s-e-Inted to the U.S. Senate, Committee on Commerce, Science and Transportation,
            July 13, 1988.

            -------- 1989. Impact of accelerated sea level rise on beaches and coastal wetlands.
            In: White, J.C., ed., Global Climate Change Linkages, Elsevier Science Publishing
            Company, Inc. pp 43-57.

            Leatherman, S.P., Dean, R.G., Everts, C.E., and Fulford, E., 1987. Shoreline and
            sediment budget analysis of North Assateague Island, Maryland. Proceedings of
            Coastal Sediments 87, American Society of Civil Engineers, New York, p 1460-1471.

            Lewis, R.R., 1982, (ed.). "Creation and Restoration of Coastal Plant Communities,"
            CRC Press, Boca Raton.

            Lyles, S.D., Hickman, L.E., and Debaugh, H.A., 1988. Sea Level Fluctuations for the
            United States 18551-1986. U.S. Department of Commerce, National Oceanic and
            Atmospheric Administration, National Ocean Service, Rockville, MD. 182 pp.

            Maryland's Forgotten Bays, 1990. (Edited by P.E. Hartman), Proceedings of. the
            Conference of the Outer Coastal Bays, Ocean City, May 5, 1990, 157. pp.

            NOAA, 1990. Fifty years of population change along the Nation's Coasts. 1960-
            2010. National Oceanic and Atmospheric Administration, Rockville, MD, 41 pp.

            Orson, R., Panageotou, W., and Leatherman, S.P., 1985. Response of tidal salt
            marshes of the U.S. Atlantic and Gulf Coasts to rising sea levels. Journal of Coastal
            Research, 1: 29-37.

            Shands, W.E., and Wells, J.B., 1987. "Overview." In: The Greenhouse Effect, Climate


                                                      95








             Change, and U.S. Forests, W.E. Shands and J.S. Hoffman (eds.). (The Conservation
             Foundation: Washington, DC). 304 pp.

             Stevenson, J.C., Ward, L.G., and Kearney, M.S., 1986. Vertical accretion in marshes
             with varying rates of sea-level rise. In: Estuarine Variability, D. Wolf, ed., Academic
             Press, New York, pp 241-260.

             Titus, J.G. Greenhouse Effects and Coastal Wetland Policy: How Americans Could
             Abandon an Area the Size         Massachusetts at Minimum Cost. Environmental
             Management, Vol. 15, No. 1, pp. 39-58.

             Woodhouse, W.W., 1979. "Building Salt Marshes along the Coasts of the Continental
             United States." SR-4, CERC, US Army Corps of Eng., Fort Belvoir, Va.

             Zedler, J.B., 1984. "Salt Marsh Restoration," California Sea Grant T-CSGCP-009.



































                                                      96



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 1                                       97
 1                                         -









                                                           Site 1. 5









                                 5 . ......


                                 4-




                                 2-


                                 1--                           Upper Qmft marsh

                                 0411
                                   0          200          400         660        860          10100       1200
                                                                       Feet



                                                           Site 3
                                14-


                                12-


                                10-


                                 8-



                                 6-



                                 4-
                                              rUppr 5-d -h

                                 ol
                                   0    20      @O      d'O    80     100    1@0 140 160 160 200
                                                                      Feet









                                                                     site 4








                                               2--






                                               0@11
                                                   0         50          100         150          260          2k          360          35' 0        400
                                                                                                  Feet




                                                                    S ite                8.55



                                               5-



                                               4-



                                               3-



                                               2-



                                               1

                                                                                                            Upper Amft mamh


                                               0-1
                                                   0            26o              460              660              860             1 doo           1200
                                                                                                  Feet







                                             Site 8.5
                              10-









                              6--




                              4-


                              3-


                              2----


                              I--
                                                           parrhidmush
                                 6    200     400    600     800 10'001200 1 @00 1600 1600
                                                                 Feet




                                             Site 12


                            4.5-


                              4--


                            3.


                              3


                            2.5-


                              2-

                            1.5-




                            0.5


                              O@ -                 -T
                                 0      100       200       360       400       500       600       76o
                                                                 Feet







                                                                   Site 18
                                            10-


                                              9-


                                              8-






















                                                                       Upper finin mmh

                                              0)
                                                 6        260          460         660          86o         1000 1200                 1@00 1600
                                                                                                Feet




                                                                    Site 19
                                              10-




                                              8-

                                              7--


                                              6-


                                              5-


                                              4-


                                              3-




                                              1


                                              0)
                                                 0       200         400        600         86o idoo 1@oo 1@oo idoo 1800
                                                                                                 Feet
                                                                          per    marsh








                               Site 27
                    16-











                     8-


                     6-


                     4-


                     2


                     0),
                       6    160    260    360    460    560   60'0   700
                                             Feet





                               S ite     28
                    16-


                    14-


                    12-


                    lo--


                     8-


                     6-


                     4-


                     2


                     0)         T-   I
                       o  20   40   60   @o  160 120 140    160 160 26o
                                             Feet







                                              Site 30
                               5-











                             2.5-









                             0.5-
                               O)l
                                 0     @0-     4,0      610    8f0    160    lk      140     160     180
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                                              S ite         34


                               9--


                               8-


                               7-







                               4-









                               0),
                                 0    200 400 600 860 1600 1@00 1400 1600 ldOO 2000
                                                                 Feet








                                                                       Site 39
                                               5-












                                           2.5-






                                           0.5'                                                                     Upper rwNt
                                              0 J
                                                 0         200          460         660         860        1600 1@00 1@00 1600 1800
                                                                                                      Feet




                                                                                           Site 41
                                                                        St. Martin Neck Cross Section




                                               5-






                                               3--


                                               2--




                                                                                              Upper rrnd marsh


                                              0
                                                 0           500          1000           1500          2000          2500          30oo          3500           4000
                                                                                                       Feet

















                                 Site 41.5

                 10-













                  4--





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                                        Feet




                                                                          @ Immillmilm;
                                                                             3 6668 14103 6584















                                                                                  . i














































































                                                                         i