[From the U.S. Government Printing Office, www.gpo.gov]
.014 Coastal Zone Information EOL Center BARATARIA BASH G, 0,,,G_11C- 1, WS OMS.A k 06". SE F FAA, E CE, M K lid, LOCT a 1,*@ Oill it 0 1". Aff, .01 _0 1" :kA 0.0 Ol Ill A" . At. .l1A a ---------- "Ah, All. .0 Al. vile WININEMw- j" X011. .'04. 01i, .,It@ it 4 S-01 d-, I olf, 4 'Mb, Ik1b., f, Iwo'. Af, It, 0 l" @I, 11'. i I ( "It Af. I%A I.. 0J,. Oll ..0'. AG. _04 f'. All- GB 428 L8 0. 1 B34 1976 c2 E oa sta I Zone f 0 ln a t i n orm Cent _jer '0 A I PR, I I AIV I o ERIE i-SH, SCOM PA M JONIA11. STNt I i @ E " .11". . %#., .0". -, '11'. .. "u" -lit At, .0f, ""i", "I... .., IC' 0 BARATARIA BASIN: GEOLOGIC PROCESSES AND FRAMEWORK R. D. Adams B. B. Barrett J.H. Blackmon B. W. Gane W. G. McIntire SEAGRANT CENTER FOR WETLAND RESOURCES LOUISIANA STATE UNIVERSITY BATON ROUGE, LA 70803 Sea Grant Publication No. LSU-T-76-008 This work is a result of research sponsored by the National Oceanic and Atmospheric Administration U.S. Department of Commerce through the Office 0f Coastal Zone Management and the Office of Sea Grant. GB 428 .L8B34 1976 c.2 JUNE 1976 Contents Page LIST-OF FIGURES . . . . . . . iv LIST OF TABLES . . .. . . . . *o v ACKNOWLEDGMENTS . . . o . . . . . . . . . . . . vi ABSTRACT . . . . . . . . . . . . ... . . . . . vii INTRODUCTION . . . . . . . . . o . . . . . . . 1 GEOLOGIC CHARACTERIZATION . . . 3 Physical Setting of Coastal Louisiana. 3 Eustatic Changes . . . . . . . . . . . . . 6 Land Subsidence . . . . . . . . . . . . . . 6 Flood Plains * * * * * * * * * * * * * 12 Recent Chenie; 'Plain . . . . . . . . . . . 13 Recent Deltaic Plain . . . * * ' * * * * 14 T* . . . . 21 BARATARIA BASIN MANAGEMENT UNI . o . . Major Deltaic Facies . . . . . . . . . . . 31 Documentation of Land Loss o . . . . . . . 38 Environmental Inventory . . . . . . . . . . 38 Dredge and Fill Activities . . . . . . . . . 39 'Coastal Retreat and Inlet Changes . . . . . 46 Grand Terre Case History . . . . . . . . 53 Marsh Deterioration . . . . . . . . . . . . 57 SUMMARY. 64 APPENDIX A : : . . . BARRIER ISLANDS . . . . . 68 APPENDIX B ENVIRONMENTAL INVENTORY . . . . . . 68 APPENDIX C DREDGE AND FILL . . . . . . . . . . 72 APPENDIX D COASTAL RETREAT AND INLET CHANGES. 77 APPENDIX E MARSH DETERIORATION. o . . . . . . 81 SELECTED BIBLIOGRAPHY. o . . . . . . . . 98 List of Figures Page Figure 1 Index map indicating major surfaces in the coastal zone. Bathymetry lines show deep water near the Modern Delta and shoal water off the remainder of the coast ... . . . . . . . 5 2 Distribution of salt domes and topographic features that may be associated with salt intrusion . . . . . 7 3 Progressive stages in natural levee development, peat accumula- tion, and subsidence . . . . . . . . . . 10 4 Delta complexes of the Mississippi Delta Plain . . . . . . . . . . . . . . 16 5 Age of prominence of each of the 16 delta lobes of the Mississippi Delta Region . . . . . . . . . . . ... . 18 6 Deltaic Plain sedimentary sequences of coastal and inland areas are depicted by major depositional en- vironments in a typical delta complex . 27 7 The Barataria Basin Management Unit . 28 8 Location of D-D' cross-section depicted in Fig. 9 and principal control borings in the Barataria Basin . . . 32 . . . . . . . . i . . . . 9 Cross-section showing delta-lobe and sedimentary facies relationships through the Barataria Basin . . . . . . 33-34 10 Bayou Lafourche stream systems and east-west trending beach ridges that dominate the southwestern corner of the basin . . . . . . . . . . . . . . 36 11 Reconstructed positions of dis- tributaries abandoned during leng thening of the Mississippi River. 37 12 Vegetation environmental units. 40 13 Dredge and fill computations by environmental unit for Lafourche Parish . . . . . . . . . . . . . . . . 42 14 Dredge and fill computations'by environmental unit for Jefferson Parish . . . . . . . . . . . . . . . . . 43 15 Dredge and fill computations by environmental unit for Plaquemines Parish . . . . . . . . . . . . . . . . . 44 iv Page Figure 16 Dredge and fill computations by environmental unit for St. Charles, St. John the Baptist, St. James, and Assumption parishes . . . . . . . . 45 17 Map showing modified'natural levee and wetland areas that have been cleared, drained, and impounded for agriculture, commercial, or urbanization purposes . . . . . . . . . 47 18 Major waterways, pipelines, and oil fields within Barataria Basin 48 19 Coastal retreat and marsh .deterioration by environmental unit and parish . . * * * * ;a' 50 20 Map depicting land loss and in on Grand Terre proper . . . . . . . . . 54 21 Inlet changes of the three major passes in the Grand Terre Island system . . . . . . . . . . . . . . . . . 55 E.1 Coastal retreat and marsh deterioration by environmental unit and parish . . . . . . . . . . . . 83 List of Tables Table 1 Characteristic swamp and marsh vegetation. . . . . . . . . . . 22 2 Environmental inventory-- Barataria Basin -Management Unit . . . . 39 3 Inventory of dredge and fill activity by environmental unit for the Barataria Basin 41 4 Rates of deterioration by marsh types within the Barataria Basin. 59 A.1 Louisiana barrier islands and barrier beaches . . . . . o . . . 69 B.1 Environmental inventory by parish, Barataria Basin . . . . . . . . o . . . 71 C.1 Inventory by canal type by parish and environmental unit . . . . . . . . . 74 D.1 Coastal retreat . . . . . . . . . . . . 78 D.2 Inlet changes . . . . . . . 79 Abstract This report describes the landforms and processes that are operative in Louisiana's coastal wetland. It also discusses processes that cause marsh dete- rioration and land loss. To obtain information on land loss the environmental units were inventoried and assessed to determine the status.of existing resources for environmental units, parishes, and basin. Study of dredge and fill activities and their intensities for each environmental unit and parish were established. Coastal erosion and inlet changes were quantified. Sea-level changes, sub- sidence, storms, and salinity intrusion were studied as a combination of natural destructive processes,- balanced by detrital sediment produced in the marshes and swamps and storm-deposited inorganic sediments deposited over the marshlands. Coastal erosion effects, marsh deterioration by water movement, and vegetation response to salinity intrusion and tidal pulses that remove organic detritus, and cause erosion of the marsh surface are also con sidered in this study. vit Acknowledgments This work is a result of research sponsored by the Louisiana Coastal Zone Management Program and the Louisiana Sea Grant Program. These respective programs are administered by the Office of Coastal Zone Management and the Office of Sea Grant, in the National Oceanic and Atmospheric Administra- tion, U.S. Department of Commerce, in cooperation with the State of Louisiana. Support from Louisiana Wildlife and Fisheries Commission is also acknowledged. The nature of this study required assistance and information from a relatively large number of individuals and agencies. Work primarily involved collection, analysis, and interpretation of exist- ing data located at a number of sources. The authors are particularly indebted to-the individ- uals, departments, and agencies listed below: The Study Management Team of the Louisiana Coastal Zone Management Program: Patrick W. Ryan, Director, State Planning Office; Lyle St. Amant, Assistant Director, Louisiana Wildlife and Fisher- ies Commission; Vernon Behrhorst, Director, Louis- iana Coastal Commission; and Jack R. Van Lopik, Director, Center for Wetland Resources, Louisiana State University, Baton-Rouge Campus. Louisiana State University, Baton Rouge Campus: James P. Morgan, Professor of Geology, School of Geoscience; Robert Chabreck, Associate Professor, Forestry and Wildlife Management; Richard Condrey, Virginia Van Sickle, P. Byrne Wells, Lewis J. Gulick, Bonnie Grayson, Bobbie Young, Deirdre A. Portnoy, and Linda McQueen, Center for Wetland Resources. Louisiana State Planning Office: Patrick W. Ryan, Director; Paul R. Mayer, Jr., Assistant Program Coordinator; John M. Bordelon, Chief Planner; Jim Renner, Economic Planner. Louisiana State Attorney General's Office, Tide- lands section. Louisiana Wildlife and Fisheries Commission: Maurice Lasserre. Editorial, manuscript, and publication services were provided by the Louisiana Sea Grant Program, a program sponsored cooperatively by the National Ocean and Atmospheric Administration's Office of Sea Grant, U.S. Department of Commerce, and by the state of Louisiana. vi Introduction The geologic characterization of the Barataria Basin that introduces this study describes the landforms and processes that are operative in Louisiana's coastal wetla'nd. It considers eustatic changes and land subsidence, and it documents land loss in the Barataria Basin Management Unit. The remaining sections expand on the land loss with studies of coastal erosion, marsh deteriora- tion by water movement, and vegetation responses to water movement. Coastal erosion effects are very dramatic where manis activities infringe on a zone that is under- going constant attack by waves and longshore cur- rents. Without replenishment of sand-size sediments from active river mouth bars, coastal processes can only rework existing beach deposits and sands are lost in the process. Groins, jetties, and other structures can alter patterns of sediment movement but select in favor of one site at the expense of another. The process most directly associated.with marsh deterioration is water movement. This can take the form of salinity intrusion that causes marsh plants to die back, or tidal pulses that remove organic detritus from the marsh and cause erosion of the marsh surface. Both of these processes destroy the ability of marsh plants to keep pace with subsi- dence. Lateral erosion caused bywaves generated I 'within the bays or lakes is another important process. Vegetation response to each of these factors is the key factor to be considered. The ability of the marsh to trap and produce sediment at a rate that keeps pace with subsidence is essential to the sur- vival of a viable marsh system. This ability is diminished when plants are stressed by salinity changes or when flushing exceeds production of detritus. The structure of the plant root system can also have a dramatic effect on resistance to erosion by waves and currents. The robust growth form of Spartina altemiflora and its extensive root system makes this salt marsh species much more resistant to erosion than most species characteris- tic of brackish marshes. A balance between sediment supply and subsidence is required for continued marsh maintenance. As long as the flow of Missis- sippi River water is confined to its channel by artificial levees, the natural processes will pro- ceed toward conversion of Barataria Basin into a shallow water body at the expense of marshlands. Existing settlements along the levees preclude returning to pre-artificial levee conditions. Therefore, imaginative and realistic water and sediment control schemes for nourishing depleted environments need be conceived and applied. 2 Geologic Characterization Physical Setting of Coastal Louisiana This report presents a digest of the salient phys- ical aspects of Louisiana's,coastal zone that are relevant to man's utilization of this vast, productive wetland. It is a companion text to the biological characterization (Bahr and Hebrard 1976) and hydro- logical/climatological characterization (Byrne et al. 1976) coastal zone management reports. These reports present a baseline inventory of significant biological, physical, and chemical parameters and describe related natural processes in this highly dynamic wetland. They comprise a scientific basis for management principles and guidelines to maximize wetland utilization, consistent.with minimal impact on natural systems. This section presents a general discussion of the geologic framework for the entire Louisiana coastal zone. A second section describes the geologic frame- work of the Barataria Basinl Management Unit, providing background for discussion of basin responses to natural and man-made stresses in a subsequent report. Louisiana's coastal zone encompasses some 10,443,400 acres of geologically Recent2 near sea-level wetland and inshore water bodies. Offshore the zone extends to the three-mile limit. Sediment- and nutrient-laden Mississippi River waters enter the north-central Gulf of Mexico, and tidal mixing and exchange of these waters between the extensive estuary systems and con- tinental shelf zone create a richly endowed habitat for marine resources. Inshore the area is about equally divided between swamps, marshlands and estua- rine water bodies. Only about 15 percent of the area 1. Barataria Basin as used in the coastal zone manage- mentreports refers to the enclosed basin with its apex approximately at Donaldsonville. It widens coastwise, with Bayou Lafourche and Belle Pass forming the western boundary, and the Mississippi River and Red Pass forming the eastern boundary. The term is synono- mous with hydrologic unit as used in the literature. The exact boundaries differ from those presented in Lindall et al. (1972) and Gagliano (1970), but the general area delineated is essentially the same. 2. The term Recent (capitalized) as used in this paper refers to offlapping sedimentary sequences associated with deltaic growth and coastal accretion. Some authors prefer the term Holocene, which had its origin 3 is subaerial land, which rises a few feet above sea level as natural levees, beaches, cheniers,3 and ele- vated areas associated with intruded salt domes. Man has.'extensively altered both the wetland and high ground through his settlement and economic activities. Dredg- ing operations associated with water-control systems, canals, and navigational channels interlace the area. The near sea-level wetlands are framed inland by the Prairie Terrace (Fig. 1) which slopes and sub- merges beneath the Recent wetlands. *Extending inland. alon g the rivers crossing this region are broad swamp- floored flood plains that contribute significantly to the nutrient supply of coastal waters. Low flood plain elevations allow marine waters to invade far inland. The Pleistocene terraces represent uplifted, weathered surfaces of deposits originally produced by processes still operating in the marine and fluvial environments of coastal Louisiana. Regional tilting of the terraces resulted in surfaces that are higher inland and lower seaward, sloping about 3.5 ft per mile (Russell 1940). Extensive near sea-level essentially flat Recent deposits onlap Pleistocene material along an irregular boundary inland from the coast. These are primarily deltaic deposits; however, the stranded beach ridge complex in southwestern Louisiana forming the chenier plain is comprised of reworked deltaic material and sediments eroded from along the coast. The landforms within the coastal zone.with the excep- tion of salt domes, -result from dynamic interactions between river deposition, waves and currents, eustatic sea level changes (worldwide changes of sea level associated with melting of the polar ice caps or isostatic adjustments of the continent) and subsidence. in Europe. Both are part of the late Quaternary record underlain by older Pleistocene deposits. There is considerable confusion in the literature concerning the application of the two terms; for additional in- formation refer to Fisk (1955), Russell (1968), and Gould (1970). 3. "Chenier" is used in southwestern Louisiana to mean old beaches now stranded in marsh (Russell and Howe 1935). "Cheniere" is used in the southern part of the Mississippi Delta to mean any high ground and ordinar- ily refers to natural levees of abandoned channels. In both cases the name refers to the oaks, which are dominant among the trees covering such eminences (Russell 1936, p. 45). 4 X, X C; LU 'LOUISIANA',, .. ........................................... . ...... ......... ............. R :::PRAIR1..E..TER .......... ............................................. ........... ............. .......... ................. ZO ........ ................ ........................... NEW ......... .................................. RLEANS H E N I I- R R A /V MARSH 0 so A MILES 0 0. A A TERRACED @ELTAIC'PLAIN GULF OF31EXIC0 PLAIN NEWORLEANS BI R DFOOT DE LTA SEA LEVEL DOWNWARPED WEATHERED SURFACE 1000, (TOP 0 -F PRAIRIE FIVI.) 50 100 150 MILES r--.7:30ELTAIC SAND, SILT, DELTAIC & MARINE SILT FLUVIAL & STRAND-PLAIN CLAY ff-I & CLAY WITH LOCAL SAND&GRAVEL SAND LENSES Fig. 1. Index map indicating major surfaces in the coastal zone. Bathymetr3 deep water near the Modern Delta and shoal water off the remainder of the co section A-A' illustrates downwarping In the deltaic plain. (After Fisk and Mc Although widespread in the subsurface throughout coastal Louisiana, salt domes (Fig. 2) only locally protrude through the marshlands and form topographic highs. The Five Islands in south-central coastal Louisiana extend along a northwest-southeast geologic activity line. Belle Isle forms the southern dome near the coast with Jefferson Island the northernmost dome where it outcrops through the Pleistocene surface. The islands are heavily wooded in contrast to the flat marshlands that surround them (except Jefferson Island). The islands are approximately two miles in diameter and the highest in elevation extend about 171 ft above the near sea-level marshlands. In the subsurface, lying at varying deptha, are several hundred domes that are known to exist. Many more topographic highs are suspected of being salt domes (Jones 1969). The domes are significantly important as sources of salt, sulfur, petroleum, and natural gas where they are present in the upwarped sediment around the periphery of the salt plug. EUSTATIC CHANGES (WORLDWIDE CHANGES IN SEA LEVEL) Sea level rise occurred as a result of the conti- nental glacial melt that concluded the last ice age. Seas were lower than at present, and the eustatic rise averaged about 0.5 ft per century during a 4.,000-year period ending about 3,000 years ago. Evidence indi- cates that minor fluctuations of sea level.have occurred since that time resulting in a net rise of about 0.1 ft per century or 3 ft (McIntire 1969). Part of this rise appears to have occurred during the last 40 to 50 years (Marmer 1954). Indications are that marsh surfaces kept pace with the relative rise in sea level through accretion of some mineral sediment (sands, silts, and clays) in addition to plant (organic) detrital accumu- lation. LAND SUBSIDENCE Submergence comprises one of the most critical problems in the coastal zone. Combined with wave attack and loss of river-borne sediment supply, it constitutes the primary cause of severe land loss in the marshlands and landward retreat of the coastline. Its causes are highly complex. Excepting mud lump emergence near major passes at the mouth of the Mississippi River and pos- sibly some salt-dome displacement, all natural vertical movements in the deltaic plain are associated with sub- sidence processes. Factors that contribute to lowering of the land surface relative to sea level inc1ddd,:- 6 MARGIN OF COASUL PROVINCE LEGEND - SALT DOME OR PROBABLE SALT DOME - TOPOGRAPHIC FEATURES oo, WHICH MAY BE ASSOCI- t ATED WITH SALT INTRU-k 4. 0 AFTER CARSEY. % SI N q 1950) A Al. q: lo, 00 GUL F OF MEXICO ADAPTED FROM MURRAY, ISM Fig. 2. Distribution of salt domes and topographic features that may be associatc intrusion (Jones 1969). 1) Eustatic sea level changes (mainly rising during late Quaternary including Recent times). 2) Regional subsidence caused by crustal.downwarping (isostatic adjustment) from sedimentary loading. Greatest downwarping along Louisiana's coast has occurred beneath the present birdfoot delta, where as much as 1,000 ft of late Quaternary sedi- ments have accumulated (Fisk and McFarlan 1955; Gould 1970; Fig. 1). Inland the Recent deposits thin out along the surface contact line where the Pleistocene surface emerges above the Recent. Down- warping diminishes westward; sediments comprising the Recent Chenier Plain in southwestern Louisiana are only about 30 ft thick at the coast. 3) Tectonic processes that include growth faulting (Jones 1969, p. 20), folding, fracturing, and flowing are phenomena that develop within the thick sedimentary section. They occur contemporaneously with downwarping (isostatic lowering), compaction of sediments, and filling in the basin with sediments. The development of salt domes and mud lumps are thought to be related to these tectonic processes. 4) Compaction of sediment through dewatering processes: a) Differential consolidation owing to textural variability in the sedimentary column. b) Consolidation of underlying sediments from weight of features such as natural levees, beaches, ,artificial levees--particularly when the features have been deposited over weak compressible foundations. C) Local subsidence of compressible materials through consolidation or displacement by objects such as buildings, pile structures, fills, bench- marks, and tide gages. d) Lowering of the water table through extraction of groundwater, salt, or sulfur; also "reclamation" practices that employ diking, construction of water control structures, and drainage of lands for agriculture or flood protection. Cumulatively, these practices become major concerns at the parish, hydro lo gi c /management unit, and state levels. e) Extraction -of --- 01_1_1 -gas, sulfur, and.water from salt domes is known to have resulted in subsi- dence. Scientists have done little in coastal Louisiana in relating extractive processes to subsidence except those connected with industry. Often, this information is privileged. A better understanding of processes related to extraction and subsidence is necessary, particularly when considerations are underway for utilizing sub- surface domes for storage. 8 f) Other phenomena and activities that contribute to subsidence through dewatering include the following: 1) Extended drought periods are thought to result in lowering the near-surface water, and compaction occurs within the dewatered, relatively thin layer. 2) Oxidation, hydration, and removal by wind are important factors in lowering of highly organic soil surfaces. This applies particularly to beaches along shorelines and coast. 3) Some observers claim that marsh burning dries out the near-surface water resulting in subtle amounts of compaction. Certainly it destroys organic litter that would other- wise contribute to maintenance of the land surface. 4) Marsh buggies traversing marshland surfaces compact underlying material leaving perma- nen.t scars. The complexity of the subsidence problem negates estimates of precise rates and cumulative amounts that would apply regionally. At a given locality all the above subsidence processes may occur contemporaneously. In addition, sediment texture and composition vary greatly from place to place and each type responds differently to loading. Organic content of sediment is an important factor in compaction. Dewatered and dried organic sediments shrink dramatically in proportion to the percentage of organics present in the sediment. Volume reductions as great as 85' percent are not uncommon in some dried marsh and swamp soils. Depositional environments associated with sediments laid down by rivers vary greatly over short distances (Fig. 3) both transversely and parallel to the stream. Silts and sands mixed with clays are the textural com- ponents of natural levees. Back slopes of natural levees grade into levee-flank depressions (low areas generally parallel to natural levees and marginal to marsh basins) or into marsh basins. Over relatively short distances downslope, natural levee sediments grade from coarse to fine-grained mineral soils to high percentages of organics. Grain size distributions and composition also change (more gradually) downstream. Within stream channels and along the coast, currents and waves winnow, transport, and deposit sediments whose forms and textural/compositional. properties relate to particular sedimentary environments. Each compacts differentially. 9 -FRESH MARSH- FRESH MARSH @U@F'FL06R SILTY CLAY A. INITIAL DEVELOPME T F 0IS RIB T R E 1 0 T U A I S A _FRESH SLIGHTLY BRACKISH MARSH FRESH MARSH MARSH INITIAL PEAT NATURAL LEVEE R INI E ROISTRIBUTARY T OUGH F@LL-j DIETERIO CHANNELrILL ENLARGMENT OF PRINCIPAL DISTRIBUTARY AND ITS NkTURA& LEVEES - CREATION OF MARSHES IN TROUGH. SWAMP MARSH--- NATURAL LEVEE ;P C. MAXIMUM DEVELOPMENT OF DISTRIBUTARY ANU 115 NATURAL LEVEES - CREATION )F SWAMP AS LEVEE SUBSIDES. SWAMP OROLCXISM MARSH ,4 A< NATURAL LEVEE FILL 171 FF D. DETERIORATION OF DISTRIBUTARY - ADVANCE OF SWAMP OVER SUBSIDING LEVEES. BRACNISH MARSH -4 SALINE MARSH sky OR SOUND ..... ..... TURAL rAE L @tl` E. CONTINUED SUIESIDLNCE WITH PARTIAL DESTRUCTION OF MARSHES. Fig. 3. Progressive stages in natural levee development, peat accumulation, and subsidence are illustrated in graphs A-E (Fisk 1955). A study made by Kolb and Van Lopik (1958) summarizes the subsidence problem as follows: It is apparent from the preceding discussion that only three of the component factors, true sea level rise (A), basement sinking (B), and consol- idation of the Pleistocene and pre-Pleistocene sediments (Cl), are sufficiently broad in aspect to permit general application to all of southeast Louisiana. Although the subsidence rates dictated by these factors vary considerably with geologic time, thus making average rates less indicative, it is felt that minimum values have been established. Therefore, the sum of the values for true sea level ,rise (0.32 ft per century), basement sinking (0.07 ft per century), and consolidation of Pleistocene and pre-Pleistocene sediments (0.39 ft per century) should provide an average regional subsidence rate (0.78 ft per century) for southeastern Louisiana at the present time. As a distinct component rate cannot be presently assigned to regional tectonic activity (E), the 0.78 figure includes the effect of this factor. In addition, it should be borne in mind that this value is a regional estimate and local deviations resulting from compaction of Recent sediments (C2), consolidation caused by weight of minor land forms (DI), consolidation caused by weight of manmade structures (D2), and local faulting or uplift (E), as well as normal deviations from the average should be expected. For the present several broad statements concerning subsidence in this region can be made: (1) subsi- dence is greatest--on the order of fiveor more feet per century--in the present Mississippi River Delta; (2) subsidence on the order of one to two feet per century is a realistic figure at the present shore line throughout the remainder of the study area; (3) subsidence decreases with distance inland and approaches zero at the surface Recent-Pleistocene contact. Subsidence caused by engineering structures (D2) can be accurately calculated. On the other hand the effect of long-range regional subsidence on these structures can only be based on data such as those presented here. Long-range planning for control of, the river depending on precise elevations, municipal developments and their future protection from floods, the effect of long-range confinemerit-of the-Mississippi River between artificial levees and the gradual inun- dation of the deltaic plain as a result of subsidence, are but a few of the items that are affected by the omnipresent factor of subsidence. For some long-range 11 considerations, subsidence of the order of magnitude prevalent in southeastern Louisiana may be negligible; for others it may be a key factor that might easily be overlooked. In any event, there can be little doubt that as the rapid industrial and commercial development of the deltaic area continues, engineers will become more and more cognizant of the factor of subsidence and its effect on engineering projects and programs. Since the above study was made investigations on eustatic rise have been refined somewhat and the 0.32 ft per century figure indicated above appears high. Coleman and Smith (1964) show eustatic level reaching its present approximate level about 3,600 years ago. Radiocarbon dating of sediments from beneath Little Chenier (McIntire 1961) in western Louisiana indicates that eustatic rise has occurred during the last 3,000 years at a rate of approximately,O.l ft per century. For more detailed information on subsidence, refer to several excellent studies including Coleman and Gagliano (1964), Gagliano (1970), Coleman, Suhayda, Whelan, and Wright (1974), Coleman and Wright (1974), Gould (1970), Frazier (1967), Shelton (1968), Bruce (1973), Carver (1968), Russell (1936), Fisk (1955), Earle (1975), and New Orleans District, U.S. Army Corps of Engineers (1975). Specific areas of concern in this portion of the study include the lower reaches of the river flood plains and back swamps, chenier plain, deltaic plain, and nearshore waters. FLOOD PLAINS River meander belts bounded by marginal back swamp basins characterize flood plains of the numerous rivers that extend to the coast in Louisiana. These features are generally low, level, and densely forested. They experience seasonal flooding. For additional informa- tion on flood plains and back swamps, see Saucier (1974) and Fisk (1944). The meander belts of the Mississippi River (Fig. 1) that are located in the coastal zone include the belt outlining the present course; the Teche-Mississippi course, which formerly flowed along the western margin of the Atchafalaya Basin when the river occupied what is now Bayou Teche; and the Maringouin-Mississippi course, which flowed down the central and eastern por- tions of what is now the Atchafalaya Basin. These belts contain river cutoffs, ridges, and swales, repre- senting former point bars and abandoned channels that may be partly or completely filled with clay deposits. 12 The dominant landscape features associated with these Mississippi River distributary systems are the broad, low, asymmetrical ridge complexes, which slope gently away from their present or former river channels, resulting from Mississippi River-constructed levees. Typically, such channels deteriorate into sluggish bayous when their flow is captured by other streams. The back swamps and flood basins have remained peripheral to the meander belts throughout their development. They receive mainly clays and silts deposited during high river stages with over-bank flow and include environments ranging from infrequently flooded forests to continuously flooded swamps and lakes. The Atchafalaya Basin is a unique back swamp feature that received an accelerating flow from the time the Atchafalaya River began to capture Mississippi River waters (during the last 100 years) until 1959 when it was brought under control--at least tempo- rakily--by the U.S. Army Corps of Engineers (com- pleted in 1963). Relict Mississippi River courses predating the Mississippi-Teche system are in evi- dence in the mid- and upper sections of the Atchafalaya Basin. Of these, natural levees asso- ciated with Bayou Maringouin and other distributaries remain as high ground. RECENT CHENIER PLAIN The Recent chenier plain of southwestern Louisiana lies out of the direct influence of the delta proper. Its development is related to westward and eastward shifts of the Mississippi River; changes in the Sabine, Calcasieu, Mermentau, and Vermilion rivers; their associated sediment supply; and dominant westward- flowing littoral currents. Westward shifts of the Mississippi River supplied sediments that resulted in coastal accretion. Eastward shifts of the Mississippi River resulted in coastal retreat and beach ridge or chenier development. Seaward extension of the shore- line was primarily by beach accretion, with subsequent marshland development in swales between beaches. Local rivers (Sabine, Calcasieu, etc.) have also contributed to seaward land growth through accretion ridges forming at their mouths. The plain dominates coastal Louisiana from Vermilion Bay westward to the Texas border. Recent deposits about 30 ft thick at the coast cover the underlying Pleistocene material and pinch out at the inland surface line of Pleistocene/Recent contact. Because of the relatively thin layers of Recent sediments, subsi- dence rates from compaction are low. The high ground (nonwetland) in this area includes remnant low Pleisto- cene islands that form outliers in the marsh, chenier 13 ridges, and beaches. Shallow waters dominate the off- shore zone; the 60-ft bathymetric line lies nearly 50 mi from the coast (Fig. 1). Extensive canal dredging and diking has occurred in this area; the Intracoastal Canal was cut in the more resistant Pleistocene deposits but is close to the line of Recent marsh contact. For detailed references on studies concerning the chenier plain consult Russell and Howe (1935); Byrne, LeRoy, and Riley (1959); Gould and McFarlan (1959); and Gould (1970). RECENT DELTAIC PLAIN A line drawn on the map between Franklin and Donaldsonville, La., separates the deltaic plain from the flood plain or alluvial valley. Figure I shows the Recent Deltaic Plain lying between two arms of the most southern part of the terraced plain. At the coast end of this line the deltaic plain fans out into a broad wetland surface with natural levees determining the course of drainage. Typically, the river networks are grouped together in distinct regions where delta growth was occurring at the time of levee formation. Sedimentary deposits that formed the deltaic plain make up a progression of seaward deepening deposits (Fig. 1, A-A'), which interfinger with deposits from contemporaneously flowing adjacent distributaries (Fig. 3, D). The mass of these deposits which build the coast seaward over marine material are classified as offlap deposits. When river sedimentation ceases through river diversion or artificial damming,, marine processes become dominant, coastal sediments are then reworked and redeposited landward by wave and current action. The mass of this redeposited material is classified as onlap deposits. Delta formation begins with the progradational (advance of shoreline) phase as a stream dumps its sediment load into a larger body of water. Most of the sand is dropped at the stream mouth'and buried by more sand, while some is redistributed laterally by waves. The finer-grained sediments are carried further off- shore where they settle out of suspension more slowly. This condition leads to the normal vertical sequence consisting of prodelta silty clays overlain by layered delta-front silty sands and clayey silts. The rate of delta advance is controlled by the kinds and quantity of material the river is transporting, and depth of water into which the stream is emptying. While the nearshore subaqueous platform is deposited, the subaerial,d6lta-plain is aggrading ([email protected]@.-' a surface) by primary deposition occurring along the 14 flanks of the sediment laden stream, forming natural levees (Fig. 3, A-C). Concurrently with levee increase in height upstream from bank overflow,the downstream levees emerge as subaeria'l features*as �tream@deposited sediments build seaward. As progradation continues through the distributary network the delta plain is enlarged (Welder 1959, p. 54-65). Once subaqueous land emerges above gulf level, vegetation inhabits the new land and initiates the formation of organic deposits. Continued progradation leads to an overextension of the distributary network. Under these conditions stream flow seeks a shorter route to the gulf and initiates the diversion process and construction and locus of a new delta. In the former delta locality subsidence con- tinues and delta deterioration sets in. Wave and current action reworks distributary-mouth bar sands along the former delta margins forming beaches and barrier islands. River diversions are usually gradual occurrences, and flow at times is shared by major courses, which, on occa- sion simultaneously form deltaic complexes in different areas. Figure 3 illustrates the sequences of natural levee and marsh development that were repeated in each river course associated with the delta development. The diagrams, illustrate the results of aggradational and subsidence processes in the coastal environment. Recent History of Deltaic Plain Five major delta complexes where the master stream has flowed in the past or is presently flowing dominate coastal Louisiana from,the western margins of Vermilion Bay eastward to and including the Chandeleur Islands (Fig. 4). These delta complexes include the following from oldest* to youngest: Maringouin-Mississippi Teche-@Mississippi St. Bernard-Mississippi Lafourche-Mississippi Plaquemines-Modern Mississippi These deposits are in varying degrees of deterioration because of subsidence and eustatic sea level changes and are characterized by partially or completely buried levee ridges flanked by marsh and swamp deposits that grade to lakes or bays. They are bordered on their seaward margins by barrier islands, sand and shell beaches, fronting mainland marshlands. Along portions .of the coast, little or no beach material has accumu- lated, and marshlands are exposed to direct wave attack. ge Frazier (1967) and Gould (1970) summarize kfi@owj:ed ' - concerning delta complex development and sequences of stream networks that form relatively discrete areas 15 won "P PLAIN ----I ;;@TURAL LIVER INFIRRIED NATURAL LEVII DWA-MA&GIN ISLAND OF BORING. L FIGURE 4 RILICT SAND 111ACH 1 0 aWC1 MUD 91ACH MMSTOCRIE OUTCROP 8 E SUBAQUEOUS N SAND ACCUMULATIONS WJKOUS ,A T E C 0 A F 91. 0 u Z Jr Ira-- j Fig. 4. Delta complexes of the Mississippi Delta Plain (Frazier 1967). where delta lobes were formed, Figure 4 outlines the delta complex areas of deposition. The Maringouin complex was functioning at a time when sea level was several feet lower than at present. Coastwise subsidence and sea level rise occurring contemporaneously with more recent sedimentation from adjacent distributaries has buried most of the coastwise elements of this delta complex. The only surface remains of this delta complex are upstream. Bayou Teche served as the course of the Mississippi River during progradation of the Teche delta complex. Then the river shifted to approximately its present course along the eastern flank of the flood plain during the growth of the St. Bernard complex. Later, Bayou Lafourche received the major flow and the Lafourche delta complex resulted. Presently the river is feeding the Plaquemines-Modern delta complex. Sixteen delta lobes have been identified among the five delta complexes (Fig. 5). These lobes developed in overlapping sequence as alternate distributary net- works received predominant flow from the Mississippi trunk stream at different times. The sequence of delta lobes has been determined by the examination of over 30,000 borings, accompanied by hundreds of radiocarbon dating measurements on delta plain peat samples (Frazier 1967). Archeological evidence, based on the position and age of sites of human habitation, has also played a key role in solving this complex puzzle (McIntire 1958 and 1959; Saucier 1962). Delta lobes named for the major,stream courses that formed them and their rela- tive ages are shown in Figure 5.. Frazier's (1967) sequence of delta lobe formation and chronology of, active phases of stream courses constitute.-major con- tributions to-,study of deltas.--. He clarified previously conceived notions held by others but never enunciated that "successive delta lobes, each defined by a complete sequence of facies and the age of its delta-plain peat, were not necessarily developed by the same trunk stream, but were in several instances developed b y different major courses which were penecontemporaneously, (originating at the same time) prograding parts of separate delta complexes." Nearshore Waters Relatively shallow water occurs along the Louisiana coast except at the mouth of the Modern Birdfoot Delta (Fig. 1). The 60-ft contour line lies nearly adjacent to the mouths of the passes in the Birdfoot Delta, whereas westward this line extends to almost 50 mi offshore. Tides are diurnal (once daily) and low, averaging 1 to 1 1/2 feet in range'. Wind effects on 17 THOUSANDS OF YEARS BEFORE PRESENT Q% PLAQUEMINES- MODERN DELTA COMPLEX A 'SIPPI RIVER BAYOU LAVOURCHE BAYOUS LAFOURCHE AND TERREBONNE LAFOURCHE BAYOU BLACK DELTA COMPLEX BAYOU BLUE BAYOU TERREBONSE BAYOU SAUVAGE %0 MISSISSIPPI-LA LOUTRE ST. BERNARD I DELTA BAYOU DES FAMILIES COMPLEX BAYOU TERRE AUX BOEVFS w MISSISSIPPI RIVER AND BAYOU LAFOURCHE .P. BAYOU CYPREMORT P%J BAYOU SALff TECHE DELTA COMPLEX BAYOU TECHE MARINGOUIN DELTA COMPLEX H@DP Fig. 5. Age of prominence of each of the 16 delta lobes of the Mississippi Delta Region (Frazier 1967). water levels often exceed tidal influences. Gently shoaling nearshore bottoms dampen wave attack along most of the coast. Under normal conditions the Bird- foot Delta receives heavier wave attack than the remainder of the coast because of its proximity to deep water. Littoral (alongshore) currents generally flow west- ward with the dominant easterly and southeasterly winds but seasonally and locally reverse their flow. Murray (1976) has assembled the present status of information on wind and wave generated nearshore cur- rents. The barrier islands that front much of the Deltaic Plain result from accumulation and transport of sediments by littoral currents. Salient Physical Features In the Deltaic Plain Several major natural features that form distinctive environmental units characterize the Deltaic Plain. These include natural levees, estuaries, coastline beaches and barrier islands, and swampland/marshland wetlands. Natural Leve es Throughout the Deltaic Plain, recently abandoned and relict stream courses and their associated natural levees remain as evidence of deltaic growths, subsidence, eustatic rise, and aggradation. The collectiveliet40'rk of natural levees, bifurcating coastwise, form.the only high ground for human habitation, roads, and farms. While levees provide high ground for north-souih move- ment, the interlevee depressions are barriers against east-west movement. All of the levees in the deltaic plain except in the Modem Delta below Venice and in the Atchafalaya Delta are deteriorating, as no natural overbank flooding has been allowed to take place for over a hundred years. The levees forming in the active Mississippi River Delta are lost almost as soon as they are formed owing to the high rate of subsidence and the deep water environment into which they are building. New levees forming in the Atchafalaya Delta should provide an area for inhabitation equivalent to the banks of Bayou Teche in a matter of 25 to 50 years (Gagliano 1975). Levees are broader and higher closer to the trunk stream and become lower and narrowerat downstream distal ends. Even areas of natural levees presently above sea level may be marginal for development in a matter of decades. Estuaries Es'tuaries represent inshore water mixing areas that are transitional between marine and terrestrial 19 environments. Estuaries include.a great variety of water bodies, related mainly by possession of charac- teristics intermediate between fresh and marine water. They are noted for rapidly changing and highly vari- able physico-chemical conditions and high biological productivity. Their importance in the coastal system stems from the fact that approximately one third of coastal Louisiana presently lies in the tidal zone (Gagliano et al. 1970). The Louisiana estuaries (including the two great riversImouths) are typically' shal- low with bars forming at their mouths. This is typical of low-tide/low-energy coasts. Bar-mouth estuaries are usually well-mixed waters with a general absence of well-developed salt wedges or vertical salinity gradients. Coastline The coastline of Louisiana is fronted by barrier islands and mainland beaches along areas exposed to the Gulf, with tidal flats and marshes in protected areas behind barriers and estuarine shores. The single most important coastline component is the string of barrier islands, which occupies more than half of the total coastline and which is limited to the central and eastern deltaic area of the coast. Louisiana barrier islands are multiple in origin and are associated with deltaic development and deterioration. Most of them originated as bay-mouth barriers on the flanks of and against abandoned natural levees and distributary mouth bars of the delta com- plexes (Kwon 1969). Details of their morphology are largely determined by sediment influx from active streams, erosion of retreating delta fronts, subsidence, and littoral currents (Kwon 1969). A summary chart listing the barrier islands and barrier beaches, their geographic coordinate location, sizes and natural environmental zones is included as Appendix A. Swamplands and Marshlands Freshwater swamplands, and fresh, brackish, and saltwater marshlands occupy the wetland basins. Vegetation communities and associated peat accumula- tions range in composition from coastwise salt marsh types to inland freshwater swamps. Plants are sensitive to water table levels caused by even slight changes in elevation. These changes are schematically indicated inTigure 3, which shows an idealized natural levee and marsh environment. Similarly, a transect from a natural levee to the swamp proper would cross a semiwooded fringe of trees and brush. Deltaic plain marshlands show more subtle differences 20 in vegetation community assemblages than those in the firmer chenier plain. Frazier has identified swamp and marsh vegetation assemblages (Table 1), which characterize macroenvironments in the deltaic and chenier plain. In the chenier plain peat development occurs between stranded beach ridges and in the flats between the inner ridges and the Pleistocene outcrop. Del- taic Plain peats form in deltaic flank depressions, interdistributary basins, and levee flank depressions (Fig. 6). Figure 6 (Block A and B) graphically shows the complexity and interrelationships of deltaic sequences. Blanket peats have developed over old deltaic surfaces in the Vermilion Bay and Marsh Island area (Coleman 1966). These wetlands generally lack naturally occurring relief features. The construction of canals and water-control structures has resulted in miles of spoil banks, conspicuously marked by vegetation characteristic of high ground. Normal marsh elevations average about 0.6 ft above mean sea level in the deltaic plain, and tides commonly inundate the marshes. The marsh zones based on plant communities are discussed in detail in Barataria Basin: Biological Characterization (Bahr and Hebrard 1976). Barataria Basin Management Unit The Barataria Basin Management Unit (Fig. 7) is closed to active river flow except for irrigation waters from Bayou Lafourche and the Mississippi River. Minimal amounts of*fresh water enter the basin through the Harvey CanalLocks in New Orleans. Local rainfall provides the main source of fresh water for the basin. During periods of high water in the Mississippi River, and under certain wind and sea conditions, fresh water from the river influences the lower Barataria Basin. The basin is a delta flank depression approximately 70 mi long with its apex at Donaldsonville. It widens to approximately 30 mi between Belle Pass (Bayou Lafourche) and Red Pass (Mississippi River). The basin forms a natural mixing area for saline and fresh waters and comprises a richly endowed habitat for a diversified flora and fauna. The physiographic setting for the basin was formed by portions of three deltaic complexes that overlap into the basin. These are from oldest to youngest: St. Bernard (lobes 3, 7, 8 and 9, Figs. 4 and 5); Lafourche (lobes 10 and 15), and Plaquemines (lobe 13) and the Modern (Birdfoot) Delta complex (lobe 16) (Frazier 1967). 21 Table 1. Characteristic swamp and marsh vegetation (from Frazier and Osanik 1968)* INLAND FRESHWATER SWAMP (Trees and Shrubs) Natural-levee flank Dwarf palmetto Sabal minor Live oak Quercus virginiana Overcup oak Quercus lyrata Willow 0aiJ- Quercus phellos Bitter pecan Carya aquatica Red maple Acer drummondi Green ash Fraxinus pennsVIvanica var. lanceolata Black willow Salix nigra Wax i@@-rtle Myrica cerifera Hackberry Celtis laevigata Red gum Liquidambar styraciflua Central portion Bald cypress Taxodium distichum Tupelo gum Nyssa aquatica Sour gum Nyssa unif lora Red maple Acer drummondi Green ash Fraxinus pennsylvanica var. lanceolata. Black willow Salix nigra Swamp elder Baccharis halminifolia 22 Table l.. Continued. Semi-wooded fringe Black willow Salix nigra Bald cypress Taxodium. distichum Red maple Acer drummondi Green ash Fraxinus pennsylvanic a var. lanceolata Possum haw Ilex decidua Wax myrtle ..Myrica cerifera Buttonbusy Cephalanthus occidentalis HERBACEOUS VEGETATION Central portion Bull tongue Sagittaria lancifolia Arrowhead Sagittaria latifolia Spider lily Hymenocaulis occidentalis Semi-wooded fringe Bull tongue Sagittaria lancifolia Arrowhead Sagitt ria latifolia Water millet Zizaniopsis miliacea STREAM-MOUTH FRESHWATER MARSH Initial natural levee Roseau cane Phragmites communis Water millet Zizaniopsis miliacea Cattail Typha latifolia 23 Table 1. Continued. St ream-mouth mud flat Fresh three-cornered grass Scirpus americanus Delta duck potato Sagittaria platyphylla Initial interdistributary flood plain Cattail Typha latifolia Widgeon grass Ruppia maritima Grayduck moss Potamogeton foliosus Dogtooth grass Panicum repens Oyster grass Spartina alterniflora INLAND FRESHWATER MARSH Chenier plain Paille fine or canouche Panicum hemitomum Cattail Typha latifolia Bull tongue Sagittaria lancifolia Saw grass Cladium jamaicense Spike rush Eleocharis quadrangulata Eleocharis pallustris Eleochiir'is cellulosa Water millet Zizaniopsis miliacea Roseau cane Phragmites communis Bulrush Scirpus californicus Deltaic plain Paille fine or canouche Panicum, hemitomum Cattail Typha latifolia 24 Table 1. Continued. Bulrush Scirpus californicus Saw grass Cladium jamaicense Delta duck potato Sagittaria platyphylla BRACKISH MARSH Chenier plain** Saw grass Cladium jamaicense Cattail Typha Angustifolia Roseau cane Phragmites communis Hog cane Spartina cynosuroides Spike rush Eleocharis palustris Water millet Zizaniopsis miliacea Deltaic plain Three-cornered grass Scirpus olneyi Paille fine or canouche Panicum hemitomum Wire grass Spart na patens Cattail Typha latifolia Typha angustifolia Arrowhead Sagittaria latifolia SALINE MARSH Chenier plain** Coco or leafy three-cornered grass Scirpus robustus Wire grass Spartina patens, Salt marsh grass Distichlis spicata Clump grass Spartina spartinae 25 Table 1. Continued. Deltaic plain Wire grass Spartina patens Oyster grass Spartina alterniflora Black rush Juncus roemerianus Salt marsh grass Distichlis, spicata Saltwort Batis maritima Glasswort Salicornia perrenis Salicornia e2E2pea Sand rush Fimbristylis castanea *After O'Neil 1949, Penfound and Hathaway 1938, Hall" and Penfound 1911, Gould and Morgan 1962. **The chenier-plain marshes are slightly firmer than the deltaic-plain.marshes. 26 MAjot OILIA-FICNI PUA LIVII-P&ANC .. IAn 'Ac.41 ll..Slo "AluRAt cowall ollit.-wAlle LIVIIS WILAND SWAMP --pp" P. 1. 7- A .1. IT P C" AT I, PRI A- A@_ 1010.0 NIC IACIIS fll@UTAIV T I'lloot". FACM BLOCK A 'A' URA-11V.1 o' I Poll COASTAL AREA I, [Poll? LIA.FRONT OVERLAPPING DELTA tONIS F.C.I. ASSOCIATIO WITN CILVA-PLAIN "o" A"' I.ICK INI,AM*- DISTRIBUTARY NETWORKS BLOCK 5 SWAMP PUT INLAND A*8A INITIAL PROGRADATION AND CONTINUING AGGRADATION AssocIATto wil", MAJON STRIAM COURSE Fig. 6. Deltaic Plain sedimentary sequences of coastal and inland areas are depicted by major de- positional environments in a typical delta complex (Frazier 1967). NEW ORLEANS c A N- THMODAUX L.AUSALVADOR UNA A cur. 1. 29'3 UTTLE L.AKE 4s %, rA % Over 5 Ft. above MSL CA v Below MSL GOLDEN MEA .W JILARATAJUA MAY.o' @* 0 Ft. Contour 5 Ft. Contour ----- 10 Ft. Contour A Inner Marsh Limits (from-N.O.S. Cho" 11352) RANDTERRE ISLANDS CA INA BAY Island Delta Stream Courses Having Surface It : - 1.- 1, 1, Expression auto Iske, Ir. %, % '4 ...... Delta Stream Courses In Subsurface A4k GULF OF MEXICO . (0 & 0) Delta Lobe Chronology According to r Frazier , 1967 4 EA Judy YeRjummint &A E, Mi. Km WOW W30' wow Fig. 7. The Barataria Basin Management Unit (map hase after Gagliano, 1970). The St. Bernard Delta Complex is represented by portions of four lobes (3, 7, 8 and 9). The earliest (3) underlies the head of Barataria Basin and the present Mississippi River system eastward. The broad delta lobe (7, Bayou des Familles) extending south- ward from New Orleans formed approximately 3,500 to 2,500 years ago. Bayou des Familles, which received a large portion of the Mississippi River discharge during its heyday, was the main distributary of this delta (7). Lobes 8 and 9 overlapped Bayou Terre aux Boeufs in the St. Bernard Delta Complex but extended into.the Barataria Basin via Unnamed Bayou northwest of English Turn. After abandonment of the Bayou des Familles dis- tributary network and subsidence of the associated delta lobe, the second Lafourche Delta Complex sequence (10), represented by the lobe that formed Bayou Blue, prograded over its drowned distal margin. Lobe 10 derives from the predominance of Bayou Blue as a major distributary of the Mississippi River during a relatively short period beginning around 2000 years B.P., according to radiocarbon estimates of its earliest peat deposits (Frazier 1967). This lobe extended into the Barataria Basin immediately east of present-day Bayou Lafourche, and, as it began subsiding, trans- gressive (encroaching) bay sediments accumulated on top of the peat and carbonaceous sediments. Grand Isle formed at the edge of the lobe during this trans- gression. Ranaia cuneata shellsincorporated in the bay facies, which was deposited in the depression between the Bayou des Familles delta plain and the Unnamed Bayou course of the Mississippi River, were dated at 1,400 years before present. Shortly after deposition of these bay sediments, another deltaic progradation occurred when Bayou Barataria, a distributary.of the Mississippi River, reoccupied the abandoned Bayou des Familles course (lobe 13). Deposition of clay and silt from floodwaters built up the'old Bayou des Familles delta plain. The silt and clay flushed into Barataria Bay raised shallow portions of the bay floor until vegeta- tion could again take hold. Peats on the Barataria delta plain (13) began forming approximately 700 years ago and are still accumulating. In addition to Bayou Barataria (13), river sediments were deposited in the bas:k. through crevasses off the Mississippi River (lobes 13 and 16). and through numerous bayous in Plaquemines Parish such as Bayou Grand Cheniere (13) and Grand Bayou (13). The Lafourche delta complex continued to develop, nearly filling the basin between Bayou Lafourche and 29 the Mississippi River. As this lobe prograded it partially filled a large moderately brackish lake. An unfilled portion of this lake is now known as Lac des Allemands.. Samples of sediment taken from the lake floor contain exclusively fresh to slightly brackish water ostracods. Bayous Boeuf, L'Ours, Matherne, Raphael, Portuguese, and the West Fork of L'Ours were active streams.during the final lobe (15) of Lafourche Delta Complex. Bayou Lafourche was artificially dammed in 1904. Subsidence is again allowing transgression and Barataria Bay is enlarging as the organic deposits are eroded. Coastal retreat was occurring rapidly at Grand Isle until groins were constructed. Groins have temporarily retarded coastal erosion at Grand Isle but erosion along adjacent coasts appears to be accelerating. The Modern Delta Complex constitutes the current lobe (16)i and, as in the past, the Mississippi River is forming a contemporaneous delta in the Atchafalaya Bay. The above discussion on the deltaic complexes that have formed the Barataria Basin is presented to illustrate the dynamic behavior and intricacy of streams and related deposits that have overlapped, interlaced, and intercalated within the basin through time. With sea level rise, marine sediments along the Gulf front accumulated and formed sand bodies such as the barrier islands. The deltaic history has resulted in a highly variable and complex surface based on un- stable, highly diverse substrates (Fig. 6). Barataria Basin is a delta flank depression between the latest Lafourche and Mississippi River delta complexes. Within the basin, levee-flank depressions have formed between natural levees of adjacent or bifur- cating stream courses. Subsidence has continued at relative rates that generally increase seaward but vary a great deal locally. The heavier sands and silts that form the natural levees and beaches compact or dewater underlying clays and organic deposits more rapidly than sections of clays and organics which are not surface loaded. Clays also have a tendency to flow either laterally or upward along lines of least resistance when loaded by heavier material. These processes, coupled with world-wide sea level rise, have produced a highly complex and variable substrate that varies in its response to erosion processes. Clays resist erosion when wet but are easily eroded after drying. Uncemented sands and silts erode rapidly. Some highly fibrous plant root systems bind the upper substrate, and thus resist erosion under permanently wetted conditions. Peats formed by fibrous and deeply rooted plants retard 30 erosion. Other plants and plant communities lack deep root characteristics and the peat deposits formed by them are fine grained, homogeneous materials that erode easily when attacked by waves and currents. In addition to substrate characteristics, subsidence, and eustatic changes, vegetative and surface physical processes affect stability of marsh surfaces. Plant die-back, marshland drowning by atorm-driven salt waters, flooding by higher-than-normal tides, and drainage below normal low waters affect vegetation growth and propagation. Winter freezes frequently kill the Black Mangrove, which otherwise forms a protective zone around the coastwise marshland shores. It remains then that marsh land deterioration, which is rapidly occurring in areas not receiving river-borne sediments, is a highly complex and vari- able process. MAJOR DELTAIC FACIES The complexity of Barataria Basin is evident from the general geologic history of its development. Responses to stresses within the water bodies and environmental units are directly related to the complex wetland surface and substrate. A two-dimensional longitudinal section (Frazier 1967) extending from Lake Pontchartrain through the middle of the basin to Grand Isle (Figs. 8 D-D, and 9) reveals the location and complexity of sedimentary deposits that underly-the surface. Figure 9 displays two cross-sectional drawings of section D-D' of Figure 8, one of which depi ct�@delta- lobe relationships and the other facies relationships. The Pleistocene boundary (Fig. 9) lies about 40 ft below the surface in the vicinity of New Orleans. From that depth it has been downwarped to approxi- mately 500 ft beneath Grand Isle. In the section showing delta lobe relationships, former deltaic sequences of offlapping, overlapping, and onlapping sedimentary deposits are indicated (Fig. 9). The oldest lie at the bottom of the section and the youngest at the surface. In the facies relationship section, progradational (seaward building) and aggradational (upward building) facies illustrate depositional facies that construct the deltaic plain. These deposits range from relatively thick sections of peat to prodelta silty clays. The peat sections are evidence that in general plant growth and organic accumula- tion kept pace with relative rise of sea level during the past few thousand years. Gulfwise, tra@@gressive (advance of the sea against the coastline) sedimentary 31 46 mLvwo 0 mm-- r QU&F OF AIIXICO Y Fig. 8. Location of D-D' cross-section depicted in Fig. 9 and principal control borings 1967) in the Barataria Basin. DEIIA,108E RELATIONSHIPS D LAK MISSISSIPPI RIVER BAYOU PONTCMA:TRAIN BAYOU SAUVAGE UNNAMED BAYOU DES FAMILIES BARATARIA 0 13,16 8,9 X11:X. oooo@@ ... ....... S.. _201- X d X -40- x: x',; I FACIES RELATIONSHIPS INTERSECTION WITH NORTH SECTION E-E' 2150 MODERN @A_ . ......... 1)0 2250 9 .... 101- 3050 2925 'PINE $LAND ... _30._ a-z' -40' S 10 is to 23 30 35 UPPER SECTION BOUNDARY BETWEEN DELTA LOBES AND BETWEEN AGGRj6DATIONAL 13 DELTA-LOBE DhSIGHATION UNITS GENETICALLY RELATED TO Di LTA LOBES. 0911 TEXT, AtAO FIGURES 11 AND 121 40vow BASE OF TRANSGRESSIVE DEPOSITS DELTA-COMPLEX BOUNDARY ERODED PLEISTOCENE SURFACE PROGRADATIONAL AGGRADATIONAL TRANSOR S FACIE$ El FACIE$ FACI:'s 'VIE Fig. 9 (in two sections). Cross-section D-DI (from Frazier 1967) showing delta-lobe and sedimentary facies relationships through the Barataria Basin. Basin location of the section shown on Fig. 8. q 0 2000 217 2 3T-1 BAYOU SAY OU BARATARIA BAY GRAND ISLE DES FAMIL IES BARATARIA DES FAMI Ll ES BARATARIA GULF OF MEXICO EEA L VIL 10 ............ ... --20' 7 -301 17 souTi I I I I I I I I Jill I I III I I II I IIIIIIIIII 111111111111111111111 1 111111111 11 Jill I I SEA LEVEL 2875 .77 '-Z@ -7 40 45 so 35 60 65 yo MILES LOWER SECTION BARRIER, TIDAL-DELTA, OR STRANDLINE SAND TRANSGRES$011 FACIE$ SAY- SILT, CLAY, & SHELL PEAT CLAYEY PEAT, PEATY CLAY, j ORGANIC MUCK AGGRADATIONAL FACIEllo INORGANIC CLAY NATURAL-LEVEE .4 SILTY. CLAY DISTRIBUTARY-MOUTN- BAR SILTY SAND DELTA-FRONT POOGRADATIONAL FACIE$ SILTY SAND & SILTY CLAY PRODELTA SILTY CLAY k-7 -4 I I LOCATION OF BORING$ a 2600 RADIOCARBON AGE YEARS BEFORE PRESENT VERTICAL EXAGWRATION: xSOO WEATHERED ERODED PL EISTOCENE SURFACE facies represent sediments that were reworked by waves and currents during the relative rise of sea level to its present position. Grand Isle and other barrier islands eastward are surface features of the trans- gressive deposits. Between the western boundary of the basin and Grand Isle are a number of tributaries off Bayou Lafourche that formerly flowed into the basin (Gould 1970, Fig. 10). Bayou Fer Blanc and Bayou Moreau are shown on the cross and longitudinal sections.(Fig. 10, A, B). Natural , levee silts and sands and marsh deposits represent pro- gradational and aggradational facies in the western section of the lower basin (Fig. 10, Section A-A'). In the vicinity of lower Bayou Moreau (Section B-B') a series of accretionary beach ridges dominate the surface. These ridges'represent reworked deposits of delta front sands. On the east side of the basin, distributary streams off the Mississippi River flowed into the basin as the Plaquemines Delta lengthened seaward (Fisk 1955, Fig. 11). Cheniere Ronquille (Fig. 7), represents,, in part a relict beach ridge that underlies the distributaries off the Plaquemines Delta complex (Welder 1959). Crevasse deposits form a nearly continuous apron of aggradational facies advancing into the basin around its upper periphery from the Mississippi River and Bayou Laf.ourche. Crevassing is an important aggradational process in delta construction; the associated fan deposits are significantly evident from both Bayou Lafourche and the Mississippi River. Barataria Bay, Lake Salvador, Lac des Allemands, and connecting water bodies form the major water links for water exchange between the gulf and the inner basin. The water bodies form significant reservoirs for nutrient accumulation and chemical change, and serve as conduits for water and nutrient exchange. Character- istics of the hydrology and climatology for the,basin are covered in a companion volume (Byrne et al. 1976). Wave characteristics (Suhayda 1976) along the Barataria Basin coast are included in the above report. Littoral currents that fashion the Louisiana coastline are described by Murray,(1976). 35 SHEET SANDS BAYOUS OCCUPYING ASANOO"ED LAFOURCHE DISTRIBUTARY CHANNELS LIME LAKE N TRACES OF ABANDONED L , (AFOURCHE DISTRIBUTARIES NOT OCCUPIED BY STREAMS) ... ......... 'CIO BAR RIDGES IN MARSHLANOS VA 'pe, A' BARATARIA sA Y @.Champagnej Bay Ir7 A .. 4,@GRAND TE.RRE ISLAND ............ 7 CAMINALIA BAY LAKE RACCOURC7 r 0 .0v ... TINBA LIER BA Y ...... 0 0 .3 MILES BA YOU BA YOU RA YOU (After Rik 1955) A' VYIOTH OF DISTRIBUTARY 1-41-OURCHE FER BLANC MINK CHANNEL FILL _@q" --. .- , . _. _. - - NE 7 GE RALIZED F.1,CIE-.; SYMBOL IDENTICAL 25- -7 7/ -25 MARS@@ & dA IL a cLAYS ON SCCTIONS 7 7. 50. T -so 0 1 2 I- @_ :1: : DE LTA.F RONTISH EET SAN DS: MILES 75 -BORING 100 - r flAYOU BA YOU BA YOU B, MIA K FER HLANC MON 1.A U 0 GULA, F ..... . .... I? I W: XICO 25 UJ 4J 2s- MAIISH BAY SILTS III A@,S ....... -@:CHANNEL FILL= SO 50- DELTA-FRONT SHEET SANDS - X ..... . .. ..... ... . -PRODELTA SILTY CLAYS 5 ...... . ... ....... 5 . . .... ........... ... 1W Fig. 10. Bayou Lafourche stream systems and east-west trending beach ridges that dominate the southwestern corner of the basin. Cross- sections A-A' and B-B' show major sedimentary sequences underlying this basin section (after Gould 1970; Fisk 1955). LAKE I .Ii@j HE VC, A 7: r 0 00 mi. !@@Cheniere a 16 Y- it* nqui I iji i ATURAL LEVEES AM HANNEL F!LL. N DISTRiBUTAIM:: Fig. 11. Reconstructed positiong of distributaries abandoned during lengthening of the Mississippi Rivet, southeast of New Orleans, La. (after Fisk 1955). The dashed lines indicate the approximate position of old beach ridges that have been essentially buried by later Plaquemines Delta dis- tributaries (Welder 1959). Documentation of Land Loss Land loss in the Barataria Basin is attributed principally to natural processes associated with a deteriorating delta mass and further complicated by manis activities during settlement of the area. Artificial flood control levees were constructed along the Mississippi River and Bayou Lafourche, and in 1904 Bayou Lafourche was artificially dammed. These practices cut off virtually all of the river- borne sediments into the basin that were critically needed for basin maintenance. Subsequently, stresses on the environment have followed a chain of events associated with more intense utilization of the wetland proper and encroachment from industry, agri- culture, and urban spread. Land loss has directly resulted from (1) removal of marsh through dredging and filling operations, (2) secondary effects of boat wake erosion and habitat deterioration by salinity intrusion into brackish and fresh waters, and (3) interruption of overmarsh flow. While it is impossible to assign values to all of these components, some quantification is possible to show historical trends of land loss and obtain some insights into possible causes. It is necessary to understandimpacts from the various uses in order to effectively formulate management practices that allow for multiple use of wetland re- sources with minimal impact. This documentation of land loss includes: an en- vironmental inventory; dredge and fill characteriza- tion; coastal retreat and inlet changes, with a Grand Terre Islands case history study; and marsh deteriora- tion. Except coastal retreat and inlets the above categories are treated by environmental unit and parish. Coupled with results of how the basin functions hydrologically and climatologically (Byrne et al. 1976) and biologically (Bahr and Hebrard 1976), this information provides background information on which to formulate and base management options.. Sa linity intrusion (Van Sickle et al. 1976) from the Gulf and eutrophic water conditions encroaching from the basin and periphery (Craig and Day 1976) provide an example of cumulative effects and stresses affecting the basin. Environmental Inventory.--Before land loss rates can be evaluated an inventory of land and water environ- ments as they presently exist is desirable. However, the only maps that cover the entire coastal zone are the US Geological Survey (USGS) quadrangles, which extend from 19.52 to 1967. While 10 year-old informa- tion is not an ideal base to measure environmental 38 units and land/water changes, the quadrangle sheets are presently the best available. A description of the methodology is provided in Appendix B. . Based on these maps the environmental unit inventory for land and water surfaces (Fig. 12) for the basin is presented in Table 2. The environmental unit break- down for each parish is included in Appendix B, Table B.1. The intermediate marsh category as presented:by Chabreck (1970) is included with brackish marsh figures. Our land loss data and biological inventories indicate that intermediate marsh is not a distinct enough entity for formulation of,separate management considerations. Table 2. Environmental Inventory--Barataria Basin Management Unit Square Miles Acres Total Area 2,427.1 1,553,344.0 Total Water Area 621.2 397,568.0 Total Saline Marsh Area 247.0 158,080.0 Total Brackish Marsh Area* 359.1 229,824.0 (Total Intermediate Marsh Area) (92.4) (59,136.0) Total Fresh Marsh Area 349.2 223,488.0 Total Fresh Water Swamp Area .378.2 242,048.0 Total Topographic High Areas 472.4 302,336.0 *Includes intermediate marsh Dredge and Fill Activities.--Calculations were made of the total land loss in the Barataria Basin resulting from dredge and fill operations. These include canals, embankments, and drainage projects within Barataria Basin. Computations were made by environmental unit for the entire basin and by the.parish portion in the basin. Dredge and fill features were classified according to their function (Appendix C) and digitized. US Army Corps of Engineers uncontrolled photomosaics (1970) mainly were used for the basin. Where coverage was not complete the latest edition of the USGS quadrangle sheets were used. The resolution for canals and impound- ments includes all features that are depicted on standard 7 1/2 minute quadrangle sheets. This means that there exists a large number of small canals that are not included and places the resultant figures on the con- servative side. Large urban areas were also not included 39 91*00' 90*3a 90*00' BARATARIA BASIN ..... .... ... ...... ..... ... ........ ........... .......... 0 z our Vegetation eas Natural Levees(Ur6on, Agricultural Ar 2V30 and Bottomland Hardwood Forest) Ilk, Forested Wetland (Swamp) Fresh Marsh Intermediate Marsh 1+3' Brackish Marsh Saline Marsh j 0 5 10 15 20 M1 0 5 10 15 20 25 30 Km Fig. 12. Vegetation environmental units are depicted. The discussion in the text includ ate marshes with the brackish category (after Palmisano 1970; and Chabreck 1972). in the results because the entire area of.settlement is impacted, and it is impossible to assign these fast lands to any of the existing environmental units. It remains then that the focus was on canals and impoundments within the basin wetlands up to 1970. Results for the entire basin by canal and impound- ment activity type are listed in Table 3. The total land loss in the basin for dredge and impoundment activities up to 1970 amounted to some 44,800 acres. Table 3. Inventory of Dredge and Fill Activity by Environmental Unit for the Barataria Basin. Environmental Unit (in square miles) 0 PQ rZ4 Rig Access Canals 5.29 11.68 5.20 1.08 23.24 Pipeline Canals 2.52 1.71 .63 0.20 5.07 Oil Field Navigation Canals 0.02 0.19 0.19 0.0 0.40 Navigation Canals 0.86 1.98 0.50 1.18 4.52 Transportation Embank- ments 0.0 0.43 0.51 0.48 1.42 Agr. Drainage Canals 0.0 0.91 0.82 0.08 2.71 Agr. Impoundments 0.0 3.55 21.39 6.07 31*01 Industrial Impoundments 0.05 0.0 0.0 0.07 0.13 Urban Drainage Canals 0.0 0.39 0.11 0.07 0.56 Agr. Commodity Trans- portation Canals 0.0 0.03 0.0 0.02 0.04 Oil Field Embankments 0.0 0.0 0.0 0.22 0.22 Mineral Extraction Navigation Canals 0.61 0.0 0.0 0.0 0.62 Other 0.03 0.0 0.0 0.0 0.03 Total for Environ- mental Unit 9.38 20.87 29.35 10.37 69.97 (1 sq. mile = 640 acres) The breakdown by canal type and environmental unit was calculated for each parish and included in Appendix C. Summary figures by parish and environmental unit are included on Figures 13-16. Utilization.of four 41 90'3U 90*00' 89*30' 0.00Total Dredge & Fill Activity (sq. mi.) 0 Rig Access Canals Pipeline Canals Oil Field & Mineral Extraction Navigation Canals Major Navigation Canals Agricultural Commodity Transportation Canals & 0 Transportation & Oil Field Embankments Agricultural & Urban 03.01 Drainage Canals 1.15 Agricultural & Industrial Impoundments other Miscellaneous Canals e. 29'30' Non - Wetland Swamp V Fresh Marsh ........ % 4., Brackish Marsh M A Saline Marsh -0 0 5 10 15 20 Mi. V 0 5 10 15 20 25 30 Km. Fig. 13. Dredge and fill computations by environmental unit for portions of Lafourche Parish within the Barataria Basin. 90-30- 90.00, WoOff 0.00 Total Dredge Rig Access tL Pipeline Co Oil Field & Major Noy Agriculturo 6 1.83 0.44 Tra 1.25 0 Trosportati E3 .14 Agricubura Agriculturc; T, Other Misc 29*30' e. Non - Wetland Swamp OZO 07 Fresh Marsh 91 3 Brackish Marsh Saline Marsh ILL. 0 5 10 15 20 Mi. 0 5 10 15 20 25 30 Krn. Fig. 14. Dredge and fill computations by environmental unit for Jefferson Parish. 90'30' 901W WOO' 0.00 Total Dredge Rig Access Pipeline Cc Oil Field & 0.00 Major Nov @@00 Agricultura 04, 1 Tra 0 Transport Agriculturol Agricultura Other Misc: 0.26 006 It . . . . . . 0.09 29'30' It Non - Wetland Swamp 41307' b -0 Fresh Marsh ,J , ,@ I I , e@k UZI r4 Brackish Marsh 4t Sh Saline Mar %r A 0 5 10 is 20 Mi. 0 5 10 15 20 25 30 Km, Fig. 15. Dredge and fill computations by envirormental unit for Plaquemines Parish. 90'30 90,00' 89o3O' V, 30'00 6.90 =.00 -0.1 S.32, 0.00 Total Dredge & Fill Activity (sq. mi.) * 0A I I . * Rig Access Canals 0 Of zz 30.0. Pipeline Canals Oil Field & Mineral Extraction @777 k Nci@igcdion Canals Major Navigation Canals 0.00 Agricultural Commodity 100 Transportation Canals e 0 Transportalion & Oil Field Em6ankmments 10" Agricultural & Ur6on Dra inage Canals Agricultural & Industrial impoundments Other Miscellaneous Conals A- e "'P 29'30 t* Non - Wetland Swamp --4 Fresh Marsh +"A\ --7-y Brackish Marsh %`9 Soline Marsh 0 5 10 15 20 mi. 0 5 10 15 20 25 30 Km. Fig. 16. Dredge,and fill computations by environmental unit for St. Charles, St. John the Baptist, St. James, and Assumption parishes. Figures rather than one for this display was for clarity in presenting information at the parish level. Total figures for dredge and impoundment activity in square miles with breakdown computations of major, groupings of activity are included on the illustrations. In Lafourche and St. Charles parishes the fresh marsh is the most severely impacted by man's activity. In';,general, the category including agricultural impoundments basin-wide is responsible for the majority of this impact. Figure 17 shows how land reclamation projects initiat'ed in the period between 1860 and 1920 dominate this area. Values for this feature represent total area impounded as this marsh surface is taken out of the food web of the natural system. In-cal- culating impacts that would occur if@`artificial levees were abandoned and breached to reestablish normal circulation to the basin, the spoil banks and canals were considered. In these cases formerly impounded marsh or resulting pond were returned back into the food web system. In the,brackish (including intermediate marsh as mapped by Chabreck et al. 1968) and saline marshes intensive dredging for rig access canals contribute the greatest percentage of the total dredging impact. Pipeline and navigation canals also represent a con- siderable percentage of the total. Pipeline and transportation canals show relatively low values in area compared to other categories. However, they produce maximum impact. If not properly planned they interrupt the natural drainage system and directly introduce salt or fresh waters into differing habitats. Rig access canals serving oil fields have prolif- erated during the last several decades (Fig. 18), reducing the marsh surface area by impoundment activity. Figure 18 depicts the general area of major oil fields and shows connecting navigation and pipeline canals that transcend environmental units and, in some cases, the entire basin. Coastal Retreat and Inlet Changes.--Coastal erosion along the front of the entire basin constitutes an additional land loss problem, resulting from a lack of river-borne sediments reaching this section of the coast. The erosion problem is tied to both natural and man- made processes. Suhayda (1976) and Murray (1976) have shown the natural processes associated with wave and nearshore current patterns respectively along the,sea- ward margin of Barataria Basin. Severance of river- borne sediments into the basin was pointed out earlier in this paper. Improper placement of pipelines parallel to the strandline has resulted in accelerated coastal erosion in some localities. Groins placed along coasts 46 90 30 90,00 BARATARIA BASI AZ 29 30 MODIFIED WETLANDS 0.. 1. 0 0@ Scale 1:250,000 SOURCE: 0 5 10 15 20 M1 $02 SGU-C-TVAL t*UISIA 6. ...' .". a. I" 'kms DAIA, 1.12 $ * $ 1ft#4A41D 0 5 10 @O 25 3 0K m Fig. 17. Map showing modified natural levee and wetland areas that have been cleared, d for agriculture, commercial, or urbanization purposes (information partially from Burke 90'30' 90,00' 30'00 4-00 4( 55 29*30' Major Waterway Systems 'C Major Oil Fields Single Pipe Line 2 Parallel Pipe Lines A C-4 3 Parallel Pipe Lines 4 Parallel Pipe Lines IZI 6 Parallel Pipe Lines 0 5 10 15 20 ML ZI 1-0 5 10 Z 20 25 30 Km. Fig. 18. Major waterways$ pipelines, and oil fields within Barataria Basin. where littoral drift constitutes an important process interrupts sediments destined for downdrift sections of the coast. This can result in local building or retarding coastal erosion along the grotned areas,,but, in the down-drift areas, erosion accelerates. In Morgan's (1976) revised studies on coastal ero- sion for the entire Gulf front of the Barataria Basin, he found a loss of 4,515 acres of Gulf front coast occurred between 1932 and 1969 (Fig. 19). A detailed listing by parish for the periods 1932 to 1954 and 1954 to 1969 is included in Appendix D (Table D.1). On Figure 19 both coastal retreat and inlet changes are summarized by parish for the Barataria Basin Gulf front. For inlets entering Barataria Basin, inlet changes were measured for the same time period as coastal retreat (1932 to 1954 and from 1954 to 1969). They are depicted graphically in Figure 19, and measurements for individual inlets by parish are included in Appendix D. Measure- ment of inlet changes between 1932 and 1969 resulted in a total widening of about one mile for the Barataria Basin Management Unit. Lack of water-depth data in the inlets constrains the possibility of relating the effect of widening to volume of water changes through the passes. In general, inlet positions have moved laterally along the coast depending on the predominant direction of wave approach to the coast and resultant littoral. Curren ts. These processes are highly variable during the year as shown by Suhayda (1976) and Murray (1976). Individual storms can cause dramatic changes in inlets, closing some completely and forming new ones through beach breaches. I The highly variable nature of inlets is indicated- by noting changes measured for individual inlets or by parish. Lafourche Parish experiences the highest rate of land loss from coastal retreat along the Barataria Basin Gulf front. Between 1932 and 1969, 2,307 acres of Gulf shoreline were lost. 'This-averag6d'approxi- mately 44 ft per year retreat along this section of the coast. When inlet changes were assessed for this sec- tion there was a net loss of about 50 percent in inlet widths for the above time period (Fig. 19). In 1932 and 1954 passes into Bay Marchand, Bay Champagne, and Pass Fourchon were open. These passes are now closed but are infrequently breached by high water. Belle Pass is maintained as the Bayou Lafourche ship channel and,although the opening across the beach has widened, the upstream width has changed little. It remains aporoximately the same width as in 1954 (Appendix D, Table D.2). Belle Pass is a natural'distributary channel of Bayou Lafourche, and the composition of 49 90030' 90*00' 30*00' Heavily A z Lightly /rnc OWY area 0.19 0.01 % Annual I +0.01 % Annual I 1.01 .30 -78 ;:z;- -1 .66 Fresh Marsh MIntermediate Marsh ........... 29'3g Brackish Marsh I AL .31 Saline Marsh + Ratio of Wal inlet change along parish coast line LO C, 1.89 r --I Relative coastline retred by parish ;r ... "32 .72 % 0 5 10 15 20 Mi. 0 5 10 15 20 25 30 Kw Fig. 19. Coastal retreat and marsh deterioration by environmental unit and parish (see Al natural levee mat erial is more resistant to lateral erosion than interdistributary marshlands. The heavy boat traffic in this channel is causing bank erosion, but the map and photographic scale from which the-measurements were made are too small to detect erosion changes of a few feet. The Lafourche section of this coast is characterized by Bayou Lafourche and distributaries Belle Pass, Pass Fourchon, and Bayou Moreau forming natural levee com- plexes and an associated system of beach ridges (Fig. 10) generally paralleling the coast that wa,@,formeA at a time when the coast was advancing seaward. The rapid rate of shoreline retreat and net reduction of inlet widths is most likely related to the general grain of the natural levee, east-west extendingbeach ridge topography, sediment characteristics of the beaches, and exposure to wave and current attack. This complex of levee and east-west trending beach ridges have pre- cluded the formation of major passes into interconnecting bays (Fig. 10). The rapidly retreating shoreline and associated coarser-grained sediment supply from the former beaches has sealed off most of the tidal passes into the confined bays of Marchand and Champagne. This section of the coast lies in the direct path of wave attack from the south and southeast (Suhayda 1976). Proceeding east of Lafourche Parish the leeward affects from the protruding Mississippi River increase in im- portance in dampening the effects of southeasterly waves. Wave approach from the south and southwest causes easterly flowing currents from the Belle Pass area to Barataria Pass (Harper 1975, and Conatser 1971). East of Barataria Pass littoral currents correspond more closely to the westerly drift-direction. In addi- tion to waves Gulf currents drift landward from the trapped vortex associated with the westward drift and protruding Mississippi River Delta (Murray 1976). The landward drifting currents strike the coast in the vicinity of Belle Pass-Bay Champagne area, where they divide and drift eastward and westward. Passage of fronts and storms further complicate current patterns through air pressure and wind direction changes. These phenomena cause discontinuities in current velocities and water body characteristics (sharp salinity and temperature gradients). The effect on this section. of the Lafourche Parish coast is rapid erosion of the coast with a net transport of sediments westward and eastward out of the area. A high'rate of coastal retreat result s. 51 Inlets in Jefferson Parish nearly doubled in width between 1932 and 1969. In 1932 total inlet widths were 6,662 ft and by 1969 they had widened to 12,775 ft. Inlet behavior is high variable, along this sec- tion of the coast, some passes have closed and others opened exhibiting dramatic changes over a relatively short time period (Appendix D, Table D-2). The relatively low coastal retreat rate of 2 ft per year (1954-69) for Grand Isle (Appendix D) is in contrast to 17 ft per year (1954-69) for the remaining coast of Jefferson Parish east of this island. The littoral cur- rent flowing eastward during parts of the year and con- struction of groins along the Grand Isle beach is likely the primary reason for the low retreat rate. The coast east of Grand Isle has neither the source of sediments for nourishing beaches nor as welL-established littoral currents as those fronting the Belle Pass-Grand Isle coast. The eastern section of the coast is sub- ject to frequent flushing and flooding of water exchanged between the Gulf of Mexico and Barataria Basin. Sediment exchange also occurs, but not at a sufficient supply to offset a net9 relatively high land loss along the coast. 52 Grand Terre Islands Case History.--A study was made by Maurice Lasserre and Barney Barrett, Louisiana Wild- life and Fisheries Commission, of landform. changes, on Grand Terre Island proper (westernmost island) (Fig. 20), and inlet changes in the island chain. The investiga- tion covered the period 1893 to 19724. The Grand Terre Islands presently comprise a chain of barrier islands that extend along the central Barataria Basin coast. In 1893 the islands were continuous from Barataria Pass to Quatre Bayou Pass (Fig. 20). Since then the island has divided into five islands and the largest remaining barrier island comprises Grand Terre proper, which lies across Barataria Pass east of Grand Isle. The s.tudy measures changes in the inlet widths of Barataria Pass, Pass Abel, and Quatre Bayou Pass between 1893 and 1972 (Fig. 21, A) and quantifies the western- most island's aerial changes in acreage between the same dates (Fig. 21, B and C). Width measurements that show inlet changes for Barataria Pass, Pass Abel, and Quatre Bayou Pass between 1932 and 1972 are listed below in feet: Barataria Quatre , Bayou Date Pass Pass Abel Pass 1932 2,148 423 2,180 1954 2 373 998 2,921 1960 3:500 1,200 3,000 1969 3,500 2,465 3 700 1971 3,480 3,200 @@known 1972 unknown 3,417 3,542 Inlet widen ing has undergone major changes since 1893 and has contributed significantly to land loss on the island (Fig. 21). Pass changes indicated by the above computations for the three passes are as follows: Barataria Pass (1932-1971) Width increase 1,332 ft Pass Abel (1932-1972) Width increase 2,994 ft Quatre Bayou Pass (1932-1972) Width increase 1,362 ft 4 Calculations were made from quadrangle maps for the 1893 and 1960.dates. Aerial photographs were used for all other,dates. Some of the maps did not show all of the passes and in 1893 the Grand Terre Islands were continuous from Barataria Pass to Quatre Bayou Pass. For this reason, comparisons of land area in 1893 with that of later dates were measured from Barataria Pass to Longitude 89'55'. Measurements after 1893 included all of Grand Terre.. Because tidal stages at the time of photography are not available, the land-water boundaries are not adjusted to the same datum for each map. 53 V4, !w C. Bay 46 Melville 4,6 tD to Ot 1*0 0.7 A ........ Ott QA -Z JETTY D G A E z ZZ. z E R ............ ........... ... ...... .. ...... ... LAND LOST SCALE uIO,OOO LEGEND 1000 0 000 2000 0: T LAND GAINED 956 1. 1911 Fig. 20. Map depicting land loss an Id gain on Grand Terre proper. Inset . Index map of t Grand Terre Islands. 3500- A Barataria Pass Ouatre Bayou Pass Pass Abel 3000- Ole 2500- w 2000- 401 6 .400, 1500- Oe 1000- 4e Oe 500 '000,1 '0 A 1890 1900 @O 6 5500- B -15500 U. 5000- F-15000 C 4500- f-14500 4000 14000 C 1000- 900- ire Island W 800- 700- Between Fort & Long. 89*55' 600 1 1 1, 1890 1900 50 60 70 Fig. 21. Graph A illustrates inlet changes of the three major passes in the Grand Terre Island system. Note the rapid changes of Pass Abel. Graph B shows the width and length of the island in feet, and C the area in acres. Barataria Pass has been relatively stable since construction of the rock jetty on the eastern end of Grand Isle in 1960. Fort Livingston, located across the pass on the western end of Grand Terre retards erosion. Most of the erosion of Pass Abel has occurred on the eastern side of the Pass. Between March 1960 and May 1972 this Pass was widened by 2,217 ft, of which only 758 ft were gained by the erosion of the eastern end of Grand Terre. The other 1,459 ft were the result of erosion of the Grand Terre Island that forms the southern boundary of Bay Melville. In 1960 this eastern Grand Terre Island was continuous from Pass Abel to Bay Dispute (Fig. 20). By October 1969, this island was severely eroded and contained only 51.7 acres. By May of 1972, only 30.1 acres remained. Pipelines dredged very near the high water line and parallel.to the beach accelerated the erosion rate of this island east of Pass Abel. Waves eroded canal banks at a relatively rapid rate. Land changes that occurred on Grand Terre proper (westernmost island) during the period 1956-71 are shown on Figure 20. Most of the erosion has occurred al ong the front beach, on the eastern end, and on the bay side of the island. Some accretion has taken place in the form of a recurved spit on the bay side of Barataria Pass (Fig. 20, D). Between 1956 and 1972 the island has decreased in size by 166 acres. The following measurements show land changes on Grand Te rre proper during the years 1956-72: Date Acres Island Length (ft) Island Width (ft) 1956 952 15,167 4,458 1960 958 15,300 4,400 1969 812 14,583 4,000 1971 818 14,583 4,060 1972 786 14,542 4,042 It is readily discernible that shoreline retreat and inlet widening is a major land-loss problem along this section of the coast. This example is typical of the destruc-- tional processes occurring along other sections of the coast. Groins constructed along the Grand Isle coast and the rock jetty at the island's eastern end restrict sediments from reaching Grand Terre during the season of easterly flowing currents. Although the westerly drift of coastal water predominates the direction of annual flow, this section of the coast receives minimum effect from this current because of its leeward posi- tion behind the seaward-protruding delta. Conversely, the vortex that develops generally offshore of Lafourche 56 Parish results in easterly moving currents during certain weather conditions and seasons of the year. Usually, this occurrence is associated with easterly winds during the fall and winter months, and is suspected to be less developed during the summer months. A major factor in addition to coastal sea conditions is the dynamic and highly variable water exchange flow between the Gulf of Mexico and Barataria Basin. Jefferson Parish's central location in the basin is likely the main reason that it possesses most of the major tidal passes connecting the basin proper with the Gulf. These passes are significant when the Barataria Basin geometry is considered: east-west trending beach ridges in Lafourche Parish block direct water flow to the Gulf. Because of this, most of the water in the western basin section is funneled through passes in the central section. Southerly and northerly winds pile up water in the basin or depress basin water levels, and the passes form the connecting water exchange links. Byrne (1976) has shown that water levels at Bayou Rigaud tide station for the year 1971 experienced water levels above mean high tide levels 128 times for that year. It remains that the inlets and barrier islands are important water control features along the Barataria Basin coast. The Plaquemines Parish coast has lost about .1,601 acres (an average 18 ft per year) to coastal retreat between 1932 and 1969 (Appendix D, Table D.1). The coast is breached by inlets nearly equaling the com- bined number for Lafourche and Jefferson parishes. The Plaquemines inlets displayed a high degree of vari- ability in change between 1932,and 1969 (Appendix D, Table D.2); however, the net change shows total channel widths slightly less than those for 1932. The topographic grain in the Plaquemines, sector is controlled by distributaries off the Plaquemines Delta complex,as it lengthened seaward.to the Modern Delta position (Fig. 11). Except along the western sections of the Plaquemines coast where inlets connect with Barataria Basin proper, passes along the eastern sector connect with more restricted interdistributary basins. This section of the coast is also sheltered from waves approaching from the east and southeast. Marsft deterioration.--This section concerns the problems of marsh deterioration and related processes within Barataria Basin. The goal for this activity was to build on the basis of land loss considerations that Gagliano (1970) introduced. He dealt with long-. term changes based an point-counting procedures for determining land-water ratios that applied to specific 57 periods through time beginning with the 1932 USGS quadrangle sheets. His studies covered large areas of marshlands, and, in general, conclusions he reached were valid. When grossly compared with short- term changes his rates are an the conservative side. This study is an attempt to obtain realistic informa- tion that would provide insight into short-term changes that are presently occurring. Secondly, it should provide information on land loss and gain responses at the environmental unit and parish level. To obtain this information sample areas were selected and measured for the years 1960, 1971, and 1974. Areas were chosen from each environmental unit (salt, brackish including intermediate ' and fresh marsh) within Lafourche, Jefferson, and Plaquemines parishes (Fig. 19). A total of 14 sample areas provided the desired coverage. The USGS quadrangle sheets (7 1/2 and 15 minute scale) were used for the initial 1960 base. For midpoint measurements, the USGS orthophoto quadrangle maps (1971) were used. When available, NASA infrared color photographs (Mission 194) were used for other examples. Infrared color photographs (NASA Mission 293) were utilized to obtain 1974 information. Details for the technique used are covered in Appendix E Man's activities have affected all areas within the basin so the sample areas were qualitatively . classified as lightly/moderately or heavily influenced by man. The results show a wide range of marsh deteri- oration or gain rates. Variability both within and between marsh types is high. High variability also exists among the three time periods (Appendix E). Annual rates shown by percentages for each of the test sites are presented in Figure 19 and Table 4. Since there was considerable variation in land loss rate for test sites within the same vegetation zone, the highest and lowest annual values are presented below (percentages converted to acres): Salt Marsh--loss, 1,262.4 to 959.3 acres/yr Brackish Marsh--loss, 3,872.0 to 1,299.2 acres/yr. Fresh Marsh--loss, 1,376.0 to 876.8 acres/yr. Total combined marshes--loss, 6,510.4 to 3,135.3 acres/yr. The long-term land loss computations (1890-1960) presented by Gagliano and van Beek (1970) were digitized by vegetation and management unit for comparison with the short-term rates presented above. They indicate changes: Salt Marsh--loss, 818 acres/yr. Brackish Marsh--loss, 901 acres/yr. Fresh Marsh--loss, 188 acres/yr. Total combined marsh--loss, 1,907 acres/yr. 58 Table 4. Rates of deterioration by marsh types within the Barataria Basin. % Annual Total Acres** Land Acres/Annual Loss or Gain Sample Area.* Loss/Gain Loss or Gain Sample Period Saline Marsh A Eastern Barataria (lightly/moderately) -0.58 -53.5 -749 B Central Barataria . (lightly/moderately) -0.31 -27.9 -391 C Western Barataria (lightly/moderately) -1.72 -12.8 -218 D Central Barataria (heavily) -0.58 -34.7 -486 Brackish Marsh E Eastern Barataria (lightly/moderately) -0.78 -75.32 -979 F Central Barataria (lightly/moderately) -1.86 -128.0 -1,664 G Western Barataria (lightly/moderately) -1.99 @-77.16 -1,389 H Eastern Barataria (heavily) -1.09 1-44.40 -710 I Central Barataria (heavily) -0.63 -60.10 -781 Intermediate Marsh J Eastern Barataria (lightly/moderately) -0.56 -80.2 -1,043 K Western Barataria (lightly/moderately) -0.57 -41.6 -499 L Central Barataria (heavily) -0.45 -48.2 -627 Fresh Marsh M Western Barataria (lightly/moderately) -1.01 -85.9 -1,031 14 Central Barataria (heavily) +0.19 +10.*0 +90 Note: These rates as reported apply only to those years for:which data was analyzed. Refer to Appendix E for measurement period dates. *A-N corresponds with sample areas on Figures 19 & E-1 **Figures represent loss or gain for sample plots A-N 59 These figures indicate an increasing erosion rate ranging from 150 percent to over 300 percent depending on.whether we use the conservative or highest figures from the short-term study. This increased erosion rate is to be expected in light of the geologic processes associated with deterioration of the delta mass that forms the frame- work for this basin. Now that the Mississippi River plays only an indirect role in the conditions existing within the Barataria Basin, subsidence occurring at a more rapid rate than marsh build up is a dominant factor affecting the basin's marsh condition and is an underlying cause of some marsh deterioration. Gagliano and van Beek (1970) state that areas of maximum loss coincide with areas of maximum subsidence--a true statement in an idealized sense. However, it is an interplay of other factors that controls this rate at which deterioration will occur. The examination of sample sites within the basin has provided an indication of marsh deterioration/growth rates and an idea of factors controlling the variability of change in the marsh. The role of each of these factors can be expected to change per sample site, and only further research may provide a meaningfu 1 answer. The Barataria Basin was formed by the deposition of sediments from three known phases of Mississippi River Delta formation--the Bayou des Familles lobe of the St. Bernard Delta Complex, the Bayou Lafourche Delta Complex, and the Plaquemines-Modern Delta Complex (Frazier 1967). Distributaries of all three complexes have at one time formed wedges of sediments in what is now the basin, and even now, minor sedimentation derived from the Modern Delta Complex appears to be occurring in. the basin's extreme southeast corner. The relict natural levees marking former active distributary courses9 form fingers where localized sub- sidence and deterioration occur. They can serve as a sediment source for reworking and deposition of sediments and the levees form partitions in separating the basin into distinct provinces with respect to rates of marsh deterioration or growth. "Tidal currents and water exchange between the Gulf of Mexico and the basin constitute an additional factor for marsh deterioration. Byrne et al. (1976) has shown for 1971 that wate@_r leveis exceed normal high water 128 times a year. This.highly dynamic flooding and flushing must play an important role in land loss processes. *Erosion of marsh by wind- generated waves within the bays and larger lakes has been noted and documented by Saucier (1963) and Morgan (i972). Any deposition of new sediment within 60 the basin must come primarily from two sources: the reworking of internally derived sediments, or the addition of sediments from sediment-laden waters offshore and from the shallow bays. The factors leading to variability in land-water ratios in lightly/moderately influenced examples are also highly significant in the sectors heavily influenced by man. The fact that man has altered the system makes each example more complex. Deterioration of the marsh is inherent in any dredging project, if only by the initial conversion of marsh to water. Other factors include: 1) Energy imparted to canal banks by boat wakes can lead to significant erosion (Doiron 1974). This factor is not of significance in many dredged canals, as many canal entrances are artificially blocked to prevent usage. Others are used only infrequently by oil and gas field personnel. 2) A dredged canal can serve as an artery of water flow or allow saline water to penetrate much more easily into marsh only previously penetrated via over- land flow at high tides or after rainfall. The result of canals dredged in closed marshl4nds is the establishment of new sediment erosion and dispersion systems. The dredging of a major navigation canal can have the same effects as those mentioned above, however, the effects may be of a greater magnitude. Canals serve as arteries for water exchange and allow greater circulation of fresh or higher salinity waters within the basin. The dredging of canals across marsh types could seriously alter the surrounding vegetation and in some cases may lead to vegetation diebacks and subsequent deterioration. There is little known about the positive effects of canals introducing water circu- lation into marsh areas removed from normal water circulation. Methods and techniques need to be developed to enharice "back" marsh areas. 3) Spoil banks, a by-product of every dredged canal, may influence the deterioration/growth rates of their surrounding marsh in quiteopposite ways. First, the spoil banks act essentially as man-made levees. This mass is subject to localized subsidence and it too can result in the loss of marsh an its periphery, forming localized levee flank depressions. On the other hand, spoil banks may behave as stabi- lizing agents in an otherwise unstable marsh. These banks can serve as barriers to flow, buffers against waves, and even sediment traps in an area of low land- water ratio. 4) Composition of the substrate is an additional factor when considering deterioration. Erosional 61 potential for the different sediment types is important. Clays,and peats formed from deep- rooted plants resist bank erosion more than silts, sands, and homogenous peat. 5) Heavy frosts kill off black mangroves, which thrive along lower bay and tidal channel shores. The frost during the winter of 1961-62 severely damaged these plants. Their root system is a natural barrier to retard erosion. The fact that the rate of deterioration in the heavily influenced examples is generally lower than in the lightly/moderately influenced examples is undeniable (Table 4). Examples in each marsh type have consistently borne this out. However, projec- tion of these rates to other examples within Barataria Basin or to the entire coastal zone should not be made until further research is done on this problem. 6) Stresses caused from storms accelerate ero- sional processes and have impact on biological phenomena. With an average annual lunar diurnal tide of about 1.2 ft, wind effects on water level changes often exceed tidal levels. North winds lower water levels in the bays and estuaries, whereas south winds raise water levels by driving Gulf waters far into the bays and estuaries., Storm-driven Gulf waters forced into the bays and estuaries introduce salt water into freshwater areas that can be fatal to vegetation. Hurricane-driven tides and waves severely erode the Gulf front, inlets, estuarine shores, and. tidal channels. Large sections of marshes can be torn from their insecure footings and become floating pads of vegetation debris. These pads are of the magnitude that they have been detected by aerial photography floating in the nearshore waters of the Gulf following hurricanes. These floating pads also come to rest over other marsh surfaces following abatement of high water. Ponds and lakes can be formed within the marshes and bay shores expanded as a result of storm activity. Storm tides overflow beaches and can result in formation of new inlets. Backwater flushing of waters flowing back into the Gulf following passage of storms is a major process influencing land loss. In general, storms disturb the sediment, vegetation, and water channel balance that develops during more normal conditions. Following a storm passage the stage is set for rapid changes to continue during the readjustment period. Although less dramatic than hurricanes, the same processes occur from storms which effect the coast many times each year. 62 It remains a highly variable, dynamic environment where normal conditions occur only in the thinking of individuals rather than in the actuality of nature. So long as there exists an imbalance between sediment supply, vegetation growth and hydrology, land loss or gain will result. 63 Summary This study characterizes the natural setting for Louisiana's coastal zone by describing the land- forms, water bodies, and the physical processes that have formed the highly productive environments. The investigation includes assessment of both natural and man-made stresses on the environments. The Barataria Basin management unit was selected as the pilot study area and receives the primary focus. Synthesis of information on the physical, biological and chemical, and man-made processes will be pos- sible with the completion of companion reports covering those categories. Information was presented on how the master stream has functioned in the past in constructing the deltaic plain, and how its present behavior is a continuum process of dynamic change. During the last 250 years man's practices in utiliz ing the rich, wetland resources have gradually affected the area either positively or adversely. As in the ancient past, the river is seeking a shorter route to the Gulf of Mexico--in recent years, through the Atchafalaya Basin. As the crow flies this dis- tance is about one-half that to the mouth of South Pass. Diversions are gradual as this case history demonstrates. New land has aggraded above tide ,level as deltaic islands in tile Atchafalaya Bay during the last few years. Some islands are already inhabited with marsh vegetation. Of more significance to this phase of the discussion are the natural and man-made processes that are chal- lenging the existence of wetlands -in the Barataria Basin. Barataria Basin war, naturally nourished with water and sediment through crevasses and over- bank flow from the Mississippi River and Bayou Lafourche. With settlement on the natural levees in the early eighteenth century, protection from flooding required levee construction. By the time Louisiana became a state the basin was virtually walled in, except in its lower reaches. River- borne sediments were funneled past the basin and deposited in deep water. In 1-904 the last source was severed when Bayou Lafourche w.-_is artificially dammed. Severance of river-borne sediment and water initiated basin deterioration. Reclamation projects within the wetland resulted in additional construction of water control structures. To determine the "state" of the basin the environmental.units were inventoried by parish. 64 Determination was made of land loss or gain and causal processes, by assessing dredge and fill activities, coastal retreat and inlet change pat- terns, and marsh deterioration rates and distribu- tion. Dredge and fill activities associated with canal and waterway construction, urban expansion into wetlands, agriculture reclamation, and flood control have been intense in the basin. Measurements showed at least 44,800 acres of wetland have been reclaimed or converted to water bodies such as canals. Oil well access canals and agricultural impoundments account for the largest acreage. Rig access canals ,in the brackish marshes are nearly double the acreage in saline and fresh marshes. (As would be expected, urban spread and agricultural reclamation are predominant in the fresh marshlands with swamp- lands following in importance). The dredge and fill measurements showed that following the original dredging (converting marsh to water) land loss pro- gressed at a lower rate than adjacent marsh areas in the natural system. A number of canals, pipelines,and waterways extend through different environmental units or stretch across the basin. Water circulation and drainage effects, and salt and freshwater incur- sions aresignificant considerations in these circumstances. Canal and pipeline routes improperly oriented or emplaced can result in accelerated erosion. Pipelines improperly emplaced parallel to the beach in the eastern Grand Terre Islands resulted in accelerated coastal retreat. Coastal retreat and inlet changes result in dramatic changes along the entire basin coast. Coastal retreat is occurring most rapidly along the coast fronting Bayou Lafourche distributaries. Averaged over a 37 year period, this section of the coast loses 44 ft per year. Southerly approaching waves directly attack this coastal section, and sediments are transported along adjacent coasts by littoral currents that drift westward and eastward ,from this general nodal area. Grand Isle lies in the downdrift area of the easterly flowing currents, and with the construction of groins have entrapped sediments. Coastal retreat along Grand Isle averages about 2 ft per year. Eastward from this area the coastline is undernourished and retreat averages about 17 ft per year. Inlet changes are highly variable along sec- tions of the coast. Over a 37-year-period combined changes show that inlets increased about one mile 65 in widths. Because of basin geometry inlets in- crease in numbers east of the beach ridge systems that dominate the area from Grand Isle westward. Beaches fronting open water conditions in Barataria Bay and interdistributary depressions eastward are more prone for breaching and changing--particularly during storms. The inlets and barriers are sig- nificantly important features to processes that occur along the coast, water exchange between the Gulf and the basin, and within the basin. . Marsh deterioration constitutes a major concern in the basin. Causal factors are complex and are shared between natural processes that occur in a waning deltaic environment, and processes associated with man's activities. Measurements within the sample sites showed highly variable results both within the sites, between sites, and between marsh- land environmental units. This is to be expected in this complex area where composition of substrate material ranges from clays, through sands to peats. Application of sample sites (A-N) results to basin-wide marshland environmental units a total of 3,130 acres per year were lost to erosion. Compu- tations covered an approximate 14 year period, and the figures used come from the low side of the range. The figure includes land loss from both man-made and natural processes. Losses within the .marshland environmental units show brackish marsh with the highest loss rates,.followed by saline then fresh. This figure does not include the 4,515 acres lost from the Gulf front of the basin. Concurrent with inlet widening and marsh deterioration, salt water is encroaching into the upper reaches of the basin. In addition to land loss the effects of salt water on brackish and fresh marshes is being felt. Distribution of oysters as determined from lease records show a gradual migration northward into the basin. In recent years oystering has moved into the Little Lake region. Storms from both the Gulf and landward side pulse waters in and out of the basin. At Lafitte water levels for 1971 extended above mean high water levels about 23 percent of the year. Pulses above mean high water occurred about 79 times for that . year. For Bayou Rigaud at Grand Isle this occurred 128 times. The information assembled in this report and in the companion volumes provides a framework of information on which to begin development of plan- nin g and management concepts for the basin. Infor- tion is lacking in many areas, but through these 66 studies identification of what is available, it's quality, and what's needed can be determined. In a general way, an inventory of the basin's natural resources is available and how the basin functions as a system is understood to a level that permits establishment of reasonable priorities. Trends in the physical processes of sea level changes and subsidence can be quantified, but not corrected. Through sediment and water control systems, it is possible to tap Mississippi River sources and manipulate specific environments. Aggradation of water bodies and marshlands can be accomplished by introducing river-borne sediments into subsiding areas. The introduction of river-borne sediments down Bayou Lafourche to the coast would offset rapid erosion occurring at the present time. Current and wave patterns are sufficiently well known to permit generalizations regarding what would likely happen if this were accomplished. The quantity of sediments introduced would determine the amount of erosion that would be reduced. Littoral cur- rents would drift the sediments both eastward and westward nourishing adjacent coasts. The river resource is available, conditions within the basin wetlands are known, and the technology is avail- able for accomplishing meaningful management practices. How this technology will be employed is largely dependent on. resolution of associated socioeconomic and political problems. 67 Appendix A Barrier Islands Barrier islands and beaches along the Louisiana coast are significant coastal features around the deltaic plain. Most of these features are undergoing rapid change because of the dynamic physical setting. Sub- sidence, absence of river-borne sediments, dynamic coastal currents, and waves combine to create an environment of high varliability and change along the .coast. These features are listed on the following table (A.1).. The table consists prim;.-i.rily of an inventory of barriers and lists some environmental considerations. Most of the barriers are only accessible by boat and, with the exception of Grand Isle, are presently not in- habited as residential property. Oil and gas production constitutes the primary use of the barriers. Data sources for the information are from the following: Linear and areal extent was measured from uncon- trolled photomosaics compiled by the New Orleans District, U.S. Army Corps of Engineers (1969), except those- reported for West and East Timbalier islands, which are based on maps prepared by the USGS showing 1954 conditions. Only those portions of marsh or mangrove considered as an integral part of the barrier have been considered. Natural zone determination was interpreted from- these same 1969 photomosaics, USGS quadrangle maps, and NASA High-altitude photography. Appendix B Environmental Inventory The Barataria Basin Management Unit is defined as the center line of Bayou Lafourche, from Belle Pass to the Ascension Parish Line, then east along this boundary to the crest of the Mississippi River levee to Venice, turning southwesterly and running midchannel of Red Pass to the Gulf of Mexico. Closing lines between the Gulf of Mexico and inside waters have been drawn in accordance with Louisiana RevLsed Statutes pertaining to shrimping waters (La. Acts 1972 #203), as these appear to most closely approximate the current definition of the coastline within the Barataria Basin Management Unit. , An inventory conducted for environmental units within the Barataria Basin Management Unit was accomplished by digitizing 7 1/2 minute USGS quadrangle sheets, 1.952-67 (latest issue). There is little doubt that changes 68 Table A.l. Louisiana Barrier Islands and Barrier Beaches COORDINATES 1969 1:20,000 FXISTING GEOGRAPHICAL LONG/LAT 'PHOTO REF. LENGTH WIDTH ACREAGE NATURAL ZONES ACCESS DEVELOPMENT 1. West Isles Derniere Racoon Point to 90*58'- 71 .13" 1. 5 595.4@25% Sand Boat None Last Island Pass 90*53'30" 21,666.66' 2500' 20% Mangrove 55% Marsh 2. Middle Isles Last Island Pass 90*52'30"- 83 @4 4 14,69.114 5 Sand Boat Oill/gas canal Dernieres to 141hiskey Pass 90'47 v6u, '"'v f 5 Mangrove 150% Marsh 196 Boat Oil/.Pas canal,;, 3. East Isles Whiskev Pass to 90*46'- 83 & 95 26.5 4 7.8110% Sand Dernieres Wine Tsland Pass @90'38' 441,166.66' 6,666.66- 80% Marsh wells, & impoundments 4. West Timbalier Cat Island Pass to 90'32'30"- 107 2 7. 5 " 3.5" . 2941.6135% Sand Boat !Oil/gas canals Island Little Pass Timbalier 90'24'30" 45,833.33' 5,833.33-i 1657 Marsh & Spoil with some structures 5. East Timbalier jl,ittl@ Pass Timbalier 90o22:30"- 107 & 117 29" 4 1274.0 30% Sand Boat Oil/gas canal s, Island to Be?le Pass 90'14 30" 48,333.33' 6,666.66' 70 % Marsh & Spoil, impoundments, and s tructures 6. Barrier Beach just From mainland to 90*05:- 125 6.5" 75 193.Oj 70% Sand Unpavedl None 0.1 1 1 south of Cheniere hminada Pass 90'03 3 10,833.33' 1250' h Road I Caminada .6@30' Mars .2136 65@ Sand & Fill Paved lRe,id.ntial, oil/gas 7. Grand Isle lCaminada Pass to 90*02'- 1.15 & 134 26 " 4 1 h Road rela,-ed industrial, lBarataria Pa5s 89'57' 43,333.33' 6,666.66 351, Mars, state park 8. Grand Terre Barataria Pass to 89 -5 7: 30 134 18.5 2.51, 11052.J ?5,' S an d f Boat 104-1/gas pipelines run lQuatre Bavou Pass 89'52 30 30,831'.33' 4,166.66'11 7, 5 % Marsh i lbehi-n3 La. ;Iildl. & iFish. Fxp- Station a t lPipe line zanal- runs 9. Barrier Beach iust IChaland Pass to 89*43'30"- 143 1 . 22 5 356.9! 15c@ San d 1011 1! Z '. I I -eLv Grand Eavou Pass 89'41' 16,666.66' 1 2 e I south of Bay Joe 083.33' 3 5 -'4 Ma:-lgrov 1immed -i a b eh i n d Wise 0 '-Iarsh Pipeline Canal runs 10. Shell Island Grand Bayou Pass 89'40:- 152 10.51, 1 3 7 1 . S 40 San J :3 a t il (includes Bastian to Pecan Island 89'38 17,500' 11666.66 3 5 Mangrove iummed i a t e v 1) e i n d Island) @@nrsh 46 -Y Sand 53at None 11. Breton Island West Point to 29'27'30".- 172F 1. 5 9. 11 @5 0 North Point @29*30' 1,2,500, 2,500' 50; miangrove Table A.l. Continued. COORDINATES 1969 1:20,000 EXISTING GEOGRAPHICAL LONG/LAT PHOTO REF@ LENGTH WIDTH ACREAGE NATURAL ZONES ACCESS DEVELOPMENT 12. Grand Gossier 29*31'- 172D 12" 1.511 370.0 60% Sand Boat None Island 29*34' 20,000' .2,500' 40% Marsh 13. Curlew Island 29*37'- 172C 9.5" V, 377.3 100% Sand Boat None 29'38'30" 15,833.33' 1,666.66' Boat None 14. Stake Island 29*39'- 172C 7.5" 259.7 80'. Sand 29*41' 12,500' 1,666.66' 20% Mangrove 0% Marsh 15! 29*43'- 172C & 172 9" 287.4 70% Sand Boat None Palos island 29*44'30" 15,000' 1,666.66' 30% Mangrove (includes Boot 0% Marsh Island) 16. Chandeleur 29*44130"- 172 69 3.5 5209.2 80% Sand Boat Relatively none; island 30*03'30" 115,000' 5,833.33' 15% Mangrove 1 oil/gas canal 5% Marsh 17. 29*47'- 171 4.5" .75" 143.9 50% Sand 29*49' 7,500' 1,250' > 50% Mangrove Boat None 29*51'30"- 171 81, 1. 5 18. North Islands 13,333.331 2,500' 604.4 5% Sand Boat None 29"!i4' 90% Mangrove 5% Marsh 29*50'30"- 171 4" 170.4 95% Mangrove Boat None 19. New Harbor @4 islands 29*51'30" 6,666.66' 1,666,661 5% Marsh z Boat None 20. South Pass 28*58'30"- 162 2,500-00' 833.33' 71.68 40% Sand Barrier Beach 28*59'30" 60% Marsh 90% Sand Boat oil and gas 21. Southwest Pass 28059'30"- 159 extremelY variable 10% Marsh activity, canals Barrier Beach 29*01'30" intersect 29*06'- 155 3,333.32' 416.67' 15.2 5% Sand Boat None 22. Pass du Bois 95% Marsh Barrier Beach 29*06'30" Table B.1 Environmental Inventory by Parish, Barataria Basin Ascension Assumption Jefferson Square Acres Square Acres Square Acres Miles Miles Miles Water area 0.5 320 1.3 832 162.2 103,808 Saline marsh 0.0 0 0.0 0 19.6 12,544 Brackish marsh* 0.0 0 0.0 0 115.8 74,112 (Intermediate marsh)(0.0) (0) (0-0) (0) (37.3) (23,872) Fresh m arsh 0.0 0 0.5 320 45.8 2%',312 Fresh water swamp 0.0 0 30.5 19,520 40.7 26,048 Topographic Highs 13.3 8,512 57.2 .36,608 55.8 35,712 13.8 8,832 89.5 57,280 439.9 281,536 Lafourche Orleans Plaquemines Square Acres Square Acres Square Acres Miles Miles Miles Water area 151.2 96,768 0.5 320 208.8 133,632 Saline marsh 52*0 13,280 0*0 0 175*4 112,256 Brackish marsh* 156.8 100,352 0.0 0 86.5 55,3,ko'.. (Intermediate marsb)(42.1) (26,944) (0.0) (0) (13.0) (8,320) Fresh marsh 178.4 114,176 0.0 0 16.6 10,624 Fresh water swamp 168.6 107,904 0.0 0 1.4 896 Topographic Highs 124.7 78,808 16.0 10,240 51.3 32,832 831.7 532,288 16.5 10,560 540.0 345.600 St. Charles St. James St. John the Ba2tist Square Acres Square Acres Square Acres Miles Miles Miles Water area 70.0 44,800 3.5 2,240 23.2 14,848 Saline marsh 0.0 0 0.0 0 0.0 0 Brackish marsh* 0.0 0 0.0 0 0.0 0 (Intermediate marsh)(0.0) (0) (0-0) (0) (0-0) 0) Fresh-marsh 95.7 61,248 1.7 1,088 10.5 6,720 Fresh water swamp 50.3 32,192 56.3 36,032 30.4 19,456 Topographic Highs 63.2 40,448 66.7 42P688 24.2 15,488 279.2 178,688 128.2 82,048 88.3 56,512 Includes intermediate marsh. 71 occurred during this period. The quadrangle sheets represent the only complete coverage for the state's coastal zone. The environmental units are: Freshwater swamp Freshwater marsh Brackish water marsh (Intermediate marsh) Saltwater marsh Water bodies and water bottoms Dry land (natural levees and beaches) In addition to the total areas of the environmental units within Barataria Basin (Table 2), areas for each environmental unit were calculated for each parish within the basin (Table B.1) . During measurements on the digitizer, areas were auto- matically computed through the use of a Calmagraphic 11 Digitizing System. Delineation of environmental units on quadrangle sheets were based on the Vegetative Type Map of the Louisiana Coastal Marshes (Chabreck et al. 1968, Pal- misano 1970) and were derived by point-counting (grid sampling) of these quadrangle sheets (7 1/2 minute series used when available) using a method developed by Gagliano and van Beek (1970). The only variation from Gagliano and van Beek's method was that they measured only two major parameters--land and water, while this study employed seven environmental units. Tests comparing digitized areas and point-counted results yielded findings similar to Gagliano's. The accuracy of the Barataria Basin computations are reliable, however, the areas of environmental units within the basin are: 1) only as accurate as grid sampling on a 1/2 mile interval will allow, 2) based on the accuracy of the USGS quadrangle maps themselves, 3) only accurate for the year of map publication, 4) only as accurate as Chabreck et al. and Palmisano were able to delineate the vegetation zones. Appendix C Dredge and Fill Areas of dredge and fill were digitized.from 1969 New Orleans District U.S. Army Corps of Engineers uncon- trolled photomosaics. Coverage of the Barataria Basin is nearly total; where coverage is not complete, the latest editions and largest scale USGS quadrangle charts have been used. The resolution of this study includes all canals and impoundments that show areal extent on a 72 standard 7 1/2 minute quadrangle chart. It must also be noted that urban areas have not been included in compilations because their entire sector has experienced intense alteration by man. These mosaics being uncontrolled lends error to the area compilations; however, features are easily delineated, boundaries can be determined with reasonable accuracy, and such widespread coverage at one date and at one scale (1:20,000) yields consistent information. Table 1 (listed in the main body of this report) lists the canal types considered for classification. Table C.1 contains an inventory of canals by type, parish, and environmental unit. Classification of dredge and fill features according to their major function at present are listed below: Rig Access--canals used solely for installment and maintenance of oil and gas field production apparatus. Pipeline Canals (65 ft and 130 ft--dredged for pipeline installation. Widths were found to approximate either 65 ft or IL30 ft and are reported in the nearest category. Oil Field Navigation Canals--dredged to as access routes and oil rigs. Navigation Canals--limited access routes for boat travel. Transportation Embankments--filling or reinforcing swamp or marsh surface for land transportation. Agricultural Drainage Canals--canals or ditches constructed. to drain marsh or swamp and to allow planting or pasture. Agricultural Impoundments--an area of former marsh or swamp converted for agricultural production. Industrial Impoundment--artificially diked and sometimes I filled marsh or swamp serving as an industrial site. Urban Drainage Canals--dredged to drain marsh or swamp to allow urban growth. Only those portions beyond the limits of the urban sector have been compiled. Agricultural Commodity Transportation Canal--dredged primarily to move goods by water (e.g. logging canals). Oil Field Embankment--constructed to install and service oil and gas field production apparatus. Mineral Extraction Navigation Canal--dredged to transport extracted non-petroleum minerals. Other--canals, embankments, and impoundments not fitting into one of the above categories. 73 Table C.l. Canal type inventory by parish portion in the basin and environmental unit. Ascension Parish--no.swamp or marsh Assumption Parish--no swamp or marsh Jefferson Parish--Environmental Unit (sq., mi.) Inter- Saline Brackish mediate Fresh Swamp Total Rig Access Canals 0.06 3.29 0.83 0.45 0 .43 5.08 Pipeline Canals - 15 ft width 0.08 0.19 0.09 0.60 0.05 0.48 Pipeline Canals - 130 ft width 0.03 0.0 0.0 0.0 0.0 0.35 Oil Field Navigation Canals 0.0 0.0 0.0 0.0 0.0 0.0 Navigation Canals 0.78 0.88 0.52 0.0 1.18 3.37 Transportation Embankments 0 0 0.0 0.0 0.02 0 0 0.02 Agricultural Drainage Canals 0'0 0.0 0.0 0.23 0'.0 0.23 Agricultural Impoundments 0.0 0.0 0.0 1.25 0.0 1.25 Industrial Impoundments 0.0 0.0 0.0. 0.0 0.07 0.07 Urban Drainage Canals 0.0 0.01 0.07 0.10 0.06 0.26 Agricultural Commodity Transportation Canals 0.0 0.0 0.02 0.0 0.01 0.04 Oil Field Embankment 0.0 0.0 0.0 0.0 0.0 0.0 Mineral Extraction Navigation Canal 0.0 0.0 0.0 0.0 0.0 0.0 Other 0.02 0.0 0.0 0.0 0.0 0.02 1.00 4.38 1.55 2.14 1.82 10.90 St. Charles Parish--Environmental- Unit (sq. mi.) Inter- Saline Brackish mediate Fresh Swamp Total Rig Access Canals 1. 57 0.07 1.65 Pipeline Canals - 65 ft width 0.0 0.0 0.0 Pipeline Canals - 130 ft width 0.0 0.0 0.0 Oil Field Navigation Canals 0.0 0.0 0.0 Navigation Canals 0.0 0.0 0.0 Transportation Embankments 0.03 0.35 0.39 Agricultural Drainage Canals 0.06 0.37 0.44 Agricultural Impoundments 5.21 6.06 11.27 Industrial Impoundments 0.0 0.0 0.0 Urban Drainage Canals 0.0 0.0 0.0 Agricultural Commodity Transportation Canals 0.0 0.0 0.0 Oil Field Embankments 0.0 0.04 0.49 Mineral Extraction Navigation Canals 0.0 0.0 0.0 Other 0.0 0.0 0.0 6.89 6.92 13.81 74 Table C.l. Continued. St. James Parish--Environmental Unit (sq. mi.) Inter- Saline Brackish mediate Fresh Swamp Total Rig Access Canals 0.0 0.10 0.10 0.0 0.10 0.10 St. John Baptist--Environmental Unit (sq. mi.) Inter- Saline Brackish mediate Fresh Swamp Total Rig Access Canals 0.09 0.0 0.09 Agricultural Drainage Canals 0.03 0.19 0.23 0.13 0.19 0.32 Lafourche Parish--Environmental Unit I(sq. mi.) Inter- Saline Brackish mediate Fresh Swamp Total Rig Access Canals 1.34 2.08 1.25 3.00 0.45 10.15 Pipeline Canals - 65 ft width 0.34 0.64 0.23 0.30 0.15 1.68 Pipeline Canals - 130 ft width 0.02 0.04 0.0 0.16 0.0 0.23 Oil Field Navigation Canals 0.02 0.0 0.1 0.18 0.0 0.40 Navigation Canals 0.0 0.10 0.28 0.49 0.0 0.89 Transportation Embankments 0.0 0.03 0.40 0.44 0.12 0.99 Agricultural Drainage Canals 0.0 0.0 0.08 0.38 .0.33 0.82 Agriculture Impoundments 0.0 0.0 3.55 14.92 0.0 18.47 Industrial Impoundments 0.05 0.0 0.0 0.0 0.0 0.05 Urban Drainage Canals 0.0 0.03 0.03 0.0 0.0 0.06 Agricultural Commodity Transportation Canals 0.0 0.0 0.0 0.0 0.0 0.0 Oilfield Embankment 0.0 0.0 0.0 0.0 0.17 0.17 Mineral Extraction Navigation Canal 0.0 0.0 0.0 0.0 0.0 0.0 Other 0.0 0.0 0.0 0.0 0.0 0.0 1.80 4.97 6.03 19.91 1.24 33.96 Orleans Parish--no swamp or marsh 75 Table C.l. Continued. Plaquemines Parish-Environment Unit (sq. mi.) Inter- Saline Brackish mediate Fresh Swamp Total Rig Access Canals 3.87 2.06 0.14 0.06 0.0 6.14 Pipeline Canals - 65 ft width 1.79 0.49 0.0 0.10 0.0 2.39 Pipeline Canals - 130 ft width 0.23 0.0 0.0 0.0 0.0 0.23 Oil Field Navigation Canals 0.0 0.0 0.0 0.00 0.0 0.0 Navigation Canals 0.07 0.17 0.0 0.0 0.0 0.24 Transportation Embankments 0.0 0.0 0.0 0.0 0.0 0.0 Agricultural Drainage Canals 0.0 0.63 0.17 0.08 0.07 0.98 Agricultural Impoundments 0.0 0.0 0.0 0.0 0.0 0.0 Industrial Impoundments 0.0 0.0 0.0 0.0 0.0 0.0 Urban Drainage Canals 0.0 0.23 0.0 0.0 0.0 0.23 Agricultural Commodity Transportation Canals 0.0 0.0 0.0 0.0 0.0 0.0 Oilfield Embankment 0.0 0.0 0.0 0.0 0.0 0.0 Mineral Extraction Navigation Canal 0.61 0.0 0.0 0.0 0.0 0.61 Other 0.0 0.0 0.0 0.0 0.0 0.0 6.58, 3.60 0,32 0.25. 0..07.. 76 Appendix D Coastal Retreat and Inlet Changes This section contains the detailed information on coastline retreat of the Barataria Basin Gulf shoreline and inlet changes measured at three different time periods--1932, 1954, and 1969. The coastline retreat information was obtained from Dr. James P. Morgan and David Morgan (personal communica- tion). Morgan and Larimore (1957) conducted a study for the state Attorney General on establishment of the Louisiana shoreline with the staff of the Coastal Studies Institute. This report, established quantitatively that the Louisiana shoreline was retreating except in a few isolated areas where sedimentation exceeded erosion. This study has been brought up to date for the Attorney General and the information collected for the Barataria Basin Gulf shoreline is included in this report. Morgan has assembled maps at a scale of 1:20,000 for the entire Louisiana coastline covering three time periods to measure comparative shoreline changes: (1) a 1932 shoreline as based on U.S. Coast and Geodetic Survey Air Photo Compilation Charts, (2) a 1954 shoreline as based an aerial photographs taken by the Jack Ammann Corporation, and (3) a 1969 shoreline interpreted from uncontrolled aerial photo- graphic mosaics compiled by the New Orleans District, U.S. Army Corps of Engineers. These maps were used in the measure of coastal retreat and inlet change. Inlet width for this paper represents measurement taken at the narrowest point in the channel that separates the two land areas. Inlet width measurements at the different time intervals indicate the variable nature of the Barataria Bay coastline, and the results show an over- all increase in inlet width. Bathymetry information on inlets does not exist in sufficient detail to calculate volume of water flow through the passes. Information collected for the shoreline changes is included in Table D.1, and the data on inlet changes are shown on Table D.2. 77 Table DA. Coastal Retreat. Barataria Hydrologic/Management Unit 1932 - 1954 2,652.56 acres lost 1954 - 1969 1,862.39 acres lost Total 1932 - 1969 4,514.95 acres lost --------------------------------------------------- Jefferson Parish 1932 - 1954 269.96 acres lost 1954 - 1969 336.24 acres lost Total 1932 - 1969 606.20 acres lost Lafourche Parish 1932 - 1954 1,485.75 acres lost 1954 - 1969 821.67 acres lost Total 1932 - 1969 2,307.42 acres lost Plaquemines Parish 1932 - 1954 896.85 acres lost 1954 - 1969 704.48 acres lost Total 1932 - 1969 1,601.33 acres lost 78 Table D.2. Inlet Changes (in feet). Barataria Hydrologic/Management Unit Total Inlet Widths (in feet) 1932 17,949.3 1954 17,274.4 1969 23,361.6 Lafourche Parish 1932 1954 1969 Belle Pass 158.6* 158.6* 158.6* Pipeline Canal 0.0 72.7 040 Pass Fourchon 152.0 185.0 0.0 (unnamed) 0.0 79.3 0.0 (unnamed) 0.0 197.6 0.0 (Unnamed) 0.0 59.5 0.0 Pass at,Parish Boundary 0.0* 33.0* 0.0* 310.6 785.7 158.6 Jefferson Parish Pass at Parish Boundary 0.0* 33.1* 0.0* (unnamed) 0.0 132.2 0.0 Caminada Pass 1,929.7 1,705.0 1,672.0 Barataria Pass 2,147.8 2,372.5 3,449.7 Pass Abel 423.0 997.9 2,465.0 (unnamed) 1,070.6 0.0 0.0 (unnamed) 0.0 105.7 1,116.9 (unnamed) 0.0 52.9 0.0 (unnamed) 0.0 535.3 2,220.5 Quatre Bayou Pass 1,090.4 1,460.5 1,850.4 6,661.5 7,395.1 12,774.5 Plaquemines Parish Quatre Bayou Pass 1,090.5* 1,460.5* 1,850.5* (unnamed) 1,057.4 660.9 984.7 (unnamed) 343.7 0.0 247.7 (unnamed) 442.8 79.3 0.0 Chalaud Pass 1,255.7 191.7 119.0 (unnamed) 297.4 237.9 0.0 Grand Bayou Pass 2,313.0 1,949.6 2,154.4 79- Table D.2. Continued. Plaugemines Parish - Cont'd 1932 1954 1969 Bastian Pass 257.7 204.9 0.0 (unnamed) 746.8 165.2 0.0 (unnamed) 211.5 0.0 Empire to Gulf Waterway 0.0 185.0 185.0 (unnamed) 112.3 0.0 0.0 Scofield Bayou 271.0 284.2 297.4 Entrance to Sandy Point Bay 2,577.4 3,674.4 4,579.8 10,977.2 9,093.6 10,428.5 *Parish b oundary splits these passes. Total width of each pass marked by asterisk is double that given. Source: Maps obtained from James P. Morgan. 80 Appendix E Marsh Deterioration Marsh deterioration constitutes a major problem in the Barataria Basin. Determination of land loss rates within environmental units should provide insights into marsh deterioration causes. This information is neces- sary for development of management methodologies and procedures concerning marsh maintenance and resource utilization. Gagliano (1970) developed a point-counting system for determining land-water ratios that has proven to be'valuable in assessment of long-term changes,in the marshlands. Information in this section concerns devel- opment of methods for measurement of short-term changes over a period of 10 to 15 years that occur in the marsh- land environmental units. This data could then be applied to either the environmental unit, parish, or basin level for considerations in resource planning and utilization. Aerial photographs, USGS quadrangle sheets V 1/2' and 15' scale) and USGS orthophoto quadrangle maps (7 1/2' scale) were used. The time period for measuring comparative changes over an approximate 15-yr period involves three time periods. The time periods for Barataria Basin coverage were not always the same because of constraints on availability of uniform map and photo coverage. Generally, the beginning period fell within the 1956-60 range, with an in-between check at about 1971 and the third and last period 1973 or 1974. Sample areas were selected within the environmental units and parishes from 9-in frames of aerial photo- graphy from available NASA missions. Selection of photos was based on the year flown, extent of coverage, and image quality. So that comparative changes could be measured, drawings were made from the photographs at the scale of the USGS quadrangle and orthophoto sheets. Computation of changes were made by utilizing the Col- magraphic 11 digitizing system in the Center for Wetland Resources. Drawings showing only land-water interface were made from the 9-in aerial photos by reproducing the imagery on 35 mm slides with camera and flat field lens, projecting them on a drawing board, and carefully inter- preting and tracing the land-water interface (Brown et al. 1975; Eng et al. 1974). Larger areas than the sample area were covered on the slide so that data near the edge of the projected image would not be utilized. This procedureminimized the effect of distortion. To achieve the best possible measurement accuracy, the projector lens was aligned perpendicular to the wall 81 90'30 90TOO 89'30' 3TOO Heavily influenced study or a. Lightly /moderately influenced Z42/ 04r study area "'c',4e 0.01 % Annual land loss .19 +0.01 % Annual land growth '40.56 --E eP 0.63 8 6 fresh Marsh 'Oe K Intermediate Marsh 29'30 ........... R . . . . . . . . . . . llrackish Marsh Saline Marsh rr, ........ ...... no Ratio of total inlet change along parish coast line "32 ........... 0. LO A lag _1-i Relative coastline retreat by parish 7r H 1-72: 0 5 10 15 20 Mi. ftV 0 5 10 15 20 25- 30 Km. L Fig. E.l. Coastal retreat and marsh deterioration by environmental unit and parish. SAMPLE AREA - A (24.28 m12) (62.89 km2) Saline Marsh - Lightly/Moderately Impacted. This sample area is located in the southeastern section of the basin near the coast and Mississippi River (Fig. E.1). The area includes natural levees of Grand Bayou, marshlands, tidal channels, bay shorelines, canals, pipelines, and is adjacent to a large oil field. Measurements of land-water changes consist of the following: m12 km2 1960 (aerial photography) - Empire,.La. USGS quadrangle map (1962 edition) 1:62,500 Total water area 40.5% 9.84 (25.49) 'Natural water area (39.4%) Man-made water area (1.1%) Total land area 59.5% 14.44 (37.40) 1971 (aerial photography) Port Sulphur, La. and Bastian Bay, La. USGS orthophoto maps (1973 edition) 1:24,000 Total water area 43.3% 10.52 (27.26) Natural water area (41.5%) Man-made water area (1.8%) Total land area 56.7% 13.75 (35.63) 1974 (aerial photography) NASA Mission 293 - Roll 7 - Color IR Total water area 45.3% 11.01 (28.52) Natural water area (43.7%) Man-made water area (1.6%) Total land area 54.7% 13.27 (34.37) Results: 1960-1974 - 4.8% land loss 1960-1974.- 1.17 mi2 land loss 1960-1974 - 0.58% marsh loss per year Average loss for 14 year period 53.5 acres/year 84 SAMPLE AREA - B (35.42 mi2) (91.76 km2) Saline Marsh -m Lightly/Iloderately Impacted. This sam- ple area lies in the northern edge of Barataria Bay (Fig. E.1) and includes St. Mary's Point and a segment of the Barataria Bay Waterway. It differs from the other tracts in that it contains more water than land. Heavy boat traffic utilizes the Barataria Waterway. Erosion of the land areas would also be influenced by waves driven by south winds over the long fetch of the bay. Few man-made waterways are present in this area. Measurements of land-water changes consist of the following: mi2 km2 1960 (aerial photography) Fort Livingston, La. USGS quadrangle map (1961 edition) 1:62,500 Total water area 59.7% 21.15 (54.79) Natural water area (59.5%) Man-made water area (0.2%) Total land area 40.3% 14.27 (36.97) 1971 (aerial photography) Wilkinson Bay, La. USGS orthopboto map (1973 edition) 1:24,000 Total water area 61.9% 21.93 (56.82) Natural water area (61.7%) Man-made water area (0.2%). Total land area 38.1% 13.49 (34.94) 1974 (aerial photography) NASA Mission 293 - Roll 7 - Color IR Total water area 61.4% 21.76 (56.38) Natural water area (61.2%) Man-made water area (0.2%) Total land area 38.6% 13.66 (35.38) Results: 1960-1974 - 1.7% land loss 1960-1974 - 0.61 mj2 land loss 1960-1974 - 0.31% marsh loss per year Average loss for 14 year period 27.9 acres/year 85 SAMPLE AREA - C (2.24 mj2) (5.80 km2) Saline Marsh Lightly/Moderately Impacted. This ex- ample is located in the southwestern section of the basin (Fig. E.1). It includes parts of Lake Palourde, Lake Laurier, and Bayou Ferblanc. Impacts by man Are mainly small. Measurements of land-water changes consist of the following: mi2 km2 1956 (aerial photography) Caminada Pass, La. USGS quadrangle map (1957 edition) 1:24,000 Total water area 48.7% 1.09 (2.82) Natural water area (48.7%), Man-made water area ( 0%) Total land area 51.3% 1.15 (2.98) 1970 (aerial photography) NASA Mission 154 Roll 37 Black and white Total water area 61.5% 1.38 (3.57) Natural water area (61.5%) Man-made water area 0%) Total land area 38..5% 0.86 (0.23) 1973 (aerial photography) NASA Mission 259 - Roll 23 Color IR Total water area 63.7% 1.42 (3.69) Natural water area (63.7%) Man-made water area ( 0%) Total land area 36.3% 0.81 (2.11) Results: 1956-1973 - 15.0% land loss 1956-1973 - 0.34 mi2 land loss 1956-1973 - 1.72% marsh loss per year Average loss for 17 year period - 12.8 acres/year The primary manifestation of deterioration for this area is the creation and enlargement of ponds in, former marsh areas. Lake shoreline erosion is of secondary importance. 86 SAMPLE AREA D (16.12 m12) (41.76 km2) Saline Marsh Heavily Impacted. This sample area is located in the east central section of the basin (Fig. E.1) that includes the portion of the Lake Washington oil field exhibiting a high density of access canals, pipeline canals, and artificial im- poundments (Fig. E.1). Measurements of land-water changes consist of the following: _m12 km2 1960 (aerial photography) Fort Livingston, La. and Empire, La. USGS quadrangle map (1961, 1962 editions respectively) 1:62,500 Total water area 41.83% 6.74 (17.47) Total land area 58.17% 9.38 (24.29) 1971 (aerial photography) Bay Batiste, La. and Port Sulphur, La. USGS.orthophoto map (1973 edition) 1:24,000 Total water area 49.07% 7.97 (20.49) Total land area 50.93% 8.21 (21.27) 1974 (aerial photography) NASA Mission 293 - Roll 7 Color IR "Total water area 46.51% 7.50 (19.42) Total land area 53.49% 8.62 (22.34) Results: 1960-1974 - 4.68% land loss 1960-1974 - 0.76 m12 land loss 1060@197'4 - 0.58% marsh loss per year Average loss for 14 year period 34.7 acres/year 87 SAMPLE AREA - E (20.72 m12) (53.66 km2) Brackish Marsh - Lightly/Moderately Impacted. This area lies in the east central section of the basin near the Mississippi River (Fig. E.1). It includes Lake Laurier, Round Lake, and part of Wilkinson Canal, a dredged navigation canal. It also has one small sector of rig access canals. Measurement of land- water changes consist of the following: m12 km2 1961 (aerial photography) Pointe a la Hache, La. USGS quadrangle map (1964 edition) 1:62,500 Total water area 27.8% 5.75 (14.89) Natural water area (26.4%) Man-made water area (1.4%) Total land area 72.2% 14.97 (38.77) 1971 (aerial photography) Lake Laurier, La. USGS orthophoto map (1973 edition) 1:24,000 Total water area 38.5% 7.97 (20.64)@ Natural water area (36.9%) Man-made water area (1.6%) ,Total land area 61.5% 12.75 (33.02) 1974 (aerial photography) NASA Mission 293 Roll 7 Color IR Total water area 35.1% 7.27 (18.84) Natural water area (33.8%) Man-made water area (1.3%) Total land area 64.9% 13.44 (34.82) Results: 1961-1974 - 7.3% land loss 1961-1974 - 1.53 mi2 land loss 19611- 1974 - 0.78% marsh loss per year Average loss for 13 year period - 75.32 acres/year 88 SAMPLE AREA F (13.25 m12) (34.34 km2) Brackish Marsh Lightly/Moderately Impacted. This example lies in the central section of the basin southeast of Bayou Rigolettes and north of Turtle Bay, a northern extension of Little Lake (Fig. E.1). There are several large oil fields nearby, but only a few man-made waterways are present within this exam- ple. Impacts by land and water changes consist of the following: m12 km2 1961 (aerial photography) Barataria, La. USGS quadrangle map (1964 edition) 1:621,500 Total water area 18..5% 2.45 6.35) Natural water area (15.9%) Man-made water area (2.6%) Total land area 81.5% 10.80 (27.99) 1971 (aerial photography) Three Bayou Bay, La. and Bay L'Ours, La. USGS orthophoto maps (1973 edition) 1:24,000 Total water area 31.1% 4.12 (10.67) Natural water area (29.1%) Man-made water area (1.9%) Total land area 68.9% 9.14 (23.67) 1974 (aerial photography) NASA Mission 293 - Roll 7 Color IR Total water area 38.1% 5.06 (13.10) Natural water area (36.1%) Ilan-made water area (2.0%) Total land area 61.9% 8.20 (21.24) Results: 1961-1974 - 19.6% land loss 1961-1974 - 2.6 mi2 land loss 1961-1974 - 1.86% marsh loss per year Average loss for 13 year period 128.0 acres/year 89 SAMPLE AREA G (7.75 m12) (20.08 km2) Brackish Marsh Lightly/Moderately IE2acted. This example lies on the extreme western side of the basin near the Bayou Lafourche natural levee (Fig. E.1). Measurements of land-water ratio are; m12 km2, 1956 (aerial photography) Mink Bayou, La. USGS quadrangle map (1957 edition) 1:62,500 , total water area 18.1% 1.40 3.63) Natural water area (17.6%) Man-made water area (0.5%) Total land area 81.9% 6.35 (16.45) 1972 (aerial photography) NASA Mission 194 - Roll 13 Color IR Total water area 37.4% 2.90 7.51) Natural water area (34.3%) Man-made water area (3.1%) Total land area 62.6t 4.85 (12.57) 1974 (aerial photography) NASA Mission 293 - Roll 7 Color IR Total water area 46.0% 3.57 ( 9.24) Natural water area (42.7%) Man-made water area (3.3%) Total land area 54.0% 4.18 (10.84) Results: 1956-1974 - 27.9% land loss 1956-1974 - 2.17 mi2 land loss 1956-1974 - 1.89% marsh loss per year Average loss for 18 year period - 77.16 acres/year This example shows the largest area of land loss for the basin. The loss is primarily due to lakeshore erosion. Poriding in former marsh is a secondary cause of loss. 90 SAMPLE AREA H (7.68 m12) (19.89 km2) Brackish Marsh Heavily Impacted. This sample area is located in the southeastern corner of. the basin (Fig. E.1) and includes the Venice oil field. Access canals encircle the subsurface dome. Water exchange is dominated by tidal flow, with a possibility of minimal exchange via backwater flooding of Missis- sippi River waters discharging through Pass Tante Phine. Measurements of land-water changes consist of the following: m12 km2 1958 (aerial photography) West Delta, La. and Forts, La. USGS quadrangle map (1958, 1960 editions respectively) 1:62,500 Total water area 17.41% 1.34 3.46) Total land area 82.59% 6.34 (16.43) 1971 (aerial photography) Pass Tante Phine, La. and Triumph, La. USGS orthopboto maps (1973 editions) 1:24,000 Total water area 26.83% 2.06 5.34) Total land area 73.17% 5.62 (14.55) 1974 (aerial photography) NASA Mission 293 - Roll 7 Color IR Total water area 31.87% 2.45 ( 6.34) Total land area 69.13% 5.23 (13.55) Results: 1958- 1974 13.46% land loss 1958-1974 1.11 m12 land loss 1958-1974 1.09% marsh loss per year Average loss for 16 year period 44.4 acres/year An extremely high rate of deterioration was seen with- in the area encircled by the major access canal, but fill is occurring on the southeast side where sediments are introduced from backwater flow out of Grand Pass. Although the rate of deterioration is high within the canal area, the overall rate for the sample area is lowered by the nearly stable marsh condition outside the ring canal area. 91 SAMPLE AREA 1 (19.69 m12) (51.03 km2) Brackish Marsh - Heavily Impacted. This example is in the central section of the basin and includes the Lafitte Oil and Gas Field and a portion of the Barataria Waterway (Fig. E.1). Measurements of land-. waterratio changes consist of the following: 1961 (aerial photography) m12 km2 .Barataria, La. USGS quadrangle map (1964 edition) 1:62,500 Total water area 24.35i 4.79 (12.42) Total land area 75.65% 14.90 (38.61) 1971 (aerial photography) Three Bayou Bay, La. USGS orthophoto map (1973 edition) 1:24,000 Total water area 32.80t 6.46 (16.74) Total land area 67.20% 34.29 (34.29) 1974 (aerial photography) NASA Mission 293 - Roll 7 Color IR Total water area 30.53% 6.01 (15.58) Total land area 13.68 (35.45) Results: 1961-1974 - 6.18% land loss 1961-1974 - 1.22 mi2 land loss 1961-1974 - 0.63% marsh loss per year Average loss for 13 year period - 60.1 acres/year Areas@of marsh on the-natural levee are stable, but areas in the levee-flank depression are extremely deteriorating rapidly. 92 SAMPLE AREA J (30.62 m12) (79.32 km2) Intermediate Marsh - Lightly/Moderately Impacted. This example lies near the Mississippi River in the northeastern.section of the basin. -It includes the Pen, a 1917 marsh reclamation project that is now flooded (Fig. E.1). Land@water measurements consist of the following: m12 km2 1961 (aerial photography) Barataria, La. USGS qqadrang le map (1964 edition) 1:62,500 Total water area 26.4% 8.07 (20.91) Natural water area (23.9%) Man-made water area (2.5%) Total land area 73.6% 22.55 (58.41) 1971 (aerial photography) Lafitte, La. USGS orthophoto maps (1973 edition) 1:24,000 Total water area 30.1% 9.22 (23.88) Natural water area (26.8%) Man-made water area (3.3%) Total land area 69.0% 21.40 (55.44) 1974 (aerial photography) NASA Mission 293 - Roll 7 Color IR Total water area 31.7% 9.70 (25.12) Natural water area (28.7%) Man-made water area (3.0%) Total land area 68.3% 20.92 (54.19) Results: 1961-1974 - 5.3% land loss 1961-1974 - 1.63 m12 land loss 1961-1974 - 0.45% marsh loss per year Average loss for 13 year period 80.2 acres/year Marsh ponding and pond enlargement primarily account for reduction of vegetated marsh. 93 SAMPLE AREA K (13.92 m12) (36.06 km2) Inte diate Marsh - Lightly/Moderately Impacted. This example lies to the east of Cl'ovelly Farms and to the west of Little Lake in the very narrow band of intermediate marsh (Fig. E.1). How much this band of intermediate marsh has changed since Cha- breck (1972) surveyed it in 1968 is unknown. M12 km2 1962 (aerial photography) Cut Off, La. USGS quadrangle map (1963 edition) 1:24,060 Total water area 17.5% 2.44 ( 6.31) Natural water area (16.3%) Man-made water area (1.2%) Total land area 82.5% 11.48 (29.75) 1972 (aerial photography) NASA Mission 194 - Roll 13 Color IR Total water area 20.2% 2.81 7.28). Natural water area (18.3%) Man-made water area (1.9%) Total land area 79.8% 11.11 (28.78) 1974 (aerial photography) NASA Mission 293 - Roll 7 Color IR Total water area 23.1% 3.22 ( 8.33) Natural water area (20.6%) Man-made water area (2.5%) Total land area 76.9% 10.70 (27.73) Results: 1962-1974 - 5.6% land loss 1962-1974 - 0.78 mi2 land loss 1962-1974 - 0.57% marsh loss per year Average loss for 12 year period 41.6 acres/year 94 SAMPLE AREA - L (19.78 m12) (51.24 km2) Intermediate and Brackish Marsh - Heavily Impacted. This sample area, fronting Bayou Perot to the east, the West Delta Farms Oil Field and Delta Farms Oil and Gas Field, is an example of a heavily impacted system (Fig. E.1). Bayou Perot flows from Lake Salvador and cuts across the Intracoastal Waterway lying just north of the example, then turns to the south and flows into Little Lake in its journey to Barataria Bay and the Gulf of Mexico. Bayou Perot, as it flows past this site, serves as the drainage route for water flowing from approximately 75% of Barataria Basin's freshwater marsh and swamp. This locale is subject to both wind-influenced tidal flow and freshwater surplus. m12 km2 1961 (aerial photography) Barataria, La. USGS quadrangle map (1964 edition) 1:62,500 Total water area 16.15% 3.19 ( 8.27) Total land area 83.85% 16.59 (42.97) 1971 (aerial photography) Barataria, La. and Bay L'Ours, La. USGS orthophoto map (1973 edition) 1:24,000' Total water area 18.03% 3.57 ( 9.24) Total land area 81.97% 16.21 (42.00) 1974 (aerial photography) NASA Mission 293 - Roll 7 Color IR Total water area 21.09% 4.17 (10.81) Total land area 78.91% 15.61 (40.43) Results: 1961-1974 - 4.94% land loss 1961-1974 - 0.98 m12 land loss 1961-1974 - 0.45% marsh loss per year Average loss for 13 year period - 48.2 acres/year 95 2) SAMPLE AREA - M (18.72 mi (48.49 km2) Fresh Marsh - Lightly/Moderately Impacted. This example is on the southwest shore of Lake Salvador and includes part of this lake (Fig. E.1). It is directly north of Delta Farms (agricultural recla- mation area). Relict natural levee.features of a small distributary are present; Waves generated in the long fetch of this lake cause erosion along its bank. Dense concentration of water hyacinth in this area produced problems in determining the boundary between marsh vegetation and hyacinth from the photographs. In this case, the figures may show less loss than actually occurred. 2 i km2 1962 (aerial photography) Catahoula Bay, La. USGS quadrangle map (1963 edition) 1:24,000 Total water area 291.1% 5.45 (14.11) Natural water area (27.0%) Man-made water area (2.1%) Total land area 70.9% 13.27 (34.38) 1972 (aerial photography) NASA Mission.194 - Roll 13 Color IR Total water area 34.8% 6.51 (.16.87) Natural water area (32.1%) Man-made water area (2.7%) Total land area 65.2% 12.21 (31.62) 1974 (aerial photography) NASA Mission 293 - Roll 7 Color IR Total water area 37.7% 7.06 (18.28) Natural water area (34.4%) Man-made water area (3.3%) Total land area 62.3% 11.66 (30.21) Results: 1962-1974 - 8.60% land loss 1962-1974 - 1.61 mi2 land loss 1962-1974 - 1.01% marsh loss per year Average loss for 12 year period - 85.9 acres/year The 1962 map shows very few ponds, however, by 1972 extensive ponding has occurred causing a 5.7% land loss. Increase in the size of the ponds and a slight increase in the area of man-made waterways caused a 2.9% increase in water area from 1972 to 1974, a significant land loss for such a short period of time. 96 SAMPLE AREA - N (9.54 m12) (24.73 km2) Fresh Marsh - Heavily Impacted. This sample area includes the Bayou Couba Oil and Gas Field that lies along the northwest shore of Lake Salvador, six miles northeast of the mouth of Bayou des Allemands .(Fig. E.1). Access to the field is limited to one canal from Lake Salvador, the canal's opening partially protected by Couba Island. m12 km2 1965 and 1964 (aerial photography) Lake Cataouatche West, La. and Lake Cataouatche East, La. USGS quadrangle map (1967, 1966 editions respectively) 1:24,000 Total water area 17.00% 1.62 4.20) Total land area 83.00% 7.92 (20.53) 1972 (aerial photography) NASA Mission 194'- Roll 2 Color IR Total water area 16.87% 1.61 ( 4.17) Total land area 83.13% 7.94 (20.56) 1974 (aerial photography) NASA Mission 293 - Roll 7 Color IR Total water area 15.61% 1.49 ( 3.86) Total land area 84.39% 8.06 (20.87) Results: 1965-1974 - 1.39% land gain 1965-1974 - 0.14 mi2 land gain 1965-1974 - 0.19% marsh gained per year Average gain for 9 year period - 10.0 acres/year Bayou Couba Oil and Gas Field showed a consistent rate of marsh and canal fill over the three study dates, 1965, 1972, and 1974. Canals consistently showed fill throughout all portions of the site and marsh areas at a distance from the canals showed not only displacement of ponds from example to example, but often complete fill. 97 lected, Bibliography. Bahr, L. M. and J. J. Hebrard. 1976. Barataria Basin: Biological characterization. Louisiana State University Center for Wetland Resources, Baton Rouge, La. Sea Grant Publ. No. LSU-T-76-005. Brown, D., R. Skaggs, J. M. Smiley, and E. Stern. 1975. Monitoring surface water dynamics in Minnesota. U. of Minn., Center for Urban,and Regional Affairs, State Planning Agency, No. 5014. Bruce, C. H. 1973. Pressured shale and related sediment deformation: Mechanism for development of regional contemporaneous faults. Amer. Assoc. Pet. Geol. Bull. 57:5. Byrne, J. V., D. 0. LeRoy, and C. M. Riley. 1959. The chenier plain and its stratigraphy, southwestern Louisiana. Trans. Gulf Coast Assoc. Geol. Soc. 9: 237-260. Byrne, P., M. Borengasser, G. Drew,.R. Muller, B. L. Smith Jr., and C. Wax. 1976. Barataria Basin: Hydrologic and climatologic processes. Louisiana State Univer sity Center for Wetland Resources, Baton Rouge, La. Sea Grant Publ. LSU-T-76-010 Carver, R. E. 1968. Differential compaction as a cause of regional contemporaneous faults. Amer. Assoc. Pet. Geol. Bull. 52:6. Chabreck, R. 1970. Marsh zones and vegetative types in the Louisiana marshes. Ph.D. diss., Louisiana State University, Baton Rouge, La. 1972. Vegetation, water and soil characteristics of the Louisiana coastal region. La. Agr. Exp. Sta. AEA Information Series No. 25. -3, T. Joanen, and A. W. Palmisano. 1968. Vegetative type map of the Louisiana coastal marshes. La. Wildl. and Fish. Comm., New Orleans, La. Coleman, J. M. 1966. Recent coastal sedimentation@- Central Louisiana coast. Louisiana State Un ersity, iv* Coastal Studies Institute Tech. Rept. 29. and S. Gagliano. 1964. Cyclic sedimentation in the Mississippi River deltaic plain. Trans. Gulf Assoc. Geol. Soc. 14:67-80. , and W. Smith. 1964. Late recent rise of sea level. Bull. Geol. Soc. Amer. 75:833-840. and L. D. Wright. .1974. Modern river deltas: Variability of processes and sand bodies. Pages 99-149 in M. L. Broussard (ed.) Deltas: Models for Exploration. Houston Geol. Soc., Houston, Tex. J. N. Suhayda, T. Whelan, and L. D. Wright. 1974. Mass Movements of Mississippi River deltas. Pages 49-68 in Proc. 24th Conf. Gulf Coast Assoc. of Geol. Soc., Oct. 1974, Lafayette, La. 98 .Conatser, W. 1971. Grand Isle: A barrier island in the Gulf of Mexico. Bull. Geol. Soc. Amer. 82:3049-3068. Conner, W. H., J. H. Stone, L. M. Bahr, V. R. Bennett, J. W. Day Jr., and R. E. Turner. 1976. Barataria Basin': Oil and gas use characterization, impacts, and guidelines. Louisiana State University Center for Wetland Resources, Baton Rouge, La. Sea Grant Publ. No. LSU-T-76-006. Craig, N. J. and J. W. Day Jr. 1976. Barataria Basin: Cumulative impact--eutrophication. Louisiana State University Center for Wetland Resources, Baton Rouge, La. Duplicated ms. Doiron, L. N. and C. A. Whitehurst. 1974. Geomorphic processes active in the southwestern Louisiana canal, Lafourche Parish, Louisiana. Louisiana State Univer- sity Div. of Engineering, Baton Rouge, La. Res. Monographs. Earle, Daniel. 1975. Land subsidence problems and main- tenance costs to homeowners in east New Orleans, Louisiana. Ph.D. diss., Louisiana State University, Baton Rouge, La. Eng, R..L., F. N. Gjersing, and M. P. Meyer. 1974. Waterfowl management using color IR. Photogram. Eng. and Remote Sensing 40:165-168. Fisk, Harold N. 1944. Geological investigation of the alluvial valley of the lower Mississippi River. U.S. Army Corps of Engineers, Mississippi River Commission, Vicksburg, Miss. 1955. Sand facies of recent Mississippi delta deposits. Proc. 4th World Pet. Cong. (Rome), Sec. .1, pp. 377-398. . 1960. Recent Mississippi River sedimentation and peat accumulation. 4th Inter. Cong., Carbonate Stratigraphy and Geology (Heerlen, Netherlands, 1958). Compte Render.. . 1961. Barfinger sands of the Mississippi delta. In J. Peterson and J. Osmond (eds.) Geometry of Sand- stone Bodies. Bull. Amer. Assoc. Pet. Geol. -, and E. McFarlan Jr. 1955. Late quaternary del- taic deposits of the Mississippi River. Geol. Soc. Amer. Spec. Paper 62:279-302.- Frazier, D. 1967. Recent deltaic deposits of the Mis- sissippi River, their development and chronology. Trans. Gulf Coast Assoc. Geol. Soc. 17:287-315. and A. Osanik. 1968. Recent peat deposits, Louisiana coastal plain. In E. Dapples and M. Hopkins (eds.) Environments of Coastal Deposition. Geol. Soc. Amer. Soc. Spec. Paper 114. Gagliano, S. 1963. Paleoecology of southeastern Louis- iana and south Mississippi. Proc. lst Nat'l. Coastal and Shallow Water Res. Conf., Nat'l. Sci. Foundation and ONR. 99 Gagliano, S., and J. Day Jr. 1972.. Environmental aspects of a superport off the Louisiana coast. Rept. No. 1: Preliminary Recommendations and Data Analyses, Louisiana Superport Studies. Louisiana State University Center for Wetland Resources, Baton Rouge, La. Sea Grant Pub.l. LSU-SG-72-03, pp. 281-317. , and J. van Beek. 1970. Hydrologic and geologic studies of coastal Louisiana. Vol. I: Geologic and Geomorphic Aspects of Deltaic Processes, Mississippi Delta System. Louisiana State University Center For Wetland Resources, Baton Rouge, La. H. Kwon,. and, J. van Beek. 1970. Deterioration and restoration of coastal wetlands@ Rept. No. 9. Hydrologic and Geologic Studies of Coastal Louis- iana.. Louisiana State University Center for Wet- land Resources, Baton Rouge, La. P. Culley, D. W. Earle, P. Light, A. Rowland, R. Shlemon, and J. L. van Beek. 1972. Environmental atlas-and multi-use management plan for south- central Louisiana. Rept. No. 18, Vol. I, Hydrolog- ical and Geologic Studies of Coastal Louisiana. Louisiana State University Center for Wetland Resources, Baton Rouge, La. and J. L. van Beek. 1975. Environmental base and management study, Atchafalaya Basin, Louisiana. Environmental Protection Agency, Wash., D.C., 227 pp. Gould, R. H. and E. McFarlan Jr. 1959. Geologic history of the Chenier Plain, southwestern Louisiana. Trans. Gulf Coast Assoc. Geol. Soc., Vol. 9. and J. P. Morgan. 1962. Coastal Louisiana swamps and marshlands. Houston Geol. Soc. Field Trip No. 9, 46 pp. . 1970. The Mississippi Delta complex. In James P. Morgan Delta Sedimentation, Modern and Ancient. Soc. Econ. Pal. and Min. Spec. Publ. No. 15. Grimes, B. H. and J. C. E. Hubbard. 1971. A comparison of film type and the importance of season for photo- interpretation of coastal marshland vegetation. The Photogrammetric Record 7(38)t213-222. Hall, T. P., and W. T. Penfound. 1939. A phytosocio- logical study of a cypress-gum swamp in southeastern Louisiana. Amer. Midlands Naturalist 21:18. Harper, J. R. 1975. Nearshore oceanography. Louisiana Offshore Oil Port, Environmental Baseline Study. Tec@. App. IV. LOOP, Inc., New Orleans, La. Howe, H. V., R. J. Russell, J. H. McGuirti B. C. Craft, and M. B. Stevenson. 1935. Reports on the Geology of Cameron and Vermilion Parishes, Louisiana. Geol. Survey Bull. 6. 100 Jones, P. 1969. Hydrology of neocene deposits in.the northern Gulf of Mexico basin. Louisiana State University Water Resources Research Inst., Baton Rouge, La., Bull. GT-2. Kolb, C., and J. Van Lopik. 1958. Geology of the Mis- sissippi River deltaic plain, southeastern Louis- iana. U.S. Army Corps of Engineers Waterways Exp. Sta., Vicksburg, Miss. Tech. Rept. 3:483. 1966. Depositional env,ironments,of the Missis- sippi River deltaic plain, southeastern Louisiana. Pages 17-61 in M. Shirley (ed.) Deltas in Their Geologic Framework. Houston Geol. Soc., Houston, Tex. Kwon, H. 1969. Barrier islands of the northern Gulf of Mexico,coast: Sediment source and development. Louisiana State University Center for Wetland, Resources, Baton Rouge, La., Coastal Studies Series No. 25. LeBlanc, R. J. and H. A. Bernard. 1954.. Resume of late Recent geological history of the Gulf coas@t:. Geologic. Mijnbouw 16:185-194. Lewis, A. J. 1974 Geomorphic-geologic mapping from remote sensor;. In J.E. Estes and L. W. Senger. (eds.) Remote Sensing Techniques.for Environmental Analysis. Hamilton Pub. Co., NY. Lindall, W. N. Jr., J. R. Hall, J. E. Sykes, and E. L. Arnold Jr. 1972. Louisiana coastal zone: Analyses of resources and resource development needs in connection with estuarine ecology. Secs. 10 and 13 in Fishery Resources and Their Needs. Nat'l. Mar. Fish. Serv., Biol. Lab., St. Petersburg, Fla. Lindsey, J.L., K. W. Patterson, and A. R. Bertrand. 1975. Citizen perception of coastal area planning and development: A study of the knowledge and atti- tudes of Louisianians. Louisiana State University Center for Wetland Resources, Baton Rouge, La. Sea Grant Publ. No. LSU-T-75-007. Marmer, H. A. 1954. Tides and sea level in the Gulf of Mexico. Pages 101-118 in Gulf of Mexico, Its Origin, Waters, and Marine Life. U.S. Dept. of Interior, Fish and Wildl. Serv., Fishery Bull. 89. McFarlan, E. Jr. 1955. Radiocarbon dating of the Quaternary in southern Louisiana (abst.). Geol. Soc. Amer. Bull. 66:1594. . 1961. Radiocarbon dating of Late Quaternary deposits, south Louisiana. Geol. Soc. Amer. Bull. 72:29. McIntire, W. G. 1959. Methods of correlating cultural remains with stages of coastal development. Louisiana State University Center for Wetland Resources, Baton Rouge, La., Coastal Studies Inst. 2nd Coastal Geography Conf., pp. 341-359. 101 McIntire, W. G., M. J. Hershman, R. D. Adams, K. D. Mid- boe, and B. Barrett. 1975. A rationale for deter- mining Louisiana's coastal zone. Louisiana State University Center for Wetland Resources, Baton Rouge, La. Sea Grant Publ. LSU-T-75-006. and C. Ho. 1969. Development of'barrier island lagoons: Western Gulf of Mexico. In Mem. Int. Symp. Coastal Lagoons, Nat'l. Univ. of Mexico, Mexico City. Morgan, J. 1972. Impact of subsidence and erosion on Louisiana coastal marshes and estuaries. In R. Chabreck (ed.), Proc. of the Coastal*Marsh and Estuary Mgt. Symp. Louisiana State University Center for WetlAnd Resources, Baton Rouge, La. and P. Larimore. 1957. Changes.,in the Louisiana shoreline. Trans. Gulf Coast Assoc. Geol. Soc. 7:303-310. Murray, S. P. 1976. Currents and circulation in the coastal waters of Louisiana. Louisiana State University Center for We tland Resources, Baton Rouge, La. Sea Grant Publ. LSU-T-76-003; Coastal Studies Inst. Bull. No. 210. Nichols, L. 1959. Geology of Rockefeller Wildlife Refuge and Game Reserve. La. Wildl. and Fish. Comm., New Orleans, La. OlNeil, T. 1949. The muskrat in the Louisiana coastal marshes. La. Wildl. and Fish. Comm., New Orleans, La. Palmisano, A. W. 1970. Plant community-soil relation- ship in Louisiana coastal marshes. Ph.D. diss., Louisiana State Univ., Baton Rouge, La. Penfound, W., and E. Hathaway. 1938. Plant communities in the marshland of southeastern Louisiana. Ecol. Monogr. 8:1-56. Price, W. A. 1955. Environment and formation of the chenier plain. Quaternaria 2:75-86. Russell, R. 1936. Lower Mississippi River Delta. Dept. Cons., La. Geol. Survey Bull. 8. - . 1939. Louisiana stream patterns. Bull. Amer. Assoc. Pet. Geol. 23(8):1199-1227. . 1940. Quaternary history of Louisiana. Bull. Geol. Soc. Amer. 51:1199-1234. 1968. Glossary of terms used in fluvial, deltaic, and coastal morphology and processes. Coastal Studies Institute, Tech. Rept. 63. _2 and V. Howe 11. 1935. Cheniers of southwestern Louisiana. Geog. Review 25:.449-461. Saucier, R. 1962. Recent geomorphic history of the Pontchartrain Basin, Louisiana. Coastal Studies Ser. No. 9. _. 1974. Quaternary geology of the lower Missis- sippi Valley. Arkansas Archeological Survey Res. Ser. No. 6. 102 Shelton, J. W. 1968. Role of contemporaneous faulting during basin subsidence. Amer. Assoc. Pet. Geol. Bull. 52:15. Shlemon, R. and S. Gagliano. 1972., Birth of a delta, Atchafalaya Bay, Louisiana. Sec. 6i pages 437-441 in Stratigraphy and Sedimentology. Proc.,Inter. Geol. Cong. stone, J. H. 1976. Environmental factors relating to Louisiana menhaden harvest. Louisiana State University Center for Wetland Resources, Baton Rouge, La. Sea Grant Publ. LSU-T-76-004. Suhayda, J. N. 1976. Barataria Basin: Wave action. In Byrne et al. Barataria Basin:.Hydrologic and Climatologic Processes. Louisiana State University Center for Wetland Resources, Baton Rouge, La. Sea Grant Publ. LSU-T-76-010. U.S. Army Corps of Engineers, New Orleans District. 1967. Bayou Lafourche and Lafourche-Jump Waterway, Louisiana. General Design Memorandum, Suppl. No. 2. Van Sickle, V. R., B. Barrett, T. B. Ford. 1976. Barataria Basin: Salinity changes and oyster dis- tribution. Louisiana State University Center for Wetland Resources, Baton Rouge, La. Sea Grant Publ. LSU-T-76-002. Welder, F. A. 1959. Processes of deltaic sedimentation in the lower Mississippi River. Louisiana State University Center for Wetland Resources, Coastal Studies Institute Tech. Rept. 12. 103 J....1 21 1 Al 1 61 1 81 1 101 1 121 1 IAI 1 161 1 181 1 20 CENTIMETERS INCHES 11 1 31 Al 51 61 71 8 21 Al 81 101 121 1AI 161 181 201 221 241 261 281 35 METERS FEET 101 -201 301 40, 501 6UI 701 -801 901 201 A01 601 801 1001 1201 1401 1601 180, KILOMETERS MILES 101 201 301 401 501 60 1 701 801 901 1001 1101 120 11 21 31 4 FATHOMS FEET 21 41 61 81 161 121 1AI 161 181 201 221 24 -601 -401 -201 01 201 A01 601 801 1001 DEGREES CENTIGRADE DEGREES FAHRENHEIT -801 1 -401 I@ 01 1 401 1 801 1 1201 1 1601 1 2001 CONVERSION FACTORS LENGTH Iinch = 2.54 centimeters 1 centimeter = 0.40 inch Iinch = 25.40 millimeters I millimeter = 0.04 inch Ifoot . 0.30 meter I meter . 3.28 feet Iyard = 0.91 meter I meter = 1.09 yards 1fathom . 1.83 meters I meter = 0.55 fathom Ifathom - 6.00 feet I meter = 39.37 inches Ifoot = 0.17 fathom I meter = 100 centimeters Imile . 1.61 kilometers I kilometer = 0.62 mile Imile = 1609.34 meters 1 kilometer = 1.000 meters Imile = 5280 feet I kilometer = 3280.84 feet AREA Ifoot2 = 0.09 meter2 1 meter2 = 10.76 feet2 Iyard2 0.84 meter2 I meter2 = 1.20 yards2 Imile2 2.59 kilometers2 I kilometer2 = 0.119 mile2 Iacre 0.40 hectare I hectare = 2.47 acres VOLUME AND CAPACITY 1foot 0.03 meter I meter3 = 35.31 feet I meter3 = 264.17 gallons (US) VELOCITY Ifoot/second = 0.68 inile/hour 1 meter/second = 3.60 kilometers/hour Ifoot/second = 1.10 kilometers/hour 1 meter/sec.ond = 2.24 miles/hour 1foot3/second = 0.03 meted/second I meter3/second = 35.31 feet3/second Imile/hour = 1.47 foot/second 1 kilometer/hour = 0.91 foot/second Imile/hour 0.45 meter/second 1 kilometer/hour 0.28 meter/second TEMPERATURE "Fahrenheit 9/5 (*C + 32) 'Centigrade 5/9 (*F 32) of Commerce WOAA Coastal rvices Center Library Se 2@34 South Robson Avenue Ciiarleston, Sc 29405-2413 A 3 6668 14101 9200