65. USA--LOUISIANA

K. Meyer-Arendt D.W. Davis Department of Geography Department of Earth Science Mississippi State University Nicholls State University Starkville, Mississippi 38759 Thibodaux, Louisiana 70301 United States of America United States of America

INTRODUCTION

Louisiana's 40,000 Inn 2 coastal zone developed over the last 7,000 years by the , , and accretion of introduced via various courses of the Mississippi (Frazier 1967). The deltaic plain (32,000 km'), through which the modern river cuts diagon­ ally !Fig , 1), consists of vast wetlands and waterbodies. With eleva­ tions ranging from level up to 1.5 m, it is interrupted by natural ridges which decrease distally until they disappear beneath the marsh surface. The downdrift chenier plain of southwest Louisiana (8,000 km') consists of marshes, large round-to-oblong , and stranded, oak covered ridges known as cheniers (Howe et al. 1935). This landscape is the result of alternating long-term phases of shoreline accretion and that were dependent upon the proximit of an active -laden river, and a low-energy marine environment (Byrne et al. 1959). Since the dyking of the , fluvial sedimentation in the deltaic plain has effectively been halted. Today, most Missis­ sippi River sediment is deposited on the outer ; only at the mouth of the Atchafalaya River is deltaic sedimen­ tation subaerially significant (Adams and Baumann 1980). Over mos of the coastal zone, subsidence, saltwater intrusion, wave erosion, canalization, and other hydrologic modification have led to a rapid increase in the surface area of (Davis 1986, Walker e al. 1987). in coastal Louisiana has been estimated to exceed 100 km 2/yr (Gagliano et al. 1981), Some researchers have attributed up to 40X of the wetland loss to m.an 's activities (Craig et al, 1979). The 500 km long shoreline, which is characterized by barrier and in the deltaic plain and by barrier beaches and mud.flats in the chenier plain, is generally transgressive with average shoreline erosion rates in excess of 10 m/yr (Adams et al. 1978, van Bee.k and Meyer-Arendt 1982). The barrier i slands, which function as the first natural line of defense against incoming tropical storms, have lost almost half of their surface area within the last 100 years because of wave erosion and subsidence (Penland and Boyd 1982). 629

H I . Walker (ed.). Arlijiclal Structures and Shorelifll!s, 629-640. e 1988 #Y K/1,wer Acadt!J11ic Publishus. 630

Shorelines in more inland estuarine settings are experienc ng bigh erosion re.tes because of fetch an.d Kave action, and t.be un.consolidated nature of the sbore sediments (Adams et al 1978). Buman settlement in coastal Louisiana was historically confined to beach ridges and natural (Davis 1983). However, with e~pansion of urban/industrial land (especially around New Orleans), extension of farmlands, development of the oil and as industry and itB associated demand for improved navigation channels, recreational demands along waterfronts, and continued construction of hurricane-protection levees, man bas extended his activities deep into the wetlands and along the shoreline (Davi and Detro 1980). Three classes of structural modifi­ cation are identifiable: (1) those associated with the harnessing of the Mississippi River, (2) those within the es uarine wetlands, and 3) those associated with the shoreline (Fig, 1),

THE MISSISSIPPI RIVER The Mississippi River, confined within a conduit of artificial levees, can no longer inundate its historic . River leveeing dates from the initial European settling of ew Orleans in 1718; by the 1850s, intermittent dykes flanked most of the lower Mississippi River (Elliott 1932), However, the present comprehensive manipulation of rivet' flow (within levees avere.iing 7.6 m above ground level) is a result of construction made after the 1927 that inundated 65,000 kml (USACE n.d,), Extensive revetments ha.ve been laid to reduce ba.nk collapse and stabilize levees, Formerly constructed of willow mats, revetments a.re now made of interlocking mats and ripra.p rubble . Complementing the levees are floodways that can re-direct flood water and reduce river flood stages, Louisiana's floodways (Old River/Atcbafalaya Morganza, Bonnet Carre, and Bohemia), ar-e designed to protect New Orleans, much of which is below sea level. Flow through the Atchafalaya Spillway is ma.inta.ined at aoi of Mississippi River at the Old River Control Structure (Kazma.nn and Johnson 1980). The Bonnet Carre Spillway, 15 km upriver from New Orleans, can divert 7 million liters/second into Pontchartrain, an embayment of the Gulf of Mexico. The structure's 350 moveable gates, completed in 1931 (USACE n,d,) 1 have been opened only 7 times~-the last in ay 1983). In addition to spillways, the United States Army Corps of En­ gineers constructed a freshwater siphon at Violet. lt is designed to stop the advance of saltKater into fresh or brackish areas and preserve the ~arsbes southeast of New Orleans. The project's uccess has led the Corps to investigate the feasibility of diverting water and sediments into the Barataria . Because the Mississippi's east south of Bohemia is unleveed, it functions as an additional overflo" spillway. Within the "birdsfoot" portion of the delta, 2 of the 3 major deltaic are presently jettied. The earliest were constructed in the 1860s, but it "as not until the 1870s that the 631

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Fig. 1. The Louisiana coastal zone and selected locations illustrating a variety of artificial structures. 632 prototype of the modern jetties (the Rads jetties at South Pass) was built (Elliott 1932). Southwest Pass, the major navigation today, has been modified by the construction of jetties, bulkheads, and channel- spur dykes since 1900 (Fig. 1, inset B).

WETLANDS DRAINAGE AND RECLAMATION When New Orleans was first surveyed in 1792, each residential block was encircled with , and the city's dependence upon a drainage network was established, By 1743, an ordinance required property owners to complete their levees or forfeit their lands (Samuel 1959 ) , As the city expanded into adjacent wetlands, it became even more dependent on levees and artificial drainage systems. One result of these modifications bas been subsidence; portions of the city are now at least 6 m below sea level (Davis and Detro 1980). Presently, New Orleans operates a total of 140 km of canals and 92 k~ of large pipelines. These conduits, along with 21 pumping stations, can remove more than 85 million liters of water/minute from the city streets through at least 50,000 curbside catch basins and 2,024 km of subsur­ face drainlines (Wagner and Durabb 1976). Drainage and reclamation endeavors are not restricted to New Orleans. Since the colonial period, privately funded levees have been built to expand cropland. This reclamation effort was especially intensified during the period between 1880 and 1930, when Louisiana's "alluvial empire" was perceived as a great agricultural frontier. Over 50 projects, which ranged in sizes from 260 to over 14,000 hat were started. Between 2% and 5% of each project's area was allocated to ditches and canals designed to transfer water from a surface that had subsided to 3 m below sea level to surrounding surface levels of one m above sea level (Okey 1914). All but 4 of these projects failed; 2 of them are now residential and industrial centers near New Orleans. Many of these projects failed because of levee breaks and subsequent inundation. Reminders of these ill-fated ventures appear as rectan­ gular waterbodies on maps and aerial images. Impoundment of wetlands for purposes of marsh management (mainly for the maintenance of desired salinities) has been popular since the 1930s, particularly in the chenier plain marshe/i (Gosselink et al. 1979). Present-day reclamation activities are primarily related to the construction of elaborate hurricane-protection levees around several of the more seaward dis­ ridges such as Lafourche and Terrebonne (USACE 1982a). Drainage of the wetlands has left an extensive network that, when combined with other canal types such as those made for trapping, logging, transportation, and hydrocarbon-extraction (Fig. 2), form the most visible structural modification within the coastal zone (Davis 1973). The canalization process has resulted in the loss of at l east 520 kma of surface area. For example, in one oil and gas field there are 68 km of petroleum-related canals, representing the removal of at least 3,2 million m3 of soil (Davis and Place 1983). Canal construc­ tion which is usually accompanied by the breation of spoilbanks on 633 ad.Jae nt 11etlands, mod i fies the bydrologic regime, accel erates sal t­ ater intrusion, and i mpedes over land flow.

THE SBORELIN6

tructural modification of the Louisiana shoreline has been conducted ~r Z basic purposes: 1) to maintain entrances to navigation channels, ind 2) to control er osion for protection of development sites, The t cooon structures utilized for the first purpose are jetti es, though offshore break If a ters can be used in conjunction with them. A 1reater variety of structures are employed for ; t~u ples include sea"a lls, revetments, gr o;rnes, T- ( causeway-­ COllll&Cted breakwaters ) , bulkheads, sandfences, nourished beaches, and ~ etatively-atabilized shorelines. The mouths of 10 navigation channels in coastal Louisiana (includ- 111 Lake Pontchartrain) are jettied; at all but one mouth they are in eta of 2. These structures confine water flow, mini111ize channel-mouth shoaling, and prevent sedimentary infilling because of longshore rif . Ho11eve r , accelerated shoreline erosion is ocourrina downdrift of 4 of t he j ettied cbaMel mouths (Fig. 1, inset D) , The earliest Jettl eti 11ere constructed at the Mississippi River mouths in the 1850s , Jettles built at Sabine Pass in 1920 are now 18 km long , The remainder • reconstructed between 1940 and 1975 (Table 1). Several of the et ies have been extended seaward si nee inl tial construct ion, reflect.­ DJ cbannel-deepenina ac tivities. The on.ly solitary j etty is found at be eaet end of Gr and Isle, where reduction in shoaling and trapping of and have been realized. The 700 m ( initially 300 min 1959) rapped one 11ill ion 111 of and ex. ended the shorelines 370 m ea11ard 11ithin 4 years of construction (Con.aster 1969) . This accreted and has subsequently served as convenient borrow materi al for local acb nourisnment and construction projects, notably following i.rricanes in 1965 and 1974 (USACK 1980). Over 61,5 km of and shoreline revetments are located in ouhiana, pri marily al ong Lake Pontcbartrian and East Timbalier ala_od. The first comprehensive protection system for the New Or l eans' lake.bore was not implemented until the 1920s ( Lewis 1976). At that , 8, 3 km I of land was reclaimed fro11 Lake Pontchartrain ( between l Rnd and Lakefront Airport--Fig. 3) and a 9. 2 km concrete as constructed to protect tnis "artificial" land. Levees totalling JS . 7 k11 in length , were built along the e ntire lake of Jeffe rson od Orleans Parishes. At the North Shore resort community of Man­ evllle, a 2. 5 bl conc rete seawall, w l th 31 groynes 60 m long and IP!cetl 77 111 apart, has been constructed ( deLawreal and Moses 1960 - - Fig, I, inset A). East Timbalier , a low- elevation over a major oil and gas field, has been heav ily modified by Mt Oil Corporation since 1966 (Anon 1982). revetments protect 1.6 kmo f the gulf shore , and a dyke of at least equal length alone the backshore area. On near by Timbalier Island, an experimental 100 • riprap y,evetment with 5 short groynes was cons truc t ed by t he TABLE l. STRUCTURAL DEVELOPMENTS ALONG THE LOOIS1ANA SBORELINE (tnct. Lake Pontchartrain)

Jetties Seawalls/Revecmenrs Grnznes[T-Groxnes Ve.,getat.ive Stabillzation 1850 Sout.hvest Pass, Pass a Lout re

1675 Eada j ett iea 1 South Pass 1900 SouthweeL Pass(im- pToved) 1910 1920 Sabine Pass N.O . Lakefront seawall {9. 2 ....) 1930 N.O. Levee/revetment (36.7 km) 1940 Belle Paas 11andevil.1 e Se.awali Calcasieu Fountainbleu (O.J km) Pas.s 1950 !iDpire-Gulf Grand Isle Waterway (14 gToynes) Grand [ale Grand Isle Barataria (l ~royne} Pass (Grand Isle) 1960 Cas- tine{Ma.n- devitle) Hiss1Bsipo1 Gr;,nd lsle RiveT"- Gulf Outlet East TimbalieT revet- ment {7.6 km)• Grand I.ale 1970 Belle Pass (enlarge- Peveto Beacb revetment Grand tale mertt) (4 .8 km) Cypremont Pt , Beach (0. 6 km) 1975 He.rmentau- Gulf Nav:lgation Timbal ier revetment Grand lsle' Channel (0.6 km) Fo unt.ai..Dbleu (0. 6 lal) Founcainbleu revetment f'ountainbleu 1980 Tl.mbalie.r {0.3 km) (0.2 km) ( I T-) East Timbal ier Grand Isle (in late Dernieres ( in progress) (5 T-Rroynes) progress) (12 b,) (1.8 Im) 1984 Grand Isle (ia progress) (12 km) TOTAL 10 jettl.,. 61. 5 km 2l g roynes/T-groynee

1 Cult f r ont age o n ly • 1 n con j unc t tan w1tl1 ea.,df 11 Jed 1,,r1~i:t r d tub~s 635

N t RED ~PASS PASS -TANTE RED PH/NE PASS -PASS TANTE PHINE

1958 0--===il Ml. 1974

, 2, Coastal marsh modiflcation due to initial canalization and hsequent land loss. The round canal netl(ork, near Venice, Louisiana, the surface expression of activities connected with the extraction or hydrocarbons from the peri me er of a subsurface salt dome. Most oil n 1as fields in coastal Louisiana are associated with salt diapirs ch penetrated through the sedimentary deposits and trapped large 1u ntities of hydrocarbons on their flanks (After Adams et al. 1976). 'EWORLEAN LAKEFRONT RECLAMATION

---·-•·••• pr1>- 1926 shoreline Sotuto. 1q~3 1;62500 USGS 1opographlc quiidt11ngle I Spi1nisb Fon. La.)

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1· 3, Ne" Orleans Lakefront reclamation. The expansion of New leans ioto Lake Pontchartrain entailed the reclamation of 8,3 km' of d fro11 the lake, the construction of a 9. 2 km long seawall, and t he Vation of the fill area to 3 m above sea level. Begun in 1927, it oom-pLeted with the construction of Lakefront Airport in 1934 (See ii 1976). 637

State Office of Public Works in 1975. Unfortunately, dolflldr i.t Leachu t Constance Beach, Cypremort Point, Cheniere Caminada, and the experienced accelerated erosion as a consequence. so;ore of Grand Isle. These modifications are primarily in the form A 4. 8 km stretch of highway, between Holly Beach and Cons t&nCf r. sher and concrete bulkheads and rubble ( concrete fragments, roc ks , Beach in southwest Louisiana, has been protected by a gobiblock met­ 'eo\ires etc, l placed along the shoreline. The success of these nt since 1970 (Dement 1977), but several sevel"e storms have retoved [ lk ' methods bas been mixed. The non-comprehensive nature of shore m~st of the revetment me.ts and undermined the highway. The State PWit \ ction in many of the water-edge communities has left a jagged, 0 reconstruct the revetment, testing a wide variety of revetment : e:ted shoreline I best exampled a long a part of Lake Pontchartrain's types , It is also c onsidering the constl"uction of 6 T-groynes al ong ,ttb Shore, this shore . Several other short experimental revet111ents were laid at fountainbleu State Park on Lake Pontchartrain in 1979 (Fig. l, inaet A); thus far, t hey have functioned satisfactol"ily (Moffatt and Nichol UFPCES 1981) . Apart from the groyne fields associated with the seal'all /revet· , R,D , and Baumann, R.H., 1980. Land building in coastal Louisi­ men ts, 21 groynes and T-groynes have been constructed in Louis iana ,i ~a: emerience of the Atchafalaya. delta. Louisiana State Univ., public or industrial money. In addition, hundreds of private pieru"~ ton Rouge, catwalks associated with recreational camps have been built, especlall

In be Lake Pontchartrain area. Three-quarters of the groynes 1 ,R.D, 1 Banas, P J., and Baumann, R.H. et al., 1978, Shoreline intended to trap longshore moving sand and minimize shoreline retreat, !.tMton in coastal Louisiana, inventory and assessment, Louisi ana are found on Grand Isle, a 12 km long barrier island that evo ved into s• t.t Univ,, Baton Rouge, the major coastal recreational beach community in Louisiana once It M connected to the mainland by highway in the 1930s (Pig. 1, inset C) , Saving a barrier island. Gulf Oil Corporation , Two groyne fields, one with 4 groynes near the western end and one Rouston. 10 groynes neat" the center of the island, were constructed in 1951 lUSACE 1972). One additional groyne was built by Humble Oil Co. in lrrae, J,V,, LeRoy, D.O., and Riley, C.M ., 1959. 'The c henier plain 1956. The groynes have not been successful, as dmmdrift erosion fon lts tratigraphy, Southwestern Loui sia.na, ' Transactions, Gulf the east side ) has left several camps standing in the , and C !Assn, of !. Societies 9, 237-260. hurricanes have intensified scour activity at t he base of the groynes and removed the sand between them ( US ACE 1980) • Also, 5 experimenta Cralg, J.J., Turner, R.IL and Day, J.W., Jr., 1979. 'Land loss in T-groynes were constructed by Gulf Oil Corporation on East Tillballer s\lll Louisi ana..' Proceedings , Third Coastal Marsh and Estuary Island in 1980 (Fig. l, inset E) . Mar.ymot Sruosium. Division of Continuing Education, Louisiana Small scale beach nourishment projects have been undertaken sinct He Universi ty, Baton Rouge. the 1940s, although stabilization by vegetation was not attempted unU, he last several years. Most of the nourishment has been conduced a! ter, lf.E ., 1969. The Grand Isle barrier island complex. Un­ Grand I le, especially following hurricanes (Table 1), At pr~e~ .ii,, Ph.D. Dissertation. Tulane Univ. 1 New Orleans, ( 1983), a S13 milli on Corps of Engineers dune construction/vegetative stabilization project is underway at Grand Isle the sand be ing dred ~l Vl& , 0.11,, 1973. Louisiana canals and their influence on we t land from offshore borrow areas ( USAGE 1980) . A sho;t ( 300 ml shoreline m:elop11ent , Ph.D. Thesis. Louisiana State Univ., Ba.ton Rouge. reach that was nourished a t Fountainbleu State Park in 1942 bas all bill eroded away . It has been proposed that J. 8 km of this ehore l' ne be -• 1983 . 'Economic and cultural consequences of land loss in nourished (USAGE 1976). Experimental Spartina plantings occupy a 60 1 ,uulsiana .' Shore and Beach 51, 4, 30-39, reach in the park's eastern portion and have successfully stabilized the ~res since i ntroducti on in 1979'. A 300 m experimental sa~­ _, 1986. 'The retreating .' Journal of Soil and Water fenc1ng/dune-building/vegetat i Ve-stabilization project was construtited ~ ervalion 41 3, 146-151. 0 ~ a Timbalier Island washover in 1980; it too bas so far been rela· tively successful. In Ve rmilion Bay, a. 600 m man-made beach tCypre Vil, O.\l', a.nd Detro, R,A,, 1980, 'New Orleans dra.in~ge and reclama­ Be~chJ was created with sand trucked in from a Mississippi River .ion a 200-year problem.' Zei scbrift Fur Geomorphologie Supple, -Bd 34 , P~rnt- in 1966, but erosion has narrowed the beach to only a few• w1de. 1 • s' In a dd 1· t 10n· to these largely public-sponsored projects, a to 8 1111 4;- 2 km of shoreline have been modified by private methods, mainl Y 8 ong the residential canals and shorelines of Lake Pontchartnan, bu' 63 639

Davis, D.'il'. and Place, J.L., 1983. The oil and gas industry of coasta U. S. Army Corps of Engineers (USACE), N,D, Mississippi: 1973 1 Louisiana and its effect on land use and socioeconomio patterns .. and . United States Army Corps of Engineers, Washington, United States Dept. of the Interior, U, S, Geological Survey, National D,C, Mapping Program, Washington, D.C. Open File Report 83-118. ~~~-' 1972. Grand Isle and vicinity: beach erosion hurricane Dement, Lawrence, 1977. 'Two new methods of erosion protection for protection. ew Orleans District, Review Report. -68 pp. Louisiana,' Shore and Beach 45, 1, 31-38 . ~~~-' 1976, Draft EIS, Lake Pontchartrain, north shore. New deLawreal and Moses, Inc., 1960. Seawall lake front development pro­ Orleans District. gram. Prep. for Town of Mandeville, July 21, 1960. unpub. 1980. Grand Isle and vicinity, Louisiana: beach erosion and Elliot, D. O. , 19 32. The improvement of the lower Mississippi River fo burrioane protection, New Orleans District. flood control and navigation. 3 vols . U.S. Waterways Experiment~ Station, Vicksburg, Ms . ~~~-' 1982a. Draft environmental impaet statement. Parish-wide forced drainage system, Terrebonne Parish, Louisiana. New Orleans, Frazier, D.E., 1967. 'Recent Deltaic Deposits of the Mississippi U. S. Army Corps of Engineers, New Orleans District. River.' Transactions, Gulf Coast Association of Geological Societies 17, 287-315. ~~~-' 1982b, Project maps. New Orleans District. 2 vols,

Gagliano, S.M., Meyer-Arendt, K. J. and Wicker, K,M , , 1981. 'Land loss van Beek, J.L. 8nd Meyer-Arendt, K.J., 1981. Sediment--asset or in the Mississippi River deltaic plain. ' Transactions, Gulf Coe,st liability, in Proceedings of the National Symposium on freshwater inflo Association of Geological Societies 31, 295-300. to , R,D, Cross and D. L, Williams eds., 2 1 197-215.

Gosselink, J.G., Cordes, C.L., and Parsons, J.W., 1979. An ecological Wagner, F, and Durabb, E,, 1976. ·The sinking city.' Environment 18, characterization study of the Chenier Plain Coastal Ecosystem of 32- 39. Louisiana and Texas. U.S. Fish and Wildlife Service, Office of Biological Services, Slidell. FWS/OBS-78/9-78/11. 3 vol. Wal ker, H.J., Coleman, J.M., Roberts, H,H., and Tye, R,S,, 1987. 'Wetland loss in Louis.iana.' Geografiska Annaler 69 (A) 1, 189-200, Howe, H.V., Russell, R.J., McGuirt, B.C. and Craft, B.C., 1935. Reports on the geology of Cameron and Vermilion Parishes. Louisiana Department of Conservation, Geol. Surv. Bull. 6.

Kazmann, R.G. and Johnson, D,B , , 1980. If the Old River~control structure fails? Louisiana Work-Resources Research Institute Bullletin 12, LSU, Baton Rouge.

Lewis, P,F,, 1976. New Orleans: the making of an urban landscape, Ballinger Publ. Co., Cambridge, Mass.

Moffatt and Nichol, Engineers, 1981. Low-cast shore protection1 U.S. Army Corps of Engineers, Wash. D.C.

Okey , C., 1914 · The Wetlands of southern Louisiana and their drain· age. U.S. Dept. of Agriculture, Washington, D.C., 652, 1-67.

Penland, S · and Boyd, R, , 1981. 'Shoreline changes on the Louisiana barrier coast.' Oceans '81, 209-219.

Samuel, R., 1959. . to a Uled Chef Menteur, , ,: the 1 _s_t_o~r-r-ac.0 .a.f---=.th::.e:=.....p1<.re..:o'!.pa::e=.crt..t~yL..!k!=n!:!:o~w~n~a~s~~~£L!..!e~a!!)nQJsLJE~a!Js~t~,r...... :!IUn~ol!.• New Orleans, La, I j Photo 1, Shore forms on the Louisiana coast. 640

Photo 2. Highway erosion on the Louisiana coast (1985),

Photo 3. Artificial levee along the Mississippi River in south Louisiana.