i._ 1....
Control Sfruclure 191430 ft of lelee ond reinforced concrele structure Structure: | 25 goted boys, opproximol ely ?8 tl between piers Alt Boys; 37.5 fr mst weir crest elevotion Floodwoy :., 5 miles in width' lined by guide levees Upper Guide Levee: l2 miles fiom Spillwoy to Eost Atchofoloyo River Levee Lower Guide Levee: l9 miles from Spillwoy to Eost Atchofoloyo ' Bosin Proteclion Levee l Bonnel Corre Soillwoy '.'': ti Locction: Mississippi R iver from 127.3 lo 128.7 AFXI : Design Copocity: 250'000 cfs Spillwoy Needle Controlled Overflow Dom al 350 Boys' 20 ft befween piers 176 Boys: l5 ft mst weir crest elevolion 174 Boys: l8 ft msl weil cresl elevofion Floodwoy i: Guide Levees from Mlssissippi Rlver fo Loke Pontchorlroin Widrh: 7700 ft ot River to 12'400 ft ot Loke Levees: 5.7 miles in length' l9 ft In height rj Bohemio Spillwoy
:: Locotion: Mississippi River f rom 45 f o 25 AHP ..t Copocily: Belween 104000 ond 290'000 cfs (depending on wind ond tide) Con?rol: Fuse Plug Levee to elevolions 6 to 9 ft msl, degroded by erosion durirrg r1 high woter l ll :.. l:
t,.l ll
:l
:_
, j
1, ll. Dcrcriptldt of th. Sttdy Aruo The Mississippi River Bosin is the fhird lorgest in the world, only the Amozon ond i t. Congo Rivers &oln o lcger oreo. Bounded fo lhe west by the Rocky Mountoirs ond fo
the Bosin encomposses I squore miles j. the eosl by the Appolochion Mounloins, t246rffrD of lond, or 4l% of lhe conliguous United Stotes ond porls of fwo Conodion provlnces.
I The Mississippi River begins in northern Mlnnesoto ord flows for 2430 miles before emptying Into the Gulf of Mexico. I During o mojor flood yeorr fhe nolume of woter dischcaed from fhe lower i Mississippi River is sufficienl lo cover lhe enlire slote of Louisiono to o dePlh of obout 26 feel. Unc€nfrolled, the Mississippi River represents o iremendous liobility lo
; inhobitonts of the qlluvlol volley os well os lo cornmerciol inlerests relying on lhe River for novigplion. Federol inlerest in flood domoge reduction begon in the olluviol
; votley during the l9th century. The Mississippi River C-ommission (MRC) wos crecied
by on Acl of Congress in June of 1879 when the need for o centrolized engineering I] orgonizotlon responsible for improving river novigolion ond flood conlrol wos
recognized. However, li wos nol trrtil ofter ihe dlsostrous flood of 1927 rhot Congress odopted o comprehensive plon for flood control through lhe possoge of the Flood
Control Act of Moy 1928.
In response to this oct ond subsequent omendments, the Mississippi River ond Tribuicries (MR&n project wos developed lo provide flood protection in lhe lower Mississippi River bosin. The ollwiol volley of fhe Mississippi River is o relotively flol ploin of obout 35,000 squore miles. The volley begins just below Cope Girordeou, Missouri ond extends lo Heod of Posses, Louisiono, irrluding porls of seven stotes!
Missouri, lllinois, Tennessee, Kenlucky, Arkonsos, Mississippl ond Louisiono. Within
this olluviol volley, fhe MR&T flood conlrol plon is designred to conlrol lhe'rproiecl
flood'. The project design flood wos developed by combining severe slorms of record l
thof hove occurred in the bosln ond ordering fhem in the time sequence likely to result i in ihe greotesl flood. This flood will resulf in o flow of obout 310001000 cfs ot Old l River, which is somewhot gredter ihon the flood of record, ond is used in the design of
flood conlrol wonks. About holf of fhls cnount is diverted to lhe Aichofoloyo bosin , i viq Old River ond the Morgonzo Flod,roy, ond onother 2501000 cfs is diverted ttuough t'- the Bonnet Corre Spillwoy to Loke Pcntchorioln, resulting in o project flood of i 112501000 cfs ol New Orleons, ond below.
I Th€ MR&T projecl includes t o voriefy of feotures, including levees olong the river moinslem ond tribulorles lo confine flood woters, reservoirs on the tributories lo I ,i. reduce peok flows, floodwoys lo dlvert exc€ss woter from the river, ond chonnel t' improvements, such os revelmenfs, dikes ond dredging, lo increose chonnel copocit),.
Within Louisiono, flood control meosures include levees, chonnel improvemenls ond l floodwoys. Mojor flood conlrol feotures of ond below Old River ore shown in Figure ll- t.
Levees
Withouf lwees, opproximotely 351000 squore miles in fhe ollwiol volley would be ,|.. flooded in lhe evenl of lhe project ftood. The moin stem levee system consists of 2203 :l miles of levees, floodwolls ond wrious control structures. Sorne 1607 miles of levees line the Mississippi River wifh onolher 596 miles of levee olong lhe south bonk of the
Arkonsos ond Red Rivers ond in the Alctofoloyo River bosin. The longest single le\re€ {- line in the MR&T project, ond probobly in the world, exfends from the high ground {. nec Pine Bluff, Arkomos clong the sotrih bonk of lhe Arkonsos River to ils mouth, ond conlinues down the Mississippi River to lerminus t ils in the vicinity of Venice, o distonce of more lhon 650 mlles.
; Chclnel lmprovurncnfr
: Siobillzotion ond protection of the river bonks serve flood control ond novigotion \ purposes. Revelmeni ond foreshore protection help prevent bonk erosion ond stop
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.l t'1 \I t, I{ I St I (r|{/ I l'- \ o \:. E I o F .l o Etr rt z al o 0a o @ i (J |/,t< 5l { e -tJ lrJ $s 1-' : =l 1".-,: t I I J I l' o t..
1. t_, I \ T I I \ Q\ Q $ \ s ;s i$ t E$ t\ s\ I Q $e- \ o s \ s i E €c \ 0 f o u ! - s river me€ndering, Below Bofon Rouge, obouf 134 miles of levee ore protected ogoinsf river wove wosh by limber slructures or levee slope povemenl. Dikes to direct flow, dredging lo reolign lhe ehonnel, ond o.tioffs lo shorlen the river ond reduce flood heighfs, ore olher elemenls of the chonnel improvement progrqm. ; Splllwoys
In Louisiono, fhe MR&T pro;eci includes fhree mojor supplementory flood outlets
designed to poss project flood woters from fhe Mississlppi River moin chonnel lnto lhe rl Gulf of Mexico. The Old River Canfrol Sfnrfureq locoted on the west bonk of the
Mississippi River ol mile 314 AHP, were built to prevent lhe coplure of the Mississippl
,t...1 River by the Atchofoloyo River ond lo conlrol fhe flow into the Afciofoloyo River ond
combined copocity the Low ond tt, Bosin. The of Sill Overbonk Conlrol Strucfures is 7001000 cfs during o project flood. The Low Sill Confrol Strucfure is o relnforced al a: concrete structure consisting of ll goted boys, eoch hoving o 44 ft width belween
piers. The fhree cenfer boys horre o weir crest elevotion of -5 ft msl for possing low flows. The other bop hove o weir cresl elevoiion of l0 fl msl. Generolly, the gqfes
of lhe Low Sill Control Slruclure remoin open to distribute low ond moderofe flows
from lhe Mississippi River into fhe Atchofoloyo River. The Overbonk Control
Sfructure is o reinforced concrefe structure consisting of 73 gcted boys, eoch with o
44 ft width belween piers. The weir crest elevotion for oll boys is 52 ft obove msl.
These goles ce normolly open to distribute flood flows belween the Misslsslppi ond Afchofoloyo Rivers.
The l{cAorzo Flodwq control structure is locofed on the wesl bonk of the Mississippi River opproximofely 35 miles norlhwest of Boton Rouge. The control
slructure is reinforced c'oncrefe with 125 goted concrete weirs, tied into guide levees
by cr eorlhen embonkment. The weirs ore eoch opproxlmotely 28 ft wide ond hove o cresl 37.5 I elevotion of ft msl. The Floodr'r,oy is desigrred to convey 6fi),000 cfs during 1... fhe project flood. The Morgonzo Spillwoy wos opened once since its completim in
1 i.. 1955, ond then only portiolly during the flood of 1973, when it c.onveyed o peok flow of I 142,000 cfs, a Woter diverted through the Old Rirrer Control ond Morgonzo Slructures posses
fhrough the Atchofoloyo Bosin Floodwoy, which is confined by the Eost ond Wesf Bosin
1 I, Protection Levees. lis upper port is comprised of the Atc-hofoloyo River chonnel, lhe :': West Atchofoloyo Floodwoy (which is controlled by o fuse plug levee ot its heod), ond lhe Morgonzo Flooduroy. These three segments merge io form o slngle flood ploin r below Butle LoRose, where o network of unleveed chonnels reploces the { moin river chonnel. The Wesf Atchofoloyo Floodwoy, which is designed to corr), floodwolers in
I excess of lhe combined copocity of the Mississippi ond Atchofoloyo Rivers ono
Morgonzo Floodnoy, hos o design capocity of 2501000 cfs ond is octivoted through I overtopping the West Atchofoloyo River levee. This floodwoy hds not been used since t'' its completio.r in l95Q ond ls eslimofed fo be needed on overoge of once e'tnery 100 yeors.
: The Borrret Ccre Splllwcy ls locoted neor lhe site of fhe old Bonnel Corre Crevosse, opproximofely 25 miles norfh of New Orleons. The diversion projecl l corsists of c reinforced concrete control struclure on the river bonk, guide levees belween lhe River ond Loke Ponlchorlroin, ond on ; overflow weir consisting of 350 individuof boys, eoch 20 ft wide. The weir crest ele\rotim for 176 of ihe boys is lg ft l'l t. msl, the remoining 174 boys hcve o weir crest elevotion of l5 ft msl. The spillwoy hos j o design copocity of 2501000 cfs, ond is operoled to prevent fhe river stoge on lhe corrollton goge from exceeding 20 ft. The spillwoy hos been operoled seven tlmes I since ils complefion in 1936, during the floods of lt3i, 1945, l9SO, 1973, 1975, 1979 t ond | 983. i The Bolprnio spillwoy is not o feoture of rhe MR&T proj ecl os ir wos built prior ll to lhe Flood control Act of Moy 15, 1928 ond no federol fund hove been used for
eilher constrr.etion or moir,tenonce of lhe spillwcp Although it is nol o port of fhe I
j federol project, the Corps of Engineers hos osserled thot lhe existence of the splllwoy
cnd lfs function during periods of higfrt woter were considered when the flood control I pfon for lhe Mississlppi River wos dewloped. The Splllwoy wos constructed in 1925-
1926 by degroding on ll mile section of the then existlng river ond bock levees ond l consiructing o side lewe to poss flood wolers from the Mississippi Rlver to Brelon l Sound. During the flood oI 1927, opproximofely 300'000 cfs were diverted from the
River. By 1950, siltotion in the Spillwoy hod decreosed its flood c-orrying ccpocily so t- improvements were undertoken in the mid 1950's to degrode the ridge lo increose flow
I through the Spillwoy. A fuse plug lewe wos consirtrted to reduce lhe freqr.ency ond : deloy the dole of overflow ond lhus limit sillotion' bul the levee wos designed lo erode t: owoy when overtopped. In lhis woy, the use of the Spillwoy is reserved fon periods of high woter. The currenl eslimoted corrying copocity of the Spillwoy during the i project flood is belween 108'000 ond 2901000 cfs' dependlng on wind ond tide
conditions. The Spillwoy hos conveyed o significont omount of woler from ?he I Mississippi River | 6 times since it wos cornpleledt during periods of high woler in t 1927, 1929, 1932, 1937, 1939, 1943, 1944, 194\ 1946, 1949, 1950, 1973, 1974, 1975,
1979 ond 1983. Asswning the most recent profile of the Bohemio Splllwoy, Mississippi t River woter is diverted inlo fhe Spillwoy whenever the Corrollton goge reoches or t exceeds o stoge of obout 15 feet. Bosed on this criticol river stoge, the Bohemio Spillwoy moy hove been inundoted ond conveyed River woter o tolol of 3l limes since t Its comoletion in 1926. i
I l
I
I l0 lll. Bdrernio Spillwoy - Hlsioriccl Pcrspcc'tive Creotion of the Bohemio Splllwoy wos outhorized by the Louislono Legislofure (Act 99 of 192Q. The Boord of Levee Commissioners of the Orleons Levee District
wos directed by legislotive oction lo reduce flood levels ond prolect the City of New
Orleors from high woter in the Mississippi River by creoting o spillwoy in Ploquemines ll Porish. The spillwoy wos lo be locoted on the eosl bonk of the river locofed ord
designed in occordonce wilh plons ord specificotions opproved by fhe Stote Boord of l Engineers ond the Mississippi River Commission. Becouse the spillwoy is under locol
I control, it is nof q feolure of the federol plon for flood control on ihe lower Mississippi ond its tributories, olthough ils funclion wos given corsiderotion in preporing the plons
for Mississippi River flood control under the Act of Moy 15, 1928. In o Mcy 13, 1935
letter frorn the New Orleors Dislrlct of the U.S. Army Corps of Engineers lo the I Mississippi River Commission, il ls stoted thot'Hod the relief oullet not existed at the
time, it is possible thof the plons (for flood control) would hove been differenl." Creotim of rtn Spilltrry
pr.rrc*rose t,,.1 The Orleors Levee Boord wos direcled to or expropricte ond poy for privotely owned property in the oreo of the proposed spillwoy. The slote, porish,
school, od volorem ond levee foxes hod proven io be o heovy burden for mony residenfs porficulorly tl in the oreo selecled for the spillwoy, where the bock levee lrod rot provided sufficient prolection frorn slorms from the seo. The residents hod ollowed
: much of ihe properfy to revert to the slote vio the tox sole route, olthough mony
redeemed their property when the Act of 1924 wos possed ond ihe slte of the Spillwoy t,...' fixed. Approximotely 48% of the 331000 ocr6 w(E purchosed from privote owners of
opproised foir mckel wlue. Less thon 3% of the lond hqd to be exproprioted. The
remoining 52% of the land wos deeded to the Orleons Levee Boord by the Stote of tl Louisiono.
ll tl The site selected for the Spillwoy included lqrd wiihin fhe botndories of the t. Grond Proirle Levee Dislrict ond Eost Bonk Levee Districl. The Orleons Levee Boord wos direcled lo ocquire ond concel fhe bonded ond unbonded indebtedness of lhe lwo l proportion lhe oreq offected by ihe Spillwoy ot June 17, 1924 1t' levee districts in to volues becouse these levee districts were unoble lo m6ef their obligotiors. In foct, the : :l Grond Proirie Levee Dislricl hod defoulted m lheir bon& lhe previous yeor. The i-l Orleors Lerr,ee Boord wos outhorized to rqise funds througfi on ornuol lery of loxes ond l :...1 olher revenues for property ocquisitlon ond construction cosls. ii ir The Orleors Levee Boord ocquired oll the lond between lhe lower line of the Bohemio Plontofion ond ihe Ostricc Lock for the Spillwoy. On Morch l0' 1925, ; opplicotion wos mode fo construcl the Pointe o lo Hoche Relief Outlet to relieve
f looding in New Orleqns. The permit wos isstred by ihe Secrelory of Wor on I Moy li 1925, bosed on fhe 30 April 1925 recommendotion of the Chief of Engineers. The l, Bohemio Spiltwoy wos construcied during the time period from November 1925 to April 19?6. The work corsisted of degrcding sn ll mile sect ion of the then existing
river levee from jusl below Bohernio 1o Boyou Lcnoque from obout 12 ft obove meon
1: seo level (msl) to 5-5 ft msl (or 25.5 Coiro Dotum). The lower bock levee wos ;! degnoded for opproximotely lhe some disionce to m elevalion of 24.0 Coiro Dqium. A li side levee wos olso clnstrucled olong lhe upper terminus of the Spillwoy. Actuol costs were opproximotely 57201000, of which over 60% were used for lond ocguisition.
Use crd ilolnrerse of thc Splll'rtay
The Spillwoy hos conveyed significont omounts of woter from the Mississippi i: River to Breton Sound 16 tim6 since il wc completed in 1926, 58 yeors ogo. In o 16 ,]i June 1950 letfer frorn the Corps of Engineers lo fhe President of the Orleons Levee Boord, the impdct of lhe Spillwoy is discussed: rl i. According lo the best records ovoiloble, it is irdicoled thof in excess of 300,000 cfs dlschorge wos cqrried by the Bo,tremio Spillwoy during the 1927 i: flood, the moximum flood of record md thot q flow of opproximotely 751000 cfs wos csrried by fhe Spillwoy in the 1950 flood. Bosed on stog€ records olong the Mississippi River ot ond below New Orleons it is estimoled lhol the diversion lhrough lhe Spillwoy in 1927 hod fhe effecl of lowering flood stoges obout 2 feef ot ond below Pointe-o-lo-Hoche ond q
t2 I decreosing omouni lpstreom to obout 0.5 fi. ot New Orleons. Similorly. during the 1950 flood il is estimoted thot the stoge lowering effects wei6 i obout 0.4 ff. ot ond below Poinie-o-lo-Hoche ond obout 0.1 ft. ot New Orleons. i' The decreose ln flow ond effecllveness irdicqted by comporison of the 1927 ond 1950 figures cited obove isp of corrrse, d-rc to fhe consideroble siltinq which hos occurred. Thot condition is noturol In diversion structures oi ;.. this kind which ore sublect to use ond consequenl silting wilh every high t woler ond which qre not mcintoined to origincl copocity by regulor mointenonce work.
I By 1950, il wos recognized thot periodic overflow info the Spillwoy hod resulted
in foreboy siltotlon which elevoted the generol bcrk level except for o number of wide
sholfow gullies fhrougfi which a mojor portion of the flow wqs cbnc€ntroted below
stoges of 9 ft msl. The nei result wos o diminished copocity to poss flood wolers ond
thus lower the river stoge. Alternolive corrective ociiors were discussed by the Corps
of Engineers, Misslssippi River Cornmission ond Orleons Levee Boord. i One option involved roising the Mississippi River levees below New Orleors to t,.: contqin lhe project flood necessor), to compensofe for totol closure of the Eohemio
Spillwoy. The Corpo of Engineers developed o cosl eslimote ossuming o levee grode which would hove provided freeboord over the new flood line equivolent i'l to thot i provided by the originol grode over the 1928 computed flood line. The estimote for
rolsing opproximotely I37 miles of levee in the Loke Borgne ond Borqtorio Levee l Disfricfs wos $3,763,000 to 561763,@0 (1951 dollcs) depending on wlrether rights of i: woy could be obloined or riverside enlargemehls i.-,1 or setbocks would be necessory. The Corps of Engineers outlined on olternole plon t'; of improvement in o lg ,i December l95l letler from the corpo of Engineers to lhe port Arorsos Institute of Mcrine Science: t. :.,.1 The generol plon for improvemenl is i-l msl lo increose the flow fhrough t,.: order to reduce moinlenonce by doie of overflow, o smoll levee will river bonk. The levee would vory in the- upslreom ord dowrslreom ends, respectively. The levee would tre i; designed to erode owoy when fhe woter flows over the toD. Recordi indicote thdt wster would hove exceeded lhe levee elevolion l0 times t.. L during the l9 yeor period, | 932 to 1950, inclusive. t.:
;: t3 :' The totol volume dischcrged Lnder presenl condifions ond the dischorge which would hove occurred lf lhe improvemenfs hod been in ploce for lhe il period 1940 to 1950, inclusive, ore given below:
Volume Acre-Ft Volume Acre-Fl Y eqr Present Condif ion lmproved Levee 8.5 to 7.5 Ft. 1940 negligible 0 l94l negligible 0 :: t942 negligible 0 1943 2,534,000 5,422,600 gl6,2oo I 1944 4, 9,306,400 t945 7 1447,400 25, 356, 800 1946 13 1 ,600 1,04t,000 1947 45,800 0 :-: t9t8 34,300 2,082,000 i,,: t949 846,600 12,298,000 t950 2,974,400 27,97Orfio :'l :'. 'i; ln o 25 July 1952 letter from Chcrles G. Holle, Chief Engineer of the Corps of Engineers, to lhe president of lhe Boqd of Levee Commissioners, the resulfs of lhe .]"1 Corpst invesligolion of the Spillwoyrs effecliveness ond recommended plon of 1.. . imorovement ore discussed: il t, Reslorolion ond moinlenonce of o reosonoble flow copocity in the spillwoy 1l is, lherefore, considered essentiol 'io moiniensrce of o moderoie flow line { in the lower river. The moximum flow copccity, which it is considered procticoble fo otloin ond mcinloin, is qpproximotely 2001000 c.f.s. which will reduce project flood sloges in lhe lower river obout 0.8 feet below 1950 flow lines. The most procticoble plon for effecting this copocify ..] corsisls of degroding lhe ollwiol deposits of lhe enlronce of the spillwoy to o uniformly sloping grode line wilh on elevotion of 4 6.0 feet m.s.l. ol l, th€ upper end ond -l 5.0 feet m.s.l. of fhe lower end. The oreq lo be i,.: degroded is colored in red oo the olloched mosoic. The work is nol continuous os indicofed on fhe mosoic. The unimprowd reoches hove been left to preclude developmenf of polenliol scour oreqs ond protect existing i: developments in fhe ores. In order to preclude o'rerflow ot lower sloges dtd fhereby reduce deposilion
I ond moinlenonce cosfs, it is believed desiroble lo retoin o low levee of smoll cross section olong the bonk. A grode vorying from +8 to +7 ot the upper ond lower ends, respeclively, is proposed. This will eliminote generol onerflow obout two yeors out of three ond will be overtopped generolly ot obout l7 feel on fhe Corrollfon goge. Periodic restorolion of fhe breoks in this levee will be less costly lhon removol of odditionol silt thol will be eliminoled by the exisfence of the levee.
t4 ! I
tlme period from Jonuory 1953 through November 1956, controcfs : During the I were let to degrode sections of lhe levee ond build fuse plug levees in lhe Bohemio period ; Spillwoy. Approximotely $388,311 were expendd during this time to increose Once Spillwoy wos completedt high I lhe copocity of the Bohemio Spillwoy. the work wqter in the Mississippi River did not require use of flood confrol devices (either the
: Bohernio or Bonnel Corre Spillwoys) for neorly 20 yeors, olthough domoge wos i.. sustoined during Hurricone Comille in 1969. High woter conditions in 1973 ollowed lhe
I possoge which eroded fuse plug In November onother t.., of woters the levees. of 1974r conlrocl wos let to reconstruci the fuse plug levee in the Spillwoy ol o cost of i-l t.: 52291912. The fuse plug levee wos designed to prevent sedimentotion in the Spillwoy I during periods of low flow so os lo mointdin lhe efficiency of the Spillwoy while 1.. ollowing erosion of the levee ond use of the Splllwoy when the river sloge ottoins the 1: t... desired height. lr Prwlqls Attcrnpts ol Clcrre J {.,..: House Bill 730 wos inlroduced by Represenlotive E. W. Grovolef, Jr. in 1950 to
close Bohernio Spillwoy I force fhe Orleons Levee Boord fo the by replocing the levees t_, which hod been degroded io form the Spillwoy. The purpose of ttre proposed bill wos {: t protect Spillwoy i,.. ostensibly to lhe oysfer induslry. The impoct of the on lhe oysler industry wos discussed os eorly os 1935, when Roberf S. Moestri of the Louisiono i'. i Conservollon Deporfment is quoled os soying:
!l Our oyster division, ofter moking on investigotion, sloles lhof it will be fo the inleresl of the oyster industry to hove fhe Boherni o Spillwoy closed, os {- hundreds of thousonds of borrels of oysfers in Ploquemines Porish ce l.' deslroyed b),, lhe exislence of this Spillwoy, which oppeors to be no longer of ony necessity.
{ { This oonclusion wos not shced by John H. Corruth, Mojor with the Corps of Engineers, who wrote on 3 Moy 1935 to ihe President of fhe Mississippi River L. Commission: t: i.. l5
1 Although the Federol Governmenl hos no direct inlerest in the Poinl o lo Hoche Relief Oullet, n preporing the generol plors for ocl of Moy 15, 1928. Hqd the re ossible thot fhe plons would hove nnot condrr with Mr. Moeslrirs suggeslion thof fhe relief ouflet is no longer necessory. The relief oullef funcliorB, os plonned by Stole Officiols, in lowering flood i sioges oi New Orleons ord below.
Boyou Lonoque (mile 33.2 AHP) wos closed with o brush dike in lfrt9-1940 to 1- prevent woler from the Mississippi River enlering Brefon Sound ot low wofer. The
{ dom wos flonked during 1943 high woter cnd the breoch enlorged in 1944. The Levee Eloord wos ordered lo repoir lhe structure in o 22 November 1944 le er from Colonel l George Hudson of lhe Corps of Engineers os reguired by condilion l0 of the permit.
An eorthen dorn wos consfructed ol Boyou Lcrnoque to impede flow in 1945-1946. i The levee between Boyou Lomoque ond Ostrico Conol wos domoged due to wove wosh,
1. ccving bcnks, etc. resulling in inundolion durirp periods of high wcfer ond o flow of o
consideroble omouni of fresh woter to oyster beds eost of the Spillwoy. The levee wos i. rebuilt c ordered by Legislofive Act 45 of 1946 ot equol cosl to the Orleons Levee Dislrict ond Grond Prqirie Le\€e District. This meosure wos designed to protect l oyster ond seofood resources os well qs the cotlle induslry in lhe oreo. This seclion of
; levee wos complefed by the end of 1947.
In 1948 ond 1949, represenfotives of the oysler ond fish indusfries requested : odditionol work be done to reslrict lhe flow of woter ond sllt from the Mississippi f-: River inio the Spillwoy through severol gops. As discussed in o 15 November l94g
letter from A. L. Willoz, Chief Engineer to the President of fhe Orleons Levee Boord:
: In the oreo between Cuselich Conol ond Nestor Conol lhere were severol boyous in lhe reor which were danmed off by the old reor levee. As lhe I woter fron lhe river flowed over the lond it built up o heod sufficienf fo ; top the reor levee, with the result thol the reor levee wos groduolly eroded owoy ond lhe old boyous reopened by the woler currents.
I ln the post fwenfy three yeors ihof this spillwoy hos been in operolion the Boyous hove been groduolly encrooching towords lhe river,'ond in iwo i" 1....
I 1.,.. t6 :-. ploces lhere se foirly lorge openings through whlch woler flows from the river to the reor boys during mosl of the yeor . . . These gops permil o lorge anounl of fresh woter ond silt to flow into the reor woters when lhe ll river goug€ ol Cqrrollion ottoins o height of six to eight feelr olthough the il generol oreo is not topped until the Corrollion gouge reods fifteen feet or more. Some portions require stoges on the Corrollfon gouge of eighteen feet or more fo be topped. . r..l ,': ln discusslng fhis motter with.lhe Orleors Levee Boord, Represenlotive Grovolel :,j of Ploquemines Porish wrof e in o I November | 948 letter:
... this possoge of woler ond sond in sr.ch greot omounts coused the destrucfion of milliors of borrels of oysters yeorly. Unless these'rgopd' ore closed, fhe oyster industry of this Seclion will be o thing of the post. ll is well fo nole fhot the ordinory flow of fhe Spillwoy ln no woy hurts the oysters . . . lf lhese I'gopst'ore closed, lhe greotesl problem of this section will be solved. :,I L.,.1 By September ol 1949, the Orleons Levee Boord hod c-onstrtrcted opproximoiely
2200 feet of levee ord revetment ocross the low sections lo olleviote comploints of
the seofood induslry. Even though thls remediol work wc completed, Representotive
Grovolef introduced House Bill 730 to the Legisloture in 1950 to close the Spillwoy by '] replocing the levee belween Cuselich Conol ond Boyou Lcnogue, ostensibly for protecfion of the oysler irdustry. However, Jcnes N. McConnell, Direclor of ihe
Division of Oy3ters ond Woler Bottoms of the Louisiono Deportment of Wildlife ond
Fisheries wrole lhe President of the Orleons Levee Boord on l6 June 1950: li . . . I wish lo moke it quite cleor thot our recornmendotion for the closing :-: of the Bohemio Spillwoy wos bcsed primorily on the foct thot Boyou i,: Lomoque would be opened ond would remoin open dt oll limes with its entronce to the River controlled so lhot erosion could not form on enlorged new poss through this ouflel. I lf Boyou Lomoque is nof opened, os stqted in my letter to Mr. Dugos, lhe closing of lhe Bohemio Spillwoy would be exceedingly detrimentol to the noturol reefs in thot oreq. i,j
However, Boyou Lornoque hod been ordered closed by the Corps of Engineers ll with the concurrqrce of the Mississippi River Commission. Colonel Chorles Holle, :-:
:l t7 Disfricf Engineer with the Corps of Engineers wrole the President of the Orleons
Levee Boord on l6 June 1950 sfotingr l
. . . the exlslence of the Spillwoy ond ils functioning during iime of high woter wos given considerollon in formuloling the generol plon for :.i Mississippi River f lood confrol mder the Act of Moy 15, 192& In considerolion of the cbove, from lhe viewpoint of flood conlrol, ihe ;l Spillwoy should not be closed ot this time. : t: Joseph P. Dovid, President of fhe Orleors Lerree Boord is quoled in o 17 June l | 950 orticle in the Times Picoyune newspoper os soying:
1, Severol yeors ogo, sfmrlly ofler I become president of the levee boord, Grovolet ond Perez ond sorne olher Ploquemines Porish officiols osked thal lhe levee boord fill in sorne gops in ttre spillwoy becouse woter wos i entering in lorge quonlities. They soid it wos endongering the oyster beds. I went down there ond mode on irspection ond five gops were filled . .. Filling these gops noturolly slowed ihe flow of water. At times lhere wos I no flow at oll. Represenfotive Grorolef wrole to me lhol he wos sciisfied the problems were solved - Gravolet's tune is differenf now since the oil leoses were mode . . . Before we mode oil leoses on lhe lond, they werentt very much inleresled. Whot wonder is, t I whether lhey're interesied in oyslers os much os lhev ore in oil?
L The bill wos defeoted, only to be introduced in similor form in 1952, o yeor in
which oil ond gc royolties rose fo 57 64,592 from Sl37,9Ol in 1951. House Bill 594 t would hove required closure of fhe Spillwoy, principolly for protection of the oyster
industry. However, the posilion of the Direcior of fhe Division of Oysfers ond Woter
Botfoms, Louisisn Deporimenf of Wildlife ond Fisheries wos discussed in o l0 June
| 952 letter fo fhe Orleors Levee Bocrd:
You hove osked my opinion os to whot effect the complete closing of the Bohemio Spillwoy would hove on fhe oysiers in lhof seclion.
For your informotion, let me siote thof our posilion hos olwoys been thot the closing of the Eohemio Spillwoy would be highly detrimental to the d.evelgprnenf of lhe noturol oysfer reefs in thol oreo unless Boyou LoMoque should be opened. lt is essenfiol for fhe propogotion of oysfers in this oieo thot o lorge omotni of fresh woier be obioined from the Mississippi River. This opinion of mine hos been concurred in by our former blologists, fhe lote Dr. Jomes Nelson Gowonloctr, ond Dr. H. Molcolm Owen, ond olso by our presenf biologisi, Mr. Lester Wollers.
t8 A l9 June 1952 ediforiol in the Times Picoyune opposed closing of the Splllwoy:
i: This spillwoy, 60 miles downstreom from New Orleons, is the oldest flood control oid of ils kind in the lower Misslssippi Volley. lr wos cut in 1925, '': ond ifs effecl in lowerlng fhe river level wos o foctor ln the plonning of the Bonnel Corre spillwo)., upstreom from New Orleons, lhree yeors loler. . . r'l
No ser ious _obj ecl ion to-use.of the splllwoy wos mode unlil comporotively recently. Then, the. objecfions followed discorrery of oil in fhe spillwoy right-of-woy. Royolti€s from this oil qe now o substonliol pot of ihi: levee boords receipfs.
In olher words, for more thon 20 yeors nobody seemed to object seriorsty to fhe Orleons Levee Boord owning the spillwoy ond using i..: it, buf oft€r oil wos forxrd ol Bohemio fhe boord wos sued io lest ifs title to the spillwoy lond ond cries for the closing of lhe spillwoy becqne loud qnd frequent. i ld remoin open. First, Bohemio spiltwoy still t urd conrinue # :t:flffi rl!*"*J purpose for which it wos bought. To do olherwise might"ff lend comfort fo inlerests seeking lo foke from the boord i its rololties on oil produced in the spi llwoy. tl This bill wos defeoted by the Louisiono Legislcture. L$etrecn lrnpcfs of Crevcses i t,, As o result of flood control efforls olong the Mississippi River, fhe number of
Il crevosses were reduced from 284 during fhe flood of 1882 to 13 during the flood of I 1927. ln o 1928 study of flods in the Lower Mississippi Volley by the U.S. Weorher { Bureou, it is stoled: t ii Any crevosse below Old River chonges the grnge relotionships moteriolly. { d-epending on the locolion of the crevqsse os relqted to the goging stqtions. The splllwoy effect is shown on the Ccrrollton goge df New Orleons in the curve ot 2l ft coused by the Poydros crevosse in 1922 ond Coernorvon : spillwoy in 1927. Chonges of I foof or more show qr the qoq€. t, Ccrrollton rising when fresh eost to southeost winds prevoil for o few doys ond fo-ttinj when northwest to north winG prevoil.
i ...1 The Corps of Engineers hqs evoluoted the impoct of crevosses on stoge in lhe l Mississippi River. In 1922, o nofurol crevosse wos creoled on the eost bonk of the
l9 ',
1: River ol Poydros (River Mite 82 Al-.P). The colculcfed impoct on river stoge is sfpwn below:
1l lmpoct of 1922 Poydros Crevosse al On River Stoge :: Locofion Relotive Stoge Locotion River Mile To Crevosse Lowerinq t_: Forl Joc{ wos fowered on eslimoted 2.7 ft ot New Orleors os o result of this crevosse.
The Coernorvon crevosse wos creoled in 1927 os ordered by the Governor of t Louisiono to reduce the height of the impending flood in ihe Mississippi River, I porticulcrly in the New Orleors oreo. A secfion of the levee wos rernoved by
dynomifing ot o sile 22 miles downstrean frorn the corrollton goge. The purpose of I lhe crevosse wos to dinert 240,000 cfs lo effecl o locol lowering of 3 ft, which would resuft in lowering of upsfreom I flood stoge olong lhe New orleors woterfront by ? to 2.5 I t.-. ft. fn o 5 Moy |.927 orticle in Engineering News-Record the preliminory indicotions of !, fhe impocf of breoching the levee below New Orleons ore discussed: l,
The river hos been slofionory ot the Corrollton goge since lhe work wcs I begun, but os oll upstrecn goges os for os Vicksburg ihow rises it is certoin fhot fhe dischorge ot Corrollton is being groduolly increosed without i' corresponding increose to stoge. The Coernorvon crevosse is now. Sundoy a forenoon, obouf 800 ft. wide ond is scouring ropidly. The results bbtoinei lhus for ore exoclly cs desired. The Corroilton goge reods 20.9 ond lfnrough preporotion hos been mode in New Orfeons lJprovide for hioher il sloges. Forecosts of the Weother Bureou ore the i,rtilt 1..: to effect thot levees be onertopped ot procficolly oll stotiors on the lower river if ihe levees hofd. The forecosl for Corrollton is for o moximum .-.: sioge ol 24 ft. ond it is :: the expeciofion ond infenfion to moke the Coernorvon crevosse of such copocity os io hold fhe Corrollton goge below 22 ft.
The botlure in front of lhe crevosse is being progressively eroded ond will L.:, doubtless be scoured down lo or below fhe surioce elevofion of ihe oround
:l 20 ;i a: :.: ii bock of the levee. No difficulty is expecied in moking the crevosse toke i,,. lhe required qnount of woter os it con be given ony required length. The qoge reodings for Moy I ot 7 o.m., jusf received, ore: Vicksburg' 57.Q up i-: 0.6 ft.; Boton Rouge, 45.8, up 0.4 ft.; Ploquemlnes, 4l.l' up 0.3 ft.; ii Donoldsonville, 35.9, up 0.2 ft.; ond Corrolllonr 20.7, down 0.1 ft.r showing results expecled ond desired. The river is rising of lhe severol stoiions obove Corollton while o f olt of 0.1 ft. is recorded ot Csrollton.
I
1..... The combined impoct of fhe Coernsvon crevosse ond Bohemio Spillwoy wos
r esfimoted by the Stote of Boord of Engineers lo hove lowered river sloge by 3.2 ft of Ccrrollton (59 mites obove fhe Bohemiq Spillwoyr 2l miles obow the Crevosse) ond 1.3 ::ll ft ot Donoldsonville (l3l mlles obove the Spillwoy ond 93 miles obove the Crevosse). r-i Inpocfr of SPll lvrqr i.l Up.trc impoct the Poydros ond Coernorron Crevosses ond Bohernio Spillwoy hove hod on river 1r stoge in ihe New Orleons oreo. This phenomenon occurs becouse lhe diversion of t: woter results in o lowering of river stoge ot thot point. This locol lowering of river tl stoge resulls in o steepening of the hydroulic grodienl or woter level surfoce in lhe riwr, which couses on increose in the velocily of woter corried in fhe moin river !i chonnel. As o result, flood woters ore corried into the Gulf more quickly, ond flood
': stog€s de reduced. I The Bohemio Spillwoy is not o federol projectr so the Corps of Engineers does not
,1 regulorly monitor its operotion. However, fhe Bonnet Corre Spillwoy is operoted ond r,. l mointoined by the Corps, so o comprehensive dofo bose is ovoiloble' ln order to
demonstrote the upstreom effecl of spillwoy operotiors, the impoct of flow diversion
ot the Bonnet Corre Spillwoy on river stoge ot Donoldsonville hos been exomined. The il Donaldsonville goge is roughly fhe some distonce from lhe Bonnef Corre Spillwoy os the Corrollton goge is from lhe Bohemio Spillwoy.
: 2l I
I Over the post 15 yeors, the Bonnef Corre spillwoy hos been opened four times os
a result of high woters in the Mississippi River. During 1973 flood, both the Morgonzo t" ond Bonnet core spillwoys were open rc on independent onolysis of the impoct of the
Bonnef corre spillwoy operotion ot Donoldsonville is not possible. The 1975 flood wos I relcfively smoll, so the pqrtiol opening of the Bonnet ccrre spillwoy did not produce o
I drornolic chonge in river sloge.
During the 1979 ond 1983 floods, however, the Bonnet Corre Spillwoy diverted o i substontiol cnount of woter from the Mississippi River. The estoblished relotionship f, belween Donoldsonville ond Bofon Rouge River stoges is sfnwn in Figures lll-l ond lll- 2. The solid line on these figures shows lhe meqsured river sfoge during these flood l : periods. The doshed line provides on indicotion of whol fhe river stoge would hove beenr hod the Bonnef corre spillwoy remoined closed. In bolh coses o drop in sloge ol t: Donoldsonville is observed for the sorne stcge ct Boton Rouge ofter opening of the Bonnet corre spillwoy. As seen, L con be operorion of the Bonnef corre spillwoy resulied in o reducfion in river sloge of Donoldsonville on lhe order of 0.5 to 1.0 ft. f, i, l t f !l l i l''
?2 i I STAGE RELATIONSHIP BETWEEN OONALDSOT,IVILLE AND BATON ROUGE I t DURING 1979 FLOOD
t.
l
I
i
I
I F t., l! t; J J z o,n i: o J 29 z. ;l o l-l F za lrJ :l .' t.. F an
f: OBSERVEO STAGE RELATION i...,:
PRO.'ECTION OF STAGE IF BONNET CARRE SPILLWAY HAO NOT BEEN i, OPENED, il i...,: 36 f-i 37 38 39 i: STAGE AT EATON ROUGE, FT,
:-'': t: li ,. FIGURE EI.I 2t t STAGE RELATIOI.ISHIP BETWEEl,,I DOI'IALDSONVILLE AND BATON ROUGE |, DURII{G 1983 FLOOD
I
I
Il
I i: ll ",l,Oft, F E i. Ulr ) z; i o (,1, 6 J t: I lV. MarlErnoticol }lodeling of fhc Misslscippi Rivtr
I The prlncipol objec-tive of thls project wcs to quonlify the impoct of the Botremio
I Spillwoy on woter surfoce elevotions in the Mississippi River ol New Orleons. To ochiwe thls objectlw, URS utillzed the computer progrom HEC-2 os o computolionol
I oid lo prepore profiles of lhe water surfcce of the River from Venice to fhe Bonnet Corre Spillwoy. The HEC-2 program wos developed by the Hydrologic Englneering I Cenfer of the U.S. Army Corps of Engineers ond is intended for colculoling woler I surfoce profiles for sleody grduolly voried flow in nolurol or mon-mode ctronnels. The compulotionol procedure is bosed on the solulion of lhe on*dimensionol energy l. equofion wifh energy loss due lo friction evolrrcted with Monning's equotion. This mothemoticol model wos used to predicl woter surfoce elevolions ol specified t locotions olong lhe River mder o voriety of circumslonces dewloped to represent il vorious flood conditions, tidol influences ond corresponding spillwoy dischorges. Comprtof imol Pltccdrre ll The HEC-2 progron, ufilizing o computdtionol procedure generolly known os the
Slondqrd Step Method, colculqtes unknown woter surfoce elevolions ot defined cross : secliors by iterotive solulion of the energy equofion. The precise computotionol r procedure used by the progran to colculote o volue for lhe woter surfoce elevoiion ot o cross seclion is os follows;
I l. A water surfoce elevotion is ossumed ot the upstreom cross seclion.
2. Bosed on fhis ossumed wlue, lhe lotol conveyonce ond raelocity heod ore rl defermined.
I Using these volues for conveyonce ord rlelocify heod, the friction slope ond the energy heod loss ore computed. i, With these computed volues lhe energy eq;otion is solved for lhe upslreom woler surfoce elevolion. i
l l
I
; 5. The compufed volue is compored with the ossurmed wlr.re ond the
computotionol procedure is repeoted until the volues ogree fo wilhln 0.01 I ,, ft. i, lnnrf ho Reqrircrncr r The HEC-2 progrom requires o minimum ornounf of inpuf doto to perform rouline l' progrdn executions to compute wqfer surfoce profiles. The bosic input doto must specif y lhe following: flow regime, slcling elewtion, dischorge, loss coeff icients,
I cross secfion geomefry ond reoch lengfhs. For oll progrom opplicotions r.red in this project, o st-bcrilicol flo* regimc wos specified dse lo the river cross sectiqls, i. velocities ond projecled wofer depths ossocialed with fhe modeled dischorges. For l, profile comgrtotiqs performed in o sr.bcriticol flow regime, fhe progrom begi rs computotion ot the downsfreom end of the proflle (i.e., ot Venice) qvC proceeds
i, upstreom towords New Orleons.
The roting curw ot Venice wos voried lo reflecf ttre differeni condifions of tide I. ond wind which offecf woter levels in the River. For lhe proiect flowline, the roting ll curve shown in Figure lV-l wos lred to obtoin slorling woler surfoce elevolions represenlotive of the Rlver dischorge ol Venice. The curve wc developed by monuolly ll compuling bockwoter elevotions olong Southwest Poss from the Gulf of Mexico to Venice ossuming an elevotion ot the Gulf of 0.0 ff. Cross sectionol informolion of :. represenlolive reoches wqs obtqined from ihe Hydroorophic Survey of the Mississippi ,. Ej5!: prepored by lhe U.S. Army Corps of Engineers tor 1973 through 1975. '1 Bockwoler elevotions were compuied for 5 seporote reoch lengths from lhe Gulf of 1; Mexico to Venice in fhe preporolion of the roling curve which correlotes dischorge with obcolute Ri\rcr stoge ol Venice (i.e., the wofer le\rels witfput \@riofions in tide
ond wind), .i :: The disctrcgEs used in the str.dy included both recorded historicol flows ond the
project flood developed the a:irl by U.5. Army Corps of Engineers. Historicol flows were
i, zo ()lr, z vo ut -oo 9
F tll u.l ^9 xzlri G = :f P o 4 - o Jo z O|! F o E
q q ID c r33J - 33rN3A rv lovls
FIGURE IV.I 27 I
selected os described further below, lo reflecl conditions ronging from low lo high l dischorge.
t, Three distinct lcs cocfflcients musl be specified in the inpul doto for oll
progrcn opplicotions. Conlrocfion ond exporsion coefficienfs were selecled os 0.1 ond i 0.3, respeclively, whic*r oe generolly occepted os oppropriote volues for groduol lronsiiiors between cross sectlons. Represeniolive Monning's n coefficienls for I modeled reoches were delermined ftroqh the collbrotion procedure described below.
I Surveyed dofo describing lenglhs ond cross seclion gEometr), for the River were
obtoined from lhe New Orleors Dislrict of the U.S. Army Corps of Engineers in o f: formot compolible with the FEC-Z progran. The cross sectionol chorocieristics of f. the River ore described ot opproximotely lwo mile intervols fhroughout the reoch from Bonnef Corre to Venice. The enfire set of cross secliorrcl doto wos used in oll progrom i. opplicotions olthough odditionol interpoloted cross sections were included in the computotiors so thot obrupl chonges in the velocily heod could be minimized ond the t oszumplion of grodwlly voried flow preserved. l Progrcn Limitotiong The HEC-2 progrom represenls stote-of-fhe-ori technology for predicling woter tl surfoce profiles in open chonnels. The progrom is bosed on stondord hydroulic principles ond therefore, o number of ossrmpficrs ce implicit in lhe onol)'ticol :: expressiors used in the progrom. These ossumptions ore trs follows:
| Flow is I . steody 1,..i 2. Flow is groduolly voried :i 3. Flow is one'dimersionol (i.e., velocity components other ihon in the direction of flow ore not occounfed for)
River chonnels hove smoll slopes (i.e., less l._i 4. thon l:10) Flow is ossumed lo be steody becouse iime dependent terms ore not included in t; the energy equotion. Flow is osswned fo be groduolly voried becouse lhe energy
28 l'l I
I equotion is bosed on lhe premlse thot o hydrostotic pressure distribution exisls ot eoch cross seclion. Flow is ossumed to be on+dimersionol becouse the conveyonce I equotion is bosed oo the premise thot the lotql energy heod is the ssne for oll points
in o cross secfion. Smoll chonnel slopes ore ossumed becouse the pressure heodr which L is o componenl in the energy equotion, is represented by the wI obserrrcd dischorge ore inpul info the progrom so fhol representolive Monningrs n
volues ore compuled for these conditions. A second option wos used lo predici the t' dischcge over fhe Bohernio Spillwoy ol periods of high flow. This option requires o descrlption of the spillwoy in lerms of reoch lenglhs ord corresponding ground I elevotiors to predict o weir-type dischcrge olong the spillwoy reoch. t: Modcl Cclibrction Prior to conducting on onolysis of the impo.cts of the Bohemio Spillwoy on River I levels ot New Orleors, URS colibrofed the HEC-Z model fo ossure thot the computed i woter surfoce profiles occurolely represent observed profiles within lhe reoch from Bonnet Corre to Venice. The colibrotian process involves the selection of Monningls n I 29 I I I
volrrs whic$ provide o meosure of the chonnel ond over bonk roughness. The objeclive i of this process is lo specify n volues which correspond to the friclion losses ossocloted
I wlth wrious flows ond wofer surfoce elevolions. The resutt of o successful collbrotim
is fhe specificotion of n volues which occurolely represent the ror.ghness of ony reoch li for ony given sloge. Collbrotion of the HEC-Z progqm for this opplicction wos o four step process I whlch wos conducted for vorlous flows ond corresponding River stoges. The first step tl in the colibroiion process involved the selectlon of R irrer flows ond correspording downstrecn sloges for sleody stcte conditions. Criterio for selecling steody stote l' conditiors were defined os o prolonged period (5 lo l0 doys) of sleody flow (within 5% vorionce), stoble river stoge (wifhin 0.3 ft vorionce) fhroughout the reoch ond :, groduolly voryirg flow (neither ropidly rising nor folling sloge). Eleven yeors of i: dischorge ond stoge doto' from 1973 to 1983r were reviewed for steody slofe conditiors to describe Rirrer condiliors under o wide ronge of circumstonces. After
I] comprehensive doto onolysis, four historicol periods of sleody slote flow ond stoge
were selecled for use in fhe colibrotisr proc€ss. These ce shown os fhe observed I. profiles plotted in Plote l. The profiles were developed by ploffirg the ronge of I sloge volues for eoch goge stofion olong the reoch from New Orleons to Venice. Stroighi lines were fitted from gcAe stotion to goge stotion ond sloge volues for t, . inlermediote locotions were obtoined from the plotted lines.
The next slep in the colibrotion process w
