Copyright 2001 Scientific American, Inc. · 78 SCIENTIFIC AMERICAN OCTOBER 2001 Overview/Why Save a...

Copyright 2001 Scientific American, Inc.Copyright 2001 Scientific American, Inc.Copyright 2001 Scientific American, Inc.Copyright 2001 Scientific American, Inc.

Copyright 2001 Scientific American, Inc.Copyright 2001 Scientific American, Inc.

THE BOXES are stacked eight feet highand line the walls of the large, windowlessroom. Inside them are new body bags,10,000 in all. If a big, slow-moving hur-ricane crossed the Gulf of Mexico on theright track, it would drive a sea surge thatwould drown New Orleans under 20 feetof water. “As the water recedes,” saysWalter Maestri, a local emergency man-agement director, “we expect to find a lotof dead bodies.”

New Orleans is a disaster waiting tohappen. The city lies below sea level, ina bowl bordered by levees that fend offLake Pontchartrain to the north and theMississippi River to the south and west.And because of a damning confluence offactors, the city is sinking further, puttingit at increasing flood risk after even minorstorms. The low-lying Mississippi Delta,

which buffers the city from the gulf, isalso rapidly disappearing. A year fromnow another 25 to 30 square miles ofdelta marsh—an area the size of Man-hattan—will have vanished. An acre dis-appears every 24 minutes. Each loss givesa storm surge a clearer path to wash overthe delta and pour into the bowl, trap-ping one million people inside and an-other million in surrounding communi-ties. Extensive evacuation would be im-possible because the surging water wouldcut off the few escape routes. Scientists atLouisiana State University (L.S.U.), whohave modeled hundreds of possible stormtracks on advanced computers, predictthat more than 100,000 people could die.

The body bags wouldn’t go very far.A direct hit is inevitable. Large hurri-

canes come close every year. In 1965 Hur-ricane Betsy put parts of the city undereight feet of water. In 1992 monstrousHurricane Andrew missed the city by only100 miles. In 1998 Hurricane Georgesveered east at the last moment but stillcaused billions of dollars of damage. Atfault are natural processes that have beenartificially accelerated by human tinker-ing—levying rivers, draining wetlands,dredging channels and cutting canalsthrough marshes [see map on pages 80 and81]. Ironically, scientists and engineers saythe only hope is more manipulation, al-though they don’t necessarily agree onwhich proposed projects to pursue. With-out intervention, experts at L.S.U. warn,the protective delta will be gone by 2090.

The sunken city would sit directly on thesea—at best a troubled Venice, at worst amodern-day Atlantis.

As if the risk to human lives weren’tenough, the potential drowning of NewOrleans has serious economic and envi-ronmental consequences as well. Louisi-ana’s coast produces one third of thecountry’s seafood, one fifth of its oil andone quarter of its natural gas. It harbors40 percent of the nation’s coastal wet-lands and provides wintering grounds for70 percent of its migratory waterfowl. Fa-cilities on the Mississippi River from NewOrleans to Baton Rouge constitute thenation’s largest port. And the delta fuelsa unique element of America’s psyche; it

is the wellspring of jazz and blues, thesource of everything Cajun and Creole,and the home of Mardi Gras. Thus far,however, Washington has turned downappeals for substantial aid.

Fixing the delta would serve as a valu-able test case for the country and theworld. Coastal marshes are disappearingalong the eastern seaboard, the other GulfCoast states, San Francisco Bay and theColumbia River estuary for many of thesame reasons besetting Louisiana. Parts ofHouston are sinking faster than New Or-leans. Major deltas around the globe—

from the Orinoco in Venezuela, to the Nilein Egypt, to the Mekong in Vietnam—arein the same delicate state today that theMississippi Delta was in 100 to 200 yearsago. Lessons from New Orleans couldhelp establish guidelines for safer devel-

opment in these areas, and the state couldexport restoration technology worldwide.In Europe, the Rhine, Rhône and Podeltas are losing land. And if sea level ris-es substantially because of global warm-ing in the next 100 years or so, numerouslow-lying coastal cities such as New Yorkwould need to take protective measuressimilar to those proposed for Louisiana.

Seeing Is BelievingSHEA PENLAND is among those bestsuited to explain the delta’s blues. Nowa geologist at the University of New Or-leans, he spent 16 years at L.S.U.; doescontract work for the U.S. Army Corps ofEngineers, which builds the levees; sits onfederal and state working groups imple-menting coastal restoration projects; andconsults for the oil and gas industry. Hisgreatest credential, however, is that heknows the local folk in every little bayoutown, clump of swamp and spit of marshup and down the disintegrating coast—the people who experience its degrada-tion every day.

Penland, dressed in jeans and a poloshirt on a mid-May morning, is eager toget me into his worn red Ford F150 pick-up truck so we can explore what’s eatingthe 50 miles of wet landscape south of

Every 24 minutes Louisiana loses one acre of land.

78 S C I E N T I F I C A M E R I C A N O C T O B E R 2 0 0 1

Overview/Why Save a Sinking City?� The New Orleans area is home to more than two million people, and it fuels a

unique part of America’s national psyche.� The Mississippi Delta is the poster child for problems threatening the world’s

deltas, coastal wetlands and cities on the sea.� Southern Louisiana produces one third of the country’s seafood, one fifth of its oil

and one quarter of its natural gas.� The state’s coastline harbors 40 percent of the nation’s coastal wetlands and

provides wintering grounds for 70 percent of its migratory waterfowl.� Facilities along the Mississippi River from New Orleans to Baton Rouge constitute

the nation’s largest port.

Copyright 2001 Scientific American, Inc.

w w w . s c i a m . c o m S C I E N T I F I C A M E R I C A N 79

New Orleans. The Mississippi River builtthe delta plain that forms southeasternLouisiana over centuries by depositingvast quantities of sediment every yearduring spring floods. Although the dryingsands and silts would compress undertheir own weight and sink some, the nextflood would rebuild them. Since 1879,however, the Corps of Engineers, at Con-gress’s behest, has progressively lined theriver with levees to prevent floods fromdamaging towns and industry. The riveris now shackled from northern Louisianato the gulf, cutting off the sediment sup-ply. As a result, the plain just subsides be-low the encroaching ocean. As the wet-lands vanish, so does New Orleans’s pro-tection from the sea. A hurricane’s stormsurge can reach heights of more than 20feet, but every four miles of marsh canabsorb enough water to knock it downby one foot.

The flat marsh right outside New Or-leans is still a vibrant sponge, an everchanging mix of shallow freshwater,green marsh grasses and cypress swamphung with Spanish moss. But as Penlandand I reach the halfway point en route tothe gulf, the sponge becomes seriouslytorn and waterlogged. Isolated roads onraised stone beds pass rusted trailerhomes and former brothels along nowflooded bayous; stands of naked, deadtrees; and browned grasses and reaches ofempty water.

Down in Port Fourchon, where thetattered marsh finally gives way to opengulf, the subsidence and erosion are ag-gressive. The lone road exists only to ser-vice a collection of desolate corrugatedbuildings where oil and natural-gas pipe-lines converge from hundreds of offshorewellheads. Countless platforms form agloomy steel forest rising from the sea.To bring in the goods, the fossil fuelcompanies have dredged hundreds ofmiles of navigation channels and pipelinecanals throughout the coastal and interi-or marshes. Each cut removes land, andboat traffic and tides steadily erode thebanks. The average U.S. beach erodesabout two feet a year, Penland says, butPort Fourchon loses 40 to 50 feet ayear—the fastest rate in the country. Thenetwork of canals also gives saltwater

easy access to interior marshes, raisingtheir salinity and killing the grasses andbottomwood forests from the roots up.No vegetation is left to prevent wind andwater from wearing the marshes away.In a study funded by the oil and gas in-dustry, Penland documented that the in-dustry has caused one third of the delta’sland loss.

Alligator ScienceTHE DUET BROTHERS know first-hand how various factors accelerate landloss beyond natural subsidence. Tobyand Danny, two of Penland’s local palsalong our route, live on a 50-foot beigebarge complex anchored in the middle of15 square miles of broken marsh, some20 miles northwest of Port Fourchon.

CYPRESS SWAMPS south of New Orleans die from the roots up as saltwater intrudes. The swampsthen erode, allowing the gulf waters to advance even farther inland.


Human beings have dramatically increased the rate of land loss in

southeastern Louisiana—and made themselves more vulnerable to

hurricanes—by restricting certain natural processes and accelerating the

delta’s natural subsidence. Even now, vast portions of the region lie only a

few feet above sea level, and another 60 acres disappear every day. At this

rate, New Orleans will be exposed to the open sea by 2090.

SOUTHEASTERN LOUISIANA is a valuable testcase for disappearing coastal wetlandsaround the world.

SOUTHEASTERNLOUISIANA

2600 B.C. TO1600 B.C.

1900 B.C.TO 700 B.C.

inhibit the river’s natural ability to sustain marshes with sediment andfreshwater during spring floods. Withoutthis supply, marshes subside and erode,and ocean water moves inland. Thisintrusion raises the salinity of marshwaters, killing trees and grasses thatwould otherwise prevent erosion.SOLUTION: REBUILD MARSHESCut one or more channels through the riverlevee on its south side and build controlgates that would allow freshwater andsediment to exit and wash down throughselect marshes toward the Gulf of Mexico.


LEVEES

LAKE PONTCHARTRAIN

NEW ORLEANS

ISLES DERNIERESAND SHIP SHOAL

MISSISSIPPI RIVER

LIKE ANY RIVER, the mighty Mississippichanges course over time. Over the past4,600 years it has built four distinct deltasby depositing vast quantities of sedimenteach year during spring floods.

LAND LOSS is exacerbated by human-madelevees that shackle the river from northernLouisiana to the Gulf of Mexico and cut off thesupply of sediment to surrounding marsh-lands. Between 1932 and 1990, the delta lostmore than 1,000 square miles of land.

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carve land from the marshes, and boattraffic and tides steadily erode theirbanks further. They also allow saltwaterto creep inland, poisoning the marshes.SOLUTION: CLOSE CHANNELSClose the Mississippi River Gulf Outlet. Without the dredging and boat traffic,the channel would begin to fill in.

have caused the Mississippi River totelescope out into the gulf instead of itsmouth opening laterally farther north,robbing the barrier islands such asIsles Dernieres of sustaining material.SOLUTION: NEW CHANNELCut the narrow neck of the delta tomake a new navigation channel. Shipscould enter the river here instead offarther south; then dredging could behalted at the end of the delta. Thechannels would fill with sediment andbegin overflowing to the west, sendingsand and silt back to the barrierislands. Engineers could also mine thevast store of sand at Ship Shoal torebuild the island.

RIVER DREDGING and LEVEES

NAVIGATION CHANNELS and PIPELINE CANALS

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is ringed with levees that fend off theriver from the south and the lake fromthe north. Most of the city has sunkbelow sea level, forming a bowl thatfills even during routine rainstorms. A hurricane-driven sea surge from theeast would make the lake overflow,drowning the city.SOLUTION: BLOCK A SEA SURGEBuild gates to block the Gulf of Mexico’saccess to Lake Pontchartrain.


Their family leased the land from oil com-panies, for fishing and hunting, 16 yearsago when it was merely wet. Now it liesunder five to eight feet of water. They fil-ter rain for drinking water, process theirown sewage, catch the food they eat andmake money hosting overnight fishingparties for sportsmen. A dozen wellheadsdot the marsh where Toby picks us up byboat. Heading out to the barge throughone canal, he says, “I used to be able tospit to the mud on either side. Now theyrun big oil containers through here.”

Inside the barge’s wide-open room,Danny offers other measures: “Two yearsago we drove a wooden two-by-four intothe mud on the edge of a canal, to stakeour alligator trap. I went past it the otherday; the edge has receded 18 feet from the

stake. Doesn’t much matter, though. Thegators are gone. Water’s too salty.”

With the marsh disappearing, thedelta’s only remaining defense is somecrumbling barrier islands that a centuryago were part of the region’s shoreline.The next morning Penland and I travel anhour down the coast to the LouisianaUniversities Marine Consortium, a scien-tific outpost in Cocodrie, an encampmentof scientists and fishermen on the coast’sedge. From there we head out in one ofthe consortium’s gray research boats.

The boat pounds across what appearsto be choppy sea for 50 minutes before wereach Isles Dernieres (“last islands” inFrench). But the open surf is never morethan seven feet deep. The vast reach ofshallow water was once thick with sway-

ing grasses, parted occasionally by nar-row, serpentine waterways full of shrimp,oysters, redfish and trout. Penland beach-es us in the bayside mud. We walk acrossa mere 80 yards of barren sand before wetoe the ocean. A similarly diminutive out-crop is visible in the distance to either side.They are what remains of a once verylong, staunch island lush with black man-groves. “It broke up ocean waves, cutdown storm surges and held back saltwa-ter so the marsh behind it could thrive,”Penland says in mourning. Now the oceanrushes right by.

Louisiana’s barrier islands are erod-ing faster than any around the country.Millions of tons of sediment used to exitthe Mississippi River’s mouth every yearand be dragged by longshore currents tothe islands, building up what tides hadworn away. But in part because leveesand dredging prevent the river’s lastmiles from meandering naturally, themouth has telescoped out to the conti-nental shelf. The sediment just dropsover the edge of the underwater cliff intothe deep ocean.

Back in New Orleans the next day itbecomes apparent that other human ac-tivities have made matters worse. CliffMugnier, an L.S.U. geodesist who alsoworks part-time for the Corps of Engi-neers, explains why from the third floorof the rectangular, cement Corps head-quarters, which squats atop the Missis-sippi River levee the Corps has built andrebuilt for 122 years.

Mugnier says that the earth beneaththe delta consists of layers of muck—a wetpeat several hundred feet deep—formedby centuries of flooding. As the Corps lev-eed the river, the city and industry drainedlarge marshes, which in decades past wereconsidered wasteland. Stopping the floodsand draining surface water lowered thewater table, allowing the top mucks todry, consolidate and subside, hasteningthe city’s drop below sea level—a processalready under way as the underlyingmucks consolidated naturally.

That’s not all. As the bowl becamedeeper, it would flood during routinerainstorms. So the Corps, in cooperationwith the city’s Sewerage and WaterBoard, began digging a maze of canals to


DANNY AND TOBY DUET live on a barge moored in eight feet of water a mile from solid ground.Sixteen years ago the site was spongy land thick with marsh grasses.


collect rainwater. The only place to sendit was Lake Pontchartrain. But becausethe lake’s mean elevation is one foot, thepartners had to build pumping stations atthe canal heads to push the collectedrunoff uphill into the lake.

The pumps serve another critical func-tion. Because the canals are basically ditch-es, groundwater seeps into them from thewet soils. But if they are full, they can’ttake on water during a storm. So the cityruns the pumps regularly to expel seepagefrom the canals, which draws even morewater from the ground, leading to furtherdrying and subsidence. “We are aggra-vating our own problem,” Mugnier says.Indeed, the Corps is building more canalsand enlarging pumping stations, becausethe lower the city sinks, the more it floods.In the meantime, streets, driveways andbackyards cave in, and houses blow upwhen natural-gas lines rupture. Mugnieris also worried about the parishes (coun-ties) bordering the city, which are diggingdrainage canals as they become more pop-ulated. In St. Charles Parish to the west, hesays, “the surface could subside by asmuch as 14 feet.”

The ScareHUMANKIND CAN’T STOP the delta’ssubsidence, and it can’t knock down thelevees to allow natural river flooding andmeandering, because the region is devel-oped. The only realistic solutions, mostscientists and engineers agree, are to re-build the vast marshes so they can absorbhigh waters and reconnect the barrier is-lands to cut down surges and protect therenewed marshes from the sea.

Since the late 1980s Louisiana’s sena-tors have made various pleas to Congressto fund massive remedial work. But theywere not backed by a unified voice. L.S.U.had its surge models, and the Corps hadothers. Despite agreement on general so-lutions, competition abounded as towhose specific projects would be most ef-fective. The Corps sometimes paintedacademics’ cries about disaster as veiledpitches for research money. Academia oc-casionally retorted that the Corps’s solu-tion to everything was to bulldoze moredirt and pour more concrete, without sci-entific rationale. Meanwhile oystermen

and shrimpers complained that the pro-posals from both the scientists and the en-gineers would ruin their fishing grounds.

Len Bahr, head of the governor’sCoastal Activities Office in Baton Rouge,tried to bring everyone together. Passion-ate about southern Louisiana, Bahr hassurvived three governors, each with dif-ferent sympathies. “This is the realm inwhich science has to operate,” Bahr says.

“There are five federal agencies and sixstate agencies with jurisdiction over whathappens in the wetlands.” Throughoutthe 1990s, Bahr says with frustration,“we only received $40 million a year”from Congress, a drop compared with thebucket of need. Even with the small proj-ects made possible by these dollars, Lou-isiana scientists predicted that by 2050coastal Louisiana would lose another


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DEPTHS DURING HEIGHT OF FLOOD

COMPUTER MODELS by researchers at Louisiana State University predict that the counter-clockwise winds of a slow-moving, Category 4 hurricane (characterized by winds of up to 155mph with storm surges) crossing the Gulf of Mexico from the southwest would drive a sea surge30 miles inland, right to New Orleans’s back door. Surging water would also fill Lake Pontchartrain,which would then overflow its western bank and pour into the city. At the height of the flood, the downtown would be under more than 20 feet of water only about 33 hours after the firststorm winds touched the southern barrier islands.

The Disaster: A Worst-Case Scenario


1,000 square miles of marsh and swamp,an area the size of Rhode Island.

Then Hurricane Georges arrived inSeptember 1998. Its fiercely circulatingwinds built a wall of water 17 feet hightopped with driven waves, which threat-ened to surge into Lake Pontchartrainand wash into New Orleans. This was thevery beast that L.S.U.’s early models hadwarned about, and it was headed right forthe city. Luckily, just before Georgesmade landfall, it slowed and turned ascant two degrees to the east. The surgecollapsed under suddenly chaotic winds.

A Grand PlanTHE SCIENTISTS, engineers and politi-cians who had been squabbling realizedhow close the entire delta had come todisaster, and Bahr says that it scared theminto reaching a consensus. Late in 1998the governor’s office, the state’s Depart-ment of Natural Resources, the U.S. ArmyCorps of Engineers, the EnvironmentalProtection Agency, the Fish and WildlifeService and all 20 of the state’s coastal

parishes published Coast 2050—a blue-print for restoring coastal Louisiana.

No group is bound by the plan, how-ever, and if all the projects were pursued,the price tag would be $14 billion. “So,”I ask in the ninth-floor conference roomadjacent to the governor’s office in BatonRouge, “give me the short list” of Coast2050 projects that would make the mostdifference. Before me are Joe Suhayda, di-rector of L.S.U.’s Louisiana Water Re-sources Research Institute, who has mod-eled numerous storm tracks and knowsthe key scientists, Corps engineers, andcity emergency planners; Vibhas Arava-muthan, who programs L.S.U.’s comput-er models; Len Bahr; and Bahr’s second-in-command, Paul Kemp. All were in-volved in designing Coast 2050.

First and foremost, they decide, builda river diversion at several critical spotsalong the Mississippi, to restore disap-pearing marshland. At each location theCorps would cut a channel through theriver levee on its south side and buildcontrol gates that would allow freshwa-

ter and suspended sediment to washdown through select marshes toward thegulf. The water could disrupt oyster beds,but if the sites were carefully selected,deals could be made with landowners.

The second step: rebuild the southernbarrier islands using more than 500 mil-lion cubic yards of sand from nearbyShip Shoal. Next, the Corps would cut achannel in the narrow neck of the riverdelta at about halfway down. Ships couldenter the river there, shortening their tripto interior ports and saving them money.The Corps could then stop dredging thesouthern end of the river. The mouthwould fill with sediment and begin over-flowing to the west, sending sand and siltback into those longshore currents thatcould sustain the barrier islands.


WALTER MAESTRI, Jefferson Parish emergencymanagement director, in his floodproofunderground command bunker outside NewOrleans, says, “Even though I have to plan forit, I don’t even want to think about the loss of life a huge hurricane would cause.”



The channel plan might be integratedinto a larger state proposal to build an en-tire new Millennium Port. It would pro-vide deeper draft for modern containerships than the Port of New Orleans andits main channel, the Mississippi RiverGulf Outlet (MRGO, pronounced Mr.Go), which the Corps dredged in the ear-ly 1960s. The outlet has eroded terribly—

from 500 feet across, originally, to 2,000feet in places—and let in a relentlessstream of saltwater that has killed muchof the marsh that once protected easternNew Orleans against gulf storms. If thechannel or the Millennium Port werebuilt, the Corps could close MRGO.

A remaining chink in the delta’s ar-mor is the pair of narrow straits on LakePontchartrain’s eastern edge where it con-nects to the gulf. The obvious solutionwould be to gate them, just as the Nether-lands does to regulate the North Sea’sflow inland. But it would be a tough sell.“We’ve proposed that in the past, and it’s

been shot down,” Bahr says. The proj-ect’s costs would be extremely high.

This list of the most promising Coast2050 projects is only one small group’svision, of course, yet other established ex-perts concur with its fundamentals. Ivorvan Heerden, a geologist who is deputydirector of L.S.U.’s Hurricane Center,concurs that “if we’re going to succeed,we’ve got to mimic nature. Building di-versions and reestablishing barrier-islandsediment flows are the closest we cancome.” Shea Penland pretty much agrees,although he warns that the MississippiRiver may not carry enough sediment tofeed multiple diversions. U.S. GeologicalSurvey studies by Robert Meade showthat the supply of suspended sediment isless than half of what it was prior to1953, diverted mostly by dams along theriver’s course through middle America.

As far as the Corps is concerned, allof the Coast 2050 projects should be im-plemented. The first to become a realityis the Davis Pond diversion, due to beginoperating by the end of this year. Projectmanager Al Naomi, a 30-year Corps civ-

il engineer, and Bruce Baird, a biologicaloceanographer, brought me to the con-struction site on the Mississippi’s south-ern levee, 20 miles west of New Orleans.The structure looks like a modest dam, inline with the levee. Steel gates in its mid-section, each large enough to drive a busthrough, will open and close to controlwater flowing through it. The water willexit into a wide swath of cleared swampthat extends south for a mile, forming ashallow riverbed that will gradually dis-perse into boundary-less marsh. Thestructure will divert up to 10,650 cubicfeet per second (cfs) of water from theMississippi, whose total flow past NewOrleans ranges from less than 200,000cfs during droughts to more than onemillion cfs during floods. The outflowshould help preserve 33,000 acres of wet-lands, oysterbeds and fishing grounds.

The Corps is bullish on Davis Pondbecause of its success at Caernarvon, asmaller, experimental diversion it opened

in 1991 near MRGO. By 1995 Caernar-von had restored 406 acres by increasingthe marsh’s sediment and reducing itssalinity with freshwater.

Who Should Pay?THE CORPS OF ENGINEERS is hiringmore scientists for projects such as DavisPond, a signal that the fragmented partiesare beginning to work better together.Bahr would like to integrate science andengineering further by requiring indepen-dent scientific review of proposed Corpsprojects before the state signed on—

which Louisiana would need to do be-cause Congress would require the state toshare the cost of such work.

If Congress and President George W.Bush hear a unified call for action, autho-rizing it would seem prudent. Restoring

coastal Louisiana would protect thecountry’s seafood and shipping industriesand its oil and natural-gas supply. Itwould also save America’s largest wet-lands, a bold environmental stroke. Andwithout action, the million people outsideNew Orleans would have to relocate. Theother million inside the bowl would liveat the bottom of a sinking crater, sur-rounded by ever higher walls, trapped ina terminally ill city dependent on nonstoppumping to keep it alive.

Funding the needed science and engi-neering would also unearth better ways tosave the country’s vanishing wetlands andthe world’s collapsing deltas. It would im-prove humankind’s understanding of na-ture’s long-term processes—and thestakes of interfering, even with good in-tentions. And it could help governmentslearn how to minimize damage from ris-ing seas, as well as from violent weather,at a time when the U.S. National Ocean-ic and Atmospheric Administration pre-

dicts more storms of greater intensity as aresult of climate change.

Walter Maestri doesn’t welcome thatprospect. When Allison, the first tropicalstorm of the 2001 hurricane season,dumped five inches of rain a day on NewOrleans for a week in June, it nearlymaxed out the pumping system. Maestrispent his nights in a flood-proof commandbunker built underground to evade stormwinds; from there he dispatched police,EMTs, firefighters and National Guards-men. It was only rain, yet it stressed the re-sponse teams. “Any significant water thatcomes into this city is a dangerous threat,”he says. “Even though I have to plan for it,I don’t even want to think about the lossof life a huge hurricane would cause.”

Mark Fischetti is a contributing editor.

Coast 2050: Toward a Sustainable Coastal Louisiana. Louisiana Department of NaturalResources, 1998. Available at www.coast2050.gov/report.pdfHolding Back the Sea: The Struggle for America’s Natural Legacy on the Gulf Coast. ChristopherHallowell. HarperCollins, 2001.Transforming New Orleans and Its Environs: Centuries of Change. Edited by Craig E. Colten.University of Pittsburgh Press, 2001.

M O R E T O E X P L O R E

With no action, one million people could be trapped.


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