Saving New Orleans

Protecting New Orl eans

COPYRIGHT 2006 SCIENTIFIC AMERICAN, INC. Hurricanes Katrina and Rita devastated the Gulf Coast. The storm season starts again this June—and every June. Can coastal Protecting New Orl eans communities ever be safeguarded?

By Mark Fischetti

Immediately after Hurricane Katrina pummeled New Orleans last August, President George W. Bush and the U.S. Department of Home- land Security declared that no one could have predicted such devastation. Yet scientists, engineers and Louisiana state politicians had warned for years that a Category 4 or 5 storm crossing the Gulf of Mexico from a certain direction would drown the region. In 1998 computer models at Louisiana State University simulated such a terrible inunda- tion. That same year the state proposed a $14-billion plan to restore the delta’s natural wetlands—which, by absorbing water, can help protect inland areas from sea surges. But Congress turned it down. What is more, engineering firms, as well as the U.S. Army Corps of Engineers, which is largely responsible for flood protection, had proposed constructing higher earthen levees as well as huge gates that could have prevented storm surges from pouring into inner-city canals and bursting their concrete flood walls. Indeed, doc- uments show that various gates had been recommended as far back as 1968 and in each decade since. None of these designs has ever been funded. The reason, for the most part, is turf battles among the Corps, local and state politicians, and Congress. In the meantime, countries such as the Netherlands and the U.K. have erected effective surge barriers that the U.S. has ignored. In Katrina’s wake, the blueprints for all these structures are rapidly being dusted off, augmented and integrated into several grand plans by L.S.U., big engineering companies, and the Corps that could safeguard New Orleans and southeastern Louisiana. Similar measures could save populated coastal communities around the Gulf, the U.S. and the globe. Poster Child the mississippi river delta is not alone in being endangered. Deltas worldwide are in trouble because human development is causing the land to sink. The soft delta earth compacts naturally, but annual river floods top-coat the slumping ground with new sediment. Yet man-made levees built to prevent floods in many of these regions also cut off the sediment supply. At the same time, underground extraction of oil, natural gas and freshwater deflates the land’s support structure. As the surface subsides, saltwater from the ocean streams in, poisoning the usually thick expanses of wetland mangroves, trees and grasses. Without these lush buffers, even moderate storms can push sea surges far inland. The earth’s oceans are also rising, compounding the problem. At current rates, sea level will be one to three feet higher in 100 years. Low-lying cities from New York to Shanghai may have to armor themselves with walls and pumps and add revetments (waterproof masonry) to the bottom few feet of every building in town, measures already under way in Venice. One third of the world’s people live in coastal zones, particularly the deltas. Rich

SCIENTIFIC AMERICAN 65 COPYRIGHT 2006 SCIENTIFIC AMERICAN, INC. Grand Plan in farmland, seafood and underground dug, and wave erosion from ships turned Three main protection schemes (top map) resources, these areas are also key exit those cuts into gashes that allow hurri- are being proposed by government, and entry points for armadas of ships cane-induced surges to race into the city. industry and university groups to hold carrying piles of goods. Cairo, at the tip Similar practices are in play at many of back floodwaters from Category 5 of the Nile River, is home to 16 million the world’s deltas, which could well ben- hurricanes. The “inner ring” (red) would people. The Red River and Mekong del- efit from plans such as those now being extend and add height and width to tas in Vietnam each support 15 million considered in Louisiana. current levees and canal walls throughout inhabitants, yet both are eroding. Shang- New Orleans, meant only to withstand hai has 13.5 million, the Ganges in Ban- Too Late to Be Saved? Category 3 storms, and connect to gladesh, 10 million. Other threatened the 1998 plan for protecting the existing Mississippi River levees. deltas include the Orinoco in Venezuela Mississippi Delta region, titled Coast A “comprehensive plan” (yellow) and the Rhine, Rhône and Po in Europe. 2050, and a modified scheme in 2003 would continue the line to the Mississippi The Mississippi Delta, home to 2.2 known as the Louisiana Coastal Area state border and west beyond Morgan million, represents the worst-case sce- plan (LCA), called for gates to be insert- City to protect more communities and nario. It is sinking and losing wetlands ed into the river levees. The gates would industry. The 440-mile levee, 35 to 40 faster than almost any place on earth open at certain times of the year to allow feet high, would loosely track the and faces the most hurricanes annually. freshwater and sediment to wash down Intracoastal Waterway to the west, the The record sea surge that prompted the into the wetlands, gradually restoring primary intramarsh navigation route. The path shown represents a consolidation of Netherlands and Britain to erect barriers them. But “a growing number of people contours plotted independently by the was 15 feet; Katrina’s peaked at 28 feet. are recognizing that Katrina and Rita Shaw Coastal engineering firm, the U.S. Fundamental to the trouble is that changed the landscape enough that they Army Corps of Engineers, and Hassan for the past century the Corps, with the may have made Coast 2050 and LCA Mashriqui of the Louisiana State blessing of Congress, leveed the Missis- obsolete,” laments Len Bahr, a leader in University Hurricane Center. sippi River to prevent its annual floods the Louisiana Governor’s Office of In each case, diversions—sluices so that farms and industries could ex- Coastal Activities for 15 years and an within Mississippi River levees—would pand along its banks. Yet the levees have architect of Coast 2050. open at certain times of the year to allow starved the region of enormous quanti- Furthermore, because the storm freshwater, nutrients and sediment to ties of sediment, nutrients and freshwa- surge entered New Orleans from Lake wash down into the marshes, reviving ter. Natural flooding at the river’s mouth Pontchartrain to the north and naviga- vegetation and building up land to had also sent volumes of sediment west tion channels to the east, “those plans counteract subsidence and sea-level rise. and east to a string of barrier islands that would not have stopped Katrina,” ob- The Bonnet Carré floodway, completed, cut down surges and waves, rebuilding serves Hassan S. Mashriqui, an assistant can siphon away flood-stage river water. each year what regular ocean erosion research professor at L.S.U.’s Hurricane Other experts prefer dikes and long had stolen. But because the mouth is Center who has enhanced the universi- chains of gates that would link the barrier now dredged for shipping lanes, the sed- ty’s 1998 surge models. He says the islands, forming an “outer shield” similar to iment simply streams out into the deep models show that gates across certain that in place in the Netherlands. (No one ocean, leaving the delta—and New Or- channels into the city would also have has plotted a complete course, but leans within it—naked against the sea. been needed to divert the surge. examples appear in pink.) Diversions The Corps and industry also tore up Those gates would have done noth- would still be installed to restore the marsh by dredging hundreds of miles ing for the rest of southeastern Louisi- wetlands, important to the environment of channels so pipelines could be laid. ana, however. Scientific American and industry. Along with any plan, a new shipping entry point is recommended Even bigger navigation channels were therefore asked a wide range of experts partway up the Mississippi, which would require dredged channels but shorten Overview/Flood Control travel times and end dredging of the river tips; they would fill, sending sediment to ■ Levees were too small and weak to hold back Hurricane Katrina’s storm the barrier islands and marshes to replace surge. Much more robust systems have been proposed for all of sand eroded by wave action. southeastern Louisiana. In each scheme, numerous gates of ■ Flood control structures already in place in the Netherlands, England different styles would be erected and elsewhere could help protect troubled deltas worldwide and also revive (bottom). They would stay open for vast, dying marshlands. shipping and for maintaining the natural ■ Engineers must embrace greater scientific input when considering the mixing of freshwater and saltwater but siting and construction of barriers—input that might have mitigated close when needed to prevent storm the Katrina disaster. surges from entering Lake Pontchartrain or navigation and drainage canals.

Slidell Pearl River Mississippi Ri

Lake Pontchartrain ver

Bonnet Carré floodway Lake Borgne New Orleans

Morgan City

Houma New entry Intracoastal Waterway (requires dredged channel)

Venice

Grand Isle

LOUISIANA Port Fourchon

North 0 10 20 miles Current entry Gulf of Mexico 0 10 20 30 kilometers

Inner ring Comprehensive plan Outer shield (sample sites) Diversion (samples) Gate Existing levee Katrina levee breach Lake Pontchartrain NOTE: Plots are approximate. SOURCES: Louisiana State University, Shaw Coastal, U.S. Army Corps of Engineers, Coast 2050; satellite data available from U.S. Geological Survey at the National Center for EROS, Sioux Falls, S.D. Funnel effect

French Quarter According to an L.S.U. plan, the so-called MRGO SAFE channel funnel of water that caused the largest HAVEN ﬂood-wall breach during Hurricane Superdome Katrina would be regulated, and the MRGO channel, a source of extensive wetland erosion, would be closed. Some experts propose a “safe haven”—walls underneath elevated highways that would create an

JEN CHRISTIANSEN unﬂooded refuge if problems arise.

www.sciam.com SCIENTIFIC AMERICAN 67 COPYRIGHT 2006 SCIENTIFIC AMERICAN, INC. MAESLANT OPEN Floating Gates Trusses Floodgates around the world stop surges from pouring inland, and building ones like them Ball joint could help New Orleans and other coastal cities. The Netherlands has the greatest variety. The Maeslant barrier (right) allows 72 feet shipping on the New Waterway from the North Sea into Rotter dam’s huge port but closes 0.22 mile during storms. Each hollow barrier is stored in a dry dock, to limit corrosion and ease Chambers Trusses Locomotive engine maintenance. For deployment, the dock is fi lled with water, the gate fl oats, and an engine turns it out. Valves then let water fi ll Wall and sink the gate. After a storm, pumps empty DockDock (dry)(dry) the chambers, the barrier is fl oated back in, and the dock is pumped dry. 689689 feetfeet Skirt

North Sea the wall.” All three plans include gates can be avoided in the future. Four teams Oosterschelde Barrier of some kind that are not now in place. are investigating the levee and canal wall S D Although each approach has its pro- collapses in New Orleans—from the Maeslant Amsterdam N A ponents, the parties agree on one thing: American Society of Civil Engineers, the Barrier L R critics who say it is foolish to rebuild in Corps, the state of Louisiana and the E H Rotterdam T such a vulnerable place are missing the National Science Foundation. E N big picture. In addition to being a cul- In October, Secretary of Defense G ERMANY tural center, “the Gulf Coast is the eco- Donald Rumsfeld announced that the nomic engine that drives the country,” National Academy of Sciences would re- ) BE LG IUM Bahr declares. “We can’t possibly aban- view all the reports to ultimately deter- don it.” The delta produces one fi fth of mine why flood walls crumbled [see map to present solutions for the region. Three the country’s oil, one quarter of its natu- Working Knowledge, on page 92]. Rums- strategies [see maps on preceding page] ral gas, and one third of its seafood. Tril- feld said the academy would fi nish by emerged: a tight ring around the New lions of dollars of goods and crops fl ow June 2006. Yet hurricane season offi cial- Orleans metropolitan area alone; a com- through the ports there. These activities ly begins June 1, and Richard Wagonaar,

prehensive, 440-mile levee system that require extensive infrastructure and tens a U.S. Army colonel and commander of ); JEN CHRISTIANSEN ( would snake from the Mississippi border of thousands of employees who cannot the Corps’ New Orleans district, says his

halfway to Texas but lie only partway to live in temporary trailers or in homes goal is to restore all federal levees to their diagrams the shoreline, leaving the coast for lost; two hours away. pre-Katrina level of protection (able to and an outer shield around the region’s withstand Category 3 hurricanes) by perimeter, such as the one in the Nether- A New Path that date. President Bush had asked Con- lands, which would spare every locale. before any plan is implemented, gress to appropriate $1.6 billion to repair The ring and comprehensive plans would designers should understand fully why levee damage from Katrina and in De- inevitably leave some people “outside the existing levees failed, so weaknesses cember requested another $1.5 billion to BRYAN CHRISTIE DESIGN (

Sluices That Slide OOSTERSCHELDE Long stretches of sluices link ﬁ rm shorelines, barrier islands and dikes to form one part of Holland’s outer shield—the Slide Oosterschelde barrier (right). These ﬂ oodgates could aid any of the New Orleans protection schemes. The Oosterschelde Pier complex, 1.8 miles long, crosses three 127 feet channels. When raised, the 62 steel gates Open sluice gate between concrete piers allow for three quarters of the original tidal movement, Average depth: which maintains the estuaries behind it. 50 feet Closed sluice gate

Average depth: 47 feet 2.9-foot2.9-foot ggapap

Protection against 16-foot surge

improve city levees at Category 3 levels. be $25 billion to $35 billion—but remem- channel called MRGO and simultane- Wagonaar and others see restoration ber, this is still in the concept stage.” ously up an adjacent channel, the Intra- as only the fi rst step, however. They agree That time frame seems unrealistic to coastal Waterway. The two wave fronts that the city’s protection must be raised O’Neil P. Malbrough, president of Shaw met where the inlets join and narrow to Category 5 levels. Congress would Coastal, an engineering fi rm that has into the Industrial Canal. This geometry have to appropriate much more money built smaller levees and fl oodgates else- amplifi ed the height of the water by 20 for this work, whether it went to the where in the country. “The Corps began to 40 percent, Mashriqui says. That in- Corps or a different contractor. building levees around New Orleans and crease raised the water pressure so high When it comes to the comprehensive Lake Pontchartrain in 1965, and there that the canal wall burst. plans, people become more contentious. are still segments that are incomplete,” Scientists had predicted the funnel Despite local differences, the plans out- Malbrough says. “That’s inexcusable. If effect, and Mashriqui says a prepared- lined by Shaw Coastal (part of the Shaw private enterprise were doing this, it ness exercise run in 2004 by the Federal Group), Mashriqui and Wagonaar fol- would cost half the money and take half Emergency Management Agency based low a somewhat similar route. To the the time. The Corps is still building the on a simulated hurricane called Pam also south and west, the course would link same wall it was building then.” involved a funnel effect in that place. and raise existing, piecemeal levees now Wagonaar says he is not familiar “The wind pushes a huge volume of wa- maintained by independent levee dis- with Malbrough or with Shaw’s plan ter into this narrow strait, and the water tricts and would protect most major and notes that companies are unlikely to just piles up,” he says. towns. The planners disagree, though, be involved unless Congress opens bids MRGO must be closed and gates on who should do the work as well as on for the work. The Corps has had a de must be put across the Intracoastal Wa- how long construction would take and facto monopoly on federally funded terway to protect the city, Mashriqui what it would cost. Wagonaar estimates fl ood protection for a century. says. Numerous other experts speaking the Corps’ plan “would take us fi ve to 10 Residents in the hurricane danger to the national press have concurred, not- OOSTERSCHELDE: SKY PICTURES; MAESLANT: RIJKSWATERSTAAT,

MINISTRY OF TRANSPORT, PUBLICyears WORKS AND WATER MANAGEMENT to build” and that the cost “would zones hope that whoever gets the job in- ing that it supports very little ship traffi c corporates new understanding of how and costs a lot to maintain. But the Corps Katrina and Rita ravaged New Orleans, built MRGO, Mashriqui notes, “and for and some worry that the Corps may not them to agree, they would be admitting be fully responsive to external scientifi c a mistake was made in the fi rst place.” information. For example, Mashriqui at Mashriqui is not the only one worry- L.S.U. has determined that a wide breach ing about the need to avoid funnel ef- in the Industrial Canal, which fl ooded fects. This very phenomenon was a chief the eastern section of the city after Ka- reason for building the Thames Barrier trina, was caused by what is called a fun- in 1982, to prevent storm surges from nel effect. Computer simulations, and piling up along the Thames Estuary close physical evidence Mashriqui obtained in to London. “As the channel narrows by October as a member of the state inspec- 50 percent, the water piles up by 100 per- tion team, show that Katrina pushed wa- cent,” says Martin Earlam, chief engi- ter from the east up a wide navigation neer for the barrier at the country’s Envi-

SCIENTIFIC AMERICAN 69 COPYRIGHT 2006 SCIENTIFIC AMERICAN, INC. Hydraulic Disks THAMES OPEN A 1953 storm that drowned the Netherlands also sent a 15-foot surge up the Thames Rocking beam Link arm Estuary, killing 300 in England. Today 10 steel gates span the river, held by piers Pier covered by shining hoods (photograph). The four central gates are each 200 feet across and lie ﬂ ush in the riverbed, full of water, to not obstruct shipping. A disk on each end of Disk the gate is mounted on a shaft. To raise a gate, hydraulic rams and arms rotate it while Mean depth: Piers 29 feet Gate air enters the gate and water drains. Water Disk Disk reﬁ lls the gate when it is brought back down. Gate

North Sea EN GL AND 200 feet S

E L Thames Barrier A W London waves that could otherwise disturb shal- neer at the Dutch Ministry of Transport, low underground pipelines, and could Public Works and Water Management, partially absorb rising sea levels. The re- which oversees the Delta Works net- English Channel gion could be walled in by connecting work, says a similar approach could pro- the barrier islands with dams and long tect Louisiana and deltas in other na- ronment Agency, which operates it. And stretches of gates—the option the Neth- tions. Although the Netherlands’s shield S. Jeffress Williams, a coastal scientist erlands embraced after a horriﬁ c 1953 may seem grandiose, Weijers says “build- with the U.S. Geological Survey who storm generated a 15-foot surge that ing the whole system right now would worked for 20 years in Louisiana and has killed 1,800 people and flooded 800 cost $15 billion to $16 billion.” Mainte- studied deltas worldwide, says funnel ef- square miles. Virtually the entire coun- nance runs about $500 million a year. fects “have been underappreciated.” try is delta; 26 percent of it is below sea But after the coast was secured, he adds, level, bottoming out at –22 feet, lower “the region got an economic boost in Outer Shield than New Orleans. The surface is sub- tourism, farming and industry.” the comprehensive plan may siding, too, accelerated by extraction of Coastal administrator Len Bahr says seem more feasible than the total shield, freshwater and peat, and is home to sev- an outer shield is a wild idea, but given but there are reasons to consider enclos- eral major lakes and river outlets. Today the delta’s alarming deterioration, “we ing the signiﬁ cant tracts of marsh that the nation is outlined by more than may need some wild new ideas.” Wil- the other plans would leave exposed to 1,000 miles of dikes (levees), dunes, liams of the USGS concurs: “Considering the sea. The marshes provide wintering dams and gates—far longer than the line grounds for 70 percent of the nation’s needed around Louisiana. IT AL Y Venice migratory waterfowl, cushion ocean Joop Weijers, a longtime senior engi- Lido Inlet

n Rising Flaps oo ag Malamocco Inlet Many low-lying coastal cities worldwide will have to fend off tidal surges and rising sea L levels. In Venice, engineers are preparing sites for barriers that will close inlets when Adriatic menacingly high tides approach, which now occurs three or four times a year (record Chioggia Inlet Sea surge, 6.5 feet). In each inlet, 20 or 40 hollow, steel ﬂ aps will rest in heavy concrete (0.25 mile across) cradles. To raise them, air will be pumped in to push water out, and they will ﬂ oat up into position in less than 30 minutes (diagrams). An adjacent lock will permit boats to pass.

VENICE 6-inch gap Air in 45- Inlet depth: 6666 feetfeet 19–48 feet (white arrows) degree SurgeSurge levellevel SeaSea levellevel DoubleDouble hingehinge angle 16 feet 9999 feetfeet Water out Valve Seaﬂ oor AirAir supplysupply

Protection against 22-foot Flap surge valve

Water

the rates of sea-level rise, land subsidence, ican during research for a 2001 article more extensively. “I don’t care who and the increasing frequency and sever- about restoring the delta [see “More to wants to control the work,” Mashriqui ity of storms, it’s a legitimate option.” Explore” below]. But collaboration may asserts. “But whoever it is has to listen to improve. In 2004 the Corps and Delta the data. If our models show that the Take a Scientist to Lunch Works leaders signed a memo of under- funnel effect will kill people, then there panicked by the devastation in 1953, standing to exchange information, and is no excuse not to close the funnel.” the Dutch quickly set out to build solid in October several Dutch engineers Bahr agrees that engineers “have not dams across several wide estuaries to the helped the Corps analyze New Orleans’s so far engaged research scientists nearly North Sea. Those berms, however, cut fl ood-wall failures. enough. And we need anthropologists off the interchange of saltwater and fresh- The need to coordinate physical pro- and social scientists to help fi gure out the water and altered the environment. In tection across levee districts and to incor- people issues. Some parishes [counties] recent decades, Delta Works has changed porate coastal restoration means a clear were virtually wiped out by Katrina. direction, emphasizing man-made bar- leader is needed. The experts interviewed Where does it make sense, socially, to riers that close only when surges are im- for this article acknowledged that politi- rebuild?” Williams, the USGS veteran minent. “It took us a long time to learn cal infi ghting in Louisiana killed smaller who also worked at the Corps for 13 that we could work with nature, not just proposals in the past. Malbrough hopes years, says scientists continually “put defy it,” Weijers says. He advises U.S. this message may be sinking in; he was data out there, but it has no effect on its planners to “really think it through.” hired by various levee boards together to own. Politicians and planners have to Wagonaar at the Corps, Malbrough present the state and federal government take it from there.” at Shaw Coastal, and Mashriqui at L.S.U. with one coordinated plan. Both he, Wagonaar, a longtime Corps mem- agree that certain aspects of the original Mashriqui and Bahr think a federally ber who took over the New Orleans dis- Coast 2050 and LCA plans that would run consortium should oversee the work. trict last July, says that in the future the THAMES: SKYSCAN

) ; revive the marshes must be incorporated They oppose putting the Corps in charge, Corps will better integrate outside ex- into any plan adopted. Diversions—large seeing it as too slow, too politicized by perts: “We are generally a lot more open maps doorways inserted into the levee along Congress, and too unwilling to entertain than we were fi ve or six years ago, espe- the Mississippi River’s banks—would novel technical approaches. “I’m inclined cially with regard to environmental is- supply freshwater and sediment to the to change horses,” Mashriqui says. sues. But we can’t study this situation wetlands. The Corps’ plan includes a He and others also strongly recom- forever either. Someone will have to signifi cant number of gates to “let water mend that scientist input be sought much make a decision.” ); JEN CHRISTIANSEN ( fl ow in and out to support the LCA ob- jectives,” Wagonaar says. MORE TO EXPLORE

diagrams Although the Netherlands and Brit- Drowning New Orleans. Mark Fischetti in Scientiﬁ c American, Vol. 285, No. 4, pages 76–85; ain probably have much advice to offer, October 2001. Malbrough says, “we don’t need the Preliminary Report on the Performance of the New Orleans Levee Systems in Hurricane Dutch to tell us how to build a levee sys- Katrina on August 29, 2005. R. B. Seed et al., Report No. UCB/CITRIS-05/01, University of California, Berkeley, and American Society of Civil Engineers, November 17, 2005. Available tem.” The Corps apparently felt that at www.asce.org/files/pdf/katrina/teamdatareport1121.pdf way at one time, too; its ofﬁ cials made Drawing Louisiana’s New Map: Addressing Land Loss in Coastal Louisiana. National Research

BRYAN CHRISTIE DESIGN ( similar statements to Scientiﬁ c Amer- Council. National Academies Press (in press, scheduled for February 2006).