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Broken Levees: New Orleans to Sacramento
Can Katrina’s lessons forestall disaster in the Delta?
By Robert Sanders
By the time Hurricane Katrina made landfall in Plaquemines Parish, 70 miles southeast of New Orleans, at 6 a.m. Monday, August 29, last year, it had weakened from a Category 5 hurricane to Category 3, its swirling winds dropping from 160 to 114 miles per hour. The city’s flood protection system—more than 400 miles of levees and floodwalls—was ostensibly built to withstand this level of storm.
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Broken levees led to massive flooding in New Orleans in the wake of
Hurricane Katrina, a disaster experts fear could repeat itself in the
California Delta, where a fragile labyrinth of levees could be seriously
damaged or fail should an earthquake occur even as far as 100 miles away.
PHOTO COURTESY FEMA
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Barreling due north, Katrina churned the waters of the Gulf of Mexico like the blade of a washing machine, whipping counterclockwise as it spun along a 150-mile wide path. Wave heights reached 25 feet as winds piled water into the bay known as Lake Borgne east of the city, spilling over into Lake Pontchartrain north of downtown. The fact that the eye passed east of the city was, in retrospect, just as bad as if it had borne down on the city center. The cyclone winds at the advancing edge of the storm blew hard, driving water into a blind pocket of bay and lake, creating high waters—so-called storm surge—16 to 18 feet higher than normal in Lake Borgne. Add to that the storm-tossed waves, and the levees were simply overwhelmed.
The first sign of trouble came even before landfall, at 4:30 a.m., when water piling into Lake Borgne funneled into the Industrial Harbor Navigation Canal, a shortcut for ocean-bound ships exiting the Mississippi River, breaching a levee meant to protect homes in the heart of central Orleans. This was followed within hours by eight other major breaches, which together flooded 80 percent of the city to depths of up to 20 feet inundating 200,000 homes, killing upwards of 1,300 people, displacing 450,000 more and running up costs, according to some estimates, as high as $300 billion. Katrina was the most costly peace-time disaster to hit an urban area in U.S. history.
It was a disaster that needn’t have happened, according to Berkeley civil and environmental engineers Raymond Seed and Robert Bea, and a disaster that could repeat itself in California, they say.
“A stunningly similar situation exists in California with the potentially catastrophic seismic risk associated with the fragile labyrinth of levees that safely passes two-thirds of California’s vital fresh water through the key node in the state’s extensive water distribution system,” Seed wrote about the levees in the Sacramento and San Joaquin River Delta.
While Sacramento is protected from flooding by riverbank levees, many built in the 1990s by the U.S. Army Corps of Engineers, none of these levees is designed to withstand earthquakes. Even a distant temblor could cause a levee break, inundating heavily populated low-lying residential areas—and more homes are being built in flood-prone areas each year. Even worse is the hodgepodge of privately owned, 140-year-old levees protecting the islands and farms of the Delta. Haphazardly maintained, they are all that stand between salty San Francisco Bay and the freshwater intake pumps supplying drinking water for much of Southern California and irrigation for the fertile Central Valley.
Aware of the disaster it could cause in the southeast, Seed and Bea followed Katrina’s trajectory for days. The morning it hit New Orleans, Seed told his 9 a.m. class to go home, turn on the TV, and watch “the engineering disaster of your lifetime.”
Bea followed Katrina with an intimate appreciation of the devastation he feared could befall New Orleans, where he lived for 10 years while working for Shell Oil. In 1965, Hurricane Betsy destroyed Bea’s home. After Betsy, a 40-year, federal project was initiated to strengthen levees around still vulnerable areas of New Orleans and top the levees with flood walls. The goal: to knit existing levees into a reliable system to protect the city. Yet, in the ensuing years, says Bea, critical corners and budgets were cut. Geotechnical oversight by the Corps of Engineers—the principal agency tasked with the massive project—was weakened, and worse, deadlines slipped by unnoticed. When Katrina hit, portions of the levee system were woefully incomplete. Many had not yet been built to their specified height; others had subsided several feet since construction.
Aware that Katrina could flood the city like Betsy had, Seed and Bea approached the National Science Foundation, asking it to fund forensic studies of the levee system failures and Katrina’s effects on offshore oil platforms and pipelines.
NSF agreed, providing $230,000, which was augmented by $50,000 from Berkeley’s Center for Information Technology Research in the Interest of Society (CITRIS). Bea and Seed quickly assembled a team of national experts, arriving in New Orleans September 27, a month after Katrina.
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Professors Seed (right, wearing Cal cap) and Bea survey the water-side face at a recently improved levee near the Antioch Bridge in the California Delta, where an earthquake, considered long overdue, could weak havoc with the existing web of levees.
MARTIN SUNDBERG PHOTO
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“Since Loma Prieta, we have become the world’s best earthquake and geotechnical forensics group,” Seed says, referring to a small group of civil engineers around the country, but in particular at Berkeley. “We have people adept at landing in the midst of chaos and confusion, who literally get in, without much notice, to retrieve crucial data before it disappears or is buried by emergency repair operations.’”
During their nine-month New Orleans analysis, the team repeatedly consulted with the Corps, and was quick to call them on the carpet. After issuing their preliminary report last November, Seed traveled to Washington D.C. to testify before the Senate Committee on Homeland Security and Governmental Affairs and meet with Lieutenant General Carl Strock, commander of the Corps, to brief him on the team’s findings.
The full force of their critique was left for the final report, an exhaustive document compiled by 37 engineers and scientists from around the world, issued in May. The authors paint a dispiriting picture of a protection system in name only, faulting levee designs throughout the system, which led to some 50 failures and breaches in the greater New Orleans region. At the heart of the heart of the problem, says Bea, was a dysfunctional Corps of Engineers “streamlined” by decades of Congressional mandates dating back to the 1970s. To save money, local levee districts had been allowed to build some of their own portions of the system without adequate oversight, resulting in a mishmash of designs that failed at the weakest links, says Bea, who began his career in 1954 with the Corps, working on levees and canals around Lake Okechobe in South Florida.
The Corps, in its final report, conceded that even though the storm surge and storm waves together exceeded what the levees were designed to withstand on the eastern flank of the levee system, many levees failed even before they were overtopped.
“Since Katrina, the Corps has rebuilt most of the levees to fix the overtopping problem, but they aren’t yet addressing underseepage, including at levees that didn’t fail during Katrina,” Seed says.
Adda Athanasopoulos, an engineering graduate student who helped oversee field studies of the levees, noted problems with the sheetpiles, “the interlocking steel palisades pounded into the ground beneath the levees and topped with a concrete wall designed to keep out water that rises higher than the earthen levee. “At sites like New Orleans’s London Avenue Canal, the sheetpiles were too short to cut off the underseepage forces through the sandy material, which created pressures that reduced the strength of the foundation soil and led to failure.”
Tromping the New Orleans levees over a four-month period, Berkeley student teams took borings with three-inch diameter “Shelby” tubes, or thin-walled core samplers, and conducted core penetration tests to determine the strength of the soils. These were the levees protecting the city from three canals piercing the heart of lower New Orleans and the sites of the most catastrophic breaches. With the experienced eye of Berkeley alumnus and University of Missouri-Rolla geology professor David Rogers, the student team discerned that the cause of the 17th Street Canal levee failure was a jelly-like layer of flocculated clay that allowed the rising waters to push the levee 50 feet sideways, “as if it slipped on a banana peel,” Bea says. This layer, which was probably thrown down by another hurricane 1,200 years ago, was evident in about half of the 20 borings.
Corps engineers could easily have missed this layer, but two other weaknesses—a layer of peat and a deep layer of soft clay—should have been caught before the levee was built.
Rune Storesund, a working geotechnical engineer and Berkeley graduate student, focused on the performance of New Orleans’ earthen levees to assess whether existing design standards were complete and accurate. “The design standards didn’t take into account all loads you should look at when designing levees; they didn’t take into consideration degradation over time, address impacts from ships or barges, or even the effect of rodent burrows, a pervasive problem,” he says.
To prevent a repeat of Katrina, Bea notes, “The Corps needs to bolster the barrier islands, plant trees and other vegetation, eliminate drainage canals, build underground culverts, and turn some backyards into fields.”
The lessons embodied in their New Orleans report apply, Seed and Bea say, to levee systems around the country, including those protecting the city of Sacramento, where recent studies suggest that those sheetpiles too, may be too short to prevent seepage through porous soils underneath.
In the Sacramento-San Joaquin Delta, however, seepage through peat and sandy foundation soils beneath the levees is the main source of irrigation for crops cultivated on some Delta islands that have sunk as much as 20 feet below river level over the past 150 years. Privately built levees protecting these islands, some dating from the late 1800s, suffer breaches every few years when Sierra Nevada storm and snowmelt runoff is heavy.
“The parallels with New Orleans are exact,” Bea says. “Only it won’t be a hurricane that’s the tester. Our hazard comes from annual flooding down the Sacramento River and from earthquakes.”
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Adda Athanasopoulos (left), Rune Storesund (center) and Kofi Inkabi use tape and hand level methods to document the levee’s geometry. Like New Orleans, the Delta levees are slowly subsiding, requiring constant maintenance to keep them at their specified level of protection.
MARTIN SUNDBERG PHOTO
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Few of the 1,100 miles of California levees in the Delta or the levees protecting Sacramento are built to withstand an earthquake, says Seed, who has studied these levees for 26 years. A quake on the San Andreas Fault more than 100 miles away could liquefy the sandy foundations, he says. Closer to the Bay Area near Antioch, a blind thrust fault runs right under Sherman Island’s levees. Seed describes a scenario where seismically induced levee failures could turn the Delta islands into a marshy sea, allowing winds to accelerate across the more open water and dash waves against the faces of other levees, generating a cascade of failures. The failures would draw salt water from the San Francisco Bay into the Delta until the intake pumps diverting water to agriculture and Southern California homes were flooded with brine.
“There’s a great Armageddon risk in the Sacramento Delta,” says Seed. “We may find it will take years, if ever, to fix these failures.” Meanwhile, what about the 23 million people throughout the state who get drinking water from the Delta and the farmers who rely on the water to turn the Central Valley into the most productive farmland in the world?
Lynn O’Leary, Delta project manager for the Army Corps’ Sacramento District, acknowledges the catastrophe a quake could unleash in the Delta, where three-quarters of the levees are privately owned and not overseen by the Corps. “But the other big risk in the Delta is high tides and high winds,” a combination common in the Delta, accentuated by spring runoff, she says. Such conditions nearly caused a New Year’s Day failure on Andrus Island near Antioch, where a combination of snowmelt, high tides and wind sent waves crashing over the top of the levee.
Seed is on the steering committee for a new joint state/federal study by the California Department of Water Resources and the Corps of Engineers of the risks posed by the levees protecting the Delta’s 60 to 70 islands, source of roughly two-thirds of California’s precious freshwater supply. “The good news is our local agencies are coordinated, and we are looking at the system as a whole, unlike New Orleans,” O’Leary says.
Seed is also concerned that an earthquake could cause liquefaction of Sacramento’s riverbank levees, flooding Sacramento’s low-lying suburbs without warning. In part because these levees are built to a lower standard than those of New Orleans, “the city of Sacramento is currently the least safe major city in North America in terms of flood protection. It’s even worse than New Orleans,” Seed says, “but efforts are now underway to address this.”
The solutions for Sacramento, like the solutions for New Orleans and other flood-prone areas, according to Bea and Seed, are a revitalized Corps given power by Congress and the President to build and maintain levees as a unified and uniform bastion against flooding, not as a patchwork quilt replete with weak links that threaten lives and property. California Governor Arnold Schwarzenegger has joined with Louisiana Governor Kathleen Blanco to lobby Congress and the President for funds to cover the billions of dollars needed to fix the Corps’ levees. Next month, voters will decide on two state propositions that, if passed, would dedicate nearly $5 billion to flood control improvements throughout the state of California. After Schwarzenegger declared a state of emergency in the Delta last February, the federal government expedited the permit process to speed repair of some 50 problematic erosion sites along the levees lining the upper Sacramento, American and San Joaquin Rivers. The State Department of Water Resources and the Corps began repairs on 29 of these sites in July. By September, that number that had grown to 110.
Governor Schwarzenegger saw the urgency, Seed says, perhaps because a series of levee failures from a single catastrophic earthquake or high runoff flow could bankrupt the state just from liability claims.
“One of the things I’ve wanted to accomplish in my professional career is to make California’s levees safer,” Seed says. A report Seed coauthored in 1999 set the stage for changes in California. But New Orleans’s tragedy may have unwittingly provided that much needed kick in the pants.
“This is likely to open the dam of public awareness for levee safety,” says
Seed. “If there’s a silver lining to New Orleans, it’s the chance to prevent
a similar calamity in California.”
For more, see www.ce.berkeley.edu/~new_orleans.
ROBERT SANDERS has covered science, engineering and medicine
for more than 25 years, the last 15 in the news office at UC Berkeley.
His stories have appeared in Berkeley Magazine, UCSF Magazine and
Forefront.
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