Energy & Environment

Defending Against A Deluge

The disaster in New Orleans has prompted a nationwide examination of man-made levees, as well as interest in restoring natural floodplains.
by | December 2005
 

A decade ago, residents of Napa, California, had grown tired of wintertime floods that swamped their downtown every five years or so. Still, they weren't overjoyed when the U.S. Army Corps of Engineers proposed funneling the picturesque Napa River between austere earthen levees and concrete floodwalls. So local leaders came up with their own idea: With the Corps' help, the city is turning the Napa back into a "living river" with replenished wetlands and a naturally broad floodplain to absorb overflowing water before it hits the town.

Napa's river restoration is roughly half finished, but officials there say some features have already kept neighborhoods dry during heavy downpours. And after Hurricane Katrina's surging waters broke through man-made levees and flooded New Orleans this fall, they're more convinced than ever that Napa will be better off rebuilding natural hydrologic processes than relying on engineered flood-control structures. "You're really trying to get in tune with nature by giving the river room to do what it's always done," says Heather Stanton, Napa's flood project manager. "That's much more effective than relying on levees and floodwalls."

Napa has just 75,000 residents, and providential topography creates a well-defined valley where it can let the river wander. More densely populated cities situated on different terrain may not have that option. In any case, the post-Katrina flooding in New Orleans has prompted thousands of cities throughout the nation to reconsider whether they can count on dams, dikes, levees, bypass channels and other man-made structures to save them from catastrophic flooding.

UNSOUND DAMS

For the foreseeable future, most communities have no choice but to depend on earthen levees built decades ago that may or may not hold the water back if rivers and streams start rising. "The questions are: 'How high are the levees, and is the earth in them still doing what it's supposed to do?'" says Gerald E. Galloway Jr., a retired Corps of Engineers brigadier general. Galloway led a Clinton administration task force that reassessed nationwide risks after the Mississippi and Missouri rivers flooded Upper Midwest communities across parts of nine states in 1993. More than a thousand levees failed, and floodwaters killed 50 people and damaged 70,000 buildings.

Galloway's task force proposed a national goal of protecting every urban area against the destruction that storms might cause once every 500 years. But in the decade since, nothing much has changed: Municipalities still design flood protection project by project. The fate of many of them hinges on the success of their state's congressional delegation in bringing federal funding home for Corps of Engineers projects.

Federal law restricts new building on chronically inundated land and requires homeowners in flood-prone areas to buy government-backed insurance. Those rules apply where federal and state hydrologists calculate there's a 1 percent chance of flooding in any given year. The Federal Emergency Management Agency is currently remapping floodplains across the country that a 100-year flood is likely to put under water. Where flood-control barriers aren't up to snuff, Galloway points out, "there's a one in four chance you'll have a 100-year flood in the life of a 30-year mortgage."

That threat puts federal, state and local officials under pressure to come up with money for flood projects to let development resume and free constituents from paying hefty flood insurance premiums. But the hurricanes that raged across Florida and the Gulf Coast this year have served notice that governments may need to prepare for something worse than once-in-a-century floods--from unexpectedly monstrous tempests to thawing mountain snows caused by climate change--that could overwhelm existing flood protections for inland regions as well as seaside communities.

In 1936, after a series of damaging floods, the Corps of Engineers took on the mission of defending communities by building high dams and lining rivers and bays with fabricated earth and concrete structures. Additional flood-control structures have been built by local agencies, farmers or subdivision developers, and their soundness is open to question. In 1976, a six-month-old U.S. Bureau of Reclamation earthen irrigation dam failed on the Teton River, killing 11 people and flooding Rexburg, Idaho, and several other towns downstream.

Congress responded to that tragedy by ordering regular safety inspections of the nation's 79,000 public and privately built dams. Even so, the American Society of Civil Engineers figures that 3,500 dams remain unsafe; 29 have failed in the past two years. Just this fall, Taunton, Massachusetts, evacuated 2,000 residents for three days when heavy rains threatened a sagging 173-year-old dam above the city. After that scare, commonwealth officials decided to start enforcing safety guidelines for 2,600 private and municipal dams--and spend $32 million to repair another 338 state-owned structures.

Around the country, 15,000 miles of dirt levees serve as the final line of flood defense for major cities, rural communities and undeveloped farmlands. Federal projects built roughly half, but most are now maintained--often haphazardly--by local governments and flood- control districts. Corps inspectors drive by once a year to check for signs that tree roots, animal burrows or other obvious changes are undermining the structure's integrity. "It's not a detailed examination. They can send a 'buck up' letter if a city is not doing a good job," says Galloway, now an engineering professor at the University of Maryland.

If faulty levees fail, Galloway worries that heavily populated parts of St. Louis, Dallas, Denver, Houston, Tacoma, Los Angeles, St. Paul and Louisville could be flooded. At greatest risk, many experts believe, is California's state capital. "If I were living in Sacramento," Galloway says, "I'd be very concerned."

CLOSE CALLS

Sacramento, in fact, is just as vulnerable as New Orleans. "Katrina was a wake-up call for anybody who lives behind a levee," says Sacramento Mayor Heather Fargo.

The city grew up where the American River rushes down from a steep Sierra Nevada watershed to feed into the Sacramento River. It relies on 125 miles of earthen levees, many dating to the early 1900s. Quite possibly, those defenses could give way if heavy rains roll in from the Pacific Ocean and melt Sierra Nevada snows above the city. The resulting flood could inundate virtually the whole city, surrounding the California state capitol with water and driving 400,000 residents from their homes.

In 1862, Governor Leland Stanford was rowed through Sacramento's streets to take his oath of office in the Capitol. Following that episode, Sacramento tried to protect itself by raising the downtown district by 15 feet and later by building hodgepodge levee defenses. To hold floodwaters upstream, the federal government finished building Folsom Dam on the American River 23 miles above Sacramento; in the mid-1960s, a bypass channel was built to divert 80 percent of the Sacramento River away from the city's core. But some levees, built when land was still being farmed, were too low and too flimsily maintained to handle even a 50-year flood, leaving Sacramento and the surrounding regions exposed.

Indeed, Sacramento has eluded close calls in each of the past two decades. In January 1986, jet-stream winds sped warm Pacific rainstorms straight from Hawaii (a phenomenon that's been dubbed "the Pineapple Express") and thawed heavy Sierra Nevada snowpacks. For 10 days, "we had a whole series of storm systems charging right at us, and we would have lost our levees if there'd been just a few more hours of rain," recalls Stein Buer, the Sacramento region's flood- control chief. Sacramento barely escaped again in the winter of 1997, when the heaviest Pacific storms swerved north of the American River watershed.

After the near-miss in '86, local governments began reinforcing levees and raising them by three feet. Two years from now, two-thirds of the city will be protected against a 100-year flood, freeing homeowners from the federal government requirement that they buy flood insurance. "We do think that a 100-year level of protection is pretty minimal," Fargo says, so California politicians are pressing Congress and the Corps to expand floodwater storage capacity behind Folsom Dam. This summer, however, the Corps tripled its original $215 million cost estimate for Folsom improvements.

Meanwhile, the metropolitan area's population of 1.5 million continues to grow, and development is extending onto delta farmlands behind questionable rural levees. This summer, the state agreed to pay $428 million to 3,000 residents whose homes were flooded when the 1986 storms broke one Yuba County levee 40 miles north of the capital. In June 2004, a levee 10 miles from Stockton, California, collapsed suddenly in good weather, and 19 square miles of cropland was flooded under an average of 12 feet of water, causing $100 million in damage. It took seven months to pump the water out and repair the breach.

With the delta sinking and sea levels rising due to global warming, geologists at the University of California at Davis calculate there's a two-out-of-three chance in the next 45 years that an earthquake or winter storm will breach enough levees to disrupt water deliveries to Los Angeles and other Southern California cities for months or even years.

"A system designed almost 100 years ago can't support the amount of change that's going on here, but so far we've shown no willingness to invest enough to fix the problem," says Jeffrey Mount, one of the UC- Davis scientists. In November, Congress appropriated $38 million over the next year to start beefing up Folsom Dam and keep shoring up Sacramento's levees. It also approved $12 million to continue Napa's project and dedicated $750,000 to emergency levee assessments in the vast delta where the Sacramento and San Joaquin rivers flow into San Francisco Bay.

California officials say they'll need millions more in federal dollars to finish those jobs. But competition in Congress will only escalate as other regions demand help to bolster flood defenses. The Corps has agreed to cover the full $1.6 billion cost of quick repairs to New Orleans' damaged levees; Louisiana politicians are also demanding that the federal government commit to a $2.5 billion upgrade to the city's flood controls. This year's destructive hurricanes also may reinvigorate support for a $14 billion federal-state proposal to replenish storm-absorbing Gulf Coast wetlands and barrier islands that riverbed dredging, oil and gas drilling, and housing construction have steadily depleted over the past century.

After the 1993 Midwest floods, Galloway's White House task force endorsed bolstering traditional engineered structures by restoring streamside wetlands and opening up natural floodplains. The Corps has adopted a broader view of flood-control projects in the decade since then, and governments around the country have torn down 30,000 houses and factories to relocate residents from floodplains. On the Mississippi, the federal government moved all 900 residents of Valmeyer, Illinois, from the river bottom and rebuilt the town two miles east and 400 feet above the river.

Moving even smaller neighborhoods requires difficult social and economic calculations. New Orleans must decide whether it makes sense to rebuild flood-prone neighborhoods in its impoverished, predominantly black Ninth Ward district. In New Jersey, the state's environmental agency and the corps decided to buy out homes along the Passaic River floodplain. Some residents have been reluctant to move, and they still fault former Governor Christine Todd Whitman for blocking a $2 billion plan that would have salvaged their homes by building a 21-mile tunnel to divert floodwaters to Newark Bay.

As they recover from severe 1998 Red River floods, Grand Forks, North Dakota, and East Grand Forks, Minnesota, are extending floodwalls through downtown historic districts, installing floodgates to move water away, and safeguarding upscale neighborhoods behind bolstered 10-foot levees. But in some poorer riverside neighborhoods, "it's cheaper to buy out homes and relocate roads and utilities than to build a concrete floodwall," says Mark Walker, Grand Forks' assistant city engineer.

RISKY DEVELOPMENT

Meanwhile, near other expanding metropolitan regions, suburban development continues to creep onto floodplains. In Columbia, South Carolina, developers and the local Sierra Club have been maneuvering for several years over loosening Congaree River floodplain regulations to open the way for 5,000 homes and a technology park. A decade after the big Midwest floods, a St. Louis Post-Dispatch study found that local governments in the St. Louis region were working closely with developers to build roads, shopping centers and residential development on farmland on Mississippi and Missouri river bottoms that had been underwater a decade earlier.

"If you're not in the floodplain already, it doesn't make sense to go into the floodplain now if there's any alternative," Galloway contends. Even in the Sacramento area, however, some counties are looking the other way while houses are built on sinking farmlands guarded by flimsy levees. The California Assembly in May sidetracked several measures directing local governments to take flood risks more seriously before approving subdivisions behind levees. The California Building Industry Association labeled one bill a "dream killer" that would drive up housing prices.

However, the California Reclamation Board, a little-known state agency that supervises 1,600 miles of levees in the Sacramento and San Joaquin Valleys, has taken tentative steps to question pell-mell subdivision development. This summer, the panel startled local officials and developers when it warned Yolo County officials to consider flood risks from a proposal to build homes, shops and a winery at a sugar mill that's protected only by an aging agricultural levee.

"We know that the majority of levees are substandard, but the counties don't want the board to go through the review process. They're afraid it will stop development," says Mount, the UC-Davis geologist who voted for intervening as a Reclamation Board member. In mid-September, after New Orleans was devastated, the board declared it would start using its authority under California's environmental quality law to review all subdivision projects close to levees. A few days later, Governor Arnold Schwarzenegger replaced the entire board, Mount included, with his own appointees. One of them, former Sacramento flood authority director Butch Hodgkins, has called the region's rural levees "certainly not adequate to protect urban areas."

Buer, the current director, says his agency has opened preliminary discussions with farmers and county governments about buying conservation easements to keep croplands from being developed. The authority also has looked at relocating rural levees to allow more room for flooding before water gets to houses. "It passes the common sense test to concentrate development behind defensible boundaries and preserve open space in areas that have lower levels of flood protection," he says.

In downtown Sacramento, the opportunities for clearing the floodplain are very limited. Although the city has established a riverside park where flooding won't do much damage, moving the state capitol out of the American River's natural corridor isn't feasible. Even in Napa, it took a concerted citizen-led process to persuade the Corps to scrap its initial plan to dredge the riverbed and erect levees and floodwalls to convey floods through downtown. After intensive negotiations, engineers came up with an alternative that's now broadening the floodplain instead along seven miles of the river.

The project is excavating 200,000 cubic yards of dirt to create riverbank terraces and restoring 650 acres of seasonal wetlands downstream from the city to soak up tidal flows where the river enters San Francisco Bay. To clear the floodplain, Napa bought out aging downtown business buildings, emptied a riverside mobile home park and relocated the tracks where trains depart for Wine Country excursion trips. "The real challenge is that this is land-intensive. We had to demolish 50 structures and move a railroad," notes Larry Dacus, the Corps' Napa project manager.

In 1998, Napa voters approved a half-cent sales tax increase to cover the city's 50 percent share of the project's cost. Napa's responsibility escalated to $260 million as land prices soared, but local officials say creating an attractive riverfront is reinvigorating the city's downtown. "It used to be said that our winter decoration was sandbags," Mayor Jill Techel says. "The project is giving us the protection we need, but it's also a project we don't feel is taking things away from us."

NATURAL BUFFERS

Reno, Nevada, is now pushing the Corps to develop a similar "living river" design for the Truckee River floodplain. Grand Forks, North Dakota, is creating a greenway as much as 1,500 feet wide along the west boundary of the Red River's floodplain. Across the border in Minnesota, East Grand Forks has established a state park to provide a similar buffer. The Corps, however, concluded that major structures remain essential because the region's flat terrain makes it impractical to empty enough land on both sides of the river to contain floods.

But Dexter Perkins, a University of North Dakota geographer, doubts that levees and floodwalls will work as advertised. Natural wetlands once kept the Red River under control before farmers drained them for planting, he says and "rather than just engineer barriers, you should go back and restore the wetlands." North Dakota scientists are developing a project that would pay the region's farmers to help protect Grand Forks against springtime floods. Instead of draining water from their fields when the river is running at its highest, farmers would delay spring planting in order to allow the soil to hold and gradually release rainfall once the flood threat has passed in Grand Forks and other downstream communities.

"Is that a dumb idea? No sir," General Galloway says. But in the event of major floods, reopening floodplains and restoring wetlands "is not going to do the job alone when you have gigantic flows," he adds. "We need to have a balance between structural--building higher levees and floodwalls--and nonstructural--evacuating areas that are most at risk in the floodplain. We have to address it in the whole."

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