Phoenix in the Swamp
Despite the obstacles, there's no shortage of rebuilding plans
Another plan would raise some areas of the city above sea level. John Marlin of the University of Illinois-Urbana-Champaign suggests starting by filling low-lying areas with crushed stone and brick debris from demolished buildings. An elevated city would continue to sink--the inevitable result of building on soft river sediments, exacerbated by pumping out groundwater, gas, and oil. Still, with subsidence rates in the city averaging about 2 inches per decade, proponents say, a major backfilling operation could protect significant areas of the city for generations.
Hardening the city's physical defenses will be a necessity, but experts say that no long-term solution can ignore natural flood control. The bayous, marshes, and barrier islands of southern Louisiana provide the best flood insurance available--every 4 miles of wetlands, for example, can reduce the height of Gulf storm surges by a foot. But coastal Louisiana has lost more than 1 million acres of wetlands over the past century. Shipping channels encourage erosion, and the levees and upriver dams that protect New Orleans from Mississippi River floods make the city more vulnerable to Gulf floods by robbing wetlands of the new sediment they need to rebuild. The solution, says Bahr, is to replumb the Mississippi River Delta to allow more water and sediment into the marshes. Engineers could help nature at both ends of the Mississippi, Marlin says, by barging excess river mud, currently choking marshes and rivers in Illinois, down to wetlands in Louisiana.
Planners and engineers will also be looking to other flood-prone countries for the latest flood control technologies. In the Netherlands, maintaining a comprehensive network of floodgates costs about $500 million per year--expensive, but effective enough to keep the 10 million Dutch citizens living below sea level safe for over 50 years. But such models are not always inspiring. In Bangladesh, where cyclone-driven floods killed more than 130,000 people in 1991, the government lacks funds for high-tech protection. Instead, it has constructed hundreds of elevated concrete shelters, which offer flood victims a safe haven.
New Orleans could become a model of smart planning and coastal protection. Or it could be rebuilt on the cheap, leaving its residents as exposed to the inevitable next hurricane as Bangladeshis clinging to a concrete tower in a monsoon. "Right now the window of opportunity to make the right decisions is open," says Bahr. "It won't be for long."
REDESIGNING NEW ORLEANS AND THE DELTA
After the floodwaters recede, New Orleans will be rebuilt. Engineers, urban planners, and geologists say Katrina's devastation provides a rare opportunity to make long-needed upgrades to the city's flood control system. Just as important, scientists say, keeping the Gulf region safe in future storms will require a radical replumbing of the Mississippi Delta.
[Map labels]
Mississippi River
New Orleans
Lake Pontchartrain; Industrial Canal floodgate; Chef Menteur Pass floodgate; Rigolets Pass floodgate; Floodgate
Lake Borgne
Lac des Allemands
Proposed artificial canals
Bayou Lafourche
Middle Barataria Basin wetlands
Breton Sound
Head of Passes
Gulf of Mexico
COMMUNITY HAVEN
This approach would surround central New Orleans with a ring of flood walls. But it's an uncomfortable compromise. Like a medieval city, the safe haven would protect the city core and serve as an emergency refuel. But outlying neighborhoods would still be vulnerable.
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