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Experts on AAAS Panel Assess How to Prevent the Next New Orleans
ST. LOUIS — The Midwest floods of 1993 along the Mississippi River and its tributaries destroyed more than 10,000 homes and caused an estimated $15 billion in damage. Recently, hurricane Katrina ravaged subsided areas of the Mississippi delta, including New Orleans, leaving more than 1,300 dead and causing over $100 billion in damage.
What do these natural disasters have in common? A panel of floodplain experts on a panel at the AAAS Annual Meeting agreed that U.S. flood control policies have failed, and have ironically helped to increase the scale of destruction.
Panel organizer Nicholas Pinter, who studies flood hydrology at Southern Illinois University-Carbondale, explained that flood control efforts have increased disaster risks primarily by opening up more floodplains to development.
“Building levees for flood control actually encourages development behind those levees,” he said. Pinter and other scientists agreed that there remains a substantial residual risk in these levy-surrounded floodplains, as the levees may fail or may not be built high enough.
The loss of life in New Orleans last year has helped underscore how important floodplain management can be, and what the adverse effect of improper management may be. Now experts worry that areas like St. Louis, on the Mississippi River, and California’s Sacramento/San Joaquin River delta, between San Francisco and Sacramento, could be the next New Orleans.
Gerald Galloway, a retired brigadier general in the Army Corps of Engineers, said the federal government needs to reassess criteria for defining what constitutes floodplains and for how levees are built. For example, he and the other panelists agreed that the extent of the so-called 100-year flood plain — the land area expected to be covered by a once-a-century flood — is significantly underestimated. Currently the National Flood Insurance Program only requires people to have insurance who live within the 100-year floodplain, they said.
Anthony Arguez, a meteorologist with the U.S. National Ocean and Atmospheric Administration (NOAA) believes that atmospheric changes have helped increase the prevalence of extreme weather events.
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"The one-hundred-year flood may now be a 50-year flood," he said. This may be due in part to rising temperatures over the last century — which sustain larger concentrations of water vapor and thus a higher potential for disproportionate amounts of rain, he said.
Jeffrey Mount, director of the Center for Integrated Watershed Science and Management at the University of California-Davis, believes that many areas of the country remain at risk for a Katrina-like disaster.
“I’m going to tell you an unhappy story that starts with a simple question: If we had known about Katrina in the past, would we have done the same things in New Orleans?” he asked. “Well, in California, we are reinventing our own Katrina as we speak.”
Mount contends that Sacramento is especially at risk, as well as the Sacramento/San Joaquin River Delta which serves as a water supply hub for 23 million people. This area, he said, is particularly vulnerable to flooding since it consists of 1,100 miles of channels and levees that “imperfectly separate those channels from the subsided islands.” Many of the islands are subsided even lower than New Orleans, some as much as 20 feet below sea level. The possibility of major earthquakes compounds the risk, he said.
Panelists shared a sense of disappointment about the lack of change in river and floodplain management following the Midwest and New Orleans disasters. Galloway attributes it to the "flood memory half-life," which he argues is very short.
"In Washington, it's already — New Orleans where?" he said. "It is very important that people keep talking about it."
Besides opening up more areas to development, said panelists, other water management decisions also help contribute to flooding. When rivers don't have floodplains to store excess water, they explained, the water is unnaturally constrained to a channel and can therefore overflow with greater velocity during a flood.
In addition, they said, riparian areas which are critical habitats for animals that are often endangered. For example, there has been much controversy regarding water management decisions on the Missouri River in recent years, which environmental groups claim threaten the habitat of the endangered Pallid Sturgeon as well as several bird species.
"Bottom line is, it’s far cheaper to have floodplain management than it is to have flood control," said Mount.
The panelists agreed that local governments need to find a way to steer development away from floodplains, which could included financial disincentives or incentives to build elsewhere.
Adolphus Busch IV, of the Anheuser-Busch brewing family and chairman of the Great Rivers Habitat Alliance in St. Louis, contends that a loophole in Tax Increment Financing law has allowed excessive development on previously pristine floodplains. Busch said that the Alliance is currently in a legal battle to preserve floodplain land near the confluence of the Missouri and Mississippi rivers north of St. Louis, and is hopeful his side will prevail.
"This whole concept of preservation and preserving these lands for [water] storage and habitat came about after the floods of '93," he said. But less than five years later, he explained, there was a renewed push to develop on land previously covered by floodwater.
Mount contends that the basic approach to flood prevention is flawed.
"When we draw a line in the sand," he said, referring to designation of the 100-year floodplain, "it is based on an analysis of historical hydrology. There’s a basic assumption which is wrong, fundamentally wrong—that the hydrology of the past is a predictor of the future… Everything we know tells us that that is not true. But yet what we have is a policy which tends to lock in place the hydrology of the future."
Panelists urged leaders to make sensible land-use policies, which they defined mostly as limiting development in flood-prone areas—while acknowledging that these decisions may be politically damaging.
"Reliable science tells us we need to change the floodplain management policies of this country," said Galloway. "The science is there. The action needs to come now."
Douglas M. Main
19 February 2006