Building boom raising flood risk

ST. LOUIS – Concentrated development in flood-prone parts of Missouri, California and other states has significantly raised the risk of New Orleans-level flooding as people snap up new homes even in areas recently deluged, researchers said Saturday.

Around St. Louis, more than 14,000 acres of flood plain have been developed since the Mississippi River lapped at the steps of the Gateway Arch during the 1993 flood. That has reduced the region’s ability to store water during future floods and potentially put more people in harm’s way, said Adolphus Busch IV, a scion of the Anheuser-Busch brewing family who is chairman of the Great Rivers Habitat Alliance.

Similar development has occurred around Dallas, Kansas City, Mo., Los Angeles, Omaha, Neb., and Sacramento, Calif., said Gerald Galloway, a professor of engineering at the University of Maryland.

“The half-life of the memory of a flood is very short. You can already hear it in Washington, D.C.: New Orleans where?” Galloway said of the lack of action in the aftermath of Hurricane Katrina last summer.

The research was presented Saturday at the annual meeting of the American Association for the Advancement of Science.

In California, development in the Sacramento-San Joaquin delta, where flood control efforts first started in the mid-1800s, represents a major risk to cities such as Stockton as they expand, said Jeffrey Mount, a professor of geology at the University of California, Davis.

“We are reinventing Katrina all over again,” Mount said.

The lack of coordination among local, state and federal officials after a flood was evident with Katrina. Similarly, even before a storm hits, coordination on issues such as land use and development is a problem, Galloway said.

“Local land decisions later result in cries for federal help. Does that make sense? No,” Galloway said, adding that the federal flood program was “rudderless.”

Bolstering levees may lure more people onto flood plains, Mount said. In California, the modest investment required to shore up a levee protecting farmland can result in a dramatic increase in the value of that land, Mount said. That in turn increases the likelihood a farmer will sell out to developers, ushering in the construction of houses on what had been flood plain.

“You actually spur development. It’s a self-fulfilling process,” Mount said.

The weather situation, too, may worsen, said Anthony Arguez, of the National Oceanic and Atmospheric Administration. “As the climate warms, we expect more extreme precipitation events. That means what once might have been a 100-year flood might be a 50-year flood,” he said.