The Louisiana Geological Survey released a report relating several of New Orleans’ characteristics to the city’s hurricane susceptibility, and a new levee system may not be the answer to the city’s problems. In the report, the researchers said drainage projects, including levees and flood-control pumps, lower the water table and drain wetland soil to facilitate urban development in New Orleans. This process compacts, oxidizes and shrinks the soil, situating the city in the bottom of a large, continuously sinking bowl. “I guess the take-home message is that in a place like New Orleans, the effects of remedial measures may be counter-productive,” said research associate Richard McCulloh. McCulloh and fellow research associate Paul V. Heinrich and researcher Bill Good began writing the report titled “Geology and Hurricane-Protection Strategies in the Greater New Orleans Area” in September 2005, in response to Hurricane Katrina. McCulloh said the report is not all original research. The writers examined existing information about New Orleans’ geology to draw conclusions for their report. In the report, the researchers said New Orleans depends on the wetlands to function as a nursery for coastal fisheries as well as a buffer zone against hurricane storm surges. Subsidence lowers the bowl and increases New Orleans’ vulnerability to severe hurricane damage because the process reduces the distance between the city and the Gulf of Mexico. “Louisiana has the highest rates of subsidence in the Gulf Coast, and it is the direct result in the geology discussed in the report,” Heinrich said. Heinrich said the major factor in New Orleans’ hurricane susceptibility is its location. He said the general conflict between navigation and flood control are also contributing factors and a problem that is common throughout the Mississippi River Basin. McCulloh said a factor that distinguishes Louisiana’s subsidence rate from other coastal areas is the Mississippi River Delta and the amount of sediment it deposits. “You can’t approach things in New Orleans like you do in Tulsa, Okla., or Boulder, Colo.,” McCulloh said. “It’s such an extraordinary setting that it does require extraordinary measures of adaptation.” In the report, the researchers said the importance of improving protection for New Orleans residents and expanding emergency public transportation systems. “Obviously, an engineering strategy using levees and pumps provides protection up to some threshold,” the report explains. “But after this threshold is surpassed, an even greater catastrophe may befall New Orleans unless the engineering strategy is combined with a greatly improved evacuation strategy.” McCulloh said most media accounts focus on a single issue that New Orleans faced during and after Hurricane Katrina. “Our intention here was to synthesize the whole complex of issues deriving from the geologic setting of New Orleans as they pertain to hurricane vulnerability,” McCulloh said. “The impression one should have is that things are not reducible to one issue.”
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