Engineers to Test Flood Defenses In New Orleans
Sunday, August 12, 2007
NEW ORLEANS -- A $3 million experiment by the Army Corps of Engineers this week will simulate the conditions that caused critical levee failures during Hurricane Katrina, leading to disastrous flooding.
In the test, engineers will gradually pump water into a section of the London Avenue Canal, one of two canals whose flood walls toppled in the storm two years ago, allowing in most of the inundation in the main part of the city.
As the canal waters rise, engineers will monitor the amount of seepage beneath the flood wall and how much the structure tilts -- while promising nervous neighbors that the test will not cause another breach. The measurements will tell them how much rising water the canal wall can withstand.
"Some computations show the wall is going to fail at certain water levels; some show it won't," said Ray Martin, a geotechnical engineer consulting with the Corps on the project. "This experiment will let us know."
The fact that such an experiment is necessary two years after the storm reflects the continuing uncertainty as to exactly what caused the city's flood defenses to fail.
Despite three investigations, disputes continue over a host of key questions. What exactly was the primary cause behind the toppling of the canal walls? Would deeper wall supports -- which, to save money, were built shorter than originally proposed -- have held the walls upright? Did earthen levees fail mainly because surging waters overtopped them, or did they crumble first because of flimsy materials? Did a major man-made shipping channel known as the Mississippi River Gulf Outlet allow the storm surge to slam the city?
Such questions must be resolved to ensure that the next set of flood defenses works as hoped, some experts say.
Equally as important -- and, perhaps more important to the thousands who are suing the Corps -- is the question of whether government agencies and contractors who built the levees and flood walls are guilty of negligence or wrongdoing.
"The bottom line is that this city was destroyed, and the public doesn't yet have an undisputed explanation," said Sandy Rosenthal, director of Levees.org, a local advocacy group. "There are a lot of questions that have yet to be answered."
Levees.org has been agitating for improved flood defenses and urging politicians to establish an "8/29 commission," a congressional body modeled after the Sept. 11 commission.
"There have been numerous studies about Katrina, without any clear direction of how to prevent a flood-control-system failure in the future," said Sen. Mary Landrieu (D-La.), who has embraced the proposal and sought to introduce it into legislation.
There have been three major engineering investigations into the disaster. The most ambitious, a $25 million effort, was sponsored by the Army Corps of Engineers and reviewed by the American Society of Civil Engineers. Another study was commissioned by the state of Louisiana. Still another was conducted by a team from the University of California at Berkeley and partially sponsored by the National Science Foundation. The reports generally agree that the catastrophe was, at least in part, an engineering failure as well as a natural disaster that overwhelmed the city.