Levees—Taking the Long View
Hurricane Katrina stormed across southeast Louisiana in August 2005, overtopping several levees and leaving the levee system in New Orleans so fractured the city continued to fill with water from Lake Pontchartrain for several days. The water rose and fell with the lake tides until the breaches could be repaired.What took days to flow in took weeks to pump out. The slow deterioration of buildings subjected to long-term inundation produced a protracted loss that kept property owners in agonizing uncertainty for months.
Through the latter part of 2005, New Orleans and its levees were constantly in the news, with the design, construction, and politics being thoroughly investigated, and the findings widely publicized. People are intensely interested—some needing simply to understand how such a thing could happen, some wanting to cast blame.Many others who live behind levees all across the country must be wondering, “Can this happen here?” Still more people, behind those same levees, are totally unaware that levees are responsible for their flood-free lifestyle.
It would compound the tragedy of New Orleans if we fail to capitalize on the public interest in levees generated by this disaster.We have an opportunity to transform that interest into actions that can help levee systems—and their owners and operators—live up to public expectation and bring public perception of what levees do more in line with reality.
This article begins with the basics of levee design and construction, distinguishing levees from dams and floodwalls. It looks specifically at potential levee failures for which knowing about the potential may lead to the kind of attention, care, and maintenance that can prevent the failure. For these potential failures, the article offers opportunities for local officials and community leaders to improve the performance of their systems. The sections on design and failures draw heavily from the 2000 edition of the U.S. Army Corps of Engineers Design and Construction of Levees manual.
The damage caused when levees fail is attributable not only to water flowing onto the land but to the property owner’s having been totally unprepared for such an event. So, in addition to looking at the levees themselves, the article suggests that levees will provide better protection if we change the way we regulate and insure development in the areas protected by them. It concludes with a discussion about how we communicate flood risk in general and specifically what messages we are sending to property owners about levee protection and their residual risk of flooding.