To save New Orleans from the next disaster, more than levees are needed

A team of engineers studying the reasons for the collapse of levees in New Orleans has concluded that portions of three levees were built on soil which was too soft, and that the steel pilings were not driven deep enough into the ground. The initial theory for the collapse “that surging flood waters went over the levees and weakened them” has thus been put to rest. The Army Corps of Engineers will now have to examine the way it chooses subcontractors to do the Corps’ work, and how it supervises them.

There is another reason to the Katrina disaster: The methodical destruction of nature’s own hurricane mitigation means — barrier islands and marshes. For at least five decades the wetlands south and east of New Orleans, which helped stop storm surges from crashing inland, have been drying up as a result of the U.S. Army Corps of Engineers’ channeling and levee-bounding the Mississippi River to stop annual floods. The levees also cut off sediment flow that builds barrier islands ringing the delta. Thus, even before engineers redesign and rebuild a single levee, they must consider a more fundamental question: Can the Mississippi Delta be restored as a robust and hardy buffer which can absorb surges and rising seas? If the answer is “No,” than the alternative may well be a 300-mile wall to hold back the Gulf.

-see Scientific American discussion