If climate scientists are right about the potential consequences of a warming globe, then New Orleans won't be the last major American city we will have to rebuild after a catastrophic weather event. It matters a great deal how we approach this, because of the precedent it sets for the future. In that vein, the guidelines that the federal government has just issued for the reconstruction of housing in New Orleans and repairs to the levee system provoke both disappointment and relief.
Many outside New Orleans would have preferred that houses in the lowest-lying portions of the city not be rebuilt at all, not just because of the recent flooding, but in light of the challenging prospect of holding back the Mississippi indefinitely. (The river is at the point of shifting its channel, as it has repeatedly over millions of years, laying down the enormous delta structure we see today. The Corps of Engineers has been fighting a rearguard action against this for years.)
Given the demography of home-ownership in New Orleans, a draconian rule was not in the cards. Instead, the guidelines require that houses rebuilt in the flood plain be elevated at least three feet off the ground, though it's not clear whether that would have been enough to prevent much of the damage from last summer's flooding. A better approach might have been modeled on that used in Galveston, TX, which prior to Katrina had suffered the worst hurricane damage in US history. The height by which buildings there must be elevated is gauged against the "base flood elevation", or the water level in a typical flood, rather than an arbitrary height above ground. Let's hope that other vulnerable coastal communities look to Galveston, rather than New Orleans, for their standards.
The good news here is the government's commitment to strengthening the levee system. This is a skill that we need to master, for potential application to other areas. The Corps of Engineers does a fine job on projects like this, but before beginning this task, they should undertake a bit of best-practice benchmarking with other flood control projects around the world, including the Thames Barrier and the Netherlands, which constitutes a country-sized sea-level management project.
Even if climate change turns out to be an exaggerated threat, we will assuredly face large hurricanes in the future, and New Orleans stands to be hit again. The new federal rebuilding standards are not ideal, but they are better than abandoning this historic city to its fate.
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