Saturday, September 10, 2005

Beware the Coming Era of Flood Control

John Tierney makes an important point in his column in today's Times. Set aside the way he focuses blame for the inadequate condition of New Orleans levees on Congress. Congress deserves blame, though Tierney should blame Bush too; he isn't exactly powerless.

In any case, the important point in Tierney's column concerns what will happen if Congress investigates the poor preparation for a hurricane in New Orleans.
My daring prediction is they would make two discoveries. First, that mistakes were made by many people outside Congress. Second, that more money must be spent on flood protection throughout America.

Amen. The Army Corps of Engineers is a big piggy bank as far as Congress is concerned. After Katrina, every Congressman is going to want a big "flood control" project.

Before we set off down that road we should remember several points:
  • Flood control projects can make floods worse. The Mississippi River wants to overflow it's banks. Building levees the length of the river not only destroys wetlands, it also insures that the river will be higher, and flooding worse, downstream, i.e. in New Orleans.
  • It isn't possible or economically productive to protect every piece of property against floods. We need a policy of flood control for vulnerable cities, especially New Orleans, and of preventing flood plain development elsewhere. Instead, I fear that we'll adopt a post-Katrina policy of mastering nature by trying to prevent floods everywhere.
  • New Orleans is a special situation, uniquely vulnerable among American cities to flooding. What makes sense for New Orleans doesn't make sense for the rest of the country.

I highly recommend Rising Tide, John Barry's superb history of the 1927 Mississippi River flood. This huge man-made disaster was caused by the Army Corps's "levees only" policy for controlling flooding. After the disaster, the Corps alleviated flooding problems along the length of the Mississippi by building channels at the mouth of the Mississippi to speed the river's flow and to push sediment beyond the mouth of the river and into the Gulf of Mexico. Unfortunately, this approach led to the erosion of the barrier islands that used to give New Orleans some protection from ocean storm surges.

After 1927, flood control policy started to incorporate floodways, in addition to levees and "channel improvements." Future flood control policy has got to make even more use of floodways-- areas designated for flooding when rivers run high. But this isn't the sort of policy that involves big spending projects like levees and navigation channels. It also requires excluding or discouraging development from substantial portions of land. So it's not the sort of thing the Congress is likely to be enthusiastic about.

So beware projects in the post-Katrina world that are sold as "flood control." They may be the opposite.

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