Thursday, May 19, 2011

Letting Mississippi run its natural course could save New Orleans from hurricanes

William Sargent in the Christian Science Monitor analyzes the stark long-term choices faced by everyone living in and near the Mississipi Delta: During the next few days the Army Corps of Engineers must continue making their Hobbesian choice between the ultimate disaster for New Orleans and an $18 billion bet that they can beat Mother Nature. To keep flood waters from breaking the levees and charging into the city, the Corps is making an $18 billion gamble that they can divert a fourth of the Mississippi’s flow down the Atchafalaya River without losing control of the situation.

The choice may seem obvious, but the Corps’ gamble also holds potentially devastating consequences for New Orleans. If it loses control of the diversion, the entire flow of the Mississippi could suddenly come thundering down the Atchafalaya – the course nature wants it to follow – never to be diverted back. Farms, towns, and oil refineries would be drowned, and the key port cities of New Orleans and Baton Rouge would be left without their river.

As the Corps begins the partial diversion of the Mississippi down the Atchafalaya, coastal scientists should seize on the opportunity to consider longer-term shifts in the river’s course. It’s possible that this crisis could lead to a less costly and more sustainable way of dealing with the problems of coastal Louisiana.

Although such a shift in the river’s path would deal a devastating economic blow to the region, allowing the Mississippi to flow west down the Atchafalaya would ultimately be in the best long-term ecological interest of the area because it would build up the southern Louisiana coast as a buffer against future hurricanes.

… For thousands of years, the Mississippi River has naturally writhed back and forth like a water hose, spewing muddy sediment loads first one place then another along several hundred miles of coast. These movements built up a number of major deltas along the southern Louisiana coast.

This shifting geography has gradually reoriented the course of the river. Now the river is running about as far east as it can possibly go, and it wants to writhe back west, away from New Orleans and down the Atchafalaya River Basin instead.

But in the late 1950’s, Congress passed a bill to save the port of New Orleans by making it illegal for more than a third of the Mississippi to flow down the Atchafalaya River basin. This is akin to passing a bill to hold back the tide….

Water is flowing through bays at the Morganza floodway, May 14, 2011. (U.S. Army Corps of Engineers photo)

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