[cnn-photo-caption image=http://i2.cdn.turner.com/cnn/2008/images/09/02/katrina.320x640b.jpg caption="Northern Chandeleur Islands, 60 miles east of New Orleans: before and after Hurricane Katrina. Storm surge and large waves from Hurricane Katrina submerged the islands, stripped sand from the beaches, and eroded large sections of the marsh. Today, few recognizable landforms are left on the Chandeleur Island chain" width=292 height=640]

Ivor van Heerden
Ph.D., Author "The Storm – What Went Wrong and Why during Hurricane Katrina 
the Inside Story from One Louisiana Scientist"

The Mississippi River, for the 7,000 years before Europeans settled in North America, built most of what is now coastal Louisiana.

The Mississippi river sediment load was deposited at the coast as the river went from a deep confined channel to the shallow continental shelf building over time a series of deltas. Approximately every 1,000 years it would switch it course because a shorter course existed to the Gulf of Mexico, the active delta having expanded many miles over its lifespan.

This switching of the loci of deposition was the basic geological framework. Every year the river flooded, every year it spread its life giving sediment and nutrient goodness over 100’s of square miles, maintaining the existing wetlands such that while they did subside, sediment additions and accumulation of organic matter from roots and leaf litter, maintained the wetland surface. In fresh water areas, cypress swamps abounded, as impenetrable walls to hurricane storm surges.

Based on old Indian mounds these surges never seem to have exceeded 6-8 feet.

However, along comes man; he must tame this Mississippi river ‘beast’; put it in strait jackets called navigation or flood control levees. By 1930 we had cut off the wetland’s ‘blood’ supply, no more flooding, no more wetland maintenance and growth.

Nature did try to flex its muscle; the Mississippi river tried one of its 1000 year switches, to the Atchafalaya River, a course to the Gulf some 100 miles shorter. Again, man stepped in and locked in the distribution of Mississippi flow down the Atchafalaya to about 30%. So instead of the Atchafalaya having the potential to build a new parish (county) it barely manages to maintain the two deltas at its seaward end.

The nation, however, has and continues to benefit enormously from the numerous ports that line the Mississippi River from Baton Rouge to the sea.

Now, to add insult to injury, man ‘cut up’ these starving wetlands with thousands and thousands of miles of canals and channels in support of mining very easily accessible and rich oil and gas fields.

Again the nation benefited, from very cheap domestic energy. Unfortunately, in the process the wetlands were devastated such that since the 1930’s more than a million acres have been lost, and storm surges are now Louisiana’s worst enemy.

FULL POST