Mississippi River Coarse Change
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Growing concern about Mississippi River course change.

The Mississippi River has changed course to the Gulf every thousand years or so for about the last 10,000 years.  Gravity finds a shorter, steeper path to the Gulf when sediments deposited by the river make the old path higher and flatter.  It’s ready to change course again.  It wants to take a short cut at the Old River Control Complex down the Atchafalaya River to the Gulf at Morgan City, Louisiana.  It’s 193 miles shorter and steeper and faster than going by New Orleans.

Gravity makes water flow downhill.  The higher the hill, the greater the “head” or force driving the flow.  Floods on the Mississippi raise the water level inside the levees and increase this force.  Floods are becoming more frequent, longer, and higher — even though average annual rainfall in the Mississippi drainage basin has been almost flat since 1940.

It has flooded every other year on average since 1972 vs. once every six and a half years 1940-72.  It has flooded eight of the last ten years at Natchez.  There have been two hundred-year floods within five years (2011 and 2016).  The odds are over a thousand-to-one against this.  The average level or stage of the river has risen ten feet at Natchez since 1972.

So, the head or force to drive a course change is increasing.  Hence, the odds of a course change are too.  Ironically, this is due in large part to work by the US Army Corps of Engineers, which is supposed to control floods.  And by the Corps operation of the Old River Control Complex (just above Baton Rouge), where it restricts the Mississippi’s flow into the Atchafalaya to 23% of its volume.  This restriction, together with work by the Corps to shorten and straighten the river and speed its flow, has caused it to rise.  And to flood more.

These floods now damage property inside the levees and along the Mississippi’s tributaries (about 1.5 million acres from Greenville to Baton Rouge).  But they could lead to a catastrophic levee failure — and course change.  And to much greater damage for Louisiana and the nation.

That’s the subject of a recent article in The Advocate of Baton Rouge and also a similar recent article in The Times Picayune of New Orleans.  It’s also something we have been talking about and testifying about before the Mississippi River Commission for the last two years.

4 Comments

  1. Jason Scott Chochola on May 8, 2020 at 1:20 pm

    when did the authorities/scientists realize the river was changing course?

    • Nancy on July 29, 2020 at 2:52 pm

      An excellent book on this subject is John McPhee’s The Control of Nature.
      You might google ” Old River Control Complex ”
      The short answer, I’m afraid, is “as long as engineers have been studying it.”

  2. Thomas Wayne Woodward on May 23, 2020 at 6:58 pm

    The water crisis in the desert SW can be averted IF the flow INTO the Mississippi is substantially reduced by doing a diversion of the Missouri River’s excess flow just South of the Platte River concurrence and pipe water to the San Juan River in SE Colorado which flows to Lake Powell. This location would save billions in pipeline and pumping station cost construction since it’s at a higher elevation than the Mississippi River just South of St. Louis and hundreds of miles farther West. This diversion project would reduce the inflow into the Mississippi River enough to offset the higher incidence of flooding downstream along the Mississippi border with Arkansas/Louisiana and into the state of Louisiana itself. From an economic perspective it’s a win, win all the way around.

    • Jeffrey George Moline on July 13, 2020 at 5:09 pm

      Thank you for a sharing insight and future possibilities.

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