Why Does It Flood Part 2

Why Does It Flood When Levees Don’t Break? And Other Questions. Part 2

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Q.  What went wrong with changes to the river intended to control flooding?

A.  Wrong focus. Politics trumped engineering. Unintended consequences.  The changes focused on containing floods and preventing levee failures instead of minimizing and discharging floods. Result: higher levees and higher floods. The Corps says $14 billion spent on the MR&TP has saved a trillion dollars in flood damages from prevented levee failures and has a benefit to cost ratio of 70:1.  It counts imaginary savings and ignores real damage from floods without levee failures.  The Corps builds levees 3 feet higher than floods to provide a margin of safety.  It keeps raising levees as the river keeps rising. Where does it end?  Will levees grow to the sky?


Q. What else went wrong?

A. Politics trumped engineering.  Cutoffs were intended to minimize floods by speeding them to the sea.  Faster floods are lower and shorter.  Sixteen cutoffs completed in the mid 40’s shortened the lower river 152 miles, and made it steeper.  They worked as intended for a while.  The river was so benign in the 1950’s that Congress passed the 1954 Flood Control Act (FCA) to keep the river’s flow to the Gulf like it was in 1950.  Congress tried to lock the river in a time capsule.

But the river broke out.  In 1950, 77% of its flow discharged to the Gulf at New Orleans via the main channel.  The other 23% flowed down Old River (a natural channel north of Baton Rouge) to the Atchafalaya River and then to the Gulf at Morgan City, LA.  This is a shorter steeper path to the Gulf than via New Orleans.  As flow downriver increased due to cutoffs and other changes, flow down Old River naturally increased.  When it reached 40% of the total, experts feared the main channel would shift to Morgan City leaving New Orleans without a port (the largest for U.S. agricultural exports) and Baton Rouge without a ship channel.

So, Congress ordered the Corps to dam up Old River and build the Old River Control Structure (ORCS) to limit the Mississippi’s flow to the Atchafalaya.  The ORCS began operating in the 60’s and cut the flow back to 23%.  Not surprisingly, the river began to rise in the 70’s.  The faster flow couldn’t get out to the Gulf fast enough.  It still can’t.  The 1954 FCA and its 23% bottleneck are still law.


Q.  What else went wrong?

A.  More politics.  Planned floodways to increase flow to the Gulf weren’t built.  A spillway (Morganza) to relieve floods doesn’t work as planned.  Not-in-my-backyard politics blocked construction of the Eudora and Boeuf floodways to add flow capacity through Arkansas and Louisiana down the Red River basin to discharge at Morgan City.  Local politics blocked a floodway in the Atchafalaya basin to discharge increased flow at Morgan City.  The Morganza spillway that replaced it has been opened twice since built in 1954, but discharged less than one third its design flow.  It’s a key part of the MR&TP Project Flood plan that’s supposed to discharge flow from rains like those that caused the 1927 flood.  It provided little relief in the lesser 2011 flood. What’s Plan B if it doesn’t relieve the great flood either when it comes?


Q.  What are the unintended consequences?

A. The river is a complex non-linear sometimes chaotic and constantly changing natural system.  It reacts to man-made changes in unpredictable ways.  Higher levees weren’t intended to cause higher floods. But they do.  Cutoffs weren’t intended to cause bank erosion and channel damage.  But they do. Training structures were intended to enhance navigation at low stages, not make floods longer and higher.  But they do.  The 1954 FCA that restricts discharge of faster flow to the Gulf wasn’t intended to cause the river to rise and flood more.  But it does.  The Old River Control Complex (ORCC), which replaced the damaged Old River Control Structure after the 1973 flood, wasn’t intended to cause a bottleneck downstream in the main channel (from silt deposits) that further restricts discharge to the Gulf.  But it does. Project Flood designed to pass a 500 – 1000 year biblical flood wasn’t intended to flood the batture every year. But it does.  And so on.


Q.  What can Congress and the Corps do now?

A.  They can’t unscramble an egg.  But they can mitigate effects of some changes.  The 1954 FCA can be amended to increase the flow at ORCC and the discharge to the Gulf at Morgan City and to vary the flow as the river’s stages and flow change.  The increased flow and dynamic operation of ORCC can mitigate flooding.  The ORCC has unused capacity.  But more floodways may be needed.  Building them won’t be politically easier now than it was 75 years ago.  But political fallout from levee failures and a course change could be much harder to deal with.  The higher the flood, the greater the risk of levee failure.  The higher the levees, the higher the floods.


Q.  What can flood victims do?

A.  Congress and the Corps have changed the river to benefit some and harm others.  Changes cause batture and backwater floods that have damaged private property without permission from or compensation to owners.   Public opinion is gradually changing as flood victims understand and complain. The Overton Window is moving.  The perception is changing from “the Corps knows best” to “the Corps makes the same mistakes over and over.”  More flood victims can speak up.  Louder!

Some property owners in Louisiana, Arkansas and Missouri have sued for damages under the “takings clause” of the Fifth Amendment of the Constitution.  Litigation is pending.  There may be more litigation from other property owners.


1 Comment

  1. Jim Dawkins on February 22, 2019 at 11:12 am

    Confirms what some of us have been thinking. It also gets down to plain common sense.

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