The 1927 Mississippi River Flood was what probability expert Nassim Taleb calls a Black Swan event. Europeans once thought all swans were white. Then black swans were discovered in Australia. The Black Swan metaphor describes rare, unforeseeable, high-impact events — that seem foreseeable after they happen.
The next great flood disaster may be a Grey Swan event: rare and foreseeable — but timing unknown. The Mississippi River will change course again. That’s foreseeable because it has happened many times. Gravity sends the river down a steeper path to the Gulf when the old channel silts in and flattens. The old channel has silted in. It’s time for another change. It could happen next year or 50 years from now.
The Mississippi started to change course in 1950 at the juncture of an old river channel and the Atchafalaya River. The US Army Corps of Engineers (Corps) predicted it would change completely by 1975 and flow to the Gulf near Morgan City, LA. The change would devastate the Atchafalaya basin and leave Baton Rouge and New Orleans and its port and industrial corridor stranded on a saltwater estuary. Its impact would be greater than the 1927 flood.
In 1954, Congress told the Corps to stop the change. The Corps built the first stage of the Old River Control Complex (ORCC) 63 years ago, which has delayed it. The ORCC diverts part of the Mississippi’s flow to the Atchafalaya and keeps the rest meandering by New Orleans.
Congress had given the Corps the job of flood control on the Mississippi in 1928. The Corps developed the Mississippi River and Tributaries Project (MRTP) — and built levees, reservoirs, cutoffs, weirs, revetments, spillways, and other structures to constrain and channel the river. The MRTP was designed to pass the largest theoretical Project Flood safely to the Gulf. It may not.
It does pass lesser floods to the lower river. But not all the way to the Gulf. Politics killed critical MRTP last-mile floodways (Bouef, Atchafalaya Basin, etc.). So floods get to a sediment bottleneck at the ORCC above Baton Rouge where they slow down, get higher, and back up.
I call the bottleneck Mudberg. It could make a high flood enough higher to overtop the ORCC and jump to the Atchafalaya.
In the 1800s, Congress gave the Corps the job of improving and maintaining navigation. Steamboat captains did it first. Captain Henry Shreve’s cutoff in 1831 shortened the river distance to Shreveport (his namesake). And it left an old river channel path for the Mississippi to the Atchafalaya.
All three Corps jobs (navigation, flood control, course stability) require Congressional funding. If there’s not enough funding to go around, the squeaky wheel job gets the most. Navigation is the squeakiest. It has the most powerful proponents and congressional patrons.
In the 1980s, the Corps took a job Congress didn’t authorize. It changed its operation of the ORCC to favor a small hydroelectric plant that started up in 1990. That change concentrated sediments in the Mississippi. They fell out and created Mudberg. It jeopardizes the missions Congress did authorize.
It slows the river’s flow, makes floods higher near the bottleneck, and longer above Baton Rouge. Corps measurements quantify this. The 2011 flood was higher at the ORCC than earlier floods with the same flow. The discharge there decreased 23% from 2008 to 2015 for floods with the same height. The height increased 7.2’ vs floods with the same flow.
The higher 2011 stage surprised the Corps and nearly overtopped the Morganza Spillway before the Corps opened it to save Baton Rouge and New Orleans. Taleb says surprises indicate fragile systems.
The 2011 flood was smaller than the Project Flood. But the Corps had to blow the Birds Point emergency fuse plug levee for the first time and open the Morganza Spillway to pass it to the Gulf. It was a near thing. It won’t be a surprise when Project Flood overwhelms the system.
The third highest and longest ever 2019 flood and the fourth and fifth highest 2020 and 2018 floods are more recent surprises. They show that the river has lost carrying capacity.
The river surprised the Corps earlier in 1973 when it tunneled under the ORCC and increased flow to the Atchafalaya. It almost changed course then.
The river is a complex system. Man-made changes have unpredictable consequences. Rainfall is unpredictable. Unpredictables interact unpredictably. The system can fail in unexpected ways. It’s fragile.
Mudberg makes it more fragile. Dredging Mudberg will make it less fragile. Taleb bets on fragile systems to fail. He buys deep out-of-the-money puts on company stocks vulnerable to fragile systems. His investments pay off when the systems fail. He doesn’t bet on if. He bets on when.
Refineries, nuclear plants, petrochemical plants, grain elevators, barges, towboats, and other investments vulnerable to the course change are bets that when comes later. Owners and managers could improve their odds if they invested political capital to get Congress to fund projects that reduce the river’s fragility.
There are two obvious projects. First, dredge Mudberg. That will also enhance navigation and reduce low-water barge canal dredging. It may cost billions.
But if that delays the course change by just ten years, the present value of maintaining operations makes it cheap insurance. Delaying trillions in course change damage makes it good fiscal policy for Congress.
The second project: direct and fund the Corps to manage the inevitable course change. That cost may be greater than all previous Corps projects combined. But it will be a bargain compared to the catastrophic destruction from Nature’s uncontrolled change. Not to mention lives saved.
The Corps Commanding General says there are no plans to dredge Mudberg. It grows. Floods get higher. Course change is coming. It will be obvious after the fact that the Corps should have acted. That Congress should have funded it to act. That disaster victims should have demanded it.
Oh well.
Kelley Williams, a Northsider, is chairman of Bigger Pie, a Jackson-based think tank promoting free markets and government efficiency.
