Treading Water

A nine-month flood has tested the colossal engineering that restrains the Mississippi River. Now, as the climate changes, experts say this system may not hold

- Boyce Uphol

BY MAY 9, 2019, THE U.S. ARMY Corps of Engineers had been in a flood fight in Louisiana for nearly 200 days. Officials gathered every morning in a conference room in New Orleans that was—perhaps thankfully— windowless, keeping their opponent out of view: just below the office snarled the overladen Mississippi River, more than 8 million gallons of water ripping past each second.

That morning the team discussed the latest forecasts and notes from inspectors, who were assessing every foot of every levee every day. They were dealing not with a river, really, but with the Mississippi River & Tributaries Project: the web of canals and spouts the lower Mississippi has become, with floodgates that can be opened or closed to redirect the water on command. The New Orleans team had been focused on the Bonnet Carré Spillway, which diverts water from the Mississippi into Lake Pontchartrain, connected to the Gulf of Mexico, during floods.

Whether to open a spillway can be an agonizing decision. When the Bonnet Carré is activated, the rush of fresh water can decimate the Gulf’s saltwater ecosystems and seafood industry. Another spillway, the Morganza Floodway, has been used so infrequently (only twice since it was built in 1954) that many people farm within its boundaries. When the Army Corps considered opening it earlier this year, ranchers scrambled to move their cattle out of harm’s way.