美国国家公共电台 NPR Louisiana Wants To Use The Muddy Mississippi To Build Up Its Coast

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The state of Louisiana is sinking. It's already lost thousands of square miles because of rising seas. The state's marshland is disappearing as a result. Now, there is an ambitious plan to divert parts of the sediment²-rich Mississippi River into those marshes³ to try and build up the coast. Travis Lux of member station WWNO in New Orleans reports.

TRAVIS LUX, BYLINE⁴: Albertine Kimble and I could have walked to the Mississippi River from her house, but it sounded like more fun to take a four-wheeler. Kimble is 56, a retired⁵ local government worker with a passion for duck hunting. She lives on a sinking patch of land about an hour south of New Orleans in rural Plaquemines Parish. We scoot up the side of a tall, grass levee built to hold the river back.

ALBERTINE KIMBLE: OK, so to the left, we're looking at the Mississippi River. This is my front yard, actually. And on the right-hand side is Highway 39 and then the marsh¹.

LUX: From the top of the levee, it's easy to see the river is murky⁶ and brown, full of sand and dirt. Kimble says there's a huge difference between this, the river side, and the marsh side.

KIMBLE: It smells fresh. Back there don't smell - it smells rot.

LUX: The marsh behind her house is dying for many reasons, but one of them is that it hasn't been getting the water and sediment from the river that it needs to stay healthy. Kimble gestures toward the river, says it's time to connect it to the marsh.

KIMBLE: This is the salvation⁷ of Plaquemines Parish.

LUX: The state thinks so too. Up and down the river, Louisiana wants to remove parts of the levee and divert some of that sediment-rich water through channels into the dying marsh nearby. The idea is that the sand and silt⁸ in the river will slowly pile up and build land. Many environmental groups support this plan; many commercial fishermen don't. They say shooting freshwater into the estuary⁹ could ruin the habitat and threaten their jobs. But the state is moving ahead. It's just built a new model to put these sediment diversions to the test.

RUDY SIMONEAUX: It looks like they're just starting to fill it up with water again.

LUX: Rudy Simoneaux is an engineer with the state's Coastal¹⁰ Protection and Restoration Authority. This model is huge - the size of two basketball courts. A deep groove¹¹ filled with water snakes diagonally across the middle of it. That's the lower Mississippi River.

SIMONEAUX: This model looks at one specific thing - the river's ability to transport bedload sand.

LUX: Engineers ran a test run the day before. You can still see a pile of black plastic beads¹² where the diversion dumped out the fake sand.

SIMONEAUX: I think we feel pretty good about what you see down there.

LUX: But a new study questions whether the river can build land quickly enough. Researcher Elizabeth Chamberlain - until recently at Tulane University - looked at how fast the river built land about a thousand years ago.

ELIZABETH CHAMBERLAIN: Between 6 and 8 square kilometers per year.

LUX: That's 2 to 3 square miles. The trouble is right now the state is losing land way faster - five times faster.

CHAMBERLAIN: It's not going to be feasible to sustain the entire Delta¹³ or to return it to what it looked like before a lot of the land was lost.

LUX: Engineer Simoneaux says he isn't surprised by the report. The state realizes that even if every restoration project is built, there will still be a net loss of land. He says that makes diverting the river even more urgent.

SIMONEAUX: You know, the longer we wait to start doing projects, it will become more difficult to catch up.

LUX: The state is setting aside more than a billion dollars to build the first diversion and is starting to apply for permits. Officials hope that by 2025, Mississippi River water will start flowing into the state's coastal marshes. For NPR News, I'm Travis Lux in New Orleans.

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