Louisiana coast to disappear despite massive engineering projects

By Mark Schleifstein

Even under best-case scenarios of building massive engineering projects to restore Louisiana’s dying coastline, the Mississippi River cannot possibly feed enough sediment into the marshes to prevent ongoing catastrophic land loss, two Louisiana State University geologists conclude in a scientific paper being published today. The result: The state will lose another 4,054 to 5,212 square miles of coastline by 2100, an area roughly the size of Connecticut. The reason: The Mississippi and Atchafalaya rivers today carry only half the sediment they did a century ago — between 400 million and 500 million tons a year then, compared with just 205 million tons today. The rest is now captured by more than 40,000 dams and reservoirs that have been built on rivers and streams that flow into the main channels. Yet even if those dams were to be torn down and the river’s full sediment load employed in restoration efforts — a politically impossible scenario — it would not be enough to turn back the tide of coastal erosion, write authors Michael Blum, a former LSU geologist now working for ExxonMobil Upstream Research Co. in Houston, and LSU geology professor Harry Roberts. “We conclude that significant drowning is inevitable, even if sediment loads are restored, because sea level is now rising at least three times faster than during delta-plain construction,” according to the paper published in the “Letters” section of Nature Geoscience magazine. …

At a loss: Even the mighty Mississippi’s sediment won’t be enough to save our vanishing coast.