Another Hour, Another Football Field

Janice_Kaspersen_Erosion_Control-Blog

It’s a paradox: We’ve heard that aggressive efforts in Louisiana have restored tens of thousands of acres of coastal wetlands and marshes over the last decade. We also constantly hear that Louisiana is shrinking, still losing something like 75 square miles of land each year to coastal erosion, or according to one estimate, a football field every hour. Both things, it turns out, are true.

Efforts like those of the Coastal Protection and Restoration Authority (CPRA) are helping to safeguard not only habitat but also infrastructure, including ports, oil and gas facilities, refineries, and more. The CPRA has restored 36,000 acres of coastal marshes in the last 10 years and, using dredged material, has built miles of protective barrier islands off Louisiana’s shore. But it’s not enough.

The mechanisms at work are diverse and complex. Saltwater inundation from the Gulf of Mexico makes its way into marshes that once supported thick forests; as the trees die, the remaining land becomes more vulnerable to erosion. Canals created to drill and access the region’s thousands of oil wells allow saltwater to penetrate deeper into the marshes, exacerbating the problem. Meanwhile, the once-meandering Mississippi River has been confined within levees over the last century or so—a process that was essential for flood control and navigation of the river, but which prevents it from depositing the silt that made up and sustained the southern portion of Louisiana and parts of many other states. The marshes are essentially being attacked from both sides, and rising sea levels are hastening the losses. (It’s too soon to assess how Hurricane Harvey might have affected the overall picture.) This article from the Economist gives a good detailed summary of the several causes of land loss along the Gulf of Mexico and how they’re interrelated.

As things stand, and even with the efforts of the CPRA and other organizations, Louisiana is predicted to lose another 1,450 square miles in the next 50 years. One of the more radical and expensive proposals to fight the loss on a large scale is to create a series of floodgates within the levees themselves, which could periodically be opened to allow the release of silt-rich water into the eroding and subsiding areas. The US Army Corps of Engineers is evaluating the possibility. It’s not only the technical challenges that might sink the proposal, so to speak, but also political ones; those who have benefitted from the salty water moving inland—namely, oyster farmers—are objecting to the idea.

And then, of course, there’s the cost. The CPRA’s current efforts run to about a billion dollars a year, and it’s hoping for $50 billion over the next 50 years for a series of ambitious projects that it says could restore 800 square miles of land. The floodgates would eat up about a billion dollars of that amount, and it’s likely that several such projects would be needed to make a real difference.

Less than a century ago, Louisiana was gaining a square mile of land a year. With all the changes that have taken place since then, do you think it’s possible to return, if not to a net gain of land, at least to a break-even point? The petroleum industry is banking on it: Billions of dollars of oil-related infrastructure is currently being built along the coast. Is there a point at which we pull back rather than continue to defend? EC_bug_web

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