Man vs. Nature


Publication:
Date: 
November 7, 2018
Can engineering save Louisiana’s coastline?

Down at the southern tip of Louisiana, on a barrier island called Grand Isle, the stilts holding up the houses are getting taller. There are about 20 feet of air between the ground and the top of the pilings holding up a new two-story house on the island’s main drag, running parallel to the Gulf of Mexico. Its neighbors, a few hundred single-family homes and weekend getaways with house names on wooden signs, are almost all raised up off the ground. C’est La Vie is propped about 8 feet up. The Salty Oyster: 12 feet. Riptide: about 15. A nameless rectangular bunker made entirely of cast concrete is 10 feet up on top of a grid of concrete columns and a cinderblock ground floor. Down the road, another set of 10-foot pilings is all that’s left.

Building at any height on Grand Isle is a bold proposition. Seven miles long, a mile across at its widest point and just a few feet above sea level, it’s a tall wave away from disappearing into the Gulf. With a steady onslaught of hurricanes, sea-level rise, and land subsidence, the island’s very existence is improbable. And yet remarkable efforts have been made to preserve this small strip of land, including the dredging and piping of sediment from the Mississippi River to build back its southern shore and replanting the disappearing marsh to its north.

Saving the island is partly about saving the homes of roughly 1,100 full-time residents and the estimated 20,000 who come to Grand Isle during the summers, but it’s also a strategic defense for coastal Louisiana and the Mississippi River Delta, where subsiding land and rising waters have caused the loss of more than 2,000 square miles of land between 1932 and 2016, according to the U.S. Geological Survey. That’s about a football field’s worth of land roughly every 100 minutes in recent years. In addition to being a scenic vacation destination, Grand Isle is a crucial buffer that’s helping Louisiana hold on to its delta a little longer.

“You see stories in the media on global climate change and cities like San Francisco or Miami, how they’re going to, 50 years from now, be having recurring tidal flooding and things like that,” says Corey Miller, outreach and engagement director of the Coalition to Restore Coastal Louisiana. “Here in Louisiana, we’re experiencing a little bit of an early glimpse at what that’s going to look like.”

Coastal Louisiana is on the front lines of a battle against land loss common to river deltas around the world, from the Nile to the Mekong, where extreme weather and rising sea levels are chewing away at coastal lands. As in many of these regions, Louisiana’s land loss has been unintentionally exacerbated by projects that were meant to be beneficial—river-control structures to make the Mississippi River’s path more dependable, levees built on its shores to prevent the flooding of cities like Baton Rouge and New Orleans, canals cut to ease the movement of goods from what’s become one of the most important ports in the country. In many ways, these projects have enabled coastal Louisiana to thrive. But they’ve also severely limited the river’s ability to deposit its sediment—the natural process that built this delta in the first place.

“The idea now,” says Ehab Meselhe, a coastal wetlands expert and former vice president for engineering at the Water Institute of the Gulf, from his office on a refurbished dock in Baton Rouge that juts out over the Mississippi River, “is how can we find solutions or strategies that can help us reconnect the river to the basin, find an effective way, as natural as possible and as self sustaining as possible, to build land while we are maintaining coastal Louisiana as a working coast?”

This balance of ecology and economy is at the root of a grand transition underway in coastal Louisiana. In the past, the delta ecology was mostly overlooked as government officials prioritized flood controls and the region’s economic growth. Today, under a $50 billion, 50-year Coastal Master Plan created in the wake of Hurricane Katrina and led by the state’s Coastal Protection and Restoration Authority (CPRA), more than 100 projects, like those on Grand Isle, are in progress to try to help the delta’s ecology recover while allowing communities and businesses to carry on. ...