A new interactive website presented by ProPublica and The Lens reveals a startling and accelerating change in Louisiana’s coastal geography. It includes a report written by Bob Marshall and is accompanied by data and maps provided by Al Shaw and Brian Jacobs.
According to Marshall, 16 square miles of the state’s coastline disappears underwater every year. Put another way, that’s one football field every hour.
In less than a century, a combination of human development and rising sea levels have turned 2,000 square miles of Louisiana into an extension of the Gulf of Mexico. The rising tide has claimed beaches, fishing camps, cypress swamps, backyards and cattle pastures, in a process that is literally unfolding before residents’ eyes.
Prior to human settlement, the low-lying wetlands of Louisiana’s coast took centuries to form. Gradually, tons of sediment carried by the Mississippi River built up into sandbars and beaches, tributaries spread the sediment over the delta, and the marsh vegetation shed detritus that built up the soil. Storms and tides carried offshore sediment back into the swamps and fortified the process.
But between 1930 and 1990, the land was redeveloped to provide easier access to the area’s rich oil reserves. Up to 16 percent of the marsh was transformed into canals, causing the land to be swallowed up by its own collapsing ecosystem.
The canals have altered the buildup of sediment in the area, which no longer allows the moisture to be squeezed out of the soil. The hundreds of feet of wet soil is now sinking below the delta, inviting in salt water and killing the root systems of the plants and trees that bind the soil together. And research confirms that the land has sunk the most where “spoil levees” have been constructed, areas where sediment has been piled alongside the canals.
In some basins around New Orleans, the land sinks one inch every 30 months. In 100 years, this will submerge the area – in some places already at or below sea level – three feet deeper. This doesn’t even take into account sea level rise, which is projected by the federal government to be between 1.5 and 4.5 feet by 2100.
Because of Louisiana’s coastal submersion, two years ago the National Oceanic and Atmospheric Administration removed 31 places from its state map – including Yellow Cotton Bay and Bayou Jacquin.
According to NOAA’s Tim Osborn, who has studied Louisiana’s coast for almost two decades, “we now know [southeast Louisiana] is sinking faster than any coast landscape its size on the planet.”
Click the link to read Bob Marshall’s full report, Losing Ground.