Army Corps of Engineers has rebuilt and strengthened the levees around New Orleans, and the state has begun restoring some of the barriers islands that protect the region. Meanwhile, 10 years later, there has been a tremendous effort by the state to restore the barrier islands that attenuate the storm surge, to restore some of the marshes, to get the sediment out of the river into to the marshes to make them more resilient.” “That would leave the coast more vulnerable to the next storm. “Overnight, during hurricanes Rita and Katrina, about 215 square miles of land were lost - natural lands eroded away overnight,” she said. Army Corps of Engineers built levees and dams along the river to preserve and solidify the Mississippi’s famously meandering main channel for shipping, trapping some of the river’s rich sediment upstream and sending the rest into the deep waters of the Gulf of Mexico, forcing it off the edge of the Continental Shelf.Īll of those local factors are aiding and abetting the submergence of southern Louisiana along with global factors such as accelerating sea level rise and increasing storm intensity because of climate change, Burkett said. That soil naturally compacts and sinks under its own weight, but with each flood and new layer of sediment, the land was replenished and its elevation stayed more or less the same. It worked like this: For millennia, the Mississippi River flooded, depositing layers of sediment in the wetlands of the Mississippi Delta, creating new land by layering the region with new soil. If you imagine a situation where the land had not subsided due to this artificial drainage, there would still be a lot of flooding, but the water would have drained relatively fast.”Īnother reason the region is sinking is that humans re-engineered the Mississippi River, shutting off its natural land-building process in southeastern Louisiana. “This added a lot to the (Katrina) disaster. “As soon as you start draining these wetlands, they start sinking like crazy,” Tobjorn Tornqvist, a geology professor specializing in sea level and climate at Tulane University in New Orleans, said. In the long run, that caused the soil to compact, or subside, forcing anything on the surface - houses, for example - to sink. Much of New Orleans, except for the oldest areas situated on higher ground, was built around the turn of the 20th Century on swampy soil which was drained by engineers. In other words, it’s as if the sea level in southeastern Louisiana is rising three times as fast as the global average. Katrina The Front Lines of Climate Change: Charleston’s Struggle RELATED Stunning NASA Visualizations: Sandy vs. “The rate of subsidence of the land’s surface here in Louisiana is two to three times the global rate of mean sea level rise.” “As sea level rises, the vulnerability of the land that is exposed to the ocean is higher if the land is sinking,” Virginia Burkett, a lead author of the Intergovernmental Panel on Climate Change’s Fifth Assessment Report and the chief scientist for global change at the U.S. That, coupled with increased tropical storm intensity driven by climate change - and the inexorable disappearance of the coastal wetlands that act as a storm surge buffer - has put New Orleans in a precarious position in a warming world. The water stayed put, however, because the city is in a bowl dipping below sea level - and that bowl is getting deeper, sinking at a rate of up to 4 feet a century, primarily because the surrounding swamps were drained so the metro area could be expanded.Īccounting for the land’s subsidence, the sea level in southeast Louisiana is expected to rise by more than 20 inches by 2050. New Orleans flooded because the levees protecting it broke after the hurricane struck.
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