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Aerial photograph of Atchafalaya Delta. (Photograph by Arthur Belala, U.S. Army Corps of Engineers)

Is Louisiana delta growth giving hope to state’s coastline?

For more than 80 years, Louisiana has been losing ground. Literally. But one area of Louisiana’s coastline is giving the state reason to hope. Two deltas in Atchafalaya Bay have exhibited phenomenal growth over the last 30 years, and the scientific community is hoping they will provide some hints on how to save Louisiana’s boot from disappearing.

The West Lake Outlet delta and the Atchafalaya River delta in St. Mary Parish have expanded into the Gulf of Mexico, building up the marsh habitat in the Atchafalaya Delta State Wildlife Management Area. The increased surface area of land in the delta region is caused by silt, which is deposited as the river flows into the Gulf. The sediment shores up existing land areas further into the Gulf, causing the area to grow.

The Atchafalaya River and the West Lake Outlet flow slowly, allowing that sediment deposit to take place over time. The Atchafalaya River is actually a distributary of the Mississippi, and according to NASA, most of the Mississippi’s water would flow down the smaller river. But in the mid-1900s, two major developments stymied the natural flow. The U.S. Army Corps of Engineers dredged a new channel in 1941, now known as the Wax Lake Outlet. About 40 percent of the water from the Atchafalaya is now redirected through the outlet.

Then in the 1960s, the Army Corps built the Old River Control Structure, a diversion system that cut the amount of the Mississippi which flowed into the Atchafalaya down to 30 percent. Because that flow is divided nearly in half by the Wax Lake Outlet, the flow of both areas slowed down significantly, allowing for more sediment deposit into shallow waters and more rapid growth in the delta of the Atchafalaya Bay area.

Image via NASA

Image via NASA

But now it looks like this:

Image via NASA

Image via NASA

Scientists are now looking to this region in the hope that it will provide clues to restoring Louisiana’s weakened swamps and marshes, but there is particular interest in efforts to save the Mississippi River’s delta. Unlike the Atchafalaya delta area, the Mississippi has consistently lost surface area.

Part of this is due to the system of levees built after the Great Flood of 1927, according to CityLab. Immense amounts of rain caused the lower Mississippi to overcome already-existing levees and devastate states in the Mississippi Valley. To ensure that those areas were safe in the future, the levee system was expanded. As a result, however, sediment brought by annual flooding could no longer be deposited in the river’s delta area, which makes up the tip of Louisiana’s boot, which weakened the wetlands that protect the coast from hurricane damage. Those levees have also forced the flow of the river directly into the Gulf at a faster pace, too quickly to ensure that silt is deposited in the shallow waters of the delta.

While levees denied the necessary deposits, the oil and gas industry proceeded to take more away. In the 1930s, oil and gas drilling expanded across the region, creating 50,000 wells and dredging 10,000 miles of canals, debilitating the wetlands and leaving Louisiana’s coast incredibly vulnerable. Over the last eight decades, it is estimated that the state has lost approximately 1,900 square miles of land, and if nothing is done, it will lose a lot more.

In 1932, this is what the area around Port Fourchon looked like:

Image via the National Oceanic and Atmospheric Administration

Image via the National Oceanic and Atmospheric Administration

By 2011, the same area had been drastically reduced to this:

Image via the National Oceanic and Atmospheric Administration

Image via the National Oceanic and Atmospheric Administration

Now the state has a plan in place to help restore the coastline and protect vital economic and environmental areas of southern Louisiana. The $50 billion lineup of projects and ideas is set to stretch to 2050. Unfortunately, this plan currently does not contain provisions to aid the Mississippi River’s final section. Although the land gains in Atchafalaya Bay won’t be enough to counteract the football field-sized area of land which sinks every area in Louisiana, the Atchafalaya River and Wax Lake deltas are being eyed by the scientific communities. If studies on the Atchafalaya delta region are successful, they could lead to more successful restoration projects along the Gulf Coast.

Such restoration projects would require more diversions of Mississippi waters, which could potentially help to slow the river’s flow and allow for the deposit of silt before it is pushed into the Gulf of Mexico. On the other hand, it would deter that some of that sediment from reaching the mouth of the Mississippi at all. Careful calculations will need to be done and areas will need to be prioritized before such projects can be undertaken.

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