Levees: The Cause of Land Loss?

New Orleans, LA, August 28, 2008 — The newly constructed Levee’s in the Lower 9Th Ward. Jacinta Quesada/FEMA

I have often heard people blame the levees for the land loss crisis here in Southeast Louisiana. Like they were a curse that starved the wetlands of sediment that originally built this Delta over a period of 3000 years. 

The word “levee” presumably is French for “raised.” It was the great flood of 1927 which resulted in the Flood Protection Act of 1928, which gave the Army Corps of Engineers the go-ahead to construct higher levees to protect the citizens from losing their property and their lives. To this day, as witnessed by recent events, these levees are crucial to the protection of New Orleans and surrounding communities.

The big misconception is that these levees, so essential, have starved our wetlands of nutrients. Scientists, like world-renowned Dr. Eugene Turner of LSU, claim this is not true. While the raising of the levees have funneled the river and reduced the annual overtopping deposition of sediment, they are crucial for the survival of our present communities.

The way the Delta was created, 7000 years ago, was by annual flooding, overtopping of these levees with “sheetflow” of river water, and then receding, dropping sediment in the process. But, that was a different river than today. 

Does the river still have sediment? Yes, but recent studies have shown, that from 1851 to 1985, the sediment load of the Mississippi River was reduced by 80%. Another study recently released by the Journal of Hydrology showed that from 1980 to 2015 that those concentrations were reduced by 50%. (Scott V. Mize., Dennis K. Demcheck).

Dr. Turner, as well as other experts, now say we could “blow up” all the levees and let the river run wild, and because of the now lack of sediment, we couldn’t keep up with subsidence and sea-level rise.

It is a historic geological fact that every 1000 to 1500 years, this mighty river changes course, and where it leaves, the land subsides. The river tried to change course at the Atchafalaya years ago, but Man intervened and built the Old River Control Structure and stopped it. Had the river changed course, our river shipping industry, so crucial to our nation’s economy, would have been halted. But as we have seen, sometimes intervention is necessary. 

Our best line of defense is our Barrier Islands. Our limited coastal restoration funding should be used for the purpose of rebuilding these crucial  ”speed bumps”. After all, the storms come in from the Gulf of Mexico. These islands should be our priority. Build land from the outside in, instead of the other way around.

So, do we curse the levees and blame them for our land loss troubles? I think not. If we want to inhabit communities that are below sea level, like New Orleans, do you sink or swim?

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