An Inland Barrier

By Jonathan Eastwood , Features Editor

Inland South Louisiana communities like New Orleans owe a lot to barrier islands like Grand Isle.

“[If] Grand Isle goes, Bourbon Street’s gonna have eight feet of water,” Grand Isle Mayor David Camardelle says. “It’s coming.”

“[If] Grand Isle goes, Bourbon Street’s gonna have eight feet of water. It’s coming.”

— Mayor David Camardelle

Grand Isle is one of many barrier islands that are made of sediment deposited by the Mississippi River. The islands’ position at the edge of the incoming tide prevents storm surges from devastating land further inland. But just as the waves build up barrier islands, they also tear them down.

On August 29, 2021, Grand Isle was devastated by Hurricane Ida. But the direct hit to Grand Isle also helped keep storm surges from destroying inland Louisiana.

Grand Isle resident Shane Holder tended to his RV park weekly until it was covered with several feet of sand.

“All of this used to look like a golf course – I mean I mowed two or three times a week,” Holder says. “[Now] it’s deep under sand all the way across to that house.”

The National Weather Service reported that the levee breach caused overflow up to 10-11 feet on the west end of the island and five to six feet on the east end. The surges removed some low-lying structures from their supports and stranded more than 200 residents in nearby Lafitte and Jean Lafitte.

Barrier islands like Grand Isle serve as more than just protection against storms. They also form a separation between estuaries and open gulf waters. The mix of fresh water and salt water along with calmer conditions in the estuaries prove vital to many species and environmental functions.

“The shrimp are dependent at certain times of coming up into the estuary with the grasses, with the calmer and slightly fresher conditions, and then later going out into the gulf,” Coastal Protection and Restoration Authority Darin Lee says.

Barrier islands form not when a delta is building from a river’s deposit of sediment, but rather when sea water starts washing the sediment away from the coast. Because of man-made canals and levees sediment is no longer being deposited in the Grand Isle region, endangering the existence of Grand Isle and other nearby islands.

“If left to their own devices at this point, the answer is ‘no – they will not come back’,” Lee says. “There will be no new delta formed and no ability for these barrier islands to rebuild.”

Mayor Camardelle wants to place rocks in the water to protect the island from storm surges and to rebuild the coast.

“You can see where it was built – where the rocks make the little V – the sand’s building up . . . I could put all the rest of the rocks for about 50 million dollars and I could break the surge – about 12 [to] 15 feet of water,” Camardelle says.

Placing rocks is not as easy a solution as it seems, however – for multiple reasons. Rocks will simply manage the existing sediment on Grand Isle and prevent its loss, meaning sand will still need to be pumped to Grand Isle occasionally. Additionally, barrier islands form in chains as an interdependent system. Sediment from one island gets washed away and deposited at another island. Rocks would prevent another island from receiving the sediment it needs to exist.

“If you put rocks at Grand Isle then it affects, maybe, Grande Terre,” Lee says. “It is not always going to solve your problems.”

Grand Isle’s role as a barrier island leaves it to protect inland Louisiana by taking the impact of storm surges, regardless of Mayor Camardelle’s steps to lessen the impact of future storms

Grand Isle will Disappear

darin lee

Coastal Protection and Restoration Authority