The plan was that building the berms would first stop oil, but the state eventually converted the plan into a coastal erosion fight. Of course, once they started building the berms, the oyster farmers/lease holders sued everyone involved for damaging their oyster beds. I guess they were pissed they didn't get oil in them, thus hurting their bp claims.
Just a couple more points on the subject...
First, they may have started to build the berm as a protection against the BP spill, but then switched to a coastal restoration project to maintain it. It's all about the revenue sources. Pull from one pile of money to buld it and pull from another pile of money to maintain it.
Second, I don't know that this berm was placed in a scientifically defensible location. Like I said, it was a rush job, but it could also very well have to do with the ownership of the headlands behind it. I do know that a lot of the coastal marshes in Southeast Louisiana are owned by large corporate interests. Years ago much of the marsh was owned by a company known as Louisiana Land and Exploration (a company wth its own sordid history) but by the late 90's much of that land had been sold. One of the buyers was the French petrochemical company Fina-Total. I imagine any number of corporate intersts in coastal Louisiana could have influenced the position of that berm.
Last, it seems that some oystermen generally hold a bunch of state water bottom leases for the sole purpose of suing the state. Many times these leases are held way up in the estuary where there never has ben oyster production, and these leases were bought on spec. It might take 50 years of salt water intrusion before they're producing oysters. But in many cases these leases are owned by large land owners or corporations that may not even be located in the parish where the lease is held, so there is very little interest in coastal restoration by the lease holders because the bay isn't creeping up on their
back door. So when the state comes along with a coastal restoration project to protect the inhabitants, some oystermen see it as an opportunity to make non-productive beds pay off. Sometimes they succeed, sometimes they don't.