The real problem is the desire to keep the Mississippi channeled. The Mississippi wants to move and meaner--look at the shape of the delta below New Orleans. This river doesn't just keep emptying in the same spot. The result is that the silt that should be continuously ditributed along the coast ends up getting stuck before it can do any good. Whcih means they also have the expense of dredging in many parts of the lower Mississippi.
Mother Nature is hard to foil in the long run.
And the problem is, it's real people who suffer. Both the taxpayers and the homeowners. It's lunacy for a supposedly "scientifically modern" society to be building like this and encouraging it with collectivist enticements that are the exact opposite of what's smart!