ohhhhh man, big bucket of worms there. It's a really, REALLY complex problem down this way in SE La with physical, economic, and socioeconomic factors in play. I'll give you some bullets below:
1.) The Mighty Miss. formed much of S. La with various deltas that constantly moved over time many many years ago
2.) The construction of levees got rid of that process of constantly putting muddy water across wetlands to nourish them and build them through sediment deposition. Now that sediment laden water just falls off the continental shelf below Venice, La.
3.) People now live in places that used to be nourished and now have been left to erosion with the river's path now controlled. The firm I work for is currently helping with an effort to relocate the nation's very first "climate change refugees"....that is a group of people, in this case an indian tribe, that's lived in a remote area of coastal Louisiana that's now inundated on a routine basis. Some want to leave, some are adamant about staying put.
4.) People dont want to leave those places but BOTH erosion AND subsidence are taking their toll, the land that is there is literally sinking. Couple that with some slight sea level rise, and you have roads flooding that didn't used to, higher storm surges from hurricanes, etc.
5.) These are sediment diversions that are proposed as part of the coastal master plan, and they take some time to show progress. Much of it is too little, too late, but there is significant evidence of new land growth in recent years where deltaic processes have been allowed to do their thing without levees (see Atchafalaya River delta/Wax Lake area).
https://phys.org/news/2017-02-nasa-rari ... eltas.html
6.) Overall these diversions will help, but at a cost. Some fisherman, both commercial and recreational, will be displaced. Game species are not big on muddy fresh water, nor are crabs, oysters and shrimp, so that will have impacts to economic engines in the region. (e.g. guys want to keep catching their fish and shrimp, crabs, oysters, etc. right where they always have, even though it may not be where they should be). These species will be displaced, that makes the fisherman work harder, they get upset.
7.) The alternative to diversions is dredging, which works, and works immediately, BUT is extremely costly.
8.) Those that want diversions are highly vocal, those that are opposed are highly vocal. Makes for interesting and fruitless public meetings.
This particular diversion near Myrtle Grove is one that's been fast tracked for permitting, there is no time to spare, each day the coast loses a whole lot, something like a football field per hour is what's widely speculated.
That's the gist of it off the top of my head. I stay on the periphery of this issue, it's a hot one down this way.