The Mississippi still follows its path to the Gulf because of human intervention. It is really little more these days than a concrete-lined barge canal critical to the US economy. The old river control structure where the Atchafalaya and Mississippi diverge has a federally-mandated water split between the two rivers. If it were up to the river, it would have gone down the Atchafalaya some time ago, leaving New Orleans and its huge port as a silting backwater on the river.

The scary thing about the Mississippi delta and Lousiana coast is that it's not growing because the mouth of the river dumps over the edge of the continental shelf, putting most of that silt load into the deep ocean. Ocean eats at the coastline, deep sediments compact, and the land sinks. No new sediments replace the lost land.

Rivers silt up. Rivers change course. It's what they do. The classical city of Troy had a harbor; The site of Troy today is Troy is fully 5 km from the coast. Ostia, the port city of ancient Rome, is 3 km from the coast. To expect that our cities should be immune from this is silly. If you want to live on the coast you need to make concessions. If your city is wiped out by a hurricane, you either build a new one in the same place and same conditions and accept that it will happen again (New Orleans) or you raise the whole city site and armor the heck out of it (Galveston, TX). Even then, you know you're going to lose eventually. If we just keep building higher levees around cities like New Orleans then eventually it will a little sucker-mark of dry land bounded by hundred-foot-high barriers out in the middle of the Gulf.