The Mighty Mississippi is trying hard to change its course. Due to the build up of silt in the lower Mississippi channel, a portion of the water in the lower Mississippi actually reaches the Gulf through the Atchafalaya River, located west of the Mississippi but connected by a vast swamp north of Baton Rouge. This process is natural. Major rivers, left to their own meanderings, frequently change their course, especially in flat, swampy country.
If left alone, the buildup of silt caused by more frequent flooding in recent years would likely have caused much more of the Mississippi water to use the Atchafalaya Basin, instead. This would have left the major port cities of Baton Rouge and New Orleans on a river too shallow for ocean liners. The Old River Control Structure, an Army Corp of Engineers project built in the early 1960s north of Baton Rouge, keeps most of the Mighty Mississippi River water flowing on down through New Orleans and on to the sea.