The Mississippi is mighty, and a by product of that might is that a lot of soil and mud gets contributed to it and washed away by it. If you want proof, just go to google maps and check out the mouth down by New Orleans. There’s so much silt being washed out to the ocean that it clouds the water for miles and is easily visible by satellite. I was treated to a nice view of Mark Twain’s favorite river on a flight from Ohio to Dallas. I grew up on one of the Missisippi’s tributaries, the Ohio River. They look pretty similar and to be honest I don’t know that I could tell them apart just from looking at a static image.