Caption: The Mississippi Delta, Louisana.

The Mississippi Delta is formed by the geological deposition alluvium (soil, etc.) from the Mississippi River.

The US Army Corps of Engineers and others spend much of the 20th century trying to straighten the channels in the Delta for flood control among other things. The result of straighter channels and other human activities is less geological deposition and the Delta is eroding away. The sediments that used to build up the Delta get deposited out in the deep Gulf of Mexico. By 2100, New Orleans could be submerged:

and like the lost city, leaving nothing,
but what is glimpsed in the green fathoms.
---Federigo da Montefeltro (1422--1482), apocryphal.

So now people are unstraightening the channels to increase geological deposition..

Credit/Permission: NASA, NASA: ISS EarthKam, before or circa 2004) / Public domain.
Image link: NASA: ISS EarthKam.
Local file: local link: mississippi_delta.html.
File: Earth geology file: mississippi_delta.html.