This thoughtful article, published to coincide with DredgeFest 2014 this week in New Orleans, considers “dredging and erosion control as a form of often unacknowledged landscape architecture.”
The point of the article—and of the Dredge Research Collaborative, which sponsors DredgeFest—is that in addition to water, rivers move a great deal of soil; the Mississippi and its tributaries, for example, annually carry 200 million tons of sediment from the US to the Gulf of Mexico. Over several millennia, that sediment has created half of the state of Louisiana. Now, because so much of the river is controlled by levees, dams, and other structures, less than half that sediment reaches its destination, and Louisiana is shrinking as a result. Since 1930, the article points out, the state has lost area greater than the size of Rhode Island.
None of this is new information, of course, but the article traces some of the historical developments that have led to the current state of affairs and some of the efforts to preserve coastal marshes and wetlands, including marsh terracing, dredge pipelines (through which dredged material is carried to areas where it’s most needed), micro-dredging, and sediment diversions.
Take a look especially at the US Geological Survey map about halfway through (also available here) that shows historical and projected land loss in southeast Louisiana.