Army Corps of Engineers

Floodplains are highly utilized for agriculture, industry, and urban centers with the rivers serving as water transportation routes. Because of these activities, sites for structures must be selected, channels maintained for navigation, and the area must be protected from flooding. Alluvial depositional environments are valuable indicators of natural conditions that can assist the engineer for project planning, design, and construction in floodplains. Principal depositional environments (exclusive of deltas) are meander belts (natural levees, abandoned channels, abandoned courses, and point bar deposits), backswamp, and braided stream deposits. Each depositional environment or feature has predictable characteristics that can be related to its behaviour as engineering materials. These features are readily recognizable and can be mapped from their unique patterns formed on the land surface. The value of identifying these features has been proven by the U. S. Army Corps of Engineers where major drainage basins in the Lower Mississippi Alluvial Valley have been mapped at a scale of 1∶62,500. These maps have applied to engineering problems concerned with erodibility of river banks, areas most susceptible to underseepage, foundation conditions, suitable sources of borrow material for levee construction, and others.