Floodplains

As rivers extend from high areas to the lower lakes or seas, they pick up silt or alluvium and deposit it further downstream. The flow of water tends to decelerate as the amount of alluvial material increases, and because the slope along which the river flows tends to flatten. Depending on the kind of ground through which the river moves, the water may continue downcutting into the ground, or else build up the floor and walls of the river through alluvial deposits. Where the latter occurs, a floodplain may be created in which the river flows laterally and covers the land during times of high flow. In these cases, the flat floodplain can be rapidly flooded and thereby bring about large-scale displacement and drowning of ...