12.2.9. Rivers in Flood Plains After the boulder stage, a river enters the alluvial plains. The bed and banks are now made up of sand and silt. The bed slope and the velocity of flow in the river are much smaller than those of boulder rivers. The cross-section of the river is decided by the sediment load and the erodibility of the bed and banks of the river. A typical cross-section of a river with a flood plain is shown in Fig. 12.1. The sediment transported by such rivers is predominantly of the same type as the material forming the channel bed. During high floods, these rivers inundate very large areas and cause considerable damage to life, property, and crops. Such rivers are also called alluvial rivers.
