ABSTRACT
Erosion (and sedimentation) occur everywhere in nature where the bottom consists of fine sediments. The scour may be caused by the structure itself, like a bridge pier in a river, or it may be the result of a natural process which the structure is meant to prevent or limit, like a protected bank in a meandering river. Awareness and knowledge of morphological processes are very important for engineering in natural systems. Local scour is a special case of sediment transport. The local velocity and the turbulence pattern determine the local erosion. When this erosion takes place in a flow in which sediment is transported, even without local disturbances, one speaks of live-bed scour. When the sediment transport is due to the local disturbance only, it is clear-water scour. Scour develops in time, reaching an equilibrium depth when the flow forces can no longer take away sediment (clear-water scour) or when the inflow and outflow of sediment become equal (live-bed scour).
