Changes to substrate conditions (rivers)

The structure and composition of the river bed (or substrate) can be altered by in-channel maintenance (where effects may be temporary) or replacement of the natural channel bed with artificial bed control structures. Substrate conditions (type, size and grading of sediment) of the river are important in providing habitat for all biological elements. Adjustment of the channel bed is also an important response of the river to changes in flow and sediment regime and preventing this mechanism by creation of an artificial bed can result in increased bed scour downstream and accelerated bank erosion.

Concrete lattice-work artificial bed on the Wynsham Stream in the London Borough of Bexley

Dredging of a land drainage ditch running through Roding Valley Meadows SSSI in Loughton, Essex

Mitigation measures