Washload and Fine Sediment Load

Washload and fine sediment load should not be used synonymously. In streams with large concentrations of fines, the sediment size D\d1\d0 may be much smaller than 0.0625 mm. The fluid becomes very viscous at low concentrations of clays and the reduced settling velocity inhibits the exchange of sediment particles between the bed and the suspension. The sediment transport capacity under those conditions remains very poorly defined. In coarse bed streams, sands and fine gravel can be considered as washload as long as the sediment transport capacity remains larger than the availability of sediment. Intermittently, different conditions prevail when the upstream supply exceeds the transport capacity.