Pollution of gravel spawning grounds by deposition of suspended sediment

Observations have shown that accumulation of fine sediment in the pores of spawning open-work gravel have a detrimental effect on stream biota. The rate of deposition is intimately linked to the concentration of suspended fines near the gravel bed. If interstitial voids in coarse sediment deposits are filled or covered with sand or inorganic fine materials, their habitat value is greatly reduced. In this paper, a simple method is proposed to predict analytically the concentration profile and transport of fine suspended sediment when a steady, uniform suspension flows from a sediment-covered bed to an open-work gravel bed. Comparisons of the analytical model predictions with previous laboratory observations show reasonable agreement. The proposed solution can be used to estimate 'clarification distances' for streams carrying fine sediments over open-work gravel beds.