The physical, chemical, and biological components of aquatic ecosystems are very complex. As with temperature, fish can be acclimated to different sediment concentrations, thus providing some explanations for variable results in studies. As with temperature, natural variation of sediment in streams is high. The process of erosion and sedimentation in streams is high. The process of erosion and sedimentation is a natural process.
Problems exist when natural sedimentation rates are exceeded.
Sedimentation will vary depending on soils, storms, and upland management. The most significant source of sediment may depend on the basin size. In the Pacific Northwest, perhaps the largest source of sediment in streams is from mass failures, roads, and gully erosion, especially in large or steep basins. Some mitigation of excessive sediment in streams can occur. Fine sediment can be cleaned from the stream bottom gravel by scouring during peak flows.