Damage from sediment is expensive, both economically and environmentally. Sedimentation destroys fish spawning beds, reduces useful storage volume in reservoirs, clogs streams, and makes costly filtration necessary for municipal water supplies. Suspended sediment can reduce aquatic plant life and alter a stream's ecology. Because the environmental damage from sediment is often additive, the ultimate effects and costs may not be evident for years. The consequences of off-site sedimentation can be severe, both for those immediately affected and for those who must cope with subsequent problems.
Sediment often carries organic matter, animal or industrial wastes, nutrients, and chemicals.
The most troublesome nutrient element is phosphorus. In freshwater ecosystems developed under very low phosphorus conditions, large additions of phosphorus can stimulate the production of algae blooms. As the algae die, organisms in the aquatic system decompose the algae to use as a food source. In the process, they also use significant amounts of oxygen. Phosphorus may come from such sources as fertilizers, organic matter, and animal manure.