It also kills the animal organisms by clogging their gills and feeding structures. The bedload, is gradually washed along the bottom and not carried in suspension. As particles are tumbling along the bottom, they knock organisms off rocks, bury and smother life on the bottom, and fill in hiding and resting sites of fish and crayfish. Aquatic plants cannot reestablish themselves at the bottom because the bottom is constantly changing. The Environmental Protection Agency ranks sediments as the number one problem for U.S. streams and rivers.
Sediments eventually settle out in a lake or pond, but they start to fill in the lake or pond.
To solve this problem, the U.S. spends billions of dollars each year dredging out the lakes and ponds. This, however, presents another problem which is disposal of the dredged sediments. In a natural ecosystem, eutrophication is a natural process. Erosion and nutrient-leaching are very low, but they do occur. Bodies of water gradually become enriched with nutrients over periods of hundreds or thousands of years.