Sediment load is the total amount of solid material transported by a river or stream, including suspended sediment, bedload, and dissolved load. Excessive sediment degrades water quality and aquatic habitats.
Sediment load refers to the quantity of particulate material carried by flowing water, encompassing three components: suspended load (fine particles such as silt and clay carried within the water column), bedload (coarser particles such as sand and gravel that roll, slide, or bounce along the channel bottom), and dissolved load (material carried in solution). Sediment load is typically expressed in mass per unit time (tonnes per day) or as a concentration (mg/L). Natural erosion processes generate sediment, but land use changes including deforestation, agriculture, urbanization, and mining can dramatically increase sediment delivery to waterways. Excessive sedimentation can bury fish spawning gravels, clog the gills of aquatic organisms, reduce reservoir storage capacity, increase water treatment costs, and transport adsorbed pollutants such as phosphorus and pesticides. The U.S. Geological Survey operates a network of sediment monitoring stations across the country, measuring suspended sediment concentration and computing sediment discharge. Sediment rating curves, which relate sediment concentration to stream discharge, are commonly used for estimating long-term sediment yields. Best management practices for sediment control include erosion control structures, sediment basins, vegetative buffer strips, and contour farming.