Sand, silt, clay, gravel, erosion, transport, deposition, suspended sediment, bedload, turbidity, rivers, reservoirs, deltas, floodplains, water quality, habitat, nutrients, contaminants, storms, and watershed management
Sediment
Sediment is loose material such as sand, silt, clay, gravel, or organic particles that is moved and deposited by water, wind, ice, or gravity.
What sediment is
Sediment is loose material produced by weathering, erosion, biological activity, and human disturbance. It can be as fine as clay, as visible as sand, or as coarse as gravel and cobbles.
How sediment moves
Water, wind, glaciers, waves, and gravity move sediment. In rivers, some particles roll or bounce along the bed, while finer material can stay suspended in the water column and travel long distances.
Suspended sediment
Suspended sediment is material carried within moving water. It often increases during storms, floods, construction runoff, bank erosion, wildfire recovery, or other events that deliver loose soil to streams.
Deposition
Deposition happens when water or wind slows enough that particles settle. This builds sandbars, floodplains, deltas, beaches, wetlands, reservoir deposits, and layers of mud on streambeds or lake bottoms.
Sediment and water quality
High suspended sediment can make water turbid, reduce light, clog filters or gills, smother habitat, and carry nutrients or contaminants attached to particles. It can also increase water treatment costs.
Sediment as habitat
Sediment is not always pollution. Gravel beds can support fish spawning, sandbars can create river habitat, mudflats can feed shorebirds, and floodplain deposits can build fertile soils.
Human changes
Dams, levees, mining, dredging, farming, construction, stormwater systems, and shoreline structures can change how much sediment moves and where it settles. Too little sediment can starve deltas and coasts; too much can bury habitats.
Why it matters
Sediment connects hillslopes, rivers, reservoirs, floodplains, deltas, estuaries, and coasts. Managing it well means balancing erosion control, habitat needs, water quality, navigation, flood storage, and long-term land building.