Silting

Silting is the process by which sediment, especially fine silt and clay, accumulates in a water body and gradually reduces its depth. It occurs when sediment transport into a basin exceeds the water’s capacity to carry it away or settle it elsewhere, leading to shoaling and altered flow patterns.

The main causes of silting include natural erosion from river basins, deforestation and land-use changes that increase sediment runoff, mining and construction activities that release fine sediments, and hydraulic works such as dams and levees that trap sediments upstream. Coastal areas can silting as a result of longshore transport and tidal action, while lakes and reservoirs accumulate sediments that settle in still water or slow-moving zones.

Silting commonly affects rivers, estuaries, harbors, reservoirs, and canals. It manifests as shoaling in navigation channels, reduced water depth for vessels, and accelerated sedimentation in floodplains or intake structures. In managed waterways, silting necessitates regular maintenance dredging to preserve depth and navigation.

Impacts of silting include impaired navigation and increased channel costs, higher flood risk due to reduced conveyance capacity, altered aquatic habitats and sediment chemistry, and potential reductions in water storage or quality. Sediment buildup can also trap pollutants and change sedimentary geology over time.

Management and mitigation strategies focus on sediment control and removal. Approaches include dredging and disposal or beneficial reuse of dredged material, sediment bypassing to maintain channel flow, upstream soil conservation and reforestation, check dams, and riverbank stabilization. Ongoing monitoring with bathymetric surveys, sonar, lidar, and satellite imagery supports sediment budgeting and maintenance planning.