riverbed

The riverbed is the bottom of a river or stream, the surface on which the flow travels and the substrate that forms the channel floor. It runs from bank to bank and, along with the banks, helps determine the channel’s cross-sectional shape and hydraulic characteristics. Bed materials can range from solid bedrock to unconsolidated sediments such as gravel, sand, and silt. The texture and roughness of the riverbed influence flow resistance, velocity, sediment transport, and the development of channel patterns.

Sediment transport involves material moving along the bed as bed load, while finer particles may be carried in suspension. Erosion can lower the bed, whereas deposition can raise it and create features such as sandbars and riffles. The bed surface exhibits forms such as ripples, dunes, and scour pools, which interact with flow, affect sediment dynamics, and influence aquatic habitats. The riverbed also serves as a conduit for groundwater exchange and plays a role in nutrient cycling.

Humans modify riverbeds through activities like dredging, dam operations, channel straightening, and flood-control projects. Such interventions can alter sediment supply, bed material, and habitat quality, with implications for ecology, flood risk, and water quality. Restoration and management efforts often aim to maintain or restore natural bed morphology and sediment regimes to support ecosystem functions and resilient river systems.