Bed load refers to the sediment particles that are transported along the bottom of a river or stream by rolling, sliding, or hopping. This process occurs in rivers with sufficient flow velocity to move larger particles, such as sand, gravel, and cobbles. Bed load transport is a critical aspect of fluvial geomorphology, influencing channel shape, sediment deposition, and river dynamics.
Reference: Bagnold, R. A. (1966). “An Approach to the Sediment Transport Problem from General Physics.” Geological Survey Professional Paper 422-I. U.S. Geological Survey.