What term describes the load of coarse sediment that moves along the riverbed?

The correct term that describes the load of coarse sediment that moves along the riverbed is bedload. Bedload consists of larger particles, such as gravel and boulders, which are transported along the bottom of the river through processes like rolling, sliding, and jumping. This movement occurs due to the force of the water current, which is strong enough to lift and carry these heavier materials along the riverbed.

Other terms related to river transport describe different types of sediment movement. Suspended load refers to fine particles that are carried within the water column, not along the riverbed, and stream load is a more generic term that encompasses all materials carried by the river, but doesn't specifically emphasize the coarse sediment that operates along the bottom. Alluvial load generally refers to the sediments deposited by flowing water, particularly at river deltas or floodplains, rather than specifically addressing the sediment movement along the riverbed. Thus, bedload accurately captures the movement of coarse sediment along the riverbed.