Bedload transport consists of mostly larger clasts, which cannot be picked up by the velocity of the streamflow, rolling, sliding, and/or saltating (bouncing) downstream along the bed. Suspended load typically refers to smaller particles, such as silt, clay, and finer grain sands uplifted by processes of sediment transport. Grains of various sizes and composition are transported differently in terms of the threshold flow velocities required to dislodge and deposit them, as is modeled in the Hjulström curve. These grains polish and scour the bedrock and banks when they make abrasive contact.