Chapter IV. Sediment Sources and Sediment Yields

Methods and procedures are analyzed for determining erosion rates from water-borne sediments, along with sediment yield or deposition rates at locations downstream from the erosion source. Emphasis is placed on the erosion types and processes which cause the most engineering problems, either by virtue of the large sediment quantities involved or by the locally severe damages incurred. Accelerated erosion and deposition rates from man's activities are of special concern; these derive from sheet erosion processes on tilled lands and from such specialized activities as strip mining, urban development, construction of highways and utilities, and sheet erosion on any portion of the land surface that is denuded or inadequately protected. Erosion and deposition rates caused by channelization or runoff waters in upland gullies and downstream drainageways are also considered. Present bases for estimating these rates, on both a storm and an average annual basis, are given.