GEOMORPHIC CONSIDERATIONS FOR EROSION PREDICTION

Current soil-erosion prediction technology addresses processes of rain splash, overland-flow sediment transport, and rill erosion in small wa tersheds. The effects of factors determining sediment yield from large r-scale drainage basins, in which sediment movement is controlled by t he combined small-scale processes and a complex set of channel and oth er basin-scale sediment-delivery processes, such as soil creep, biotur bation, and accelerated erosion due to denudation of vegetation, have been poorly evaluated. General suggestions are provided for the develo pment of erosion-prediction technology at the geomorphic or drainage-b asin scale based on the separation of sediment-yield data for channel and geomorphic processes from those of field-scale soil loss. An emerg ing technology must consider: (1) the effects on sediment yield of cli mate, geology and soils, topography, biotic interactions with other so il processes, and land-use practices; (2) all processes of sediment de livery to a channel system; and (3) the general tendency in most drain age basins for progressively greater sediment storage in the downstrea m direction.