INTERNAL REPORT 72 A CONCEPTUAL MODEL OF SOIL MASS MOVEMENT, SURFACE SOIL EROSION, AND STREAM CHANNEL EROSION PROCESSES Erosion Modeling Group

The conceptual framework of an erosion model has been designed to link processes of mass wasting, surface erosion, and channel storage and transport. A program to stimulate mass wasting will be based on a variation of the factor of safety approach which balances forces tending to drive mass movement against those resisting it. Surface erosion will be treated by using a form of the universal soil loss equation adapted to account for dry ravel processes as well as precipitation generated surface erosion. These processes move material eroded from hillslope landscape areas into the stream channel. Channel erosion may occur either as bedload and suspension load transport or in episodic debris torrents, triggered by debris dam failure or by mass movement from a hillslope. The model will be driven primarily by hydrologic processes and will also receive key inputs from vegetation components of the general ecosystem model. Model development will aim at producing a computer model which will have sufficient realism and predictive capability to be useful to land managers