MODELING SEDIMENT PROCESSES ON SMALL WATERSHEDS: A CONCEPTUAL FRAMEWORK Ⅱ. CONCENTRATED FLOW PROCESSES

摘要

A general modeling framework is presented for developing sediment process models by concentrated flow systems on small watersheds. A survey of fundamental principles for developing sediment process models is made with particular emphasis on the effects of space and time averaging on the governing equations. Starting from the most general one-dimensional. unsteady model of sediment processes, simpler model structures are obtained and the successive simplifications made on the governing equations in order to obtain simpler and less detailed formulations are described. Examples of computer implementations of the different approaches using specific formulations are given. Al-though some progress has been made in modeling sediment processes by concentrated flow on small watersheds. the development of improved modeling approaches should be based on better understanding of runoff mechanisms and sediment processes as functions of space and time scales over a wide range of climatic and land-use conditions. Identification and quantification of differences and similarities of watershed behavior remain important and active areas of experimental research on process-based sediment modeling. Future research priorities in the area of runoff and sediment process modeling must address the development of boundary conditions; model components (system complexity); the scales over which the equations are valid: and integration of the equations in space and time.