Deterministic Models of Channel Headwall Erosion: Initiation and Propagation

Channel erosion in small upland watersheds is the general topic of this research effort. Specifically, the effort is directed toward fundamental mechanics of channel erosion resulting from the development of channel gully headwalls and scour holes, from channel sidewall failure and from general shear excess. The emphasis is on erosion in cohesive channel materials. Entry of sediment into our nations waterways is a serious pollution problem, intensified by the chemicals adsorbed on the exchange phase of clay particles in the sediment. The subject of upland erosion form rill and interrill areas has been the subject of intensive investigations, both empirical and physically based. Channel erosion has been studied primarily from an empirical basis, with virtually little physically based information on channel headwall development and propagation and of channel bank failure. In the research conducted under this project, models are developed which predict channel erosion resulting from shear in gradually varied flow, shearing forces resulting from submerged and partially submerged jets and shearing forces resulting from free jets impinging a plunge pool. These models are linked with a runoff routing algorithm to develop the channel model. This model predicts general channel erosion resulting from time varying gradually varying flow as well as predicts the development and propagation of channel headwalls.