| Abstract: | A physically-based overland flow model focusing on the movement over complex surfaces is presented, e.g. as the basis for relevant sediment transport modelling. The sediment movement over interrill areas is treated as a two-dimensional "sheet flow" process. The relevant conservation equations, for slope gradients over 5% reasonably approximated by the kinematic wave, are locally averaged over an interrill section to account for interacting overland flow towards the rills. The transport in rills is understood as one-dimensional "channel flow" using again the kinematic wave approximation as plausible as well as economical solving approach. The locally averaged transport equations for rills and interrill areas are then average along the large-scale distance of a hillslope transect or contour line gaining the expected values of the stochastic parameters. The probability of the occurrence of rills in a combined and averaged rill-interrill transport equation finally reduces the quantitative parameter estimation and computation problem occurring in the point-scale methodology. The space-time variation of the spatial rill density, rill geometry and other stochastic parameters during storm events is assumed as constant-these changes are presently not understood at all-but can be incorporated into the model. |
