Drainage Basin Sensitivity to Tectonic and Climatic Forcing: Implications of a Stochastic Model for the Role of Entrainment and Erosion Thresholds
نویسنده
چکیده
Long-term average rates of channel erosion and sediment transport depend on the frequency–magnitude characteristics of flood flows that exceed an erosion threshold. Using a Poisson model for rainfall and runoff, analytical solutions are developed for average rates of stream incision and sediment transport in the presence of such a threshold. Solutions are derived and numerically tested for three erosion/transport formulas: the Howard–Kerby shear-stress incision model, the Bridge–Dominic sediment transport model, and a generic shear-stress sediment transport model. Results imply that non-linearity resulting from threshold effects can have a first-order impact on topography and patterns of dynamic response to tectonic and climate forcing. This non-linearity becomes significant when fewer than about half of flood events are capable of detaching rock or sediment. Predicted morphology and uplift-gradient scaling is more closely consistent with observations and laboratory experiments than conventional slope-linear or shear-linear erosion laws. These results imply that particle detachment thresholds are not details that can be conveniently ignored in long-term landscape evolution models. Copyright © 2004 John Wiley & Sons, Ltd.
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