Application of a diffusion‐erosion model to alluvial channels which degrade due to base‐level lowering

The applicability of a diffusion‐erosion model that predicts transient longitudinal profiles of degrading alluvial channels has already been demonstrated in laboratory experiments, and is here applied to some field examples. By fitting simulated longitudinal profiles to measured ones for several streams (with discharge 0.04< Q 5 <680 m 3 s −1 ) diffusion‐erosion coefficients, K , were determined which are well correlated to discharge and drainage area. Headward knickpoint migration which results from base‐level lowering was also treated through the diffusion‐erosion model. Theoretically, the distance of a knickpoint from the mouth of a tributary should be proportional to the square root of the time that elapsed since the base‐level was lowered. Field observations are in accordance with these theoretical considerations. Use of the model is discussed for prediction of erosion and for assessment of the age of alluvial fault scarps crossed by streams.