ABSTRACT
A computer simulation models landform evolution by wash and creep/splash over a two-dimensional 64 × 64 grid. The same process law is used for all points to allow the development of a valley network minimally constrained by model rules to represent erosion on a surface of constant composition. The initial surface consists of a uniform slope perturbed by subtracting a low-relief fractal surface from it. Fractal perturbation was chosen to minimize scale constraints; and some form of perturbation in either the process law or in the initial surface is necessary, as symmetry otherwise prevents the formation of channels at all.
Three model runs are presented, differing mainly in the critical unit area (i.e., area per unit contour width) at which wash transport becomes equal to creep/splash. Critical unit areas of 5000, 1280， and 320 m gave respectively no channels and average channel spacings of 2200 and 560 m. Contour crenulations indicating an eroded channel occurred at unit areas of about twice the critical values. Simulation results are compared with the theoretical criterion for unstable growth of surface hollows, and good agreement is found, supporting the theory and suggesting ways of making it operational.
