Microtopography as an indicator of modern hillslope diffusivity in arid terrain

Abstract

Diffusion of topography is normally considered a smoothing process, but at the scale of the diffusive disturbance, diffusion becomes a roughening process. Roughening is exemplified by topographic features associated with disturbances such as animal burrows, hoof prints of grazing animals, and small landslides (here called large-scale processes). Diffusive processes that make small or indistinct topographic landmarks, such as rain splash and rheological creep (here called small-scale processes), tend to erase these roughness elements. The ratio of the small-scale diffusion coefficient to the large-scale diffusion coefficient can be estimated by a measurement of the areal density of large-scale disturbances. In lightly vegetated, arid terrain, small-scale diffusion is dominant unless large-scale roughness elements cover a large fraction of the surface. The values of large-scale and small-scale modern diffusion coefficients can be estimated if the rate of generation of large-scale disturbances is known. Such estimates are performed for a burrowed fault scarp in Nevada.