Soil properties effect on random roughness decay by rainfall.

ABSTRACT Rainfall modifies random roughness (RR) at varying rates for different soils. Methods to estimate RR decay are needed for computer models which simulate physical processes occurring at or near the soil surface. The objective of this study was to estimate RR decay curves as a function of soil properties. Surface roughness has been reported for selected soils before and after simulated rainfall (5 to 80 mm on five soils, 35 to 300 mm on one soil) and before and after natural rainfall (7 to 350 mm on two soils). The soils represent a wide range of textural and physical properties. A modified exponential function was fit to normalized RR values (RR after rainfall/initial RR) using rainfall amount as an independent variable. The coefficients of this function were tiien approximated as a function of two soil properties: percentage organic carbon and percentage clay. Surface stability increased with greater amounts of organic carbon. Surface stability increased with clay content to about 31% and then decreased with greater amounts of clay. Random roughness decay curves may be estimated for specific soils by using the exponential function.