THE EFFECT OF RAINDROP IMPACT AND SHEET EROSION ON INFILTRATION-RATE AND CRUST FORMATION

Soil crust formation can result from the beating action of falling dro ps (structural crust) or the deposition of entrained eroded suspension in shell flow (deposional crust). To determine the relative importanc e of the two processes, an experiment was carried out with rainfall si mulation under laboratory conditions. Clay soil exposed to the beating action of rain drops produced sheet erosion, which was deposited on a layer of clean sand downslope of the same continuous slope. The thin crust that was formed on the two parts of the slope, the clay and the sand, reduced the infiltration rates in time to values of 1 to 5 mm h( -1). In comparison with the uniform clay slope, the main difference wa s the longer time needed to reach the low infiltration rates. Preventi ng the sand part from any rain impact beating extended the time needed to obtain the low infiltration rates that were nearly the same as tho se of the clay slope. The results provoke the question is the common t heory of compacted crust by rain impact such an important factor?