A MICRORELIEF ~ D E X TO ESTIMATE SOIL ERODIBILITY BY WIND

Surface microrelief is an effective wind erosion control measure used frequently in areas where it is difficult.to maintain surface residues. The objective of this study was to develop a surface roughness index which can estimate microrelief effects on soil susceptibility to wind erosion. A soil microrelief index is developed based upon the shelter angle which is defined as the maximum angle from the horizontal between measured elevation points within a 0.3 m distance along a transect on the soil surface. Calculatin! this parameter for a large number of points within a 1 m area and determining the cumulative distribution provides an index of surface roughness known as the Cumulative Shelter Angle Distribution. The Cumulative Shelter Angle Distribution is sensitive to tillage-induced oriented and non-oriented roughness and surface smoothing by rainfall events. Points with a shelter angle less than 15 deg are considered susceptible to impact by saltating soil particles. The effect of soil ridge height on the fraction susceptible to impact at 15 dcg was similar to measured ridge height effects on soil erosion by wind