Effect of hillslope aspect on landform characteristics and erosion rates.

Abstract

Understanding the effect of aspect on landform characteristics and erosion rates is an important prerequisite for soil and water conservation in hilly areas. In a cultivated area of the Chinese Loess Plateau, hillslope length, gradient and aspect (east, west, south, and north) were measured on two typical Mao (round loess hill), and net soil loss and location (upper, middle and lower positions) were studied using the 137Cs tracing loss ratio. Hillslope length on different aspects was in the order, north > west > east >south, but gradient changes were inconsistent and more complicated. Southern slopes were shorter and steeper, while on northern slopes, it was the opposite. Erosion rate on hillslopes with different aspects ranged from 1440 to 2631 t/km2 · a, and on northern slopes they were c.24-81% larger than on southern slopes. Upper and middle hillslope positions usually had higher erosion rates than lower positions. The greatest erosion rates were at upper positions on northern slopes, and upper positions on south slopes had relatively lower erosion rates. For hillslope positions influenced by wind erosion in winter and spring, the 137Cs loss ratio could be > 80%, while for the same positions on south slopes without wind erosion, it was < 80%. Our findings demonstrate that aspect is a key driver of landform characteristics and erosion rates on hillslopes, and they could be usefully employed for the prevention and control of soil erosion in this region.