A Study of Soil Erosion on a Steep Cultivated Slope in the Mt. Gongga Region near Luding, Sichuan, China, using the 137 Cs Technique

This paper reports the results of an investigation of soil erosion on a steep cultivated slope in the Mt Gongga region of the Upper Yangtze River Basin, Southwest China, using the 137Cs technique. The effective 137Cs reference inventory for the study field, estimated from the bottom layer of a 137Cs depth profile at the deposition zones, is 2373.9 Bq/m2, accounting for 65.8% the local 137Cs reference inventory of 3607.7 Bq/m2. It strongly indicates that a considerable amount of 137Cs input was lost prior to incorporation into the ploughing layer from the study field during the nuclear weapons testing period because of 137Cs surface enrichment. The average erosion rate is estimated to be 4914 t/km2 yr for a typical cultivated steep slope with an angle of 34°at the subtropical zone in the Mt Gongga region. It can reach to 22856 t/km2 yr for a failure slope under cultivation