Abstract

On Loess Plateau of China, silt dams play important role in controlling soil and water loss and kept much information of sediment yield and sedimentation in the past. The objectives of this investigation are to understand the sedimentation characteristics and to estimate the sediment sources of the silt dam in the past 27 years by ¹³⁷Cs tracing method. The soil samples taken from hill slopes, gully sides and each cycle of sedimentation in the silt dam in Guandigou watershed on Loess Plateau of China were measured in the year of 2005 using the resident cesium-137 deficit technique. By comparing the concentration of cesium-137 in the soil samples, the sediment sources of the silt dam were calculated by proportion method, which showed that the inter-gully area is the main sediment source area, which takes about 70% of the deposited sediment, and in the initial stage after the silt dam was constructed the sedimentation was very strong and then it reduced gradually. The soil and water conservation measures and rainfall variance have great influence on the sedimentation characteristics.

Keywords: Silt Dams; Soil Erosion; Cesium-137; Sedimentation; Loess Plateau