The effect of rainfall pattern on sediment source in a small catchment on the Chinese Loess Plateau

Understanding the influence of rainfall pattern on suspended sediment source on catchments and river basin scales is of great importance for reasonable implementing of soil conservation and sediment control measures. Such information, however, is unavailable or difficult to assemble. According, this study used the rainfall data from 2011 to 2013 recorded by pluviograph to analyze the effect of rainfall pattern on sediment source in the Qiaozi West catchment on the Chinese Loess Plateau. The suspended sediment in six erosive rainfall events were continuous collected at the outlet of the catchment and surface soil samples were collected from potential sediment sources  including, inter-gully (farmland, forest, grassland) and gully areas (gully slope and gully wall) of the watershed. A total of 54 rainfall events were divided into four patterns according to the variation of rainfall intensity in rainfall processes, which were advanced, intermediate, delayed, and uniform patterns. The rainfall was dominated by the advanced pattern in the studied catchment, which accounts for 43% of all observed rainfalls. There were six rainfall events had suspended sediment samples, two intermediate pattern erosive rainfall events generated the largest percentage of the total sediment yield of six events. The results based on the composite fingerprinting approach indicated that farmland and gully wall were the main sediment source in the catchment regardless of rainfall patterns. However, cultivated field having loose topsoil created in tillage has relatively high contribution to suspended sediment in runoff at the advanced pattern, while loose materials from collapsed gully walls has relatively high contribution to suspended sediment in runoff at the intermediate and delayed rainfall pattern. Further studies are necessary to gain better insight into erosion pattern variation under different rainfall pattern.