Sources of sediments during rainfall in the dry-hot valley region of China on a small watershed scale

The dry-hot valley region in China is one of the most severely affected soil erosion areas in the world; however, little research has been conducted on sediment source contributions for various land uses during rainfall events. In this work, we collected sediment samples during a rainstorm in four types of land-use areas in the Yuanjiang dry-hot valley region of China. Results showed that gullies are the primary source of sediments in all catchment areas, and the contributions varied between 43.6% and 93.9%, with an average of 64.9%. This was followed by farmlands (21.3% to 30.4% with an average of 25.9%) and then fruit forests (6.1% to 36.5% with an average of 20.5%). Natural forests had the lowest sediment contribution as their contribution varied between 0.6% and 6.1%, with an average of only 3.3%. During runoff-induced erosion and sedimentation, the sediment contributions of gullies decreased initially and then increased. The sediment contribution of potential sediment sources located on slopes (i.e., fruit forests, natural forests, and farmlands) initially increased over time, and then declines were detected after a certain point