Sediment concentrations in run‐off varying with spatial scale in an agricultural subwatershed of the Chinese Loess Plateau |
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| Authors: | Mingguo Zheng Runkui Li Jijun He |
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| Institution: | 1. Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China;2. College of Resources and Environment, University of Chinese Academy of Sciences, Beijing, China;3. Base of the State Laboratory of Urban Environmental Processes and Digital Modelling, Capital Normal University, Beijing, China |
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| Abstract: | Information is scarce on the spatial‐scale effect on sediment concentrations in run‐off. This study addressed this issue within an agricultural subwatershed of the Chinese Loess Plateau, using data observed at a hilltop plot, three nested hillslope plots, two entire‐slope plots (a combination of hillslope and valley side slope) and the subwatershed outlet. Dominated by the splash and sheet erosions, the hilltop plot has a minimum Cae (mean sediment concentration for all recorded events) of 45 kg m?3. Unexpectedly, the high sediment concentrations at the hilltop do not occur at high rainfall intensities or large run‐off events because of the protection of surface soils by relatively thick sheet flows. Because of the emergence of rills, Cae is as high as 310 kg m?3 even on the most upper hillslope. Downslope, both Cae and ESC (extreme large values of recorded sediment concentrations) increase; such a slope length effect attenuates with increasing slope length and event magnitude as a result of insufficient sediment availability associated with rill development. Active mass wastings ensure sufficient sediment supply and thus a spatially invariant Cae (approximately 700 kg m?3) and ESC (approximately 1000 kg m?3) at the scale of the entire slope and subwatershed. Detailed examination shows that most small events experience a decrease in sediment concentrations when moving from the entire slope to the subwatershed, indicating that the spatially invariant sediment concentration is valid only for large run‐off events. This study highlights the control of the spatial scale, which determines the dominant erosional process, on erosional regime. Copyright © 2015 John Wiley & Sons, Ltd. |
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| Keywords: | soil erosion sediment yield scale hyperconcentrated flows Loess Plateau |
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