title: Spatial scale effect on sediment dynamics in basin-wide floods within a typical agro-watershed: A case study in the hilly loess region of the Chinese Loess Plateau.
abstract: Scale issues, which have been extensively studied in the domain of soil erosion, are considerably significant in geomorphologic processes and hydrologic modelling. However, relatively scarce efforts have been made to quantify the spatial scale effect on event-based sediment dynamics in basin-wide floods. To address this issue, sediment-runoff yield data of 44 basin-wide flood events were collected from gauging stations at the Chabagou river basin, a typical agro-basin (unmanaged) in the hilly loess region of the Chinese Loess Plateau. Thus, the spatial scale effect on event-based sediment dynamics was investigated in the basin system across three different spatial scales from sublateral to basin outlet. Results showed that the event-based suspended sediment concentration, as well as the intra- and inter-scale flow-sediment relationships remained spatially constant. Hence, almost all the sediment-laden flows can reach at the detachment-limited maximum concentration across scales, specifically for hyperconcentrated flows. Consequently, limited influence was exerted by upstream sediment-laden flow on downstream sediment output, particularly for major sediment-producing events. However, flood peak discharge instead of total flood runoff amount can better interpret the dynamics of sediment yield across scales. As a composite parameter, the proposed stream energy factor combines flood runoff depth and flood peak discharge, thereby showing more advantages to describe the event-based inter-scale flow-sediment relationship than other flow-related variables. Overall, this study demonstrates the process-specific characteristics of soil erosion by water flows in the basin system. Therefore, event-based sediment control should be oriented by the process to cut off the connectivity of hyperconcentrated flows and redistribute the erosive energy of flowing water in terms of temporality and spatiality. Furthermore, evaluation of soil conservation benefits should be based on the process of runoff regulation to comprehensively assess the efficiency of anti-erosion strategies in sediment control at the basin scale.
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China. Electronic address: zhangletao10@mails.ucas.ac.cn.
authors.forename: Le-Tao
authors.initials: LT
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, PR China; Key Laboratory of Northwest Water Resources and Environment Ecology of Ministry of Education, Xi'an University of Technology, Xi'an, Shaanxi 710048, PR China. Electronic address: zbli@ms.iswc.ac.cn.
authors.forename: Zhan-Bin
authors.initials: ZB
authors.lastname: Li
authors.affiliation: State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, PR China; University of Chinese Academy of Sciences, Beijing 100049, PR China.
authors.forename: Shan-Shan
authors.initials: SS
authors.lastname: Wang
mesh_terms: D000383:Agriculture; D002681:China; D004784:Environmental Monitoring; D055868:Floods; D019015:Geologic Sediments / Q000032:analysis*; D012987:Soil
chemical_list: D012987:Soil
keywords: Flow–sediment relationship; Runoff regulation; Sediment control; Spatial independency