• A higher river sinuosity increased riparian soil structural stability on the downstream of a dammed river.

      Ran, Yiguo; email: ranyiguo@cigit.ac.cn; Liu, Yan; email: yan.liu-23@postgrad.manchester.ac.uk; Wu, Shengjun; email: wsj@cigit.ac.cn; Li, Wenjuan; email: liwenjuan@cigit.ac.cn; Zhu, Kai; email: zhukai@cigit.ac.cn; Ji, Yongyue; Mir, Yaseen; email: yaseenghp@mails.ucas.ac.cn; Ma, Maohua; email: mamaohua@cigit.ac.cn; Huang, Ping; email: huangping@cigit.ac.cn (2021-08-25)
      Hydropower dam constructions and operations have dramatically changed the original hydrological regime of natural rivers. Because of significantly slashed and suspended sediments blocked by damming, discharged "clear" water was found to play a strong undercutting effect on the riverbank and to exacerbate riparian soil erosion on the downstream near dams. Yet, it is still an unsettled issue whether the instability of riparian soil structure would be simply correlated negatively with the distance to a dam. In this study, soils along the downstream riparian zone of a huge dam on the River Yangtze, China, were sampled to examine the distance effect on the riparian soil structural stability. Water-stable aggregates were fractionated by the wet-sieving method. Mean weight diameter (MWD) and geometric mean diameter (GMD) were used to indicate riparian soil stability. Further, the fractal dimension (D) and soil erodibility parameter (K) were used to represent the likelihood of riparian erosion. Our results revealed that riparian soil structural stability demonstrated a high spatial heterogeneity along the River Yangtze, and was less affected by the spatial distance to the dam. Rather, the soil stability was primarily influenced by a river shape index (sinuosity) and local edaphic properties. The river sinuosity index demonstrated a positive relationship with soil structural stability. Additionally, soil organic matter was found as a major edaphic factor in stabilizing soil structure. The results indicated that river sinuosity plays a crucial role in stabilizing soil by accumulating soil organic matters. Our findings implied that the potential negative impact of damming effect on soil stability may be attenuated by maintaining a higher sinuosity of the river. Against the risk of riparian soil erosion along the dammed river, the configuration of river morphology shall be considered as one of the potential managements in offsetting the negative impacts of damming. [Abstract copyright: Copyright © 2021. Published by Elsevier B.V.]