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出版SSRN, 2023
URLhttp://books.google.com.hk/books?id=bmtH0AEACAAJ&hl=&source=gbs_api
註釋The aim of the present study is to understand the mechanisms underlying the influence of dams on downstream bedload transport in three gravel-bed rivers in the Morvan massif, France. The hydrological disturbance caused by four dams is examined at a short and longer (21-28 year) time scale. Morpho-sedimentary characterization of the bed substrate was performed at 8 study sites around the dams, and combined with analyses of the long profile evolution and the current cross profile. Finally, bedload displacement was monitored (RFID) at the same sites for almost three years. The results indicate that the flood regime has been to a varying extent durably reduced by the dams depending on their size and purpose (flood control, hydroelectricity production, water sports). A clear influence of the dam-altered water and sediment supply was identified in the current bed substrate characteristics (sediment availability or deficit, loose or consolidated structures, armoring process) and in the channel plan forms (sedimentation, vegetation encroachment). We show that these morpho-sedimentary features significantly affect the current bedload dynamics, creating conditions more or less favorable for the mobility of the present and incoming bedload. We also show that the current flow management of the dams has only a moderate effect on the bedload distances recorded. Thus, the main influence of dams on current bedload transport may be driven by several decades of morphodynamic adjustments to dam construction and regulation. Indeed, our results demonstrate how modifications of dams on flow and bedload discharge altered the downstream morphology, but also that this inherited morphology is now a key controlling factor of bedload transport. These findings invite further discussion about the most appropriate ways to restore rivers downstream of dams when dealing with multi-decadal inherited morphological features.