Author(s): Teresa Serra; Marianna Soler; Aina Barcelona; Jordi Colomer

Linked Author(s): Teresa Serra

Keywords: Sediment transport; Sediment replenishment; River restoration; Artificial water discharge; Particle size distribution

Abstract: Dams and impoundments constructed in rivers have produced changes in the rivers’ hydrological and sediment records in rivers. The flow regulation has led to a reduction in the supply of sediments downstream, impacting on the river ecology, producing habitat fragmentation and the reduction in biodiversity. Meanwhile, upstream from the dam, the accumulation of sediments produces a reduction in the storage capacity of the reservoir, but downstream from the dam, there is a lack of sediments that causes bed erosion, a reduction in morphology diversity and a loss of connectivity with different nearby areas, especially in drought periods. Water discharges from dams are artificially induced in order to contribute to the sustainability of the rivers. Sediment replenishment during flushing floods it a technique that has been used to recreate natural sediment transport using the supply of sediments that have been retained upstream the dam and, thus, are lacking in the river reaches. Therefore, sediment replenishment enhance the sediment supply to the rivers’ catchment areas, counteracting the negative impact of the presence of dams. In this study, sediment replenishment discharges have been compared to their non-sediment replenishment counterparts through the use of hysteretic loops. The use of normalized hysteresis loops to further the knowledge of sediment transport has been used in different studies, helping to determine the sediment sources and pathways during the discharge between different watersheds. In the current study, the hysteretic loops between the suspended sediment concentration and the water discharge present low normalized hysteresis indices, close to zero, when compared to the discharges carried out without sediment replenishment. Therefore, sediment replenishment strategies produce a balanced sediment transport which contrasts with the without-sediment-replenishment cases. Normalized hysteresis indices varied between the different particle sizes studied and for the same water discharge. This result indicates that different types of particles are transported differently despite being in the same water discharge. Furthermore, both the transport and the sedimentation rate of particles during the discharge was greater for the sediment replenishment cases than for the non-sediment-replenishment cases. All in all, sediment replenishment combined with artificial water discharges provides a management strategy that succeeds in a more balanced sediment transport, (compared to non-sediment replenishment water discharges), and that could be used as a river restoration practice.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022702

Year: 2022