Abstract
Reservoir construction may modify the downstream flow and sediment transport, and correspondingly result in adjustments in morphodynamics of a river, especially riverbed instability. Based on hydrological datasets from 2003 to 2019 during the post-dam period using the topographic data of 57 fixed cross-sections in the Wuhan reach of the Yangtze River, we calculated the indexes representing the channel stability. Moreover, considering the effects of flow, sediment concentration, grain size of sediment, and water depth, we propose a method for calculating the equilibrium values of cumulative erosion and the lateral migrate intensity of thalweg in this paper, and the method combines with the delayed response model (DRM) to comprehensively analyze the variations in the longitudinal and lateral stabilities of the riverbed. The results revealed that the channel has been obviously eroded in the downstream reach, resulting in a 76% decrease in sediment discharge after the impoundment of the Three Gorges Reservoir (TGR). Specifically, in the past 17 years, the cumulative erosion in the Wuhan reach of the Yangtze River reached 1.72 m, while the bankfull depth increased by 1.87 m. The lateral migrate intensity of thalweg increased in response to Coriolis force, with an increase of 22.3%. Taken together, the results show that the proposed formula can effectively simulate the variation process of channel stability, and it also quantifies the extent of the influence weight of interannual flow and sediment regimes. The morphodynamics adjustments in the channel stability of our studied reach were closely related to the previous five-year flow and sediment regimes, implying that channel evolution may lag behind the changes in flow and sediment discharges.
Highlights
From the four different stages, the proportion of runoff and sediment discharge in the flood season in total declined in turn, indicating that the runoff and sediment discharge decreased during the flood season but increased in the non-flood season, under the influence of the Three Gorges Reservoir (TGR) operation
The forms of Equations (14) and (21) in the two models reveal that the variations in channel morphology are positively correlated with the flow dynamics of the upstream water, and the larger the sediment concentration in the inflow, the smaller the riverbed degradation capacity, which is consistent with the basic laws in riverbed evolution
Conclusions reach in the Yangtze River were comprehensively analyzed in this study, based on the flow
Summary
The variations in the characteristics of flow and sediment transport can lead to adjustments in channel morphology, resulting in riverbed instability [2,3]. Riverbed deformation is mainly divided into longitudinal and lateral variations [4,5]. Showed that the downstream riverbed of the Yangtze River has been scoured and cutdown to varying degrees, and that the thalweg has generally been cut-down after the impoundment of the TGR. Gierszewski et al [7] found that the downstream channel of Wloclawek Dam has been scoured, and such scour has been inhibited, the river bank erosion has intensified, and the channel has widened since the roughening of the riverbed
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
