Channel deposition induced by bank erosion in response to decreased flows in the sand-banked reach of the upstream Yellow River
2013
Ta, Wanquan | Jia, Xiaopeng | Wang, Hai-bing
Sand-banked rivers are characterized by severe lateral channel erosion due to weak bank resistance. High lateral channel erosion rates occur in most natural rivers in response to flood flows and contribute to increased suspended sediment loadings; however, evidence from our study shows that low flows also cause high lateral channel erosion rates in sand-banked rivers. Using the profile data of 113 channel cross-sections taken in 1962, 1982, 1991 and 2000 in the Kubq desert reach of the Yellow River, we show that the lateral channel erosion rate remained relatively constant of 0.6–0.67∗108tyr−1 despite flow decreases of 58% and led to the development of a unique bank-to-channel sediment transfer (BCST). This BCST process, in combination with the decreased flow which caused suspended sediment effluxes to decrease by 30%, enhanced sediment deposition in the channel and provided a mechanism of channel adjustment to decreased flow in sand-banked rivers. Our results also show that this high lateral channel erosion rate accounted for about 64% of the total measured sediment deposition rates, which showed, on average, to be as much as 0.90–1.15∗108tyr−1 in the channel shrinkage period of 1982–2000. Even in the channel widening period of 1962–1982, the lateral channel erosion was also found to cause about 0.41∗108t of sediment deposition in the channel annually. As the lateral channel erosion is a substantial sediment source of river sediments and leads to lateral channel shifts for sand-banked rivers, channel bank stabilization should be a priority in river management and flood control in sand-banked rivers.
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