水力发电学报
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JOURNAL OF HYDROELECTRIC ENGINEERING ›› 2017, Vol. 36 ›› Issue (6): 12-22.doi: 10.11660/slfdxb.20170602

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River bend planform evolution in Jingjiang reach of the Yangtze since Three Gorges Reservoir operation

  

  • Online:2017-06-25 Published:2017-06-25

Abstract: Effects of the Three Gorges Reservoir (TGR) on its downstream hydrologic and sediment regimes and riverbed erosion have been much addressed, but planform evolution of river bends was less known. In this work, we studied the planform evolution of river bends in the Jingjiang reach of the middle Yangtze since TGR operation using three multi-temporal remote sensing images acquired in low water period. Results showed that (1) significant changes occurred in central-line length, convex bank length, concave bank length, sinuosity, and central-axis length of the bends, (2) that the changes in the lower Jingjiang were more remarkable, and (3) that the evolution of convex and concave banks as well as the evolution in the upper and lower Jingjiang were non-synchronous. In the upper Jingjiang, changes in concave banks occurred prior to those in convex banks, and erosion on concave banks and their extensions played a leading role in the evolution; while in the lower reach, erosion on convex banks and their shrinking were dominant and prior to the occurrence of concave bank erosion. Most of the river bends, especially those in the lower Jingjiang, showed evident increases in bend area and average width and remarkable decreases in central-line length, sinuosity and central-axis length. All this implies that since TGR operation, river bend curving has been weakening and river channels have been broadening. The relation of planform evolution to changes in concave and convex banks is also discussed in this paper.

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