Impact of the operation of a large‐scale reservoir on downstream river channel geomorphic adjustments: A case study of the Three Gorges. (31st October 2018)

• Record Type: Journal Article
• Authors: Yang, Yunping; Zhang, Mingjin; Zhu, Lingling; Zhang, Huaqing; Liu, Wanli; Wang, Jianjun
• Is Part Of: River research and applications. Volume 34:Number 10(2018)
• Page Start: 1315
• Page End: 1327
• Publication Date: 2018-10-31
• Subjects: fluvial erosion intensity -- geomorphic adjustment -- Three Gorges Reservoir -- Yangtze River; Rivers -- Regulation -- Periodicals; Rivers -- Periodicals; 551.483
• DOI: 10.1002/rra.3372
• Languages: English
• ISSNs: 1535-1459

Abstract

Abstract: To evaluate the effects of reservoir construction on the geomorphology of downstream reaches, a case study is performed on the Three Gorges Reservoir (TGR) by comparing data collected before and after impoundment of the reservoir. This study focuses on a 1, 183‐km‐long reach downstream from the TGR and investigates the temporal and spatial characteristics and patterns of geomorphic adjustment in the downstream reaches. The amount of erosion in flood plain channels and the annual average intensity of erosion in downstream reaches after 12 years of impoundment are larger than the predicted values before the impoundment of the TGR. The maximum intensity of erosion was found at 410 km from the dam, with an average thalweg incision of 1.5 m, and the main zone of erosion migrated approximately 80 km downstream. At both preimpoundment and postimpoundment, erosion occurred the along beaches and channels in the Yichang–Chenglingji reach. The pattern of erosional channels and depositional river floodplain changed to erosional channels and erosional river floodplain in the Chenglingji–Hankou reach after the trial impoundment stage. In the Hankou–Hukou reach, the erosional channels and depositional river floodplain pattern changed to erosional deep channels, erosional low beaches, and depositional high‐river floodplain during the early impoundment stage. After the trial impoundment stage, erosion continued in the deep channels, but minor deposition occurred on the river floodplain. Moreover, the discharge of clear water increased, and the duration from middle to low‐water levels increased, leading to more concentrated erosion in low‐water channels. The intensity of the erosion along the river floodplain decreased due to the shortened duration of high‐water levels and reduced human activity.