Journal of Geographical Sciences ›› 2018, Vol. 28 ›› Issue (5): 629-646.doi: 10.1007/s11442-018-1495-8

• Research Articles • Previous Articles     Next Articles

Immediately downstream effects of Three Gorges Dam on channel sandbars morphodynamics between Yichang-Chenglingji Reach of the Changjiang River, China

Jie WANG1, , Xuefei MEI1, Yaying LOU1, Wen WEI1, Zhenpeng GE1   

  1. 1. State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China
    2. Laboratory for Marine Geology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266061, China
  • Received:2017-09-08 Accepted:2017-12-07 Online:2018-03-30 Published:2018-03-31
  • About author:

    Author: Wang Jie, Master Candidate, specialized in fluvial and estuarine morphodynamics. E-mail: jiewang.ec@gmail.com

  • Supported by:
    National Natural Science Foundation of China, No.41576087;National Science Foundation for Young Scientists of China, No.41706093;Fund of the Key Laboratory of Coastal Science and Engineering, Beibu Gulf, Guangxi, No.2016ZZD01

Abstract:

Sandbars are of vital ecological and environmental significance, which however, have been intensively influenced by human activities. Morphodynamic processes of sandbars along the Yichang-Chenglingji Reach of the Changjiang River, the channel immediately downstream of the Three Gorges Dam (TGD), are assessed based on remote sensing images between 2000 and 2016. It can be found that the entire area of sandbars reduces drastically by 19.23% from 149.04 km2 in 2003 to 120.38 km2 in 2016, accompanied with an increase in water surface width. Owing to differences in sediment grain size and anti-erosion capacity, sandbar area in the upstream sandy gravel reach (Yichang-Dabujie) and downstream sandy reach (Dabujie-Chenglingji) respectively decreases by 45.94% (from 20.79 km2 to 11.24 km2) and 14.93% (from 128.30 km2 to 109.14 km2). Furtherly, morphological evolutions of sandbars are affected by channel type: in straight-microbend channel, mid-channel sandbars exhibit downstream moving while maintaining the basic profile; in meandering channel, point sandbars show erosion and deposition in convex and concave bank respectively, with mid-channel sandbars distributing sporadically; in bending-branching channel, point sandbars experience erosion and move downstream while mid-channel sandbars show erosion in the head part along with retreating outline. We document that the primary mechanism of sandbars shrinkages along the Yichang-Chenglingji Reach can be attributed to TGD induced suspended sediment concentration decreasing and increasing in unsaturation of sediment carrying capacity. Additionally, channel type can affect the morphological evolution of sandbars. Along the Yichang-Chenglingji Reach, sandbars in straight-microbend channel are more affected by water flow than that in bending-branching channel.

Key words: sandbars morphodynamics, Three Gorges Dam (TGD), remote sensing images, Yichang-Chenglingji Reach, Changjiang River