Relationship ...iver in China_YANG Yunping.pdf

J.Geogr.Sci.2023,33(3):547-575 DOI:https:/doi.org/10.1007/s11442-023-2096-8 2023 Science Press Springer-Verlag Relationship between potential waterway depth improvement and evolution of the Jingjiang Reach of the Yangtze River in China YANG Yunping1,LI Ming2,LIU Wanli1,*CHAI Yuanfang3,ZHANG Jie1,YU Wenjun2 1.Tianjin Research Institute for Water Transport Engineering,Ministry of Transport,Tianjin 300456,China;2.Changjiang Waterway Institute of Planning and Design,Wuhan 430040,China;3.Institute of International Rivers and Eco-security,Yunnan University,Kunming 650000,China Abstract:Given the importance of waterway depths in river development,the effects of the evolution of bars and troughs on waterway expansion play an important role in river man-agement and water depth conservation.This study aims to expand the waterway dimensions of the Jingjiang Reach of the Yangtze River.To achieve this objective,determining the rela-tionship between river evolution processes and the potential for waterway depth improvement and navigation hindrances is vital.Therefore,the sedimentation,hydrological,and terrain data of the Jingjiang Reach from 1955 to 2020 are analysed to elucidate the above-mentioned relationship.Since the commissioning of the Three Gorges Dam,the scouring of the low-flow channel has accounted for 90%95%of all scouring in the Jingjiang Reach.Furthermore,the central bars and beaches have shrunk by 9.4%and 24.9%,respec-tively,and 18.3%overall.Considering the bed scouring and waterway regulation projects in the Jingjiang Reach,we investigated the continuity of a 4.5 m 200 m 1050 m(depth width bend radius)waterway along the Jingjiang Reach,and find that navigation-hindering channels account for over 5.3%of the waterway length.Furthermore,part of the Jingjiang Reach is an important nature reserve and shelters numerous water-related facilities,which inhibits the implementation of waterway deepening projects.The findings of this study demonstrate that numerous challenges are associated with increasing the waterway depths of the Jingjiang Reach.Keywords:beach trough evolution;branching relationship;waterway depth;Jingjiang Reach;middle reaches of the Yangtze River 1 Introduction Inland shipping plays an important role in global transportation and logistics systems Received:2021-11-17 Accepted:2022-03-15 Foundation:National Natural Science Foundation of China,No.52279066;Fundamental Research Funds for Central Wel-fare Research Institutes,No.TKS20190406;Follow-up Scientific Research Project of the Three Gorges Pro-ject,No.SXHXGZ-2022-1 Author:Yang Yunping(1985),PhD and Associate Professor,E-mail:yangsan520_*Corresponding author:Chai Yuanfang(1993),Senior Engineer,E-mail: 548 Journal of Geographical Sciences (Rohcs et al.,2007;Willems et al.,2018);thus,the development of riverine shipping is significant for watershed resource utilisation.The shipping potential of a river is limited by its carrying capacity,which mainly depends on hydrogeomorphic factors,such as river depth,width,flow rate,and duration of icing events(Hijdra et al.,2014).Furthermore,considering the recent implementation of environmental conservation strategies in waterways,the effects of waterway engineering on river environments cannot be ignored(Weber et al.,2017).The middle and lower reaches of the Yangtze River are known as the Golden Waterway(Cao et al.,2010;Wang et al.,2020b)because they play a central role in the socioeconomic devel-opment of the Yangtze River.As of 2020,the Yangtze River trunk line contained a freight volume of 3.06 108 tyr1,and accounted for 78.2%of the total inland waterway freight transport in China.The Jingjiang Reach,located in the middle reaches of the Yangtze River,is 60 km away from the Three Gorges Dam(TGD)and has no major tributaries or confluences(Figure 1).Therefore,its hydrologic and sedimentary conditions are directly affected by the TGD oper-ations.Over the past 60 years,the runoff flowing through the Jingjiang Reach has not sig-nificantly changed(Chai et al.,2019,2020;Yang et al.,2019).However,its sediment load has decreased over time,owing to the implementation of water and soil conservation measures and dam construction upstream(Yang et al.,2006;Yang et al.,2015b).Ever since the TGD began to hold back water,the sediment load has gradually decreased(Hassan et al.,2010;Dai et al.,2018;Li et al.,2018a;Gao et al.,2020;Peng et al.,2020;Tian et al.,2021),resulting in a higher scouring rate for the Upper Jingjiang Reach compared with the Jingjiang Reach(Dai and Liu,2013;Xia et al.,2016,2017;Lyu et al.,2018).Furthermore,the sedimentary regime of the Lower Jingjiang Reach changed from groove scouring with bar deposition to groove and bar scouring(Xu,2013;Xu et al.,2011,2013;Yang et al.,2018,2022a).Additionally,there have been numerous instances of riverbank collapse(Xia et al.,2016;Xia et al.,2017;Zhou et al.,2017;Zong et al.,2017;Deng et al.,2018,2019;Lyu et al.,2020),shrinking beaches and central bars(Yang et al.,2