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                  Evolution of channel bars in the Jingjiang River reach after the impoundment of the Three
                      Gorges Reservoir and its combined effects with hydrological regime on vegetation


                                        LI Zhiqing，CHEN Li，FENG Kai，SUN Zhaohua





                      （State Key Laboratory of Water Resources Engineering and Management，Wuhan University，Wuhan  430072，China）


                Abstract：After the impoundment of the Three Gorges Reservoir，it has become a consensus that the increased dura‐
                tion of low and medium flows in the Jingjiang River reach，combined with sub-saturated sediment-containing flows，


                has caused sustained scouring of the main channel. However，a unified understanding of the evolution characteristics
                of channel bars above the basic channel has yet to be established. This study focuses on the Jingjiang River reach and
                analyzes  changes  in  channel  bar  areas  within  different  discharge  based  on  observational  data  collected  after  the
                impoundment of the Three Gorges Reservoir. Based on morphological change method and remote sensing analysis，
                variations in channel bar areas across different sections and time periods were examined. The deformation characteris‐

                tics of channel bars at different elevations were analyzed at both river reach and local scales，and the adjustments in
                suitable vegetation zones resulting from changes in channel bar evolution and hydrological conditions were assessed.
                The results indicate that the adjustment of channel bars in the Jingjiang River reach primarily occurred after 2008. In


                the  Zhicheng-Yangjianao  section，channel  bars  exhibited  continuous  degradation  and  shrinking，while  in  the
                Yangjianao-Jianli  section，low  and  middle  bars  shrank，and  high  bars  showed  slight  aggradation.  In  the  Jianli-


                Chenglingji section，low bars shrank while middle and high bars experienced significant aggradation. Under the over‐


                all trend of low bar erosion，although channel regulation projects can prevent localized erosion and may even promote
                deposition，their  impact  on  middle  and  high  bars  is  not  significant.  In  the  section  influenced  by  backwater  from



                Dongting Lake，the deposition of channel bars is mainly reflected in the increase in elevation，but the change of the

                planform is not significant. After the normal operation period of the Three Gorges Reservoir began，changes in chan‐
                nel  bar  deformation  and  hydrological  conditions  together  resulted  in  a  32.0%  increase  in  areas  suitable  for  high-
                frequency vegetation coverage in the Jingjiang River reach. The increases in the Zhicheng-Yangjianao，Yangjianao-



                Xinchang，Xinchang-Jianli，and Jianli-Chenglingji sections were -5.6%，6.5%，13.3%，and 95.6%，respectively.




                There is potential for high bar deposition and an increase in vegetation-covered areas in the lower Jingjiang River，
                particularly downstream of Jianli，which may increase resistance to flood discharge and should be given due attention.


                Keywords：Jingjiang River；Three Gorges Reservoir；channel bars evolution；vegetation changes



                                                                             （责任编辑：鲁  婧  韩  昆）
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