Abstract
Significant channel adjustments have occurred in the Jingjiang Reach of the Middle Yangtze River, because of the operation of the Three Gorges Project (TGP). The Jingjiang Reach is selected as the study area, covering the Upper Jingjiang Reach (UJR) and Lower Jingjiang Reach (LJR). The reach-scale bankfull channel dimensions in the study reach were calculated annually from 2002 to 2013 by means of a reach-averaged approach and surveyed post-flood profiles at 171 sections. We find from the calculated results that: the reach-scale bankfull widths changed slightly in the UJR and LJR, with the corresponding depths increasing by 1.6 m and 1.0 m; the channel adjustments occurred mainly with respect to bankfull depth because of the construction of large-scale bank revetment works, although there were significant bank erosion processes in local regions without the bank protection engineering. The reach-scale bankfull dimensions in the UJR and LJR generally responded to the previous five-year average fluvial erosion intensity during flood seasons, with higher correlations being obtained for the depth and cross-sectional area. It is concluded that these dynamic adjustments of the channel geometry are a direct result of recent human activities such as the TGP operation.
Highlights
Bankfull geometry in an alluvial river refers to the channel dimensions associated with the bankfull discharge, which is usually represented by the channel width, cross-sectional area, and the corresponding mean depth at bankfull level[1,2,3]
Continuous channel adjustments have occurred in the Jingjiang Reach of the Middle Yangtze River, because of the operation of the Three Gorges Project (TGP) and the construction of various river regulation works along the reach[11,12,14,20,21,22,23]
The aims of the current study are to: (i) present the altered flow and sediment regime and the process of channel degradation in the study reach owing to the TGP operation; (ii) calculate the reach-scale bankfull channel dimensions based on an improved reach-averaged method and surveyed cross-sectional profiles; and (iii) develop empirical relationships between these bankfull dimensions and the corresponding incoming flow and sediment regime
Summary
Bankfull (channel) geometry in an alluvial river refers to the channel dimensions associated with the bankfull discharge, which is usually represented by the channel width, cross-sectional area, and the corresponding mean depth at bankfull level[1,2,3] These bankfull dimensions are important design parameters in various river regulation works and flood control management, and it is necessary to investigate the variation of these parameters in an alluvial river undergoing continuous channel degradation, such as the Jingjiang Reach of the Middle Yangtze River. A reach-scale concept is appropriate to investigate the bankfull channel dimensions of an alluvial river, and reach-averaged variables can provide a more representative geometry and statistics characterising longitudinal variability[3,4,9] Human activities such as dam construction can significantly alter the natural flow and sediment regimes in alluvial rivers, which can have important consequences for variation in channel morphology[8,10,11,12,13,14]. The aims of the current study are to: (i) present the altered flow and sediment regime and the process of channel degradation in the study reach owing to the TGP operation; (ii) calculate the reach-scale bankfull channel dimensions based on an improved reach-averaged method and surveyed cross-sectional profiles; and (iii) develop empirical relationships between these bankfull dimensions and the corresponding incoming flow and sediment regime
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
