Differential Scour of Two Mid-channel Bars in Wuhan Reach of the Middle Yangtze River
Over the past two decades,mid-channel bars in the branching sections of the Middle Yangtze River have experienced substantial scouring or even retreating,yet the specific variances in scouring between slightly meander-ing and straight channels remain unclear.Baishazhou Sandbar and Tianxingzhou Sandbar,located in the Wuhan reach of the Middle Yangtze River,were selected as study sites to investigate the causes of morphological changes and differential scouring.This investigation utilized a combination of multi-source remote sensing imagery,hydrolog-ical data,and field surveys.The findings reveal significant alterations in the morphology of Baishazhou Sandbar,shrinking in size by approximately 43.83％between 1989 and 2020.Meanwhile,the head of Tianxingzhou sandbar underwent notable changes,although the overall exposed area remained relatively stable.Analysis of the normalized vegetation index(NDVI)indicates generally low vegetation cover on both sandbars,with diminished spatial dis-crepancies.During dry season,variations in exposed area primarily correlate with the bar head region.Specifically,on the Baishazhou Sandbar which is located in straight channel,scouring was observed on the head and lateral side,while local collapse on the left side,both due to the obstruction of Baishazhou Bridge piers.Similarly,on Tianxingzhou Sandbar which is located in slightly meandering channel,the bar head has experienced scouring fol-lowing the impoundment of the Three Gorges Project.However,the implementation of protection measures,inclu-ding artificial rock rip-rap in 2004,effectively mitigated scouring and facilitated deposition.In conclusion,differen-tial scour of mid-channel bars manifests in several aspects,including channel planform,the relative positioning of mainstream and branches,and the presence or absence of protective infrastructure.
国家科技期刊平台
NSTL
万方数据
