中文摘要：

为研究近期荆江段崩岸过程及特点,利用实测水下地形图及固定断面资料,分析了三峡工程运用前后该河段平面及断面的形态变化过程。平面形态对比结果表明：2002—2013年荆江段多年平均崩退速率约为15.0 m/a,崩岸总长达42.3 km,左岸占59.2%;下荆江岸线崩长约为上荆江的2.2倍,且石首、调关及荆江门等河湾凸岸一侧受低含沙水流长期冲刷不断崩退,其岸线崩长约占下荆江崩岸总长的35.5%。断面形态对比结果显示：2002—2015年荆江段约有21%断面存在明显的崩岸现象,且近74%的崩岸断面位于下荆江。故近期荆江段崩岸分布规律主要表现为左岸多于右岸,下荆江多于上荆江,且下荆江部分河湾凸岸崩退显著。定量分析了河岸土体组成与分布、来水来沙条件等因素对崩岸过程的影响,发现来水来沙条件的影响占主导地位。建立了上、下荆江典型断面平滩河宽与前期水沙条件之间的经验关系,除工程守护良好的断面外,相关系数均高于0.85,提出的经验公式可较好反映水沙条件变化对平滩河宽调整的影响。

英文摘要：

The Jingjiang Reach is undergoing considerable channel degradation, and significant bank retreat processes have occurred at local sites due to the operation of the Three Gorges Project（ TGP）. By investigating the adjustments in planform and cross-sectional geometries based on the measured topographic and hydrological data after the TGP operation,it is discovered that the process of bankline migration was remarkable in the Jingjiang Reach,with the average annual bank-erosion rate of 15. 0 m/a and the cumulative bank-erosion length of 42. 3 km; 59. 2% of the bank-erosion regions were located at the left bank,and 68. 7% of them were located in the Lower Jingjiang Reach（ LJR）; and severe bank retreat processes also occurred at convex banks,with 35. 5% of the bank-erosion regions in the LJR. In addition,the variation in cross-sectional profiles indicates that 21% of all the cross-sections underwent obvious bank retreat processes,of which 74% occurred in the LJR. In summary,the bank-erosion regions were mainly located at the left bank and the bank retreat intensity was much higher in the LJR. Various factors influencing bank retreat in the Jingjiang Reach have been presented,and the results indicate that the incoming flow-sediment regime is a dominant control factor. Finally,empirical relationships were developed between the section-scale bankfull widths at typical sections with severe bank retreat and the previous five-year average fluvial erosion intensity during flood seasons,with the correlation coefficients of being higher than 0. 85. Therefore,the proposed empirical relations can better consider the effect of the altered flow and sediment regime on the variation in bankfull widths at typical sections.