近400多年下荆江河段古河道演变过程及特征

为研究下荆江河段古河道演变过程及特征，利用20世纪30年代和50年代的历史地形图、1954年航片、1968年美国KH-4B军事卫星影像及2016年国产GF-1卫星影像，结合古籍资料，全面分析了下荆江古河道的演变特征并反演了其明万历年以来400多年的历史变迁过程.下荆江河段的古河道横向摆动频繁，受河道坚硬岸坡和人工护岸工程约束，空间上为20~32 km的古河道平面摆动带，形态上分为沿主泓线侧向渐变式摆动和河道突变迁徙两种古河道类型，它们是反演下荆江河段古河道的定位依据.历史上，下荆江塑造经历了漫流、支汊分流、单一顺直河道形成和曲流演化发展等复杂过程.明弘治年间，曲流主要出现在监利-城陵矶段，石首至监利段仅微弯；明末清初，东港湖弯道和濠河弯道均自然裁弯取直，下荆江蜿蜒型河道已全面上溯到石首境内，并形成了一系列河曲弯；19世纪中叶，下荆江的河曲发展突出表现在横向移动、河曲颈变窄、凹岸环流侵蚀后退、凸岸堆积淤高推进等特点.此后，下荆江没有出现大的变迁.下荆江河段近代河弯的演变模式有凸岸淤积推进、凹岸崩坍后退型，凸岸撇弯切滩、弯顶消减型和心滩漂移并岸、凹岸串沟过流型.河流的本身作用是其演变的主要原因，但人工修建大堤与大规模围垸是重要外因. 

Evolution Process and Characteristics of Lower Jingjiang Paleo-Channel in Recent 400 Years

Based on the historical topographic maps of the 1930s and 1950s, the 1954 aerial photo,the 1968 US KH-4B military satellite imagery,and the 2016 domestic GF-1 satellite imagery,in this paper,it comprehensively analyses the paleo-channel under the Jingjiang River. It evolved characteristics and inverted the historical changes of its 400 years since the Ming Dynasty. The results show that the paleo-channel of the Jingjiang River section is frequently oscillated laterally,and is constrained by the hard bank slope and artificial revetment project,there are 20-32 km space sway zone along the paleo-channel plane,the morphological form are two: lateral gradual swing along the main squall line and sudden migration of river channels,which are the bases for the inversion of the paleo-channel in the Jingjiang River. Historically,the shaping of the Lower Jingjiang River has undergone complicated processes,such as overflow,branching and diversion,formation of a single straight channel and evolution and development of meandering. During the period of Hongzhi in the Ming Dynasty,meandering currents mainly occurred in Jianli-Chenglingji section,while the section from Shishou to Jianli was only slightly curved. In the late Ming and early Qing Dynasties,Donggang Lake bend and Haohe River bend were cut and straightened naturally. The meandering channel of the Lower Jingjiang River had been traced back to Shishou in an all-round way and formed a series of meandering bends. In the middle of the 19th century,the development of the meander of the Lower Jingjiang River was characterized by lateral movement,narrowing of the meandering neck,retreat of the concave bank circulation erosion,and high thrust of the convex bank. Since then,there has been no major change. The evolution mode of modern river bend of Lower Jingjiang River includes deposition-propelled in convex bank,collapse-back in concave bank,cut-bank and thrown-away-elbow in convex bank,cut-bend,combing drifting central bar with the bank,cluster ditch-flow in concave bank.The role of the river itself is the main reason for its evolution,but the artificial construction of the levee and large-scale cofferdams are important external factors.