长江中下游河道与岸线演变特点

分析了长江中下游河道岸线变化的主要因素，它们分别是河岸崩塌，泥沙淤积及人类活动等，其中河岸崩塌是河道岸线演变的最主要原因。总的来说长江中下游干流河势是稳定的，但五个河段有各自演变特点和规律，其中宜昌－枝城段河道与河床比较稳定，岸线顺直，但葛洲坝和三峡水利枢纽建成后对河床的冲刷作用较大；荆江段是长江著名的河曲段，其冲淤变化较大；城陵矶至湖口段为节点和分汊河床组成，一般来说节点较为稳定，而分汊河床不太稳定，湖口至江阴河段岸线一般较为稳定，但弯道河床变化较大；河口段不但受江流作用影响，还受潮流与波浪等共同影响，所以河口河床演变迅速，主要表现为汊道主泓迁移摆动。

CHANNEL EVOLUTION OF THE MIDDLEAND LOWER REACHES OF THE YANGTZE RIVER

The main factors influencing the channel and bank lines of the middle and lower reaches of the Yangtze River were analyzed in this paper,which include collapse of riverbank,silting up of mud and sand,etc.The collapse of riverbank is the most important cause for changes of channel and bank lines. In general,the mainstreams of the middle and lower reaches of the Yangtze River are very stable,although each of the five sections has its own changing characteristics and regularities.In the Yichang Zhicheng section,the channle is very stable and the bank lines are smooth and straight,but the channel would have been strongly eroded after the building of Project and the Three Gorges Project.The Jingjiang reaches,the famous meandering channel of the Yangtze River changes remarkably due to eroding and silting.The reaches Chenglingji to Hukou is composed of nodes and braided channel.The nodes of river are very stable,while the braided channel is not stable enough in this reaches.The bank lines of the reaches from Hukou to Jiangyin are very stable,but channel of its winding bends change markedly.The Hekou reaches is not only influenced by river streams but also jointly affected by tidal currents and waves;therefore,its channel changes rapidly,which is reflected by moving and swaying of main stream line of the distributary.