三峡水库175m蓄水后荆江典型分汊河段演变趋势预测

Recent fluvial processes of typical braided channel in upper Jingjiang reach

三峡水库蓄水后,长江中游局部河段冲刷调整剧烈,尤以分汊河段最为显著,给航运及河势稳定带来了一系列不利影响。以荆江典型分汊河段——沙市河段为例,分析了三峡水库蓄水前后的演变特点,明确了水动力条件、来沙变化及洲滩相互作用对河床演变的重要影响,并提出了影响滩槽变化的特征流量级的概念。在此基础上,采用数学模型对河床演变的趋势进行预测,结果表明,该河段的滩槽格局将进一步调整,通航安全问题仍然存在。

Serious scour was found in the middle Yangtze River since the operation of Three Gorges Reservior （TGR） , especially in braided channel, caused a series of negative effects on the navigation and the stability of river regime. As an example of the typical braided channel in Jingjiang reach, Shashi reach is well known for the complicated fluvial processes and fairway problem. By analyzing the evolution features before and after the water-impoundment of TGR, the impact of hydrodynamic condition, incoming sediment and interaction of beaches on the fluvial processes in Shashi reach were analyzed. A concept of characteristic flow discharge is proposed, which affects the erosion and deposition of beaches and channels. Finally, the numerical model is used to predict the evolution trend of Shashi reach, and the result shows that the pattern of beaches and channels will further readjust, and the problems of navigation safety are still exist.