1968~2018年洞庭湖江湖连通河道松滋口冲淤变化特征

Channel Erosion and Deposition of Songzikou Outlet, A River-Lake Connected Channel of Dongting Lake During 1968-2018

探究江湖连通河道演变态势是评估重大人类活动事件对江湖关系变化影响的重要环节。以洞庭湖—荆江三口中松滋口河道为研究对象,通过建立其河道长期的水位—流量关系曲线分析其河道的冲淤变化特征,对其河道冲淤变化驱动因素进行分析,并采用实测河道断面资料验证其结果的可靠性。结果表明:水位—流量关系曲线法分析河道地形冲淤演变特征与实测横断面地形资料分析结果一致,松滋口河道同流量下水位下降对应于该时期河道冲刷,同流量下水位上升对应于河道淤积。不同时期松滋口东西分支河道冲淤变化主要驱动因素不同。1968~1981年间,下荆江裁弯引起的河势变化是西支新江口河道冲刷与东支沙道观河道淤积的主要诱因。1981~2003年间,其东西两支河道淤积主要是由于葛洲坝运行后引起的上荆江河道冲刷导致的。2003~2018年间,其河道冲刷主要是由于三峡大坝运行引起的河道水沙比例的大幅改变导致的。

Exploring the evolution situation of river-lake connected channel is an important link for assessing the impact of major human activities on the river-lake relationship.This paper takes the Songzikou outlet,a river-lake connected channel of Dongting Lake as the research object.The long-term water level-discharge relationship curves of Songzikou outlet were established to analyze the change characteristics of channel erosion and deposition.The reliability of the results is verified by the measured cross-section data.At the same time,the driving factors of channel erosion and deposition changes in Songzikou outlet were analyzed.The results show that the water level-discharge curve method is consistent with the measured cross-sectional topographic data.The decrease of water level under the same discharge corresponds to the channel erosion in this period,and the rise of the water level under the same discharge corresponds to the channel deposition in songzikou outlet.The main driving factors of channel erosion and deposition are different in different periods at Songzikou outlet.From 1968 to 1981,the main factor was the channel planform change caused by the river bend cutoffs of the lower Jingjiang River.From 1981 to 2003,the channel deposition was mainly caused by the channel erosion at the upper Jingjiang River due to the operation of Gezhouba Dam.During the period of 2003-2018,the channel erosion was mainly caused by the sharp change in the proportion of water and sediment due to the operation of the Three Gorges Dam.