湘江长沙综合枢纽下游河段典型江心洲演变规律

长沙综合枢纽建成后,对湘江下游分汊河段江心洲演变产生较大影响。选取该河段3个具有代表性的江心洲(甄皮洲、萝卜洲和沙坪洲),通过Landsat遥感影像和1983、2008和2015年江心洲河段的实测地形数据,以及湘潭站多年实测水沙数据,分析近30余年河段内江心洲演变过程及主要影响因素。结果表明:径流量年际变化较小且年内分配趋于稳定,年输沙量呈现周期性波动下降的趋势,1990年代枯水期输沙量相比1980年代同期有所增加。1984-1994年期间,江心洲处于自然发育状态,面积和体积都有所增加,1994-2005年,3个江心洲也均有不同程度的增大。至2009年,江心洲面积继续扩大。2012年后由于长沙综合枢纽的建成运行,下游河段江心洲进一步萎缩。

Evolution law of typical mid-channel bars in Xiang River below the Changsha Comprehensive Hydraulic Pivot

The completion of the Changsha comprehensive hydraulic pivot had a great influence on the evolution process of mid-channel bars in the bifurcated reach of the lower Xiang River. Three representative bars(Zhenpi Bar, Luobo Bar, Shaping Bar) in the reach were selected to analyze the evolution process and main influencing factors of mid-channel bars in the past 30 years, based on Landsat remote sensing images, measured topographic data of this reach in 1983, 2008 and 2015, as well as measured water and sediment data of Xiangtan hydrological station of years. The results showed that the inter-annual runoff variation in the lower reach of the pivot was small and the distribution basically maintained stable during the year, but the annual sediment transport volume showed a downward trend of cyclical fluctuation. However, the sediment transport load in the dry season of the 1990s increased compared with the same period of the 1980s. The 3 mid-channel bars were in a state of natural development, with an increase in area and volume from 1984 to 1994. They all increased by different degrees from 1994 to 2005. They kept expanding in 2009 until the operation of the Changsha Comprehensive Hydraulic Pivot in 2012, after which the bars started shrinking.