长江口滩涂地形冲淤分析研究

ANALYSIS ON EROSION-DEPOSITION OF FORESHORE LANDFORMS OF THE YANGTZE RIVER ESTUARY

为获得长江口滩涂地形的冲淤演变规律,运用GIS的数据处理与空间分析功能,提出了基于分区的冲淤量时间序列分析、冲淤量与上游来沙量相关分析、沙洲质心推移分析、典型断面分析的滩涂地形综合分析方法,即以滩涂分区和江心沙洲为对象、分时段定量研究冲淤变化的方法。在对全系列实测滩涂地形资料逐年分析的基础上,对长江口滩涂地形进行分区域的冲淤分析,并选取1991、2001和2008年3个代表年份,研究了长江南支上段主要沙洲地形演变规律。总体上,崇明东滩、长江南支、长江南港、长江北港、南汇东滩、九段沙近期冲刷大于淤积,而崇明北沿、横沙东滩以淤积为主,长江南支冲刷作用明显,江心沙洲往东南方向推移,分析表明长江入海泥沙年输移量以及年均含沙量变化是造成长江口江心沙洲冲淤演变的重要因素之一。

In order to obtain the evolution of erosion-deposition in the Yangtze River Estuary,the synthesizing analysis method based on the time series analysis of sediment quantity of scour-silt,correlation analysis of the amount of upstream sediment and sediment quantity of scour-silt,drift analysis of the middle sand-bank and typical cross-section analysis was put forward using the data-processing and spatial analyzing of geographical information system （GIS）.This synthesizing analysis method was targeted to the zoning of foreshore landforms and the middle sandbank of the Yangtze River Estuary,and quantitatively analyzed the change of erosion-deposition in different time periods.The year of 1991,2001and 2008were selected to analyze the topographic evolution of the major sandbanks in the upside of south branch of the Yangtze River Estuary,based on the analysis of whole series of actually measured data.As a whole,in Chongming tidal flat,southern branch,southern channel,northern channel,Nanhui tidal flat and Jiuduan sandbank,the erosion effect played a dominant role in the recent years.Deposition was the key trend in Chongming northern branch and Hengsha tidal flat.The erosion in southern branch of the Yangtze River Estuary was serious and the major sandbanks in southern branch were all moved to the southwest.It indicates that the change of annual sediment discharge and the annual suspended sediment concentration of the Yangtze River into the sea is one of the important factors in the evolution of erosion-deposition in the middle sandbanks of the Yangtze River Estuary.