长江口冲积岛浅滩演变的可视化分析

GIS-Based Visualized Analysis of Shoals Evolution around Alluvial Islands in the Changjiang Estuary for the Recent 120 Years

为了解剧烈开发背景下长江口浅滩的演变特征,运用GIS技术建立1879年以来长江口地区水下数字高程模型(DEM),再现百余年来长江口长兴岛—横沙岛和九段沙浅滩的演变过程,并计算浅滩的面积、体积、冲淤量和冲淤厚度。结果表明:百余年来长兴岛—横沙岛和九段沙浅滩总体上呈淤涨趋势,并沿东南方向向海推进;长江流域中上游的开发和保护以及河口地区重大工程对浅滩演变的影响越来越大。

The purpose of this paper is to visually analyze the evolution characteristics of the shoals around alluvial islands in the Changjiang estuary for the recent 120 years. Supported by GIS,6 pieces of charts of the Changjiang estuary from 1879 to 2000 are digitized and digital elevation model（DEM）of the Changjiang estuary in different periods is established with Kriging gridding method, based on which the evolution of shoals around Changxing-Hengsha island and Jiuduansha is visualized, the change of area, volume and the amount and thickness of erosion-accretion are calculated. The results show that： 1）GIS and DEM are effective means for visualized analysis and quantitative analysis of environmental evolution; 2）the trend of the shoals in the recent 120 years is that deposition is as a whole and progradation seaward along southeast with deposition rates is faster than that of previous time; 3）the impact of human activities, including development in upper and middle stream of Changjiang drainage basin and coastal engineering in the estuary,on the shoals in the study area is becoming more and more intense.