Shi Haiyun, Gao Chao, Dong Changming, Xia Changshui, Xu Guanglai
School of Marine Sciences, Nanjing University of Information Science & Technology, Nanjing 210044, China.
Department of Geography & Spatial Information Techniques, Ningbo University, Ningbo 315211, China.
Sensors (Basel). 2017 Sep 27;17(10):2213. doi: 10.3390/s17102213.
River islands are sandbars formed by scouring and silting. Their evolution is affected by several factors, among which are runoff and sediment discharge. The spatial-temporal evolution of seven river islands in the Nanjing Section of the Yangtze River of China was examined using TM (Thematic Mapper) and ETM (Enhanced Thematic Mapper)+ images from 1985 to 2015 at five year intervals. The following approaches were applied in this study: the threshold value method, binarization model, image registration, image cropping, convolution and cluster analysis. Annual runoff and sediment discharge data as measured at the Datong hydrological station upstream of Nanjing section were also used to determine the roles and impacts of various factors. The results indicated that: (1) TM/ETM+ images met the criteria of information extraction of river islands; (2) generally, the total area of these islands in this section and their changing rate decreased over time; (3) sediment and river discharge were the most significant factors in island evolution. They directly affect river islands through silting or erosion. Additionally, anthropocentric influences could play increasingly important roles.
江心洲是由冲刷和淤积形成的沙洲。它们的演变受到多种因素的影响，其中包括径流和输沙量。利用1985年至2015年每隔五年的专题绘图仪（TM）和增强型专题绘图仪（ETM）+影像，对中国长江南京段的七个江心洲的时空演变进行了研究。本研究采用了以下方法：阈值法、二值化模型、图像配准、图像裁剪、卷积和聚类分析。还使用了南京段上游大通水文站实测的年径流量和输沙量数据，以确定各种因素的作用和影响。结果表明：（1）TM/ETM+影像符合江心洲信息提取的标准；（2）总体而言，该河段这些江心洲的总面积及其变化率随时间下降；（3）泥沙和河流流量是江心洲演变的最重要因素。它们通过淤积或侵蚀直接影响江心洲。此外，人为影响可能发挥越来越重要的作用。
