苏北近岸水域"五条沙"侵蚀发育的卫星监测

利用2000年3月26日、5月20日和9月18日Landsat-5卫星的TM和Landsat-7卫星ETM多波段多时相图像数据,经几何、辐射校正、海洋潮汐订正和多波段合成处理后,采用图象等灰度线-海图主特征地形10 m等深线配准相关法,对覆盖区内苏北岸段(32°00′~34°00′N,120°00′~123°00′E)范围内的岸滩,水下地形,潮流沙脊等重要地貌特征及其走向进行了分析和解译,并利用减法对研究区的沙洲沙脊进行点对点的经纬度计算,进而给出研究区内沙洲沙脊的逐点侵蚀与发育量值,获得了研究区内水下沙脊侵蚀发育的分析数据。结果显示,近15 a来,位于北凌河和九洋河外的蒋家沙南部有明显的侵蚀特征,范围明显收缩,而其北部有明显的向NE方向发育的特征;位于北侧的外毛竹沙等3条沙脊向N或向NNW方向延伸的趋势明显,其范围也显著加大。对比由卫星图象解译获得的10 m等深线和1986年出版的海图(10 m等深线)发现,外毛竹沙向北延伸了30 km;蒋家沙向北偏东延伸了11 km;而毛竹沙与太平沙之间的菱形“无名沙”向北延伸了约11 km。

Satellite Monitoring of Erosion and Growth of the Five Finger Sandbanks in the Northern Jiangsu Offshore Area

The corrected Landsat-5 TM and Landsat-7 ETM multiband image data of March 26,May 20 and September 18,2000 were used for analyzing and interpretating the main characters and trends of beach,underwater topography and tidal sand ridge in the northern Jiangsu offshore area by aligning the satellite image data with the 10 m isobaths of main characteristic topography on the nautical chart.The interpretation data of Landsat-7 images in 2000 were then compared with the 10 m isobath data on the nautical chart in 1986 to study the erosion and growth of underwater sand ridges in the study area.It is shown from the comparison results that in the period 1986 to 2000,the southern Jiangjia Sandbank in the southern study area was eroded obviously,but the northern Jiangjia Sandbank extended northeastward obviously;three sandbanks in the northern study area extended to the north or the north northwest obviously,the sandbank growths are as follows: the Wainaozhu Sandbank was extended northward for 30km,the Jiangjia Sandbank was extended northnortheastward for 11 km,and the Wuming Sandbank between the Maozhu and Taiping Sandbanks was extended northward for 11 km.