基于遥感的广西钦州湾海岸带造陆过程及环境影响分析

An Analysis on Epeirogenic Process and Environmental Impact in Qinzhou Bay Coastal Zone Using Time Series Landsat Images

利用钦州湾海域1987-2011年的3个时期多时序TM影像为信息源,通过提取水体指数并以最大类间方差法计算水陆分割阈值,从而分类得到水陆分离图像;对各时期海陆分类图像进行变化检测,统计出水体与陆地变化信息,并初步分析了水陆变化的驱动力及造陆对海洋环境的影响.研究结果表明:1987-2011年钦州湾海岸带造陆9218.96 hm2,新造陆地较集中分布在龙门港镇诸岛、钦州港口岸和钦江入海口等地;龙门港造陆已经使茅尾海与外海连通的水道宽度减少64.89%,严重影响了茅尾海与外海的物质、能量及海水交换速度,增加了茅尾海承接的陆源污染物不能及时稀释和扩散而引发环境问题的风险.

Erosion and deposition is a major concern for coastal zone management. In order to detect and analyse the coastal zone wa-ter-land transform characteristics and its driving force in Qinzhou Bay of Guangxi,Time-series Landsat TM images from 1987 to 2011 were used as the data source. Modified Normalized Difference Water Index（MNDWI）was extracted from pre-processed Landsat images and the proper threshold which can separate land and water was worked out by Otsu algorithm. Water-land information in Qinzhou Bay was classified by image threshold segmentation. Water-land change difference map and their statistic were computed by ENVI change de？tection model. We makes a preliminary analysis about epeirogenic＇s impact on the marine environment. The results show that the formed land area in Qinzhou Bay is 9218.96 hm2 from 1987 to 2011. New formed land mainly distributed in Longmengang town is-lands,Qinzhou port and Qin river estuary. Because of the new formed land around Longmengang town,the channel width is reduced by 64.89%in the past 25 years which connect Maowei Sea to open seas. This has seriously affected the exchange efficiency of matter,energy and water between Maowei Sea and the open seas,and increased the risk of Maowei Sea’s environmental problems for the pollution origi-nated on land can not dilute and diffuse as before.