基于数字海图及遥感的近60年崇明东滩湿地演变分析

Evolution analysis of Chongming Dongtan wetland in recent 60 years based on digital nautical chart and remote sensing

利用9幅崇明东滩湿地1951—2006年海图数据,10幅MSS,TM及ETM+卫星数据,采用水边线及等深线叠加技术,将湿地陆面及水下部分作为相互关联的整体,定性与定量相结合,综合分析崇明东滩湿地近60 a的演变。结果表明:①东滩湿地目前的演变过程已趋于稳定,在长江口河势稳定的情况下,将保持"南冲北淤、部分交替、中部淤涨"的态势;②人类活动是东滩湿地自然演变的重要驱动力,白港潮汐通道的封堵使东滩湿地成陆过程大大加快,东滩湿地0 m线较为稳定地向东部扩展,在人类逐年围垦活动的干预下,湿地面积虽然逐年增加,但潮间带结构已偏离湿地自然状态,高潮滩面积所占比重减少,且成不连续分布,海堤直接暴露于外部海洋环境中,将降低对灾害天气的防御能力。

The spatial variation of Chongming Dongtan wetland was monitored using 10 remote sensing images including Landsat MSS, TM and ETM ＋ data. Nine nautical charts were employed to analyze the evolution of underwater terrain from 1951 to 2006. With the above/under water topographic changes as an entirety, the authors made quantitative and qualitative analysis of geomorphic evolution in the past 60 years at Chongming Dongtan wetland using waterline method and depth contour overlaying. Some conclusions have been reached： ① The dynamics of Chongming Dongtan tend to be stable, characterized by erosion in the south part, deposition in the north, rapid propagation in the middle and alternate erosion and deposition in some coasts under the stabilities of the current Yangtze estuary; ② Human activities made important effect on the wetland. Especially, damn in the Baigang tidal channel accelerated deposition in the wetland. Then the 0 m isobath expanded to the east at a stable rate. Although the wetland area was increasing with the human reclamation year by year, the inter - tidal structure of wetland was deviated from the nature state. The proportion of high tidal fiat was decreasing and it showed discontinuous spatial distribution at Chongming Dongtan. Because the damn was directly exposed to the outside marine environment, it would reduce the capability of disaster weather prevention.