1984～2017年太湖岛屿的动态变化及驱动因子分析

Dynamic Change and Driving Factors Analysis of Taihu Islands, 1984-2017

近些年来,围堰、跨区域调水、清淤等人类活动导致太湖中的岛屿面积的变化及其边界的迁移。基于Landsat遥感影像探究太湖内岛屿面积的变化趋势及边界的迁移方向,一定程度上反映人为因素对岛屿动态变化的的影响,进而指导太湖治理工作。通过波段分析、非监督分类以及分类后处理的方法从Landsat影像中提取岛屿信息,获得1984~2017年不同时期的岛屿面积和边界数据,并对岛屿面积和边界数据进行动态变化趋势的分析,最终结合从文献、年鉴和其他与太湖相关资料中总结的与太湖岛屿相关的人为活动信息分析引起太湖主要岛屿动态变化的原因。研究表明:小贡山、漫山岛和三山岛屿总面积均呈下降趋势,但下降程度与年际间波动幅度不同,岛屿面积变化的人为驱动因素可归纳为清淤和旅游开发,自然驱动因子为流水侵蚀;岛屿边界的迁移与"禁止围网养殖"、"湿地公园建设"等政策实施呈现显著相关性,且具体变化与政策颁布之间存在时间上的滞后性。

In the past decades, anthropogenic activities, including cofferdam, interregional water transfer and dredging, have significant influences on the dynamic change of the boundary and area for Taihu islands. This study aims to research the total area change and boundary swift of the main Taihu islands using Landsat imagery, which reveal the impact of human disturbance on Taihu islands and will provide fundamental information for the governance of Taihu lake. To achieve this goal, the authors extract the area and boundary of Taihu islands via band analysis, unsupervised classification and post-classification analysis from Landsat imagery, analyze the dynamic trend of the total area and boundary of the islands, and then evaluate the driving factors for the dynamic change of the island area and boundary based on the information of anthropogenic activities organized from pervious literature, census and other Taihu offfical reports. The results show that the total area of Xiaogongshan、Manshandao and Sanshandao islands are all on downward trend, while the decrease amplitude and inter-annual fluctuation are different. The anthropogenic driving factors are summarized as dredging and tourism, while environmental factor is water erosion;the swifts of island boundaries show significant relationship with the governance policy such as "prohibition of seine aquaculture" and "wetland park construction", and more importantly there is a time lag between the actual happening of island change and the policy promulgation.