基于短基线DInSAR的白鹤滩库区蓄水期滑坡隐患广域快速动态识别

Study on the Spatial-Temporal Variation of Vegetation Cover and its Topographic Effect in Hainan Island based on Remote Sensing

白鹤滩水电是国内继三峡水电站之后的第二大水电站,于2021年4月开始蓄水,水位上升约150 m,库区运行期随着水位线的快速变化,改变了库区的地质环境,极易引发突发性的地质灾害。为了保障水电站的正常运行及库区的居民生命财产安全,需要对库区进行快速动态的地质灾害识别。因此,基于短基线DInSAR方法对金沙江流域白鹤滩库区重点库岸段(葫芦口—象鼻岭地段)蓄水期展开了地质灾害隐患识别。通过Sentinel-1A/B数据进行联合监测,将重返周期提高到6 d1景,获取了研究区蓄水期2021年4月至11月共66景数据,结合SRTM DEM数据进行基于同一主影像的DInSAR处理,再将干涉对进行组合分析以达到快速动态的形变监测。最终共识别出92处存在显著形变的强形变区,均分布在金沙江两岸,其中8个强形变区域已被目前最高水位线800 m淹没,38个强形变区域位于水位线附近,部分出现小规模塌岸。同时选取了4个持续形变的区域结合实际地形地貌进行分析,发现形变迹象较为明显,且强形变区域位置与DInSAR方法监测结果相吻合,证明了将DInSAR方法应用于快速动态的发现新隐患点的情况的可行性,进行了蓄水期灾害分析与监测预警对保障白鹤滩水电站的正常蓄水发电具有重要意义。采用该方法进行广域地质灾害高效快速动态监测,在第一时间发现隐患点并进行定性分析,为水库岸蓄水期因水位变化引起的突发性潜在地质灾害的识别提供了一种新思路。

Vegetation cover plays an important role in maintaining the stability of the ecosystem and preventing the loss of water and soil.Hainan has developed in a rapid pace since its establishment as a province in 1988,which has led to tremendous changes in the vegetation cover across the Hainan Island.To shed light on the impact of topographic factors on the vegetation cover on the Hainan Island and provide a basis for a more reasonable ecological and environmental protection strategy for the island,this study targets the Hainan Island for research,and applies the normalized differential vegetation index and the dimidiate pixel model for the vegetation cover extraction based on the Landsat TM/OLI multispectral images of 1988,1998,20082017 and 2020,and provides a linear trend analysis in the characteristics of the vegetation cover changes on the Hainan Island in the last 30 years.Combined with the altitude,slope and aspect data obtained through 30m.DEM,it offers further explorations over the characteristics of the spatial distribution of vegetation cover on the Hainan Island with different topographic factors.The results show that:(1)The average vegetation cover on the Hainan Island from 1988 to 2020 is between 0.58~0.88,and the general trend is first downward and then upward;(2)High vegetation cover is mainly distributed in the central,southwestern and southeastern parts of the Hainan Island,while low vegetation cover mainly appears in areas of the island with man-made interference such as residential and coastal areas.(3)With the increase of altitude,the vegetation cover of various levels in the Hainan Island decreases,and the areas with an altitude of less than 100 meters have the largest vegetation cover;at O~5°of the slope,the vegetation cover reaches the maximum,and with the increase of slope,the vegetation cover shrinks;and there is little difference in the vegetation cover between the shady and sunny slopes that are primarily characterized by high vegetation cover.