遙測與地理資訊系統應用於大甲溪流域之崩塌災害的調查與分析

Abstract

本研究之主要目的是結合福衛二號遙測影像與地理資訊系統（GIS）等資訊技術，分析民國90年桃芝颱風與93年敏督利颱風肆虐所造成72水災後，對大甲溪 中上游流域內坡地崩塌災害的分佈與變化情形。因此本文首先利用福衛二號遙測影像之監督性分類與常態化差異植生指標（NDVI）分析敏督利颱風之崩塌災區， 並和農委會水土保持局（SWCB）坡地災害資訊系統的桃芝風災資料進行對比，探究此二次風災對大甲溪流域坡地崩塌的範圍與衝擊，研究發現累積雨量從桃芝颱 風的300～400mm上升至敏督利颱風的750～1000mm後，崩塌數增加一倍以上，崩塌面積擴大60％，其中谷關水庫以上之大甲溪主支流域之崩塌增 加最多，而重複崩塌區域則達87％。其次結合GIS系統，建置相關環境資料數據庫，並以敘述統計、相關分析等方法發現崩塌範圍不僅與降雨規模有關也和地形 （坡度、坡向、高度）和地質（岩性、構造）等因子有密切相關；最後此研究成果可利用不安定指數法，轉製為坡地崩塌潛感分析圖，提供作為災害防治決策系統的 參考。

Applying remote sensing and GIS technique this paper attempts to analyze the landslide hazard after two typhoon events. First of all, by comparing the landside data from SWCB and satellite images from FORMOSAT (processed by supervised classification and NDVI index), the landslides of Midulle Typhoon increased 100% for number and 60% for area than that of Toraji Typhoon. The new born landslides located in the valley slope of main course and tributaries in upper stream. Another, over 87% of landslide reacted in Mindulle Typhoon when the precipitation from 300-350mm (Toraji Typhoon) up to 750-1000mm. Secondly, based on GIS database and statistic processing, it shows that the concentration in space may resulted from not only the intensity of precipitation also the geomorphic (steepness of slope) and geological factors (resistance of rock and weakness of structural line). Finally, the vulnerability of landslide hazard in Tachia basin could be shown by the index of unstable formulated by weighting of environmental parameters.