| Abstract: | 受全球氣候變遷的影響，近年來重大的乾旱、水災與地質災害頻生，使得臺灣地區飽受缺水、洪氾、山崩與土石流等天然災害之苦。全面進行區域水文地質的調查與分析，將有助於水資源及國土資源之完整規劃與保護。本研究考量現地調查需要耗費大量人力與經費，且無法遍及廣域的範圍及獲得多時序的資料，蒐集國內、外有關水文議題之衛星任務與文獻，提出多元的衛星遙測與GIS技術整合成果，搭配現地觀測以及模式分析比對，進而提取區域水資源與坡地災害訊息。本研究針對臺灣山區替代性水資源開發、平原區水資源保育及坡地防災所面臨的關鍵課題，分別提出：山區地下水潛能場址評估、平原區地下水入滲判釋、土壤含水量反演與坡地防災應用等議題。
研究成果指出，臺灣山區因板塊運動作用，造成複雜的地形與地質環境，欲瞭解區域的地下水蘊藏之影響因子，本研究蒐集了經濟部中央地質調查所的比例尺五萬分之一數值地質圖，以及空間解析度為30 m x 30 m的ASTER的全球數值高程圖(GDEM)與Landsat衛星影像，分別進行水文地質單元劃分、坡度、地形濕度指標與水系密度等GIS空間分析、以及線性密度與土壤濕度等衛星影像處理及計算，綜合評比繪製出常規化地下水潛能指標與分布圖，且比對現地72個地下水觀測井之井出水量，發現該指標與井出水量有其正相關性，而指標值選擇0.63，作為判釋地下水潛能場址與非潛能場址之閥值，其準確性可達84.7%，故具有高效益評估的實用性。平原區地下水入滲判釋以台中盆地為例，創新結合遙測與GIS技術及水文模式分析成果，提供工程實務之應用，透過Landsat與MODIS衛星影像分析成果，比對WetSpass水文模式評估成果進行驗證，有效地提供人為活動影響程度少的地下水入滲潛勢區之判釋。坡地防災應用方面，建立了嘉義縣油車寮崩塌地鄰近區域之ATI-MODIS反演土壤含水量模式，及2009年莫拉克颱風事件後SPOT影像判釋之山崩目錄，由於颱風降雨事件後所發生的崩塌地，在事件前土壤含水量已相對較高，於降雨事件後，增加了更多的土壤含水量，使得岩層的孔隙水壓增加且有效應力減少，故導致誘發坡地災害之可能性；而在油車寮崩塌地中，搭配現地觀測成果及Landsat線性構造分析，可提供判釋該區域的優勢水流路徑與高潛勢致災區，作為後續治理工程規劃與評估之參考。因此，透過多元的衛星影像處理及GIS技術，並比對現地調查成果，有助於水資源開發與保育及坡地防災等議題，提供高經濟效益之評估成果，以作為後續產、官、學、研等單位之參考依據與應用。;Natural disasters might have become more severely and occur more frequently worldwide due to the influence of global change in recent years. Taiwan, located in the subtropical monsoon climatic zone and arc-continent collision between the Luzon volcanic arc and the Eurasian continent, suffers from the natural disasters, such as drought, flood, geohazard. Its annual precipitation is about 2.5 times higher than the world’s average. Its complex geological terrain, uneven spatiotemporal distribution of rainfall may cause slope disaster and water scarcity. As a result, water supply available to the people per capital is only 20% of the world’s average. Comprehensive investigation is necessary for the decision-makers of natural resources management. However, due to extremely high cost of pointwise exploration with inconvenience in conducting on-site campaign in remote areas, remote sensing technique becomes an alternative solution. To achieve cost effectiveness on groundwater exploration and geohazard analysis, the use of comprehensive remote sensing (RS) data and GIS-based models appears to be feasible.
The results of this study shows that, in the mountainous regions, seven categories of terrains were defined by topographic position index, topographic wetness index and slope degree. Seventeen hydrogeological units were delineated from digital geological maps. Besides, the regional lineament and abnormal surface temperature favorable to groundwater have been considered and derived from remote sensing data. Compared with in-situ well yield data, the accuracy of the interpreted groundwater potential site (GWPS) varied with rock types and terrains. However, assessing the normalized groundwater potential index in the comprehensive RS-GIS model has improved the results to achieve a cost-effective objective in terms of identifying GWPS. The accuracy of the interpretation of groundwater potential sites is improved from 48.6% to 84.7%. In the case of Taichung Basin, integrating GIS, Landsat and MODIS imageries, WetSpass Model successfully provides the interpretation of potential groundwater infiltration. For the research of slope disaster, the soil water content retrieved from ATI-MODIS was considered during typhoon event. It is indicated that the slope area may be triggered as a landslide with increased pore water pressure and reduced effective stress. The comprehensive analysis results provide important information on the disaster prevention and mitigation. |
