花東土砂災害集水區崩塌地潛感分布及地景變遷之研究

Assess Potential Landslide Distribution and Landscape Change of Eastern Hualien and Taitung Debris Disaster Watershed Areas

10.6346/NPUST.2008.00256

白林奇

土砂災害 ； 集水區 ； 遙感探測 ； 崩塌潛感圖 ； 地理資訊系統 ； Landslide ； Watershed ； Remote Sensing ； Potential Landslide Maps ； Geographic Information System

屏東科技大學森林系所學位論文

2008年

碩士

陳朝圳

繁體中文

隨著台灣經濟及人口快速成長，台灣平地面積日漸不足，山坡地之開發已成為趨勢，然而在坡地開發的過程中，破壞了坡地間原有的穩定性。花東地區之主要土砂災害集水區如壽豐溪、秀姑巒溪、知本溪及太麻里溪，境內地質脆弱且常年有颱風侵襲。因此每逢颱風、暴雨山區經常發生崩塌或土石流等災害，嚴重危害當地居民生命財產安全。本研究以花東地區主要土砂集水區為研究區域利用1996年、2002年、2005年及2007年等四期SPOT衛星影像，以人工數化之方式取得各時期土砂災害區域，並利用地理資訊系統來套疊集水區之高程、坡度、坡向及地質圖層，分析四集水區崩塌地之特性。本研究另利用地理資訊系統，配合誘發土砂災害因子，包含坡度、坡向、高程、地質及距溪流道路遠近，計算各因子指標權重。並推估崩塌潛感圖，研究結果將可提供相關單位做集水區治理規劃之參考。 本研究之重要結論，分述如後：(一)研究結果顯示花東地區主要土砂災害集水區在1996年至2007年間，崩塌面積多呈現逐漸上升之趨勢(二)分析結果發現花東地區集水區之崩塌地多分布於高程1000-2000 m，坡度為30-60°，坡向以東南方、南方為主，地質則以大南澳片岩及廬山層居多(三)利用不安定指數法分析誘發土砂災害因子之權重，結果依次為地質、坡度、坡向、高程、與道路距離及水系距離(四)本研究所繪製之崩塌潛感圖，利用多時期崩塌地圖層來檢核其準確度，分析結果顯示實際崩塌地落於高潛感區者達57%，但當新增崩塌地超過一定比例時，會造成潛感圖預測之準確度降低(五)地景指標分析結果得知崩塌地之發生會使集水區內嵌塊體數、嵌塊體密度以及地景多樣性指標上升，造成集水區內地景破碎化，另森林面積在1996年至2007年間為逐漸下降，且有更加破碎化之趨勢。

The rapid economic growth and the population explosion resulted in the absence of usage of level ground in Taiwan formerly. As the result of that, the exploitation of hillside has been therefore practiced to seek more squares nowadays. However, this action affected the original stability among mountain slopes. The Eastern Hualien and Taitung debris disaster watershed areas, such as Shoufeng stream, Xiuguluan stream, Taimali stream and Zhiben stream occurs collapse and mudflows when typhoon and torrential rain strikes on mountainside area, which seriously threat local residents. This study utilizes the multi-temporal SPOT satellite images which were captured from the watersheds of Shoufeng stream, Xiuguluan stream, Taimali stream and Zhiben stream in year 1996, 2002, 2005 and 2007. This digital approaching can acquire the illustration of the periodic landslide areas. Matching with GIS function to overlay the landform layers identifies the characteristics of landslide areas which includes information of elevation, slope, aspect, geology and shape files. Furthermore, collaborating with the factors of landslide including slope, aspect, elevation, geology, distance to streams and distance to roads calculates the individual index factors. Following that, the analytical results accordingly is introduced to map out potential landslide maps. The results can provide references of watershed management for related government organizations. The conclusions of the study are stated as following：(1) The results of this study show that the area of landslide have been increasing from 1996 to 2007 in the Eastern Hualien and Taitung debris disaster watershed areas; (2) The results show that the landslide area is mostly happened at the height of 1000~2000 meters, and the slope grade is at 30~60°. The major aspects of landslide are towarding to southeast and east. The main rock stratus of landslide is Tananao schist and Lushan formation; (3) The Dangerous-Value method to analyst the weights of landslide factors are geology, slope, aspect, elevation, distance to streams and distance to roads respectively; (4) By using the multi-tempral landslide layers, the accuracy of the potential landslide maps can be compared, The analytical results show the predict landslide precisely where 57% landslide fall on the high susceptibility zone, However, over that scale will result in low accuracy of prediction; (5) The landscape indicators presents that landslide occurred in the value of indictors raising, such as numbers of patches, patchiness density and landscape diversity index, and the fragmentation of watershed. Moreover, the area of forest has been gradually decreasing and even tending to be more fragmented.

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