南化水庫集水區坡地崩塌災害特性變遷之空間分布趨勢分析

The Spatial Trend Analysis of Landslide Disaster Characteristical Variation on Slopeland at Nanhua Reseriour Catchment in Southern Taiwan

蔡光榮(Kuang-Jung,Tsai) ； 李明熹(Ming-Hsi Lee) ； 陳怡睿(Yie-Ruey,Chen) ； 李佳諠(Jia-Xuan Li)

《臺灣鑛業》 71卷4期 (2019/12) Pp. 16-28

摘要

臺灣南部集水區坡地崩塌災害特性變遷之轉折受2009年8月莫拉克（Morakot）侵襲臺灣帶來驚人雨量影響甚鉅，南臺灣嘉南高屏等縣市轄區內累積連續3天最大降雨量高達2,884公厘（阿里山站），幾乎占臺灣全年平均降雨量之82.4%，因此造成嚴重山崩與土石流災害。依據水土保持局之莫拉克風災後衛星影像判釋分析顯示，區域內即有多達1萬904處崩塌與多處堰塞湖形成，總崩塌面積高達1萬8,113公頃。有鑑於此，本研究並配合立法院於2010年通過水利署研提之曾南烏特別條例，期能以GPS／GIS／RS科技整合技術，應用於曾文、南化、烏山頭等3水庫集水區內坡地崩塌土砂災害區之崩塌災情空間分布資訊調查分析，俾期能掌握曾南烏三水庫集水區內相關坡地致災因素之交互影響、大規模土砂運移機制崩塌之空間變遷分析、致災區域範圍，並應用高解析度衛星影像判釋分析河道沖淤特性之變化。本研究在民國106（2017）年首先選擇南化水庫集水區為研究重點區域，針對該水庫集水區內之坡地於承受極端降雨事件發生下，水庫集水區之自然環境受劇烈變化後所衍生之大規模坡地崩塌土砂災害變遷運移、空間分布特性與坡地穩定性進行分析探討，並據以研擬南化水庫集水區內之坡地崩塌土砂災害防治與國土保育規劃利用因應對策。因此如何考量於極端降雨變異之外在條件改變下，進行坡地崩塌土砂災害發生機制、運移行為分析與大規模崩塌變遷資訊之探討，終至作為研擬土砂災害防治策略與疏散避難決策之參考，以提昇南化水庫集水區之自然環境耐災度與抗災性，進而達到國土永續利用目標。本研究中蒐集至少近10年（2007－2017）來之極端降雨事件，據以探討在極端氣候變遷下之南化水庫集水區土砂災害發生誘因、災害風險認知、坡地崩坍發生機制及大規模崩塌後之土砂災害運移變遷特性等綜合性調查分析，最後提出水庫集水區之永續經營治理方案與坡地保育利用策略，以期未來可作為南化水庫集水區現行治理策略之檢討與未來永續經營對策研擬之參考依據。

關鍵字

極端降雨 ； 崩塌災害 ； 集水區治理

並列摘要

The characteristics change of landslide disaster on slope land of Southern Taiwan can be positively related to the extremely heavy rainfall which were brought by Morakot typhoon on August, 2009. The accumulated rainfall amount within continuous 3 days was closed to 2,884mm according to the record of A-Li-San rainfall station at Chiayi. This heavy rainfall amount was occupied almost 82.4% of annual precipitation in Taiwan. Very serious large-scale landslides and debris flow were induced by this heavy rainfall event. As a result, we proposed this project mainly focuses on applying field investigations integrated with GPS/GIS/RS technique to analyze and investigate the characteristics, movement and mechanism of these landslide disasters. According to the satellite image analysis project was conducted by Soil and Water Conservation Bureau after Morakot event indicated that more than 10,904 sites of landslide with total sliding area of 18,113ha were found in this disaster area. Characteristics and mechanism of debris flow, landslide and large scale soil mass movement are collected on the basis of sediment related disasters recently happened on slope land located at Zengwen, Nanhua and Wusanto reservoir watersheds in the southwestern Taiwan. However, Nanhua reservoir was 1^(st) priority to be selected as a studied area due to its main purpose to play an important role of public water supply systems in southern Taiwan. In order to decrease the risk of large scale landslides on slope land, the strategy of land conservation, landslide control treatment, and sediment related disaster prevention should be executed as soon as possible. Meanwhile, consideration on the mechanism and behavior of large scale landslide disasters induced by heavy rainfall become an important issue which was seriously concerned by Taiwan government. The mechanism of large scale landslide disaster spatial analysis and watershed management under the condition of extreme rainfall resulted from climate change during the past 10 years (2007~2017) would be recognized as a critical issue by this research. Hopefully, all results can be used as references for the disaster prevention and hazard mitigation systems operated by Nanhua reservoir watershed agencies in southern Taiwan.

並列關鍵字

Extreme rainfall ； Landslide Disasters ； Watershed Management