極端降雨事件下淺層崩塌潛勢衝擊評估分析

Shallow Landslide Disaster Impact Assessment under Extreme Rainfall Event in the Climate Change Scenario

施虹如(Hung-Ju Shih) ； 吳亭燁(Ting-Yeh Wu) ； 蘇元風(Yuan-Fong Su) ； 劉哲欣(Che-Hsin Liu) ； 李欣輯(Hsin-Chi Li) ； 陳永明(Yong-Ming Chen) ； 張志新(Chih-Hsin Chang)

《工程環境會刊》 34期 (2015/01) Pp. 77-95

https://doi.org/10.6562/JEE.2015.34.5

摘要

本研究以未來極端事件之情境，來模擬極端降雨事件對淺層崩塌災害衝擊，並以莫拉克颱風作為驗證之案例。研究主要應用美國地質調查所（USGS）所發展的TRIGRS淺層崩塌物理模式，進行崩塌災害之分析。極端降雨事件是採用臺灣氣候變遷推估與資訊平台計畫（TCCIP）所提供之世紀末（2075-2099年）累積雨量最大之颱風事件，作為情境設定，並選取曾文水庫上游集水區為研究區域。為建立崩塌潛勢模型，本研究分別比較單一地質分區以及全區出露之11類地層之參數設定，來進行崩塌潛勢模擬。研究結果顯示，單一地質分區並不足以表現出整體之水文地質特性，而由較詳細之地質分區所模擬之結果表現較佳，且套疊歷年崩塌圖層後，模式的評估皆有不錯的成果。因此以地質分區之參數組合，在莫拉克颱風降雨事件的崩塌量模擬推估的結果顯示，進入水庫之土砂量約1億5千萬立方公尺，而滯留於坡面土砂量約為1億3千萬立方公尺，該分析得到之量與莫拉克颱風後因崩塌進入水庫之土砂量相近。最後，比較氣候變遷下之極端降雨事件，選定基期（1979-2003）和世紀末（2075-2099）之TOP1事件，分別評估其崩塌潛勢和衝擊，分析結果顯示，世紀末TOP1降雨事件所誘發的崩塌區位，以及相對保全對象之衝擊，相較於基期TOP1降雨事件皆有增強之趨勢。

關鍵字

淺層崩塌潛勢 ； 崩塌土方量 ； 崩塌區位 ； 極端事件災害衝擊

並列摘要

The main purpose of this study is to clarify the shallow landslide disaster impact under extreme rainfall event. A model for shallow landslide potential analysis was established by Transient Rainfall Infiltration and Grid-based Regional Slope-stability Model (TRIGRS) and was validated by disaster records during typhoon Morakot. After the model was established, authors intend to clarify the landslide potential in the climate change scenario. Therefore, an extreme rainfall event was determined from the one with maximum rainfall amount at the end of century period (2075-2099). A upstream part of river basin with a reservoir is the study area. The landslide potential analysis model shows apparent hydrologic and geologic features when considering multi geologic conditions rather than single geology type. Therefore, authors compared analysis result with landslide inventory and attained a better result through criterion of Modified Success Rate (MSR) according to this model. The result also represents the estimated landslide volume during typhoon Morakot. Sediment entering the reservoir is about 150 million m^3 and the part remained on the slope is about 130 million m^3, which is similar with the investigated data of the part entering reservoir. Finally, authors also estimated the sediment volume and landslide disaster impact by climate change scenario of baseline period (1979-2003) and at the end of century period (2075-2099). The landslide potential and estimated sediment volume has an increasing trend with the event at the end of century. The disaster impact also shows the same result after comparing with the community and important transportation.

並列關鍵字

Shallow Landslide Potential ； TIRGRS ； Landslide Volume ； Landslide Spots ； Landslide Disaster Impact Under Extreme Event