氣候變遷下降雨與淺層飽和層水位引致坡地災害之風險評估-以新北市南勢溪為例

Risk Assessment of Hillslope Disaster Caused by Rainfall and Water Table of Shallow Aquifer under Climate Change -A Case Study in Nanshi River, New Taipei City

王涴雅(Wan-Ya Wang)

指導教授 ： 童慶斌

國立臺灣大學/生物資源暨農學院/生物環境系統工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU201904303

摘要

由於氣候急遽變化，各地不斷有自然災害傳出，其中也包含損失慘重的坡地災害，尤其台灣因山坡地占地廣泛，相關災害更為頻繁，在眾多造成坡地不穩定的原因之中，主要以降雨與其補注之淺層飽和含水層水位為評估依據。

本研究以新北市南勢溪為例，參考科技部氣候變遷調適科技整合研究計畫（TaiCCAT）氣候調適六步驟，將步驟一至步驟四付諸執行，發展風險評估流程，以無限邊坡法計算安全係數，設定安全係數為1時為坡地滑動之臨界值，其所對應之淺層飽和含水層水位為門檻值，進行超越機率分析作為危害之指標，並考慮區域內暴露與敏感度，進行氣候變遷風險評估。未來風險評估方面包含產生未來氣象資料，以福山觀測站所得歷史降雨資料，比對大氣環流模式(General Circulation Models, GCMs)之最劣情境產生未來降雨，並以Soil Water Assessment Tool (SWAT)模擬地下水文循環，以取得模擬之淺層飽和含水層水位。

研究結果顯示，區域範圍內上游的第五子集水區淺層飽和含水層水位最高，是為淺層坡地危害風險最高之區域，應為治理層級進行調適行動時應當優先考慮風險相對較高地區。根據風險地圖，未來氣候情境之下各子集水區風險等級確實有變劣的趨勢，坡地災害在氣候變遷之下確實受到威脅，若要降低損失，氣候調適行動勢必為重要對策。

關鍵字

坡地災害 ； 氣候變遷風險評估 ； 淺層飽和含水層水位 ； SWAT

並列摘要

According to the climate is changing rapidly, natural disasters occur in various places continually, including hillslope disasters with heavy losses. Due to the extensive area of hillsides in Taiwan, related disasters happen more frequently recently. Among the many cause of slope instability, the rainfall and the water level of the shallow saturated aquifer are the mainly the basis for risk assessment in this study.

The research area is located at Nanshi River, New Taipei City. The main purpose of this study is to take Climate Smart Adaptation Algorithm (CSAA) which is developed by TaiCCAT and to develop the process of the risk assessment into practice. Infinite slope method for calculating the Factor of Safety (FS) is the way to set the threshold and undertake probability analysis as an indicator of hazard. When the Factor of Safety is set to 1, the corresponding shallow saturated aquifer water level is the threshold value. Risk assessment will be complete after combine the hazard, exposure and sensitivity in study area. In terms of hydrologic factors, the historical observation rainfall from Fushan station and the future data from GCMs (General Circulation Models) were the input datas to simulate the water level of the shallow saturated aquifer in the baseline and the future by operating the SWAT model.

The water level of the shallow saturated aquifer in the fifth subbasin is the highest, and it is also the area with the highest hillslope disasters risk which should take some climate adaptation actions priorly. According to the result of the risk map, the risk level of each subbasin in the future is indeed deteriorating, so slope disasters are indeed threatened by climate change in this area. To reduce losses under the disasters, climate adaptation actions are bound to be significant actions.

並列關鍵字

Hillslope Disaster ； Climate Change Risk Assessment ； Water Table of Shallow Aquifer ； SWAT

參考文獻

1.Arnold, J. G., S. L. Neitsch, J. R. Kiniry, and J. R. Williams (2009), “Soil and water assessment tool theoretical documentation version 2009”

2.C.W. RICHARDSON(1981), Stochastic Simulation of Daily Precipitation, Temperature, and Solar Radiation.

3.David Eckstein, Marie-Lena Hutfils, Maik Winges (2019), Germanwatch, Global Climate Risk Index 2019.

4.Emanuel,K.A.(2005),Increasing destructiveness of tropical cyclones over the past 30 years.Nature, 436, p686-p688.

5.Haasnoot, M., Middelkoop, H., Offermans, A., Van Beek, E., & Van Deursen, W. P. (2012). Exploring pathways for sustainable water management in river deltas in a changing environment. Climatic Change, 115(3-4), 795-819.