考量降雨與土壤參數不確定性之坡地淺崩塌警戒曲線研擬

Abstract

有鑑於山坡地崩塌的發生，極有可能造成生命與財產的損失，若能建立預警系統，對於災害的防治及應變有莫大的幫助。本研究以坡地淺崩塌數值模式為工具，提出可考慮坡地重要參數與降雨之不確定性，不同預報可靠度之坡地淺崩塌降雨門檻曲線製作方法，使管理者能以預報可靠度為依據，利用此曲線進行坡地淺崩塌即時預報作業。本研究結合定率模擬法與回歸誤差分析法，考慮降雨以及土壤保水曲線、摩擦角、凝聚力、以及初始地下水位等條件不確定性對預報正確性之影響，建立在不同預報可靠度下之崩塌前N小時降雨門檻曲線。本研究以嘉義縣阿里山鄉美寮道路做為應用區域，整理49場降雨事件，其中35場事件用於建立門檻曲線，另以剩餘之14場事件進行驗證，結果顯示崩塌前三小時之預報可靠度相當接近設定之值，證明本研究所提警戒曲線分析方法之正確性與適用性，並探討如何使崩塌前六、八、十二小時之預報可靠度能夠更加接近設定之值。

Rainfall induced landslide can cause huge loss of life and property. Establishment of an early warning system could offer a great help for the prevention and response of landslide related disasters. This study aims to develop a framework which enable the consideration of rainfall and soil parameters uncertainties to derive the rainfall threshold curves for shallow landslide under stipulated forecast reliabilities. To incorporate the uncertainties from rainfall, water retention curve, friction angle, cohesion, and initial groundwater level into landslide forecasting, the deterministic simulation approach along with the regression error analysis were adopted to derive the rainfall threshold curves for various lead-time and forecast reliabilities. The Mei-Liao Road located in Alishan Township, Chiayi County was the study site. Forty-nine historical hyetographs were collected among which 35 hyetographs were used to derive the threshold curve and the remaining 14 hyetographs were used to examine the accuracy. The examination results show that the forecast reliability for three hours lead-time is close to the stipulated value which indicates that the framework proposed is applicable. A discussion was also presented regarding the improvement of forecasting accuracy for 6, 8, and 12 hours lead-time.