大規模崩塌之初步風險評估架構與應用

A Framework for the Preliminary Risk Assessment of Large-scale Landslides and Its Application

鄭筠諺(Yun-Yen Cheng)

指導教授 ： 潘以文

國立交通大學/工學院/土木工程系所/碩士(2018年)

摘要

台灣因為地震與強降雨多，時有大規模崩塌，造成大量傷亡與經濟損失。各地發生大規模崩塌的機率與造成的災損都不同，為了災害管理的需求，最好能夠引入風險之概念。透過風險分析可整合、比對不同場址發生大規模崩塌之風險，挑選出風險較高之潛勢區，評估該處之風險是否可容忍；若該風險不能容忍，則須藉由工程手段或非工程手段來達到防災及減災之目標。針對資料齊全之邊坡，其崩塌風險的評估較易於執行，執行方法也相對成熟；對於大規模崩塌而言，風險評估則往往有困難，尤其在初期缺乏詳細的現地調查資料以及地質資訊情況下，勢必無法對所有具有大規模崩塌潛勢區都付出人力與金錢。本研究目的在建構大規模崩塌之風險評估架構，透過可以取得的基本資料，以簡易方法評估台灣南部數個案例之風險。
　　本研究所建立的大規模崩塌之簡易風險評估架構中，涵蓋潛勢、危害度、脆弱度、判別保全對象、風險等級與潛勢分級並考量潛勢區之活動性，以描述發生大規模崩塌之易發程度。由於架構追求簡易，故所使用資料皆須快速取得，評估之元素皆以定性方式描述，雖無精確數值但卻仍能夠比較相對差異。於評估崩塌體的運移行為時，係以統計方法評估的崩塌規模為參考，並依實況圈繪來源區位置，再使用面積-體積經驗式與到達角度法計算運移距離，最後以經驗方法劃設影響範圍。由於初期風險評估階段尚難以評估完整的致災性參數進而評估破壞程度，本架構假設影響範圍內之保全對象皆全毀，影響範圍內之保全對象可經航空影像與門牌系統調查，再依保全重要性評分。最後得以定性方式評定個別案例之風險等級。

關鍵字

大規模崩塌 ； 風險評估 ； 潛勢 ； 活動性 ； 危害度 ； 脆弱度 ； 到達角度

並列摘要

Because of frequent earthquakes and heavy rainfall, landslides often occur in Taiwan and cause casualties and economic losses. The probability of large-scale landslides is different from site to site so is the degree of damage from location to location. For hazard management, it would be better to adopt the concept of risk. It is possible to assess and compare the risk levels of large-scale landslide sites through risk analysis, then examine whether the risk level will be tolerable. Disaster prevention and mitigation should be activated either by engineering or non-engineering measures if the risk is not tolerable. It is relatively feasible to conduct a detailed risk assessment for a slope with complete and detailed data. For common large-scale landslides, a detailed risk assessment becomes very difficult, especially in the preliminary stage. This is even true prior to when detailed field investigation and geological information are available; it is generally cost ineffective to pay lots of human resource and large budget for every large-scale landslide susceptible area. The objective of this study is to establish a framework of preliminary risk assessment for large-scale landslides; this approach should only require available simple information to assess the risk of each large-scale landslide site.
The included components in the preliminary risk assessment framework for large-scale landslides proposed in this study includes susceptibility, hazard, vulnerability, discriminating elements at risk, risk level and susceptible level accounting for activity for susceptible area. For the purpose of simplification, the information required in the proposed framework has to be obtained quickly and each element for the assessment can be described qualitatively. This framework does not use quantitative value; yet, it is able to compare the relative level of each risk component. The landslide magnitude assessed by a statistical method is used as a reference for the analysis of the runout of a landslide and the location of the source area is inferred according to the actual site condition. Subsequently, the proposed approach incorporates the area-volume empirical formula and the reach angle method to estimate the runout distance, then delineate the influence zone by empirical method accordingly. For the sake of conservative consideration in the preliminary risk assessment, the framework assumes that the elements at risk within the range of the impact are all completely destroyed. The elements at risk within the influence zone can be determined from the aerial photo and the official house-number system; elements at risk are classified according to their importance levels. Consequently, the risk level of individual cases can be evaluated by integrating all components of risk assessment.

並列關鍵字

Large-scale landslide ； Risk assessment ； Susceptibility ； Activity ； Hazard ； Vulnerability ； Reach angle

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