A methodology for the quantitative risk assessment (QRA) of the impact of debris flow in a road environment has been developed and applied to two sites that are typically subject to high frequency-low magnitude and low frequency-high magnitude events. The methodology considers the probability of an event of a typical size, and the conditional probabilities of a vehicle being affected, given an event, and of damage (fatality) occurring given that the vehicle is affected. Scenarios covering a vehicle being hit by a debris flow and of a vehicle hitting a debris flow are considered. The computed Personal Individual Risk (PIR) is used to calculate worst case fatality probabilities for commuters and logistics truck drivers. The overall risk to society is expressed both by the annual probability of fatality amongst all road users, the Potential Loss of Life (PLL), and using the F-N diagram and is used to demonstrate the effect of a programme of management and mitigation works on the societal risk at one of the sites. The authors believe that this is the first full, formal quantitative risk assessment for debris flow risk to road users. The PIR for a single trip through the sites ranges between 1.147E-10 for the low frequency-high magnitude site and 1.583E-09 for the high frequency-low magnitude site. These figures increase to 1.248E-07 and 1.922E-06, respectively, when more frequent travellers are considered. The PLL for the two sites ranges between 2.616E-04 for the low frequency-high magnitude site and 4.083E-03 for the high frequency-low magnitude site. The F-N diagrams illustrate the Broadly Acceptable level of risk at the low frequency-high magnitude site and the partially Unacceptable level of risk at the high frequency-low magnitude site. The risk at the high frequency-low magnitude site is reduced to ALARP levels when management and mitigation measures extant as of October 2014 are considered. The QRA proves an effective technique for understanding, comparing and articulating the differences in levels of risk and the temporal changes in risk at a given site as a result of landslide risk reduction activities.

中文翻译：

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评估泥石流对道路使用者的定量风险

已经开发了一种道路环境中泥石流影响定量风险评估（QRA）的方法，并将其应用于两个站点，这些站点通常会发生高频-低强度事件和低频-高强度事件。该方法考虑了典型大小的事件的概率，给定事件的情况下车辆受到影响的条件概率，以及考虑到车辆受到影响而发生的损坏（致命性）。考虑了涵盖被泥石流撞到的车辆和被泥石流撞到的车辆的场景。计算出的个人个人风险（PIR）用于计算通勤者和物流卡车驾驶员的最坏情况下的死亡概率。对社会的总体风险既可以通过所有道路使用者的年度死亡概率来表示，潜在生命损失（PLL），并使用FN图，用于演示管理和缓解措施计划对其中一个地点的社会风险的影响。作者认为，这是首次对道路使用者的泥石流风险进行全面，正式的定量风险评估。通过站点的单程PIR范围在低频高幅度站点的1.147E-10和高频低幅度站点的1.583E-09之间。当考虑到更频繁的旅行者时，这些数字分别增加到1.248E-07和1.922E-06。两个站点的PLL在低频高幅度站点的2.616E-04和高频低幅度站点的4.083E-03之间。FN图说明了低频-高强度站点的广泛接受风险水平和高频-低强度站点的部分不可接受风险水平。当考虑到2014年10月时已存在的管理和缓解措施时，高频低强度站点的风险降低到ALARP级别。QRA证明是一种有效的技术，可用于了解，比较和阐明由于滑坡风险降低活动而导致给定地点的风险水平和风险随时间变化的差异。