Societal risk evaluation for landslides: historical synthesis and proposed tools
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Alex Strouth I Scott McDougall
Societal risk evaluation for landslides: historical synthesis and proposed tools
Abstract When a life-threatening landslide is recognized, the questions most relevant to community leaders are as follows: is our community safe enough, and if not, how much should we spend on protection? A risk evaluation tool that helps answer these questions, which compares landslide risk faced by a group of people to perceptions of tolerable risk, was first proposed in Hong Kong and is now being used widely in Western Canada within a quantitative risk management framework. After more than a decade of sporadic application in Western Canada, challenges of applying this tool are becoming apparent. For example, its use has resulted in landslide mitigation designs that are unaffordable, and it has failed to persuade funding authorities that proposed risk management solutions are a justifiable allocation of governments’ limited resources. This article suggests that the risk evaluation tool designed in Hong Kong should not be universally applied. We propose modifications believed to be more appropriate for Western Canada, including tolerating landslide risk levels similar to other natural hazard types and emphasizing cost-effectiveness of landslide risk reduction options. Although the proposed tools were developed for the sociopolitical context of Western Canada, we hope the discussions included in this article motivate others to modify these risk evaluation tools for other societies and hazard types and that ultimately this will lead to more rational and consistent decisions that, with time, save lives and resources in landslide-prone regions of the world. Keywords FN criteria . Group risk evaluation . Risk management . Cost to save a statistical life . Mitigation design Introduction Scientists and engineers who study landslides tend to focus on the kit of tools, technologies, methods, and judgment that the profession uses for making assessments. Their efforts are commonly directed towards the mechanics of landslide initiation and motion, informing assessment of where and why. This article focuses on what comes next—the public policy and political decisions related to:
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Is my community safe enough from landslides? How much of our limited resources should be invested in landslide protection? Would that money be better spent to protect against floods, fires, and earthquakes? When can evacuees return home? How do we communicate the risks and empower stakeholders to help manage risks?
A risk management framework that informs these decisions is well established (Whitman 1984; Fell 1994; Fell et al. 2005; VanDine 2012; Corominas et al. 2014; Porter et al. 2017; ISO 2018) and recent
advances, such as the Sendai Framework for Disaster Risk Reduction (UNDRR 2015), suggest that forward-looking and actionoriented approaches will be more widely adopted and further developed. This article focuses on the “risk evaluation” step of a quantitative risk management framework (Fig. 1). Risk evaluation is the comp
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