Integrated multihazard mapping

A primary goal of the US Disaster Mitigation Act of 2000 is to slow the increase in disaster losses by emphasizing a proactive approach focusing on predisaster hazard mitigation, rather than postdisaster relief. The legislation requires local communities to produce hazard-mitigation plans that include multihazard maps, signifying a de facto prioritization of mitigation dollars on the basis of areas with the greatest vulnerability. However, there is little formal or practical guidance for communities on how to produce such maps. We propose a methodology for hazard-vulnerability assessments using multihazard mapping, where hazard frequency is a measure of risk, historical dollar losses are a proxy for infrastructure impact or exposure, and the Social Vulnerability Index (SoVI) evaluates human vulnerability. Using a test case of one county, Charleston, South Carolina, a geographic information system spatially combined these dimensions of vulnerability across multiple hazards. The resulting maps provide a tool for hazard-mitigation planning, which contains an initial screening element to highlight zones of highest multihazard vulnerability. The approach helps to generate a view of not just what is at risk, but who is at risk, and where, thus enhancing the implementation of targeted impact-reduction strategies.