Social vulnerability gaps: Dynamics of the unsheltered homeless and wildfire hazards

Demographic and socio-economic omissions in social vulnerability assessments are not uncommon. However, conclusions from incomplete population characterization contribute to inequity and marginalization of at-risk segments of society, individuals who require care, resource assistance, and tailored public policy. The unsheltered homeless are considered here as an underrepresented segment of socially vulnerable people in hazard assessment. The unsheltered suffer disproportionately higher levels of direct exposure to natural and human-caused disasters, yet their lack of stable housing and often frequent moves make them both hidden and invisible in traditional census information. An exploratory spatial data analysis framework is developed to combine geographic information systems (GIS), statistics, and geostatistics to assess the implication of this omission. This research treats the integration of annual government counts and continuously updated, community-contributed information as a means of capturing regional spatial patterns of unsheltered homelessness at a fine geographic level. Comparison is then made to approaches based on traditional social vulnerability measures to evaluate consistency and representativeness. The findings suggest a significant gap in existing approaches. This study sheds light on potential avenues for more inclusive and accurate assessments of social vulnerability in the context of hazards. • Population and geography need to be reflected in social vulnerability assessment. • Indexes do not reflect regional heterogeneity, especially for unsheltered homeless. • Volunteered Geographic Information is critical to study high mobility populations. • Unsheltered homeless have persistent spatial patterns that expose them to hazards.