Comparing Heat Vulnerability Indicators and Household Experiences in Phoenix, Arizona

Assessing vulnerability and resiliency of urban systems is a key component of managing risks associated with a variety of natural and man-made hazards. Indices have been used to understand hazard vulnerability in urban systems. The development of these indices have continued to reflect the combinations of social, infrastructural, and environmental factors that are believed to suppress or elevate vulnerability to hazards. However, less is known about how well vulnerability indicators translate to experienced vulnerability and adaptation strategies employed at an individual or household scale. We analyzed closed-ended survey data collected from 163 households in Phoenix, Arizona, in summer 2016 as part of the interdisciplinary 3HEAT project to quantify how individual or household experiences with extreme heat relate to larger scale vulnerability indicators. Vulnerability was explored by categorizing survey questions into three components of vulnerability: exposure, adaptive capacity, and sensitivity. Household responses were only partially consistent with expectations based on traditional vulnerability indicators. For example, households located in higher vulnerability census tracts had a greater concern for health risks associated with heat waves than those living in tracts identified as lower vulnerability. Conversely, there were negligible differences in perceived heat exposure across vulnerability groups, with respondents from households in high and low vulnerability tracts indicating being too hot inside ones home at similar frequencies. We also observed a high degree heterogeneity in experiences within vulnerability groups for some questions. Respondents in high vulnerability tracts perceived the health risks of heat waves more similarly to one another than respondents in low vulnerability tracts. In general, vulnerability indicators often aligned as expected for questions that reflected sensitivity as opposed to exposure or adaptive capacity. Most vulnerability indices do not account for potential adaptation strategies, which is an important focus area for future research. This work addresses previously stated concerns of representativeness of vulnerability indicators and highlights the strengths and limitations of employing vulnerability indices to understand household experiences.