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Shades of risk: a mixed-methods approach to designing and testing a new hurricane map graphic

Abstract

Map graphics are a popular tool for hazard risk communication, layered with numerical, verbal, and visual information to describe an uncertain threat. In the hurricane context, graphics are used to communicate the probability of different threats over a forecasting period. While hurricane graphics have been studied in the past, they have not been analyzed from the design phase through to the intended audience. Additionally, hurricane graphics have not been designed with colorblind-friendly accessibility in mind. This dissertation presents the results of a three-phase, mixed methods study: (a) graphic development, (b) testing with expert user groups, and (c) testing with a public sample. In the development phase (a), I used the best practices for using probability language, color schemes, and localization into map graphics from literature in forecasting, communication, universal design, and emergency management. Additionally, I held informal interviews with professionals from the National Hurricane Center to develop the prototype with their recommendations for the design. In the first testing phase b, I interviewed 19 expert users (emergency managers and meteorologists) from Florida and Louisiana about their preferences for and feedback on the design elements of a new hurricane graphic, as well as if there were individual characteristics that influenced how accurate they were in interpreting wind exceedance data, such as risk perception, confidence, experience, spatial cognition, and numeracy levels. In phase c, I tested the wind exceedance graphic prototypes using a public sample (n = 624) from Louisiana and Florida to gather data on the accuracy of their interpretations for the graphic, again measuring confidence, experience, spatial cognition, and numeracy levels, as well as their design preferences and risk perceptions. The results of the two testing phases (b and c) center around how accurate experts and the public were with interpreting the graphic, as well as if there were other factors that influenced this accuracy, such as spatial cognition or numeracy. Additionally, the results describe both groups' design preferences, risk perceptions of the color schemes and overlays, and how experts think about vulnerability when using the graphic. In both groups, numeracy and spatial cognition were found to predict accuracy of interpretation for a wind exceedance graphic prototype. Likewise, both confidence and experience were found to have a positive relationship with accuracy. Regarding the design choices, both experts and the public preferred a yellow-to-red scheme, though experts thought the yellow-to-red scheme presented the hazard as riskier and the public thought the reds-only was riskier. Adding overlays to the graphic, such as interstates or city landmarks, helped the participants to orient themselves on the map. Experts and the public preferred that there were overlays added to the graphic and scored this version of the graphic as risker than a version without any overlays. The addition of the overlays prompted expert users to think more about the risk and vulnerability of the people in those areas on the map. Vulnerability was conceptualized from both a physical and social standpoint by the experts and applied to how they would use the wind exceedance graphic in a briefing to communicate to their community partners. Overall, this research provides a model for how hazard risk map graphics can be studied from design through implementation. Additionally, I captured how experts think about vulnerability in their communities when shown a forecast map graphic. The conclusion of this dissertation also provides practical recommendations for experts who want to apply the universal design aspects into new hurricane graphics.

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2023 Summer.
Includes bibliographical references.

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