Improvement suggestions for problems of hazard map from the viewpoint of color scheme

Abstract. Local governments often rely on hazard maps to plan for and respond to local natural disasters. These maps often rely on the use of many colors, but their exact color scheme and style differs in each area. As a result, we hypothesize that some users, specifically colorblind individuals, may have difficulty correctly understanding the information on some of these hazard maps. In this study, we test that hypothesis by conducting a survey of Japanese liquefaction hazard maps and their visual accessibility. To this end, we first undergo a survey of the color schemes used in these maps and investigate whether they are easily understood by people with colorblindness. We next specifically analyze several maps we deem particularly problematic in terms of color scheme and visibility, using these as case studies to discuss issues with accessibility and to summarize possible countermeasures. Our survey found that liquefaction hazard maps use one of three main color schemes: “diverging color scheme,” “Sequential cold colors,” or “sequential warm colors.” However, while there were issues with several maps, including difficulty reading the background map or correctly understanding the risk of liquefaction, these difficulties were not related to the color scheme used. To improve the accessibility of hazard maps, therefore, is necessary to create a unified manual that contains the following information: an examination of colors, the utilization of a universal design check tool, and the use of GIS vector data.