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

Ryo Endo,Takayuki Nakano

doi:10.5194/ica-proc-2-25-2019

Abstract

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.

Highlights

Hazard maps are often used by local governments and residents both to help take necessary measures against disasters and to effectively respond to them once they occur
Our cluster analysis found that most liquefaction hazard maps investigated in this study use one of the following patterns of colors: (1) sequential color schemes that include red, yellow, and green; (2) warm color schemes that include colors such as red, orange, and yellow; or (3) cold color schemes that include colors such as blue, cyan, and achromatic shades
We found that many maps use this same color scheme, and it is a common tool for expressing liquefaction risk in Japan

Summary

Introduction

Hazard maps are often used by local governments and residents both to help take necessary measures against disasters and to effectively respond to them once they occur Such maps frequently use colors to illustrate relative risk or to make the map stand out, a phenomenon that has become even more common with the development of computer technology and growing ubiquitous nature of color printing (Ito, 2012). The more information a hazard map includes (i.e., hazard risk level, background diagram, location of shelters, and/or adaptive evacuation routes), so the more colors it is likely to use This may cause reduced visibility for some users, especially for people with colorblindness, who may difficulty in distinguishing specific colors. Such people occupy a sizable minority of the population (4–8% of men, 0.5% of women; Okabe and Ito, 2008), and ensuring these individuals can accurately read and interpret hazard maps is importantin the case of disaster

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Discussion

Conclusion