Flood Evacuation Mapping Using a Time–Distance cartogram

Abstract

When flooding occurs, people should be evacuated safely to designated shelters along the optimal routes to minimize serious damages on lives and properties. However, in general, only limited information related to evacuation procedures and using a directional arrow to indicate existing shelters is provided on the evacuation map. Moreover, the evacuation routes leading to nearby shelters are not presented effectively to people in an emergency situation. This paper aimed to provide an approach to generate a flood evacuation cartogram based on an actual evacuation. The proposed time–distance cartogram preserves the topological characteristics by minimizing distortion in transforming the evacuation routes. To empirically evaluate its application, we applied the proposed method to Siheung city in Korea. As a result, optimal shelter and evacuation routes were derived by considering significant factors influencing the actual access to the facilities. Moreover, the flood evacuation cartogram provides a more intuitive visualization than classic topographic maps, by relocating shelters and reshaping the routes intended for evacuation. The suggested method is significant as it provides practical flood evacuation information effectively and intuitively, and the generated cartograms as empirical results also provide helpful insights for more efficient evacuation plans.

A GIS-Based Evacuation Route Planning in Flood-Susceptible Area of Siraha Municipality, Nepal

“…The assembly points in this study were identified based on the location having the highest population density. A place where the population is high can be considered a place that requires evacuation urgent [68]. Since it was not possible to obtain the population of every location in the study area, the buildings were extracted from OpenStreetMap, and the place with the highest building density was considered the location with the highest population density.…”

“…An immediate evacuation is necessary at the time of flooding, so it is not possible to evacuate the people through vehicles or any form of transportation. In this study, the main way of evacuation is by walking from the assembly point to the sheltered zone through the optimal route [68]. The average walking speed of the evacuee during evacuation is set to be 1.5 m/s, which changes according to different time groups as shown in Table 7.…”

“…In this study, the area which is in the high susceptibility zone is considered a flooded zone. The maximum depth of the flood that a pedestrian can evacuate through is 0.55 m [68]. Considering these, the modified speed after considering the flood is calculated using Equation (6) [75]:…”