An Integrated GIS-Based Framework for Tsunami Evacuation Planning: Shelter Accessibility and Route Network Analysis in Palabuhanratu, Indonesia

Abstract

Palabuhanratu is located along the southern coast of Java and is at high risk of tsunami disasters owing to seismic gaps along the Sunda subduction zone. The seismic gap could generate earthquakes up to 9.1 Mw, potentially triggering tsunamis as high as 20.2 meters. Mitigation efforts require evacuation sites that can be reached within a limited evacuation time, yet existing temporary evacuation sites are moderately to poorly accessible, with a substantial proportion of the affected population unable to reach them within 30 minutes. This study develops an integrated GIS-based framework linking tsunami hazard mapping and inundation modeling with affected-population assessment, shelter location planning, and evacuation route analysis. The methodological approach uses existing evacuation sites as a baseline and progressively evaluates alternative shelter configurations based on population coverage within a 30-minute travel-time constraint, followed by network-based evacuation route analysis for the selected shelter configuration. GIS-based spatial analysis estimated inundation areas of 3.57 km² and 6.44 km² under 10- and 20-meter tsunami scenarios, affecting 13,553 and 23,574 people, respectively. Existing evacuation sites were reachable by only 38% of the affected population under the 20-meter inundation scenario. The addition of three proposed shelter locations increased the modeled accessibility to 100% within the 30-minute travel-time threshold. Network analysis subsequently identified 55 evacuation routes connecting tsunami-affected areas to designated evacuation sites. The integrated framework provides a systematic basis for comparing shelter configurations and linking shelter planning with evacuation route development, thereby supporting comprehensive tsunami mitigation planning in vulnerable coastal communities.