Urban Morphology and Tsunami Evacuation Accessibility: A Comparative Spatial Analysis of Cilacap and Kuta, Indonesia

Abstract

Urban morphology shapes how effectively coastal populations can evacuate during a tsunami. While existing research has established that urban form influences evacuation outcomes, limited attention has been given to how these relationships manifest across cities with different land-use contexts. This gap is particularly relevant for tourism-dominated coastal areas, which concentrate short-term visitors unfamiliar with local evacuation routes. This study addresses this gap through a comparative spatial analysis of two Indonesian coastal areas: Cilacap, a residential-industrial port city, and Kuta, Bali, a tourism-dominated coastal area. Using GIS-based and network-based analysis on a 500 m grid, the study characterizes each city's morphology through intersection density, block configuration, and building coverage ratio, and evaluates pedestrian evacuation accessibility through permeability, cell-to-cell detour ratio, and network bottlenecks. Findings indicate that, despite comparable coastal exposure, Kuta exhibits more constrained evacuation accessibility than Cilacap. Large blocks and lower permeability produce higher detour ratios and concentrate evacuation flows into fewer critical roads. These results suggest that evacuation capacity is shaped not only by hazard exposure but also by the morphological conditions that development produces over time. Morphological assessment should therefore be integrated into tsunami mitigation planning, particularly where land-use intensification may have outpaced the existing urban structure.