Coastal areas adjacent to active subduction zones are at risk of tsunami disasters. Therefore, it is crucial to develop evacuation plans to minimise casualties should a disaster occur. This study examines evacuation accessibility along the coast of Cilacap City, Indonesia, using agent-based modelling. The modelling was conducted using the MATSim platform, which integrates the road network, the distribution of buildings as evacuation origin points, and population distribution data. The simulation involved 4,979 individuals from three coastal villages, using various modes of transportation, such as walking, motorcycles, and cars. The simulation results show that each mode of transportation has a different travel time for all agents to reach the evacuation point. Evacuation on foot took 26 minutes for all agents to reach the evacuation site, 13 minutes by motorcycle, and 4 minutes by car. The effective evacuation time (golden time) was set at approximately 35 minutes; within this timeframe, 90.1% of agents successfully reached the evacuation site, while 9.9% exceeded the golden time and were at risk of being affected. These results highlight the importance of integrating spatial data with an agent-based approach to identify weaknesses in evacuation accessibility and support evacuation planning for vulnerable coastal communities.
Ayodya Rido Nugraha, J. Jumadi, Novian Andri Akhirianto et al.· E3S Web of Conferences· 0 citations
Periodic river flooding occurs in Klaten Regency, consistently striking within close time intervals; however, spatial documentation for this area is currently unavailable. This study applies the Ratio Image method to Sentinel-1 SAR imagery processed using Google Earth Engine, to delineate floodwater distribution during two flood events that occurred in Klaten Regency in 2026. The First event, on January 12–13, was caused by the overflow of the Jabang Bayi and Gawe Rivers, and the second, on March 3– 4 event caused by the breach of the Dengkeng River embankment. An empirical threshold of 1.5 was established based on the bimodal distribution observed in the histogram, after which post-processing steps were applied, comprising the masking of permanent water bodies, slope, HAND, land cover, and a connectivity filter. Detection results indicated a total inundation area of of 1,150.46 ha across 24 subdistricts for the January event and 666.24 ha across 23 subdistricts for the March event. All subdistricts reported by the Klaten Regency Disaster Management Agency (BPBD) for each respective event were successfully identified within these results, a level of agreement that points on the realiable performance of the ratio image method on alluvial plains irrespective of flood source.
Dyah Ayu S. N. Alfath, J. Jumadi, A. Saputra et al.· E3S Web of Conferences· 0 citations
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