Pemanfaatan Foto Udara Format Kecil (FUFK) Untuk Analisis RIsiko Banjir di Desa Sirnoboyo Kabupaten Pacitan

Abstract

This study aims to flood modelling in Sirnoboyo village to find out the benefits of small format aerial photographs as flood analysis input data, compiling flood hazard maps, flood vulnerability maps and flood risk maps due to overflowing rivers in Pacitan City. The research method is used air photo mosaic, filtering analysis for digital terrain model (DTM) extraction, plan discharge analysis, river geometric analysis, flood modeling, flood hazard potential analysis, flood vulnerability analysis, and flood risk analysis. Flood modeling uses HEC-RAS 5.0.3 software. Hazard analysis resulted from flood depth modeling and flood flow velocity of 50 year return period. Vulnerability analysis is derived from the structure of buildings, building contents and socio-economic conditions of the community. Flood risk analysis is conducted with overlay of hazard maps and vulnerability maps referring to the risk indexs. Small format aerial photography capable of providing input data for flood modeling with high spatial resolution reaching 0.5 x 0.5 m. The HEC-RAS 5.0.3 are capable of modeling the depth of flood and flow speed. Validation of the depth of flood shows the accuracy of the modeling results of 83.94% by comparing the results of modeling with the depth of flooding that occurred in the field through surveys and direct interviews. The highest structural vulnerability in the research area occurred in the type of building structure 6 (wood, lepahan and asbestos) with foundation height <30 cm. The level of building risk to flood in the research area shows most of the buildings in the study area do not have a building risk of 29.57%. Buildings with low and medium risk of 12.17% and 39.13%. While the risk is high and very high by 13.04% and 6.09%. Priority areas for flood handlers in the research areas are Krajan, Suruhan, and Mendole hamlets.