The zoning of flood disasters by combining tidal flood and urban flood in Semarang City, Indonesia

Abstract

Semarang City, situated along the northern coastal region of Java Island, Indonesia, grapples annually with the dual challenges of tidal flooding and urban inundation. Establishing a comprehensive flood disaster zoning for both tidal floods and urban inundation to identify priority areas for effective flood mitigation and reducing disaster risk. This study aims to assess the potential inundation of tidal floods, urban floods, and their combined impact on Semarang City, using an integrated approach that combines Geographic Information System (GIS) technology with the Analytic Hierarchy Process (AHP). By leveraging data from Digital Elevation Model Nasional (DEMNAS), Google Earth, Rupa Bumi Indonesia (RBI) maps, and the Open Street Map (OSM) database, we obtained elevation, landcover, distance to the river, buildings, and administration data, which were used as criteria in the analysis. The research findings unveil three distinct flood inundation scenarios within Semarang City: tidal floods, urban floods, and a combination of both. Each scenario is categorized into low, medium, and high levels of inundation, providing a granular assessment of flood risk across the city. Importantly, the study extends beyond spatial analysis to evaluate the impact of inundation on affected buildings. The results indicate that the area inundated by the combination of tidal and urban floods is as follows: 86.87% high inundation, 13.12% moderate inundation, and 0.01% low inundation.