Flood hazard mapping of the Welang river, Pasuruan, East Java, Indonesia

Abstract

The availability of a flood hazard map is beneficial during flood risk reduction. However, there is a lack of high-resolution topographic data, which is a map realization obstacle. Therefore, this study aims to construct flood hazard maps based on hazard levels for various flood return periods. The 2D-hydrodynamic from the Hydrologic Engineering Center's River Analysis System (HEC-RAS) and Digital Surface Models (DSM) from Unmanned Aerial Vehicle (UAV) imagery were used for generating inundation maps. The results showed that simulation of return periods for 2 and 10 years illustrated a 37% increase in flood hazard levels. Furthermore, there was an increased danger level for locations that were exposed to flood inundation. This occurred in housing, some roads, and rice fields. Ultimately, this study mitigates flood hazards through the determination of evacuation directions, urban spatial planning, and informed flood mitigation measures.