Flood Modeling and Inundation Mapping using the HEC-RAS 2D Hydrodynamic Model with a Meteorological Rain-on-Grid Approach: A Case Study of the Banyakan Area, Kediri Regency

Abstract

Sustainable water resources management requires a comprehensive hydrological approach, specifically in watersheds experiencing significant pressures from land-use changes and infrastructure development. The Bendo Krosok and the Maron Watershed in Kediri Regency, which form an integral part of the western Brantas River hydrological system, experienced significant flooding in late 2024. This flooding event is closely associated with watershed degradation, influenced by the construction of key infrastructure projects such as the Dhoho Kediri Airport and the Kediri-Kertosono Toll Road, which are located near the Bendo Krosok and the Maron Watershed. Therefore, this study aims to evaluate flood modeling and inundation mapping using the HEC-RAS 2D hydrodynamic model with a meteorological Rain-on-Grid (RoG) approach. Extreme rainfall data (R24) from December 22, 2024, recorded at 127 mm, resulted in a peak flood hydrograph of 156.9 m3/s in the Bendo Krosok River and 159.75 m3/s in the Maron River. Inundation mapping produced flood depths consistent with field observations, indicating a maximum depth of 2-3 meters in Tiron Village and about 1 meter along the Kediri-Nganjuk road near the downstream section of the Maron River. The results are expected to enhance flood risk management by identifying the most vulnerable areas within the Bendo Krosok and Maron Watershed, thereby supporting effective disaster mitigation strategies.