The Utilization of RRI (Rainfall Runoff Inundation) Model for Inundation Forecasting in Tallo Watershed

Abstract

The method used to identify flood-prone areas is the utilization of the RRI (Rainfall Runoff Inundation) model. In the initial stage of flood risk reduction, inundation modeling can be carried out using rainfall data from radar, GSMap satellite, GPM satellite, and direct rain gauge measurements. The modeling approach involves real-time data, integrating rainfall amounts with existing watersheds. Floods that affected the city of Makassar and several areas in the Tallo Watershed were due to continuous rainfall from December 22, 2022, to January 31, 2020, resulting in several areas being submerged for several days. This study focuses on flood forecasting based on rainfall distribution over a specific period. The modeling utilizes the RRI model with input data from various rainfall sources, resulting in improved flood predictions regarding inundation height and extent. The research findings indicate that the RRI model using radar data provides the best validation results with a correlation (R) value of 0.85, Root Mean Square Error (RMSE) of 0.18, Nash-Sutcliffe Efficiency (NSE) of 0.39, and Pbias of -0.46. Radar data can effectively depict the inundation or flood distribution patterns in the Tallo Watershed, with inundation heights ranging from 0.5 m to 2.5 m and an extensive inundation area. Spatial flood modeling in the Tallo Watershed during the 2022 flood event accurately represents the real occurrences that affected the Manggala, Tallo, Tamalanrea, and Biringkanaya districts and surrounding areas.