Abstract
Flooding in residential areas remains a recurring problem in Makassar City, particularly in the Governor’s Housing Complex, Kassi-Kassi Subdistrict. This study aims to analyze the effectiveness of rainwater harvesting (RWH) systems in reducing flood risks. The methodology includes hydrological and hydraulic analysis, as well as catchment area mapping. The RWH system design is based on estimating the potential rainwater volume from annual rainfall intensity and rooftop catchment areas. The results show that the average flood volume in the study area is 61.66 m³. The effectiveness of the rainwater harvesting system varies with storage capacity and roof area. In the first scenario (8 m³), flood volume is reduced by 4.61- 60.06%; in the second scenario (10 m³), it achieves a 5.77-75.08% reduction; and in the third scenario (15.6 m³), it results in a 9.01-80.12% decrease. Differences in rooftop size influence the variation in percentage reduction, which affects the volume of harvested rainwater. The third scenario demonstrates the highest effectiveness, indicating that rainwater harvesting is a feasible and efficient strategy for urban rainwater management and flood mitigation. The study concludes that integrating rainwater harvesting (RWH) systems is a practical and sustainable solution for urban flood mitigation, especially in flood-prone areas such as KassiKassi, Makassar.