FLOOD MODELLING OF RIAM KIWA WATERSHED USING HEC-HMS

At the end of 2021 to early 2022 several areas in Banjar Regency were flooded. This incident had a major impact on surrounding area and became national concern. One causes disaster was high-intensity rainfall which caused water Riam Kiwa River overflow. HEC-HMS software used simulate designed flood discharge. research aims model magnitude discharge with return periods 5, 25, 50, 100 years. Due limitations data from field, satellite GSMaP collected. In distribution frequency analysis, Log Pearson type III method chosen for calculating rainfall. Then, Modified Mononobe Method applied calculate hourly intensity. Other i.e., soil types, slope gradient land use analyzed using ArcGIS application. These three produced hydrological parameters as input values Soil Conservation Service (SCS) method. Three parameters’ show that watershed has more than 90% clay 83.58% (steep slope) is predominantly consisted mixed dryland agriculture (47.73%). From simulation, it found an 1781.77 km2 produces maximum ranges 8,822.3 m3/s 17,058.6 m3/s; volume 182,991.9 m3 340,889.6 5 years periods, respectively. results, can be concluded impermeable steep are two factors contribute flooding occurrence area.