A combined hydrological and hydraulic model for flood prediction in Buah river subsystem area, Palembang city

Flood and inundation are problems that vastly impact all sectors and cause huge losses. This study aimed to determine the characteristics of drainage channels, hydrology, and hydraulic flow in the Buah river subsystem to design flood control through various scenarios of discharge analysis for a 10-year return period. This study was carried out to investigate the drainage channel plan's effectiveness to reduce peak flood discharge and occurrence. By using the hydrologic engineering center's – river analysis system (HEC-RAS) and hydrologic engineering center – hydrologic modeling system (HEC-HMS) software, hydrological and hydraulic analysis was performed to examine the drainage channel's capacity in the Buah river. The hydrological and hydraulic methods employed Muskingum-Change and Saint-Venant formula, respectively. The 2008 to 2017 rain data used were obtained from Meteorology Climatology and Geophysics Council (BMKG) of Palembang City. The log-Pearson III method was used to determine design rainfall with return periods of 2, 5, 10, 25, 50, and 100 years. Rainfall intensity was analyzed using the Mononobe method for five-year return period to hyetograph. Also, rainfall intensity was analyzed using the intensity-duration-frequency (IDF) curve to determine the number of years required for the full release of the channel to pass. Based on the results, the highest intensity was detected in a 2-to-100-year return period, where the 5-minute rainfall duration had a value of 200–350 mm/hour. Meanwhile, for 2 hours duration, the highest value recorded was 25-50 mm/hour. The maximum rainfall distribution for 5 minutes of rain was 10 mm, while 120 minutes covered 3 mm. The highest elevation of the Buah river subsystem was in the 100-year return period with a height of 10.3 m, but the lowest occurred in the 2-year return period with a water level of 9.89 m.