The best synthetic unit hydrograph for peak discharge analysis. Case: the Bengawan Solo River, section Dengkeng–Pusur

This paper aims to analyse the flood discharge based on the Synthetic Unit Hydrograph (SUH), using the Soil Conservation Service method (SCS), the SUH of Nakayasu method, and the SUH of Gama I method. Modelling formed the basis of the research conducted on the Bengawan Solo River, Indonesia. The embankment construction on the Dengkeng–Pusur Section was designed as a method of flood control in 1988. The problem was that around its location are densely populated cities, industrial areas, and agricultural areas. In order to measure the risk of embankment failure and water structure planning in general, it is necessary to analyse the maximum flood discharge. There are several methods for analysing maximum flood discharge, so finding a suitable method is essential due to the lack of measuring tools to calculate flood discharge in some areas. The calculation is compared with the observation data at the Serenan AWLR station, which is in the Dengkeng–Pusur section. The observation rainfall data was covered a 20 year period (1999–2018). According to the method used, the analysis is based on series data on four rainfall stations, the watershed characteristics, and other parameters. Furthermore, the maximum flood discharge from the calculation is compared with the observational data at the Serenan station. The result shows that the best SUH is Gama I method compared to the observation maximum flood discharge in AWLR Serenan Station, with an 8.0% error. The other method, the SUH Nakayasu method with a 16.6% error, and the SUH SCS method with a 39.5% error.