Abstract
In the water resource plan, analysis of the peak flood discharge is needed. Until now, there are several synthetic unit hydrograph methods can be used. The problem faced by engineers is determining the right method to be applied. Some engineers use the largest yield as the safer method, while others prefer the smallest yield as the less costly method. This study proposes an alternative prosedur to the problem-solving faced by these engineers. Three methods: Synthetic Unit Hydrograph of the United States Soil Conservation Service (US-SCS), Nakayasu and Modified Nakayasu were used in demonstrating the proposed procedure. Data on daily maximum annual rainfall for 12 years, flood height data from the Automatic Water Level Recorder (AWLR), and data on the characteristics of the Babak River Basin were used in this study. From the research results it is known that the proposed procedure for selecting the appropriate method can be reasonably applied. With this procedure, the peak flood discharge with a 5-year return period is 271,451 m3 / s for the Nakayasu HSS method, for the Nakayasu Modification HSS method of 482,486 m3 / s, and for the US SCS HSS method of 3619,019 m3 / sec. From the results of the statistical test of correlation (R) and deviation of volume error (VE) for the HSS Nakayasu method is R = 0.84 and VE = 0.4, for the Nakayasu Modified HSS method is R = 0.37 and VE = 0.91, and for the US SCS HSS method is R = 0.85 and VE = 9.25, so it can be seen that the most appropriate and suitable method for the Babak watershed is the Nakayasu HSS method