The representative synthetic unit hydrograph in Juana watershed

Abstract

Rainfall-runoff transformation is carried out when the series of discharge data is limited or unavailable. One of the components of rainfall-runoff transformation is unit hydrograph, which can be derived synthetically. The selection of the representative synthetic unit hydrograph is fundamental related to the results of the further calculation. This study compared three types of synthetic unit hydrograph, that were Gama I, Nakayasu and SCS. The study was conducted in Juana Watershed, which is located in Central Java Province and composed of 52 sub-watersheds. The calculation was carried out in the control point of Sentul Weir by using HEC-HMS version 4.2.1, in the case of January 2014 flood events. The results showed that the peak discharge from Gama I, Nakayasu, and SCS synthetic unit hydrograph were 80.78 m3/s, 85.32 m3/s, and 78.89 m3/s respectively. Those results then compared with the flood mark in Sentul Weir, which was estimated 76.53 m3/s. Therefore, the SCS method was determined as the representative synthetic unit hydrograph in Juana Watershed, refers to the minimum error value of 3.08%. Then the analysis of design flood hydrograph for the 52 sub-watersheds in Juana Watershed can be approached by using the SCS synthetic unit hydrograph method.