ANALISA PERBANDINGAN KINERJA HIDROGRAF SATUAN SINTETIS GAMA 1, LIMANTARA, DAN NAKAYASU PADA SUB DAS LESTI, JAWA TIMUR

Optimal watershed planning in terms of the strength and age of the building is a fundamental. This is done so that when the building is flooded to its maximum height, so that it remains safe and does not suffer damage. The Synthesis Unit Hydrograph (HSS) is a method that is often used in flood discharge analysis for watershed planning. This method is used by adjusting to the realtime conditions of the watershed or the Observation Unit Hydrograph (HSA). This research was conducted in the Lesti sub-watershed in Malang district. This Study compares several HSS methods, namely Gama I, Limantara and Nakayasu. From the result of the study, it was found that HSS Gama I have peak discharge of 21,72 m3/s, peak time 3,86 hours and a volume 383000,00 m3 while for Limantara the peak discharge of 12,90 m3/s, peak time was 3,61 hours and volume 383000,00 m3. Meanwhile, Nakayasu have a peak discharge of 15,21 m3/s, a peak time 3,16 hours and a volume of 383000,00 m3. Based on the assesment instrument using the RMSE, the HSS Nakayasu is the best method according to the HSA where the RMSE value is 1.009 compared to Gama I of 2.307 and Limantara 4.701. The RMSE value that is close to zero indicates that the HSS model applied is in accordance with the realtime (HSA) conditions