The analysis of alpha parameter on Nakayasu Synthetic Unit Hydrograph in Timor Island watersheds

Benenain and Noelmina river are rivers on Timor Island which have large watershed area. With a large watershed area, it is necessary to observe and calculate the peak flood discharge deeply. One of the methods used for calculate the peak flood discharge Nakayasu Synthetic Unit. In calculating the peak flood discharge with Nakayasu Synthetic Unit Hydrographic Parameters difficulties often encountered in determining the accuracy of the α (alpha) value coefficient. To calculate the α (alpha) value coefficient required data in the form of area and length of river. The results of analysis using software IBM SPSS version 23 the (alpha) value coefficient on Timor Island can be obtained using equation α = 2,461. (L)^−0,417. (A)^0,214 so that the α (alpha) value for each watershed varies depending on the size of the watershed and the length of the river. Thus, with the confidence level of the results of the analysis is 95% and the coefficient of determination (R2) is 0.826 then the watershed area and river length give an influence of 82.60% on the value of α (alpha) obtained. (paper)