2017 2nd International Conference on Applied Mathematics, Simulation and Modelling (AMSM 2017) ISBN: 978-1-60595-480-6 Parameters Estimation of Synthetic Unit Hydrograph Model Using Multiple Linear and Non-linear Regressions I Gede TUNAS 1,* , Nadjadji ANWAR 2 and Umboro LASMINTO 2 1 Department of Civil Engineering, University of Tadulako, Palu 94118, Indonesia 2 Department of Civil Engineering, Institut Teknologi Sepuluh Nopember (ITS) Surabaya 60111, Indonesia *Corresponding author Keywords: Parameters estimation, Synthetic unit hydrograph model, Multiple linear regressions, Multiple non-linear regressions. Abstract. The use of synthetic unit hydrograph model (SUH) is remain popular used to transform rainfall into run off for water resources development. The typical feature of this model is that the main equation represents the shape of the curve expressed by the relationship between time and discharge. In addition, the SUH model is also expressed in three parameters i.e. peak time (TP), peak discharge (QP), and base time (TB), representing the hydrograph curve equation. In general, SUH model is developed based on morphometry parameters of watershed, especially watershed area (A), main river length (L) and main river slope (S). Another approach in hydrograph modelling is based on the fractal characteristics of watershed. This study aims to develop a synthetic unit hydrograph model based on a combination of morphometry and fractal characteristics of watersheds. The three model parameters (TP, QP and TB) were predicted using multiple linear regression and compared with multiple nonlinear regression. The results of the analysis show that the two methods showed excellent performance. The estimation of SUH parameters using linear regression resulted peak time equation (TP) as function of river length (L), ratio of river length (RL) and density of drainage network (D) with determination coefficient of 99.8%, a base time equation (TB) as the function of watershed area (A) and river slope (S) with determination coefficient of 98.2%. Using multiple non linear regression, estimation of SUH parameters formulated peak time equation (TP) as function of river length (L), ratio of river length (RL) and ratio of watershed area (RA) with determination coefficient of 99.9%, a base time equation (TB) as the function of watershed area (A) and ratio of watershed area (RA) with determination coefficient of 97.9%. Peak discharge equation (QP) is stated as a function of peak time and a simple single curve equation derived from Gamma Distribution Equation. Introduction In hydrological modelling, one of the rainfall-run off transformation models is hydrograph-based modelling [1,2]. Hydrograph-based modelling is generally developed to accommodate the limitations of hydrological data, especially rainfall data and discharge data in a watershed where the model is developed [3]. Oftentimes, discharge data is not available at all or available with very limited range of data [4]. This is related to the availability of hydrological and hydrometry gauge networks, especially the limited discharge gauges. Hydrometric stations that function to monitor and record river water level data, in addition to the limited number, generally only installed in certain places considered by the managers have significance function [5] in this case the potential development of a region in terms of water resources. This is due to very high installation and management costs. Besides that also due to the high level of sensitivity of this instrument, not infrequently give dubious results even not work at all. The implication is that the recording of discharge data in certain years is incomplete or even absent, so that when needed for hydrological analysis the data is not available or available in a very short period of time. On the other hand, the existing hydrometric stations are equipped with a set of automatic water level registers, so to obtain discharge data, It is needed calibration from the water 202