Alpha Modeling of Nakayasu Synthetic Unit Hydrograph for Part of Watersheds in Indonesia

Abstract

The lacks of hydrograph data in the field has become the drawback of the hydraulic structure planning. However, such a conditional deficiency in particular, has urgently placed the Synthetic Unit Hydrograph (SUH) models to be very great utility. The Synthetic Unit Hydrograph (SUH) is a popular model that is used in many water resources designs especially in design flood analysis in ungagged watershed. One of the SUH that is usually used in Indonesia is Nakayasu SUH. This model is depended on the α parameter that is influencing the unit hydrograph ordinate and time base. This research intends to build a model of α parameter that is as the characteristic factor of part of watersheds in Indonesia. The methodology consists of observed unit hydrograph analysis for obtaining the α parameter in each watershed, to collect the characteristic data in each watershed, and then to formulate the α parameter model that is as the function of watershed characteristic. The result is formulation model of α that can be used to analyze the design flood in the watershed in Indonesia