Prosedur Umum Perhitungan Hidrograf Satuan Sintetis Dengan Cara ITB Dan Beberapa Contoh Penerapannya

. Synthetic unit hydrograph methods are popular and play an important role in many water resources design especially in the analysis of flood discharge of ungagged watersheds. These methods are simple, requiring only watershed characteristics such as area and river length and in some cases it may also include land use characteristics. Therefore, these methods serve as useful tools to simulate runoff from ungagged watersheds and watersheds undergoing land use change. To develop a synthetic unit hydrograph, several techniques are available. Several most popular unit hydrographs methods such as Nakayasu, Snyder-Alexeyev, SCS, and GAMA-1 are popular and commonly used in Indonesia for computing both peak discharge rate and the shape of flood hydrograph. This paper presents a simple approach for determining a consistent dimensionless unit hydrograph based on mass conservation principles. The unit hydrographs are synthesized by using either a simple single function (ITB-1) or using two simple functions (ITB-2) combined with an automatic adjustable peak rate factors based on the ratio between catchment area and area of unit hydrograph computed numerically using a simple tabulation procedure