Among the most basic challenges of hydrology are the quantitative understanding of the processes of runoff generation and prediction of the flow hydrographs and their transmission to the outlet. Traditional techniques have been widely applied for the estimation of runoff hydrographs at the outlets of gauged watersheds using historical rainfall-runoff data and unit hydrographs derived from them. Such procedures are questioned for their reliability due to the climatic and physical changes in the watershed and their application to ungauged, arid and semiarid catchments. To overcome such difficulties, the use of physically based rainfall-runoff estimation methods such as the Geomorphologic Instantaneous Unit Hydrograph (GIUH) approach has evolved. In this study, the lately developed GIUH model is applied to Al-Badan watershed of Faria catchment located in the northeastern part of the West Bank, Palestine. The Faria catchment characterizes a semiarid region, with annual rainfall depths ranging on average from about 150 to 600 mm. The Geographical Information System (GIS) techniques are used to shape the geomorphological features of the catchment. The application of the GIS supported GIUH model has proved reasonable agreement between the simulated runoff hydrograph and the recorded flows. The paper has elaborated on the applicability of the unit hydrograph theory and the GIUH to semiarid regions.