Among the most basic challenges of hydrology are the quantitative understanding of the processes of runoff generation and prediction of flow hydrographs. Traditional techniques have been widely applied for the estimation of runoff hydrographs of gauged catchments using historical rainfall–runoff data and unit hydrographs. Such procedures are questioned as to their reliability 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. This paper models the rainfall–runoff process of Faria catchment using the lately developed KW–GIUH. Faria catchment, located in the northeastern part of the West Bank, Palestine, is characterized as a semiarid region with annual rainfall depths ranging on average from 150 to 640 mm at both ends of the catchment. The Geographical Information System (GIS) techniques were used to shape the geomorphological features of the catchment. A GIS-based KW–GIUH hydrological model was used to simulate the rainfall–runoff process in the three sub-catchments of Faria, namely: Al-Badan, Al-Faria, and Al-Malaqi. The simulated runoff hydrographs proved that the GIS-based KW–GIUH model is applicable to semiarid regions and can be used to estimate the unit hydrographs in the West Bank catchments.