This study uses QGIS-3.28 to extract the geomorphological features for the ungauged watershed of Swaqa and employs SWMM-5.2 to simulate its 1-hr unit hydrograph (UH). Visualizing the watershed as an impervious surface of virtual curve number equals 100 subjected to an effective rainfall of 1cm depth, the SWMM has successfully simulated the 1-hr UH after computing the watershed width as this study proposes. The simulated 1-hr UH follows the common pattern of synthetic UHs. It has peak flow of 133m3/s which requires 4.5 hours to attain its value after the runoff has begun. The watershed has lag-time of 4 hours and it drains rainwater to around 45 hours. The derived UH is useful to obtain storm hydrograph for flood analysis and rainwater harvesting studies in the arid region of Swaqa. From regression analysis, a strong relationship was observed between the UH peak flow and the geomorphological attributes of the watershed. Based on that, this study introduces a general equation to predict the UH peak flow given the watershed area, stream length, surface roughness and slope. The predicted peak flow is close to the SWMM simulated value; therefore, this equation is useful to construct synthetic UHs for ungauged watersheds.