High-intensity and short duration monsoon rainfall can induce severe flash flood in arid region, especially in Arizona. As climate becomes warmer, climate models predicted more intensified precipitations in arid region, so flood frequency and magnitude will increase. Civil infrastructure design needs to withstand the peak flow of 100 years event. Hydrologic Modeling System (HEC-HMS) is the most commonly used rainfall and runoff model incorporated the start-of-art knowledge in hydrology, hydraulics, and sediment transport. This study applied HEC-HMS model to predict surface runoff and sediment yield from Munds Draw watershed in Prescott National Forest in Northern Arizona. The watershed is ungagged and located in a remote mountain area. To verify the applicability of HMS model, we applied the model to a gaged watershed within the Walnut Gulch experimental watershed. The model was used to simulate multiple precipitation events, and parameters were optimized to match the observed surface runoff and sediment load. Since the Walnut Gulch watershed has the similar climate conditions as the Munds Draw, we applied the calibrated model to the Munds Draw watershed. We obtained the 100 year design rainfall from NWS national precipitation map, and used SCS distribution function to generate the rainfall hyetograph. Multiple grids were tested until the errors between two simulations convergence to nearly zero. This study illustrated the procedures to apply HMS model to an ungagged watershed as no observed data is available to verify the simulated results.
