A mathematical watershed model of 1.456 square miles was developed to route runoff through overland flow and through the channel system. Excess rainfall was used as input data and the flow was routed by the successive numerical solution of the kinematic wave equations to produce outflow hydrographs for elementary (first order) watersheds. These hydrographs were used as input to the channel system where the flow was routed by the successive numerical solution of the dynamic wave equations to yield the outflow hydrograph for the model watershed. Backwater effects were considered at most of the junctions of the model watershed. The model was used to study the effects of the time distribution and areal distribution of rainfall, storm movement and watershed shape on the runoff hydrograph. In each study, attempts were made to find a relationship between an appropriate input parameter and a modification (peak flow) coefficient, to be used in adjusting the peak discharge estimated by conventional methods, which normally assume a stationary, constant intensity storm uniformly distributed over the watershed. The results of this study indicate that, in general, the selected factors have significant effects on peak discharge. (WRSIC Abstract).