Analytical Probabilistic Approach for Estimating Design Flood Peaks of Small Watersheds

An analytical probabilistic approach was developed in earlier studies to estimate design flood peaks from small urban areas. Developed in this paper are methods of incorporating the curve-number procedure for rainfall loss and Clark’s unit hydrograph for runoff routing calculations into the analytical probabilistic framework. These methods are verified by applying the analytical probabilistic approach to 12 urbanizing watersheds in the Chicago metropolitan area, with calibrated parameters representing two degrees of urbanization. The results are compared with those from single-event design-storm rainfall-runoff modeling. Generally comparable results demonstrate the potential of the analytical probabilistic approach as an efficient alternative for the estimation of design flood peaks from small watersheds.