Balanced Design Storm UH, Rational, and Regression Equation Methods

Abstract

In practice, runoff peak flow rates are typically estimated by the rational method, a design storm unit hydrograph (UH) method, or a statistical regression equation. In this technical note, the balanced design storm UH procedure is used to derive a rational method peak flow rate equation that, in turn, is used to derive a regression equation. This new mathematical linkage across these three widely used peak flow rate estimation techniques provide a foundation as to how these approaches differ or agree, and may also provide an answer as to which method is “best”; specifically, the methods are essentially the same for many practical conditions, and where they differ, the underpinnings of their mathematical structures are illuminated.