Urban Storm Runoff Inlet Hydrograph Study Volume 4; Synthetic Storms for Design of Urban Highway Drainage Facilities.

The main objective of this study is to develop an accurate design method for computing inlet hydrographs of surface runoff, with average recurrence intervals of 10, 25, and 50 years, from typical urban highway by flood routing technique. Knowledge of the time distribution of rainfall in heavy storms constitutes a basis for the design of an urban storm sewer system. A unified time-coordinate system and the rainfall intensity-duration-frequency relationships are used to develop the generalized synthetic (design) hyetograph equations for all types of storms. The hyetograph equations are further normalized for identifying the dimensionless parameters that play predominant roles in the formulation of a design storm pattern. The method of least squares and an optimization technique are applied to the evaluation of the storm parameters through the use of the rainfall intensity-duration-frequency maps in the U.S. Weather Bureau Technical Paper No. 40. It is found that the parameter evaluation method can greatly be simplified by establishing relationships among the storm parameters. However, ana analysis of available actual hyetographs failed to establish any relationships between the storm skewness and the other storm parameters