Surface Runoff Determination from Rainfall without Using Coefficients

In hydraulic engineering practice, the relation between rainfall and runoff has generally been represented as a ratio or coefficient. It has been recognized that the form of this relationship should be “rainfall minus losses equals runoff.” Heretofore the inadequacy of hydrologic data has discouraged attempts to evaluate losses as they occur during a storm period. In this paper the writers call attention to the recent improvement in hydrologic data with respect to precipitation and stream flow, and to the information with respect to infiltration that has developed from the research program of the U. S. Department of Agriculture; and they outline a method of applying this information to the evaluation of surface runoff from precipitation data without the use of a coefficient. The method is presented as being generally applicable to all drainage basins, and is described in detail as it would be used in urban storm drainage.