Modified rational method for sizing infiltration structures

A simple method is presented to size infiltration structures like infiltration basins and trenches to control storm water runoff. The runoff hydrograph is assumed to be trapezoidal in shape with a peak runoff rate calculated using the rational formula. Given the watershed time of concentration and the allowable runoff rate, the method determines the required size of the infiltration structure. A practical application section is included to demonstrate the use of the method.Key words: rational method, infiltration basin, infiltration trench, capture volume, storage time.