This workbook applies the Rational Method to estimate stormwater runoff and peak flows from small urban catchments (typically less than 90 acres)  

1. To calculate the area-weighted runoff coefficient, C for a subcatchment

2.  To calculate the time of concentration, and then compare with the regional time of concentration limit used for the Denver region.  The smaller value is recommended as the rainfall duration for use with the Rational Method.

3.  To calculate the design rainfall intensity and resulting peak flow rate.   

4.  To calculate the combined peak flow rate at design points for sizing inlets and storm drain systems.  Considers the cumulative drainage area, area-weighted runoff coefficient, and total travel time  through the storm drain system to each design point.        

Download Current Version Here: UD Rational (v.3.00)