Flow Balance at Junctions

The modified rational method is based on the standard rational method (see Rational Loading ), but is modified to improved the accuracy of the peak flow calculations when applied to typical urban catchments in the UK.

The modified rational (UK) formula used in StormCAD is:

Note: The modified rational method (UK) used in StormCAD to compute peak flows should not be confused with the hydrograph method of the same name used in other parts of the world to compute a trapezoidal runoff hydrograph.