The porous pavement of industrial and commercial areas is a form of sustainable urban drainage (SUD) system which has been developed to reduce runoff flow rates and volumes. This study reports on the modelling of the 20-month-old porous pavement at the Royal Bank of Scotland Headquarters in Edinburgh. A hydraulic model was developed using the Stormwater Modelling Program Erwin. Fifteen events were available for use in the calibration and verification procedure. The modelling results have shown an excellent prediction of the outflow behaviour of the site investigated.