An approach to stimulation of dual drainage

The paper presents the development in the field of urban drainage modelling known as dual drainage - an approach to rainfall runoff simulation in which the numerical model takes into account not only the flow through the sewer system but also the flow on the surface. The steps in model development are described and necessary data, assumptions used and operations to be performed using GIS are discussed. The numerical model simultaneously handles the full dynamic equations of flow through the sewer system and simplified equations of the surface flow. The surface excess water (due to the limited capacity of inlets or to the hydraulic head in the sewer system reaching the ground level) is routed to the neighbour subcatchment (not necessarily the one attached to the downstream network node), using surface retentions, if any. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved.