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 whic h the numerical model takes into account not only the flow through the sewe r system but also the flow on the surface. The steps in model development a re described and necessary data, assumptions used and operations to be perf ormed using GIS are discussed. The numerical model simultaneously handles t he full dynamic equations of flow through the sewer system and simplified e quations 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 th e ground level) is routed to the neighbour subcatchment (not necessarily th e one attached to the downstream network node), using surface retentions, i f any. (C) 1999 IAWQ Published by Elsevier Science Ltd. All rights reserved .