MODELING OF INUNDATION MANAGEMENT DURING EXTREME STORMS

The ''major/minor'' approach is being adopted as standard urban draina ge design practice in many countries. Further to the normal primary dr ainage design for minor storms, this approach now requires management of inundation during extreme storms of return period fifty years or mo re. Surface flows then have to be investigated over an urban topograph y which is highly irregular and initially dry, and the transition from these conditions to major storm flows is difficult to analyse. The pr oposed modelling solution is based on the full integral hydraulic equa tions incorporating possible shock fronts. Wetting and drying simulati on, careful channel resolution at low flows, and implicit solution met hods with flat response properties are also important Key points are i llustrated by case studies.