City scale urban flood modelling and mapping

Inadequate drainage capacity often fails to offer the desired response in urban flooding. This aim of this study was to develop a flood hazard map through a field survey and numerical modelling. The field survey comprises cross-sectional data for tertiary drains; these are then transferred for setting up the numerical model. To feature flooding conditions, both hydrological and hydraulic model studies were carried out using the Hydrologic Engineering Center-hydrologic modelling system (HEC-HMS) developed by the US Army Corps of Engineers, and the personal computer storm water management model (PCSWMM). The use of HEC-HMS generated the runoff; the PCSWMM model simulation was carried out for 760 conduits and 693 junctions in the city that was studied. Three major outlets were considered for model calibration for 2014, the model simulated runoff showed a reasonable match with field records - that is, R-2=0.782, R-2=0.719 and R-2=0.768 for the reaches Chaktai Khal, Rajakhali Khal and Mahesh Khal, respectively. Thus, the validated model was used for flood hazard mapping. It is envisaged that development authority and city planners would benefit from this coupled model.