Comparison of two modelling approaches for a pilot catchment flood study in Qatar

A country-wide flood study involving two-dimensional (2D) hydraulic modelling is being undertaken to estimate and map flood risk across the State of Qatar. An extensive data collection and literature review activity were initially undertaken to gather rainfall, topographical and environmental records from Qatar and neighbouring countries. This was undertaken to allow appropriate selection of flood modelling approaches and flood model calibration parameters. During this early phase of the study, it was found that there is a lack of available good quality flood calibration data and that detailed 2D hydraulic modelling had not been widely undertaken in the Gulf region. Due to the lack of model calibration data compounded by the relatively flat nature of the study area, two alternate flood modelling approaches were tested on a pilot catchment and a preferred modelling approach was identified for application across the entire State of Qatar. The first method involved the application of a coupled hydrologic/hydraulic modelling approach whilst the second method was based on a 2D "rain on grid" hydraulic modelling approach. An assessment of the results from both the methods demonstrated that the 2D 'rain on grid' hydraulic modelling approach was the most appropriate methodology for implementation in the Qatar national flood study. This was primarily because the rainon- grid approach provided a more realistic simulation of the rainfall runoff process, higher resolution model outputs, and greater efficiency and potential for automation in model setup phase.