Integrated modeling of 2D urban surface and 1D sewer hydrodynamic processes and flood risk assessment of people and vehicles

In order to accurately simulate the whole urban flooding processes and assess the flood risks to people and vehicles in floodwaters, a 2D-surface and a 1D-sewer integrated hydrodynamic model was proposed in this study, with the module of flood risk assessment of people and vehicles being included. The proposed model was firstly validated by a dual drainage laboratory experiment on the flood inundation process over a typical urban street, and the relative importance of model parameters and model uncertainties were evaluated using the GSA-GLUE method. Then the model was applied to simulate an actual urban flooding process that occurred in Glasgow, UK, with the influence of the sewer drainage system on flood inundation processes and hazard degree distributions of people and vehicles being comprehensively discussed. The following conclusions are drawn from this study: (i) The proposed model has a high degree of accuracy with the NSE values of key hydraulic variables greater than 0.8 and the GSA indicates that Manning roughness coefficients for surface and sewer flows, inlet weir and orifice discharge coefficients, are the most relevant parameters to influence the simulated results; (ii) vehicles are vulnerable to larger water depths while human stability is significantly influenced by higher flow velocities, with the overall flood risk of people being less than that of vehicles; and (iii) about 88.7% of the total inflow volume was drained to the sewer network, and the sewer drainage system greatly reduced the flood risks to people and vehicles except the local areas with large inundation water depths, where the sewer drainage increased the local flow velocity leading to higher flood risks especially for people.