Investigation of the importance of different factors of flood inundation modeling applied in urbanized area with variance-based global sensitivity analysis

Flood modeling provides useful information to support flood risk assessment and management and reduce flood impacts in urbanized area. The accuracy of urban flood simulation results is highly dependent on the quality of input data for which the appropriate values are generally difficult to determine for complex urbanized environment and from which various uncertainties are induced into the modeling procedure. In this study, variance-based global sensitivity analysis is applied for the hydrodynamic modeling of urban flood to explore the relative importance of the factors of interest as model inputs and their contributions to the final results of the numerical model for different outputs. The factors include the spatial resolution, the forcing condition and the characteristics of the underlying urbanized surface. The global sensitivity analysis results are examined in both spatially lumped and distributed perspective. Findings indicate that importance of the input factors varies with regard to different model output and the influence of the spatial resolution is more tightly related to the flood flow movements whereas that of the rainfall inputs is more relevant to the flood water volume. Spatial variability in the influence of the input factors is revealed to be hidden by the spatially lumped results and the importance of the factors describing the underlying urban surface is found to be largely dependent on the location of the analyzed model output associated with the land-use type. Improved understanding of sensitivity of hydrodynamic modeling of urban floods may help the modelers to decide which input factors to prioritize on according to which model outputs are assessed and where they are assessed.