A two-dimensional raster gridded urban hydrological model has been developed to simulate the hydrologic response to urban land surfaces with consideration of the hydraulic characteristics of urban areas, and to produce mappings of urban inundation associated with rainstorms. The model is forced using radar-observed QPEs, in conjunction with parameter sets of land use and land cover (LULC) derived from satellite multispectral images and high spatial resolution GIS datasets relating to urban hydrology and land surface hydrodynamic properties. Urban drainage flow capacity is derived from a GIS road-network dataset using a generalization method. Submodels deduce runoffs of both the impervious and the pervious. Methodologically, the D8 method (eight slope directions) is used to derive the channel paths for gravity-driven nondispersive streamflow, which its hydrodynamics can be described by the hydraulic model based on simplified 1D − 2D St. Venant equation. A case study was undertaken to reproduce the urban flash flooding that occurred in Beijing following thunderstorms on 21 July 2012. The model results were verified qualitatively using media reports of the flooding. Through manipulation of model parameters, the test on the sensitivity of flash flood intensity to urban LULC variability and drainage network settings revealed the following: 1) flood intensity is enhanced slightly if the current urban LULC is substituted with a pure impervious, 2) increasing the pervious surface area (PSA) attenuates flood intensity considerably, and 3) flash flood intensity will increase by 30–60% in the absence of an underground drainage system.