SWMM5 has been integrated with a Geographic Information System (GIS) for analysis of inundation consequences resulting from extreme flood events. The GIS-based environment processes readily-available digital elevation models (30-m from the USGS), land use/cover data (30-m NLCD), stream networks from the National Hydrography Dataset (NHD) and soils data from the NRCS (STATSGO) to create stream network, sub-basins, and cross-section shapefiles for river basins selected for analysis. Rainfall predictions are made by a numerical weather model and ingested in gridded format into the simulation environment. Runoff hydrographs are estimated using Green-Ampt infiltration excess runoff prediction and a 1D diffusive wave overland flow routing approach. The hydrographs and the channel morphology are used to generate a SWMM5 compatible input file. The input file is seamlessly passed to SWMM5 using a Dynamic Link Library (DLL) to model the flood wave propagation using the dynamic wave model. The resulting hydraulic grade lines are subsequently passed back into the GIS framework for transformation into inundation maps to be used in damage assessment. This model has been applied to modeling of dam breaks, hurricanes, and extreme flooding events in the U.S. Results of these simulations are presented in the paper along with a discussion on the performance of SWMM5 for these applications.