Abstract

SWMM5 has been seamlessly integrated with a Geographic Information System (GIS) for simulation of inundation and analysis of consequences resulting from extreme flood events. The GIS-based environment processes digital elevation models, land use/cover data, stream networks and soils to create stream network, sub-basins, and cross-section shapefiles for river basins selected for analysis. The following readily-available public-domain datasets are utilized: 30-m topographical data from the United States Geological Survey (USGS), Natural Resources Conservation Service (NRCS) (STATSGO), and National Hydrography Dataset (NHD).

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 one dimensional 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 United States. Results from dam break simulations are presented in this chapter along with a discussion on the performance of SWMM5 for this application.

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