Converting a NEXRAD Rainfall Map into a Flood Inundation Map by ...

Generate a suitable water surface model, represented by a cell-basedcontinuous surface of water elevations in grid/raster format.Subtract the land surface elevation from the water surface elevation toobtain a continuous surface of water depths.These steps require a much more elaborate sequence of geoprocessesalready available in GIS.For the Map2Map application, the terrain surface model is considered agiven input that does not need to be further processed inside the Map2Mapapplication. Contours are a common source of detailed digital elevation data forlocal and regional studies. For Rosillo creek, the digital elevation model (groundsurface model) was created from survey field studies that generated 2-footcontour line maps in the form of CAD files (.dwg, dgn, dxf). Spatial analystfunctionalities were used to convert the contour line map into a TIN (TriangulatedIrregular Network) and the TIN in turn is used to generate a DEM (rasterrepresentation on the surveyed terrain elevations).Even though national databases (like the USGS National ElevationDataset, NED) are available through the internet and supply digital elevationmodels for the United States, the resolution of these datasets is too coarse (up to10 m resolution based on 24K scale maps) for use in flood studies which require amore detailed representation of the terrain model (less than 10 m resolution) forthe river’s main channel and lateral overbank sections as well as the inclusion ofrelevant soft and hard break lines in addition to mass points for the representationof infrastructure (like buildings and roads footprints) over the floodplain. Figure163