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

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

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Figure 4.4 Radar2GDB Model Component4.1.2 The Time Series Transfer Script ToolThe Time Series Transfer script tool transfers time series associated withthe <strong>NEXRAD</strong> cells/pixels onto the Watersheds (Subbasins) of interest as definedin the hydrologic model being used (the HEC-HMS setup). By doing this, theinput rainfall hyetographs are associated with each watershed in the basin asrequired <strong>by</strong> the hydrologic model. The tool performs the transfer operation <strong>by</strong>analyzing the extent to which each <strong>NEXRAD</strong> cell covers a given Watershed, andthen based on that areal extent; relative weights for each intersecting subbasinarea are assigned to compute a weighted average of rainfall for that subbasin ateach time step (areally weighted precipitation values). Figure 4.5 shows the arealdisaggregation of subbasin RC6 RU based on covering <strong>NEXRAD</strong> cells (568154,569154, 568153, and 569153) to calculate the precipitation values for thesubbasin.75

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