WMS:Define Flood Inundation Polygon

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HY8 Modeling Wizard showing the Define Flood Inundation Polygon step.

The Define Flood Inundation Polygon step is used to define a flood inundation polygon if a drainage coverage with a polygon defining the inundation area does not already exist. It's necessary to define a flood inundation polygon for any culvert crossings with no outlets (and no basin polygons) assigned but with a hydrograph. The purpose of this inundation polygon is to compute a storage capacity curve and to define a flood barrier when running the floodplain delineation.


Selecting the Define flood inundation polygon button allows creating arcs that represent the flood inundation boundary. Normally, use the roadway as one of the arcs and build arcs for the rest of the inundation boundary. If selecting Delete flood inundation polygon then clicking on an arc or inside that polygon, the polygon is deleted and all the generic arcs (not the roadway centerline arcs) making up that polygon are deleted from memory. Selecting Build polygons builds all the polygons in the HY-8 coverage and assigns them as flood inundation polygons without prompting to use all the arcs to build polygons.