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DFIRM Depth Grid:1% Annual Chance Flood Depth Grid for Allegheny County
Federal Emergency Management Agency
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A 1% Annual Chance Flood Depth Grid represents the height of a 100 year flood surface elevation above ground or bottom of a stream channel measured in feet. The values are captured per cell of a defined area. The cell size for 1% Annual Chance Flood Depth Grids is variable. It is calculated by subtracting the height of the ground surface elevation from the surface height of the 1% annual chance flood. A Flood Depth Grid can assist a community in understanding, communicating, and relaying the variability and severity of flooding in a mapped floodplain.