operational area

The operational area for the Urban Flooding Demonstration Program (UFDP) was defined using a geographic information system (GIS) to spatially assess digital information consisting of elevation, land cover, classification of ecoregions, precipitation, temperature and potential evapotranspiration. Three maps reflecting different ways of identifying arid and semi-arid regions within the lower 48 states resulted from this analysis. They show average annual precipitation, vegetation and Bailey’s (1996) ecoregion domains - and are stratified on 20-inch, shrub abundance and humidity classes respectively.

Left: A composite map identifies the UFDP arid and semi-arid domains for the lower 48 states, Alaska and Hawaii. In the lower 48 states the area includes all three map definitions and is 2,244,000 km2 (867,000 mi2).

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Bailey, R.G. 1996. Ecosystem Geography. New York, Springer-Verlag. 216 p.