GIS
The total impervious area (TIA), commonly referred to as impervious cover (IC) in calculations, can be expressed as a fraction (from zero to one) or a percentage. There are many methods for estimating TIA, including the use of the National Land Cover Data Set (NLCD) with a Geographic information system (GIS), land-use categories with categorical TIA estimates, a generalized percent developed area, and relations between population density and TIA.