Impervious area includes pavement and building areas such as driveways, parking areas, rooftops, patios, garages and out-structures. The amount of impervious area on a property directly correlates to its contribution of runoff volume and pollutant loading to the city’s storm water management system.
Impervious surface means those disturbed or hard surfaced areas that either prevent or retard the natural entry of water into the soil. Rooftops, buildings, streets, parking lots, sidewalks, asphalt, concrete, other paving, driveways, gravel, patios, artificial turf and storage areas are all examples of impervious surfaces.
These improvements effect natural infiltration, creates more runoff, increases the rate of runoff and alters runoff patterns of stormwater that drains from an area.