Synonyms: Hard Surfaces, Impenetrable, Impermeable, Paved Surfaces

Impervious surfaces are surfaces that allow little or no stormwater infiltration into the ground.  Other than exposed natural rock croppings, impervious surfaces are completely human-created and are an unnatural part of most ecosystems.  Impervious surfaces are the main contributor to excess stormwater runoff that would otherwise have been retained on site in natural forests or meadows.  Everything that falls on an impervious surface (pollution, trash, animal waste, chemicals, oils, sediment, etc.) washes off of those surfaces during rain events, often on a direct path to local streams or water bodies.

Examples of impervious surfaces: Streets, roofs, parking lots, most patios, walkways, or anything else that does not allow water to flow through and into the ground (asphalt, concrete, plastics).

In extreme examples of soil compaction, some turf areas or other areas where water has direct soil access can become impervious and also problematic for water quality and homeowners alike.


Credit: U.S. Environmental Protection Agency