What Are Impervious Surfaces and
Why are They Important?
Impervious surfaces are any hardpacked surface
(predominantly man-made) that impede the natural percolation of
water from the surface of the terrestrial environment through the
soil and substrate and into the groundwater. They prevent
groundwater recharge and more importantly, significantly increase
- Impervious surfaces significantly effect
the hydrology of a watershed and the storm water
management of urban areas.
- Impervious surfaces significantly increase
runoff and consequently the flow rate and volume of
rivers and stormdrains.
Impervious surfaces alter the biota, ecology,
hydrology, and overall environmental balance of a watershed.
What are considered impervious
- Buildings/structures, garages, sheds,
shelters, patios, decks
- Paved roads and major dirt/gravel roads
- Paved parking areas and major dirt/gravel
- Paved, dirt and gravel driveways
- Paved sidewalks and bikepaths
- Ponds, lakes, rivers, streams
- Swimming pools