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 runoff.

• 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 surfaces?

• Buildings/structures, garages, sheds, shelters, patios, decks
• Paved roads and major dirt/gravel roads
• Paved parking areas and major dirt/gravel parking areas
• Paved, dirt and gravel driveways
• Paved sidewalks and bikepaths
• Ponds, lakes, rivers, streams
• Swimming pools

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