Impervious surfaces disrupt natural hydrology from occurring


Impervious surfaces are any surface that prevents water from being absorbed into the ground. These areas include pavements, rooftops, decks, and compacted soils. As natural areas are replaced with these hardened surfaces, water runoff volumes are increased. Soil, forests, and wetlands (pervious surfaces) act as sponges and soak up the rain. Through this natural system, the water is infiltrated into the soil and then released slowly into the streams, rivers, and bays through groundwater. With absorption occurring in the ground and being released into streams; flooding, erosion, and droughts are minimized, as well as nutrient and chemical pollution.

Heavy rain on large impervious areas, like parking lots and roadways, causes urban storm water runoff. (Photo courtesy of A. Dungan, IAN)
Heavy rain on large impervious areas, like parking lots and roadways, causes urban storm water runoff. (Photo courtesy of A. Dungan, IAN)
Incised stream banks, like this one that runs into Bush Creek in Monocacy National Battlefield, are caused by increased erosion when water runs off at high speed from nearby impervious surfaces. (Photo courtesy of J. Thomas, IAN).
Incised stream banks, like this one that runs into Bush Creek in Monocacy National Battlefield, are caused by increased erosion when water runs off at high speed from nearby impervious surfaces. (Photo courtesy of J. Thomas, IAN).