The amount of stormwater runoff originating from individual properties is significantly increased by the amount of impervious area on each property. The impervious area consists of houses, buildings and other structures; driveways, patios, parking lots, and other manmade surfaces that do not allow precipitation to infiltrate into the ground. Pervious surfaces include grass, pasture, cropland and most undeveloped land. Impervious surfaces decrease the amount of infiltration into the ground and increase the amount of runoff that will enter the county’s stormwater system.
Over the long term, the amount of impervious area on a property is related to the amount of stormwater that flows off the property and into the nearby streams and creeks. Impervious surfaces also increase the amount of pollution that is carried by stormwater runoff that is carried into the county’s drainage system and surface waters.