What Is Stormwater?
Stormwater is water from rain, snow, sleet or hail that flows across the ground and pavement, or when snow and ice melt. The water seeps into the ground or drains into the storm drain system. These are the drains you see on the sides of streets. The storm drain system consists of storm drain pipe, catch basins and detention/retention basins. Collectively, the draining water is called stormwater runoff and is a concern in all areas, including residential, commercial, industrial, and roadway areas. Stormwater that does not seep into the ground drains into the storm drain system, which is a system of underground pipes and may travel for many miles before entering bodies of water. In a natural setting only a small percentage becomes surface runoff, but as development occurs this percentage increases. This runoff usually flows into the nearest stream, creek, river, lake, or wetland.
What Is Stormwater Management?
Stormwater management involves the control of that surface runoff. The volume and rate of runoff both substantially increase as land development occurs. Construction of impervious surfaces, such as roofs, parking lots, and roadways, and the installation of storm sewer pipes which efficiently collect and discharge runoff, prevent the infiltration of rainfall into the soil. Management of stormwater runoff is necessary to compensate for possible impacts of impervious surfaces such as decreased groundwater recharge, increased frequency of flooding, stream channel instability, concentration of flow on adjacent properties, and damage to transportation and utility infrastructure. It is also now known that non-point source pollution washed off from those impervious surfaces is a leading cause of impairment to bodies of water.