What is stormwater runoff?

Stormwater runoff is the rain that flows over the ground and into the city’s storm sewer system or directly into places like Blacks Run and other streams, rivers and lakes. In undeveloped areas such as grasslands and forests, the surface flow of water is slowed by vegetation; some of the water then seeps into the ground. In urban areas, buildings, roads, parking lots, and other impervious surfaces decrease the abundance to soil and vegetation, resulting in increased amounts and faster flow of storm water runoff. A storm water drainage system is necessary to channel this runoff out of urban areas and reduce the occurrence of flooding.

What is the problem with stormwater runoff?

Each time it rains, the resulting runoff of stormwater picks up debris, litter, pesticides, chemicals, motor oil and sediment as it flows across rooftops and lawns, streets, and parking lots. A common misconception is that water running off streets and into storm drains goes to a wastewater treatment plant. It does not. In fact, stormwater receives no treatment. 

Excessive contamination of runoff can cause sedimentation and erosion of our streams, water quality degradation, and unhealthy water conditions for humans and wildlife.

To learn more about runoff, visit the Cleanstream.org website. 

What kind of drainage system does the city have?

The city's storm water system is called a Municipal Separate Storm Sewer System (MS4). This means that the city's storm sewer system is completely separate from the sanitary sewer system. The city's sanitary sewage flows to a wastewater treatment plant, while stormwater drains untreated directly into local surface waters. A variety of structures and landforms, both natural and artificial, are considered to be part of the MS4. These include inlets, pipes, grass and concrete channels, earth berms, ditches, box culverts, detention basins, and even sinkholes. All of these are part of the terrain which storm water travels on its way to streams, lakes, and rivers. (Graphic courtesy of City of Charlottesville.)

For more information on Municipal Separate Storm Sewer Systems  (MS4)

Why is storm water management important?

Urbanization can increase the quantity and decrease the quality of runoff. Historically, cities have focused their storm water management programs on reducing the effects of flooding.  In recent years, in response to Federal and State initiatives, the focus has begun to also include the issue of water quality degradation. Today, storm water management programs address issues from preventing pollution to controlling erosion. Water quality is often addressed through implementing Best Management Practices, public education and involvement, and reduction of illicit pollution discharges.