The Stormwater Runoff Process Stormwater Runoff Stormwater runoff can become an issue when As surface water runoff is channelized to & it is not properly managed. Management comes stormdrains, pollutants carried in the runoff in the form of controlling, containing, cleaning make their way down the pipes and are directed Associated and slowing runoff, as to mimic as closely as towards waterbodies. Negative Impacts possible the natural drainage of an area. Mitigation Without properly managed stormwater, impacts Due to the negative affects associated with occur to local streams, creeks, rivers and lakes. stormwater runoff, it is important to mange runoff in a proper manner. This can be accom- The image below depicts conventional methods plished through the use of stormwater controls. of controlling stomwater through the use of in- For more inormation on the use of stormwater ground stormwater infrastructure (i.e. gutters, controls, please refer to the Lincoln County stormdrains and piping). “Stormwater Contols “ Pamphlet. 1. A storm cloud results in rainfall. The rainfall drops onto two types of surfaces: “Impervious” and “Pervious”. “Impervious surfaces” such as roofs, driveways and roads don’t allow the rain to soak into the ground, while “pervious surfaces” do. The “impervious surface” results in an overland flow of stormwater runoff. 3. The stormwater runoff carries the pollutants often times to storm drains that eventually lead to nearby creeks, rivers and lakes. Thus the stormwater acts Lincoln County Planning and as a mechanism by which Inspections Department polluants can reach our in conjunction with waterways, and often Lincoln County Soil and Water times our watersupplies. Conservation District This causes Non-Point 302 N. Academy St., Suite A Source Water Pollution. Lincolnton, NC 28092 Phone #: 704-736-8440 2. The Stormwater flowing off of and over the Fax #: 704-732-9010 “impervious surfaces” picks up pollutants. The pollutants include heavy metals, fertilizers, fecal matter and sediment. Stormwater Facts Natural Ground Cover 10%-20% Impervious Surface Coverage Stormwater is the act of rainwater runoff. Run- off can occur on any surface during and after a 40% Evapotranspiration 38% Evapotranspiration rain event, although it has been identified as a major issue when the runoff occurs due to an “impervious surface”. Impervious surface is a term that defines any 10% 20% type of surface that does not allow for rainwater Runoff Runoff to soak or infiltrate into the ground. Types of impervious surface can range from hard packed soils to concrete and rooftops. Negative affects associated with impervious 25% Shallow 25% Deep 21% Shallow 21% Deep surface runoff include: Infiltration Infiltration Infiltration Infiltration • Increased stormwater velocities • Higher water volumes 35%-50% Impervious 75%-100% Impervious • Transportation of pollutants Surface Coverage Surface Coverage • Erosion and Sedimentation of streams • Lack of Ground Infiltration 30% Evapotranspiration • Increased Stormwater Temperatures A Picture Is Worth a 35% Evapotranspiration Thousand Words The diagrams on the facing pages depict differ- 30% 55% ent percentages of impervious surface coverage Runoff Runoff and how this affects stormwater runoff. As you move towards greater impervious surface cov- erage you increase runoff and decrease infiltra- tion. 20% Shallow 10% Shallow 15% Deep 5% Deep Infiltration Infiltration The data contained within these images was provided by Infiltration Infiltration the “Federal Interagency Stream Restoration Working Group”.