Runoff 101

algae in a trash trap


Runoff 101

Did you know that because of non-porous surfaces like pavement and rooftops, a typical city block generates more than 5 times more runoff than a woodland area of the same size?

Runoff is water from rain and outdoor water use that drains from roofs, driveways, sidewalks and other surfaces that doesn’t soak into the ground. Runoff can pick up pollutants that can adversely affect water quality. Common runoff pollutants include oil, paint, household cleaning supplies, sediment, pesticides, fertilizers, trash, yard waste and pet waste. 

Preventing runoff is key in preserving the integrity of our waterbodies. Without prevention or treatment, runoff can directly enter our waterbodies, taking pollutants along with it. Increased runoff, especially during storms can cause local flooding and stream bank erosion. To protect our waterbodies, Leon County and others use stormwater controls, known as best management practices (BMPs) to help prevent pollution by controlling it at the source. 


Water Runoff Graphic

Population growth and urban development significantly contribute to the amount of pollutants in runoff. Urban runoff can be either rainwater or water waste that flows from developed landscapes into storm drain systems and ditches that lead to our local water bodies. In urban and suburban areas, much of the land surface is covered by buildings and pavement, which does not allow rain to soak into the ground as shown in the above graphic. Instead, most developed areas rely on storm drains or ditches to carry large amounts of runoff from roofs and paved areas to nearby waterways. Altogether, these changes can cause negative impacts to water quality as well as habitat loss, increased risk of flooding, decreased biological diversity and increased erosion. In response to addressing issues with urban runoff due to increased development, Leon County recently added an action item in its updated 2019 Integrated Sustainability Action Plan that specifically calls out to identifying opportunities to pilot permeable pavement options in our community. 

Sources of Water Pollution


How Leon County Manages Runoff Pollution

Unfortunately, the varying intensities and types of runoff make it challenging to build a treatment system that can handle all runoff flows. As a county government that owns and maintains stormwater infrastructure, such as roadside ditches, underground stormwater pipes and stormwater ponds, Leon County is required to obtain a Municipal Separate Storm Sewer System (MS4) permit and comply with the National Pollutant Discharge Elimination System (NPDES)  program, which is regulated by the U.S. Environmental Protection Agency. In addition to complying with NPDES regulations for its municipal separate storm sewer system, Leon County has a runoff management program with six minimum control measures that work to reduce pollutants discharged into receiving waters, including:

  1. Public education and outreach on runoff pollution impacts
  2. Public involvement and participation
  3. Illegal discharge detection and elimination
  4. Construction site runoff control
  5. Post-construction runoff management
  6. Pollution prevention/good housekeeping for municipal operations


What You Can Do to Prevent Runoff Pollution

The everyday activities we do around our businesses, homes and yards can impact the quality of the runoff that drains into our waterways. Ideally only clean rain water should go into a storm drain; however, common examples that contribute to harmful runoff include over fertilizing our yards or fertilizing before a heavy rain, not picking up pet waste and excessive use of pesticides. To minimize runoff, you should keep pollutants safely away from the runoff's path. In addition, residents can help prevent runoff pollution by implementing Florida Friendly Landscaping Techniques and considering using rain collection methods such as barrels or cisterns. Staff at the Leon County Cooperative Extension office can assist you with making changes to your yard to help prevent runoff pollution. 



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