Stormwater 101

What is stormwater?

Impervious surfaces, such as rooftops, driveways, sidewalks, and roads prevent rainwater from soaking into the ground. When it rains on these hard surfaces rainwater becomes stormwater runoff, which picks up pollutants that have been left on the ground--such as pet waste, excess fertilizers, litter, oil, and gasoline--and sweeps them downstream. Some of this runoff may flow directly across the land into a nearby waterway, while some may enter a ditch or storm drain and follow an underground path that eventually discharges to a waterway. Either way, stormwater is untreated, so all of the pollution we leave on land can ultimately end up in the water downstream. As a result, stormwater runoff is considered the greatest threat to water quality in the United States. In South Carolina more than 1,150 of our waterways have been classified as "impaired," which means they are too polluted or degraded to meet accepted water quality standards. Because we all contribute to stormwater pollution, it is up to all of us to take action to protect water quality.

What causes stormwater pollution?

Stormwater becomes polluted when runoff flows over pollutants that have been left on the ground. Common sources of pollution include bacteria from pet waste, sediment from construction sites and areas of bare soil, litter, pesticides, nutrients from excess fertilizers, improperly stored or disposed of household chemicals, oil from leaky automobiles, detergents from car washing, paint residues, and more. These items only pollute stormwater if they are left on the ground and are swept up the next time it rains. Properly disposing of these items, and avoiding lawn treatments and fertilizer applications right before a rainfall, are good ways to prevent stormwater pollution.

What are stormwater BMPs?

Stormwater Best Management Practices (BMPs) are landscape-level features that are installed to help water soak into the ground, slow runoff, and prevent pollution from heading downstream. While some BMPs are more complex to install and require the assistance of an engineer, there are others you can easily put on your own property to reduce stormwater runoff and pollution. Consider implementing some the BMPs and actions listed below!

There are many additional actions you can take to protect water quality. Consider adding one or two at a time to your daily routine; even small actions taken by individuals can add up to a large impact across your community. Not sure where to begin? Here are just a few easy examples:

  • Keep dumpster and garbage can lids closed.
  • Keep fats, oil, and grease out of your sink—store them in an old can instead and dispose of in the trash.
  • Wash your car at a commercial car wash where the wash-water is treated, or if washing at home, park your car on the grass so wash-water will soak into the ground.
  • Dispose of prescription drugs during a collection event instead of flushing or throwing in the trash.
  • Reduce fertilizer use.
  • Do not flush wipes.
  • Plant a pollinator garden.

And don’t forget, only rain down the drain! Water that flows into storm drains empties directly into local waterways untreated - avoid dumping anything down the drain that does not belong there.

Stormwater in action