Stormwater and Watershed FAQs
What is a watershed?
A watershed is an area of land that drains to a single common waterway or outlet such as a stream, lake, estuary, wetland or ultimately, the ocean. Watersheds are also known as drainage basins or catchments. Watersheds come in many shapes and sizes. Your neighborhood could act as a small watershed if all of you have a pond that collects water from streams or gutters that drain rainwater from your streets, driveways and sidewalks.
Watersheds also cross county, state, and national boundaries. The watersheds for our local rivers in northeastern South Carolina cover many cities and counties in our own state and also extend into North Carolina.
How am I connected to a watershed?
We all live in a watershed, and what we do in one single location can affect people throughout the entire watershed. Think of it as everyone living downstream from someone else. Watersheds are areas of land that are interconnected by waterways. If something happens upstream—pollution is dumped into a river, for example—then others downstream throughout the watershed where that river flows are going to be affected. We must understand those connections and take care of our actions to ensure that we don’t harm others downstream, just as we would like others upstream from us to take the same care not to harm us.
What is stormwater?
Stormwater is water from rain or melting snow that “runs off” across the land. You have probably noticed water flowing down the side of the street or off of your yard on a rainy day. This runoff flows into curbs and gutters into the nearest storm drain. From there, it flows into a storm drain system, a vast network of underground pipes and tunnels that carry it to nearby streams and lakes. Contrary to popular belief, this stormwater does not go to the sewage treatment plant to be cleaned.
Is all stormwater polluted?
No. Stormwater runoff is a natural process that occurs in both undeveloped and urbanized landscapes. Stormwater runoff only becomes polluted if there are contaminants present that it can pick up as it washes over a landscape.
What happens to stormwater as it runs off?
When stormwater flows over the land – over rooftops, lawns, driveways and streets – it picks up nonpoint source pollution and debris. These pollutants include pesticides and fertilizers from yards and agricultural lands, oil and heavy metals deposited on pavement by our cars, sediment from eroding land or construction sites, debris and litter from various places, bacteria from pet waste, and others. Even nutrients from decomposing leaves and grass clippings can pollute water. In natural areas, a lot of these pollutants are cleaned out of the water as it soaks into the ground and is filtered by soil and vegetation. In developed areas, where much of the land surface is covered by buildings, pavement and other impervious surfaces, water cannot soak into the ground. Rather, it carries those pollutants with it into the storm drains and into our local waterways. It is important to recognize that stormwater is not necessarily polluted. Stormwater runoff is a natural process. It only becomes polluted if it picks up contaminants as it flows over the landscape.
What is nonpoint source pollution?
Nonpoint source pollution is that which cannot be traced to a single source. The pollution that contaminates stormwater runoff is considered nonpoint source pollution because the contaminants cannot be linked to one particular location, but rather, are picked up throughout the landscape. This is in contrast to “point source pollution” that is traceable to a specific site, such as a pipe that directs wastewater directly from a factory into a river. Nonpoint source pollution—whether nutrients from lawns, bacteria from pet waste, or sediment from erosion—is recognized as the leading source of water contamination in the country today.
What is impervious surface?
An impervious surface is simply a surface that water cannot pass through. For example, paved surfaces such as driveways, sidewalks, streets, and parking lots are impervious, as are rooftops of houses and buildings. Sometimes, even grassy areas like soccer fields or lawns can act as impervious surfaces when the soils beneath them are hardened and don’t allow water to pass through, or when rainfall is so heavy that the soils cannot absorb all the water, resulting in runoff as would occur on a paved surface. Have you ever noticed water puddling in the grass or running off your lawn during a big storm? Impervious surfaces contribute to stormwater pollution because they accumulate contaminants, such as heavy metals and oils, which are easily washed away by stormwater. As our cities become more developed, it is important to consider alternative paving and development practices that include more pervious surfaces to allow water to penetrate into the soils below. This helps filter out contaminants before they reach local waterways, and also facilitates the recharge of groundwater resources.
Why is stormwater a concern?
When pollution carried by stormwater makes its way into local waterways, it can have many negative impacts on humans and the environment. It contaminates drinking water supplies, makes local lakes, rivers and beaches unsafe for swimming or recreation, and contaminates fish and shellfish that people eat, which can lead to serious illness. It also has negative effects on the wildlife that also depend on our local waterways to survive.
What is a stormwater pond?
Stormwater ponds, also known as detention and retention ponds, are designed to capture stormwater runoff, and help reduce flooding and erosion by slowing the flow of stormwater. Gutters and storm drains direct stormwater off of paved surfaces and out of ditches and through a series of underground pipes which discharge into stormwater ponds. Stormwater ponds are not meant to hold water permanently, and therefore connect to receiving waterways. These ponds are designed to trap sediments and other large solids carried from the landscape via stormwater. In addition to sediments, stormwater ponds also collect a number of other pollutants such as bacteria, oils, heavy metals, and organic contaminants such as pesticides and herbicides, all of which can be very dangerous to those who come in contact with the water.
Stormwater ponds are a common feature in the South Carolina coastal landscape, and are often advertised as “amenities” to homebuyers who wish to live near a water feature. They are also common around commercial developments to collect stormwater from parking lots and roads. However, these ponds pose a risk to people and animals (such as pets and wildlife) that come into contact with the water. Additionally, because many ponds connect to receiving waterways, they present a contamination risk for streams and rivers. Many of these ponds are not fenced off and are easily accessible. While they may seem enticing to some on a hot day, it is very important not to swim in, play in, or eat fish from stormwater ponds. See our section on Local Stormwater Issues for more information about stormwater ponds.
Why should I care about water quality?
We all depend on clean water for our survival. Not only do we need clean water for drinking, but wildlife, including some animals that many of us depend on for food, also need clean water to drink and to live in. In addition, contact with contaminated waterways can make people sick. In an area like coastal South Carolina where citizens enjoy endless access to rivers, estuaries and beaches for fishing, swimming, and other recreation, good water quality is essential to our way of life. In addition, water quality is important for the tourism industry and for fishermen who make their living by harvesting species from the water. Thus, poor water quality can threaten not only our health but also our economic well-being and our businesses, affecting all aspects of our communities. We must also remember how connected we all are by waterways. Some people may think that stormwater only affects rivers and streams, or that a polluted stream only affects those in and around that stream. However, we must consider the stormwater ponds that connect to local rivers and streams, and just how many rivers and streams there are in coastal South Carolina that are all connected to each other. Therefore, pollution of one waterway can result in pollution of many.
I can't control the rain, so what can I do about stormwater?
While it's true that stormwater runoff is a natural process when it rains or snows, the pollution that is picked up by stormwater runoff throughout a watershed is not natural. As the landscape changes with continued growth and development, we can be more responsible in our daily lives to prevent those pollutants from getting into our waters. There are many actions you can take to protect water quality by helping to manage stormwater. We have dedicated an entire section of our website to help local citizens do just this. You can click here to find that more detailed information, but a few simple actions are listed below:
- Remember, storm drains lead to the rivers, which lead to the sea. Never put anything into a storm drain!
- Pet owners should pick up after their pets and dispose of pet waste in the garbage!
- Don't litter!
- Plant rain gardens, vegetated buffers, and maintain vegetation!
- Properly maintain your septic system!
- Maintain your car to prevent oil and fluid leaks!
- Wash your car at a car wash or over the grass to prevent the soap and wash water from flowing into nearby storm drains!
- Use fertilizers and pesticides sparingly and only as directed. Consider organic, non-toxic alternatives to these chemicals!
- Do not allow yard waste such as leaves and grass clippings to blow into gutters or onto paved surfaces to be washed into storm drains!
- Report erosion and sediment problems from construction sites!
- Minimize impervious surfaces!
- Get involved in local river and beach clean ups, and other projects that help protect water quality!
- Please visit our What Can I Do? section to learn more about actions you can take to help improve local water quality by reducing stormwater pollution!
What is a BMP, or Best Management Practice?
The term Best Management Practice refers to a recommended practice or technique that, through research and experience, has proven to reliably lead to a desired result. The term applies to stormwater management, agriculture, forestry, road construction, among many other fields of work. Stormwater BMPs refer to practices such as placing silt fences along construction sites to prevent erosion, trap sediments, and avoid sediment transfer into local waterways. Agricultural BMPs may include responsible fertilizer use to prevent unnecessary chemical contamination of soils, wildlife, and waterways. Homeowner Best Management Practices may refer to things you can do in your yard to help protect your local natural resources, such as using native vegetation in your landscaping practices to support local, native wildlife and reduce the need for additional watering and fertilization.