If not properly managed, stormwater runoff can have detrimental and costly impacts to personal property. Particularly during severe weather, high-intensity or long-duration rainfall can lead to erosion and flooding in communities. Residents can plan for water management with site level assessment and applying best management practices in the home landscape.
From a water quality perspective, water that flows across the landscape into the street, storm drain, or ditch is being discharged into a nearby water body. The pollutants that are picked up along the way, such as sediment, excess fertilizers, pet waste, gasoline, and litter, can wreak havoc on downstream water quality. By managing stormwater on-site, we reduce the amount of water leaving our property and the associated pollutants. For additional information about stormwater runoff and pollution prevention actions, visit Clemson Extension’s Carolina Clear program at clemson.edu/carolinaclear.
Track the Rain
Rainfall amounts can be highly variable; install a rain gauge to understand conditions specific to the property. A rain gauge is a simple and inexpensive tool used to record precipitation. This information is helpful for irrigation planning and in determining how the property handles larger storm events. Install the rain gauge in an open area. After it rains, check and empty rain gauge. Another free, digital tool is the Community Collaborative Rain, Snow, and Hail Network (CoCoRaHS); this citizen science monitoring effort measures and maps precipitation. Learn more and find a station nearby at cocorahs.org.
Site Assessment and Maintenance
Treat the yard like a small watershed. During a rain event, make observations of the source and destination of stormwater runoff. The primary sources are impervious surface areas. These are areas where water is unable to infiltrate, such as a rooftop or driveway. The destination is areas where stormwater is traveling; the destination can be located on or near the property and may include a ditch, storm drain, backyard creek, stormwater pond, adjacent property, or low spot in the yard. When considering how to manage water, knowing the path stormwater travels is helpful in identifying management strategies.
Once the conveyance areas have been identified, assess these paths to ensure that they are clear. Check gutters at a minimum of two times annually and remove debris, such as leaves, pollen, and sticks, which may impede flow. Check ditches and storm drains, ideally before and after every rain event, and remove accumulated yard debris and litter. If vegetation is blocking the flow of water in a ditch, remove or prune as needed. Bag or compost leaves and yard debris to avoid this material ending up in storm drains and ditches. If significant issues or maintenance needs are noted in drains and ditches, such as structural damage or blockage, call the local government. A system located on private property and not part of the public maintenance system may require hiring a professional to help. If extreme weather is expected, such as a tropical storm or hurricane, take action to ensure conveyance is functioning as intended before the weather arrives.
Identify signs of erosion that indicate the need to dissipate the energy of water flow. Check for soil splashback along the foundation of the home. Note gullies or runnels beneath the roof drip line. Look for bare spots where stressed or dying plant material is present. All of these areas can be most susceptible to soil loss. Consider adding vegetation and or mulch to help stabilize. Mulch comes in many forms, including pine straw, pine bark, and shredded hardwood; regardless of the material selected, coverage of 2 to 3 inches thick will protect soil and reduce erosion. In areas of high stormwater runoff velocity, establish vegetation to slow stormwater runoff rather than rely on mulch that may be washed away.
Stormwater Management Practices
Establishing or protecting trees in the yard can help manage water. Trees are nature’s heavy lifters in managing stormwater all the way from the leaf canopy to the roots. A mature tree can handle up to hundreds of gallons of water during a single rain event.
Where possible, avoid soil compaction. Turfgrass becomes increasingly compacted when vehicles regularly drive or park in these areas. Once compacted, an area that functioned as a pervious surface can transform to an impervious surface, or hardpan and exhibit decreased ability to allow water to infiltrate, or soak, back into the ground. If additional parking is needed, consider installing a gravel pad.
Incorporating landscape beds into lawns can help manage water. Plants native to the southeast, including perennials, grasses, and shrubs, typically have deeper roots than traditional turfgrass. The deeper root system can assist by providing a path for water to travel into the ground. Additionally, native plants appropriately selected for site conditions often require little to no irrigation once established. Regardless of lawn area or native plant landscaping, avoid excessive watering before a rain event to help ensure soil is not saturated. If a low or wet spot exists on the property, identify plants suitable for these conditions. In South Carolina, many native plant options exist and can serve to beautify the area, stabilize soil, and manage water. The Carolina Yards plant database, found at clemson.edu/cy, can help with plant selection based on site conditions.
When installing a patio, walkway, or driveway, consider using a diverse array of pervious materials available, including interlocking pavers, gravel grid systems, permeable asphalt, or porous concrete. These surfaces have improved porosity over traditional paver systems, allowing water to soak back into the ground. Another pervious or semi-pervious option is creating walkways using stepping stones, gravel, or mulched paths.
Consider installing a rain garden to intercept the path of water between the source and destination. A rain garden is a planted depression that allows rainwater runoff from impervious urban areas, like roofs, driveways, sidewalks, and compacted lawn areas, the opportunity to be absorbed. The name rain garden is really a misnomer as these landscaped features are more often times dry then wet. If rain gardens are designed correctly, water collected in the rain garden should drain in under 72 hours. Rain gardens offer an aesthetically pleasing landscape feature that has low irrigation needs, creates backyard habitat, and manages stormwater runoff. Avoid locating a rain garden within a conveyance area, such as a ditch. For additional information about rain gardens, visit the Carolina Rain Garden Initiative at clemson.edu/raingarden.
A rainwater harvesting system provides temporary storage and later use of rainwater typically for irrigation purposes. During a rain event, rainwater is collected from a roof surface and directed towards a tank using gutters, downspout, sheet flow, and or rain chains. Rainwater harvesting tanks are available in a range of sizes from less than 100-gallon storage capacity, typically referred to as rain barrels, to hundreds, even thousands of gallons of storage capacity referred to as a cistern. Rain barrels are the most popular form of rainwater harvesting as the tanks are increasingly readily available for purchase, relatively inexpensive and manageable system setup and maintenance. With appropriate design considerations, rainwater harvesting systems can assist with water management and water conservation by reducing the demand on municipal water for irrigation. In order for a rainwater harvesting system to effectively manage stormwater, the captured water must be used to allow for volume holding capacity during the next rain event. For additional water management, direct the overflow of a rain barrel or cistern towards a rain garden.
Regardless of the site conditions, when managing water, a combination of practices will lend the best results. Consider the site holistically and identify areas where practices can be applied. In some cases, additional measures may be necessary. A sump pump, French drain, or swale will physically move the water in the yard. If needed, consult with a professional on the most appropriate options.