As the planet continues to warm, addressing the effects of a changing climate is crucial — especially if we hope to restore water quality in the French Broad River. Traditional gray infrastructure directs large volumes of untreated stormwater from hard surfaces into nearby waterways. As the #1 source of pollution in this watershed, unmitigated stormwater runoff worsens flooding, erosion, and harms water quality. In contrast, green infrastructure offers nature-based solutions for managing stormwater that provide numerous benefits. By design, green infrastructure allows rainwater to soak into the ground where it falls, where it is filtered naturally and can “recharge” groundwater. Let’s take a closer look at the many approaches and benefits of going green to protect this essential natural resource.

Fill Your Cup

Groundwater is water beneath the Earth’s surface that collects in aquifers; in the mountains, that means water gathering in channels in the bedrock. If you own a drinking water well, this is where your household water comes from. As groundwater is removed from the aquifer, it must be replenished by rainwater that returns through a network of tiny underground channels in the soil. Recharging groundwater keeps wells full and supports freshwater springs and streams (and growing things) during dry periods.

Hard surfaces such as pavement and roofs prevent water from soaking into the ground, interrupting the groundwater process. Green infrastructure can promote groundwater even in urban environments by slowing down rain runoff and providing opportunities for it to absorb into the soil. Climate change is predicted to affect rainfall patterns causing storms of greater intensity and also more frequent droughts. By promoting groundwater recharge, green infrastructure promotes resilience to anticipated dry periods. So, fill your cup and share a toast to green infrastructure!

Did You Know?

A whopping 62% of Madison County residents rely on well water. In urban Buncombe and Henderson Counties, 38% and 37% of residents still depend on wells for water.

Shades of Green

In addition to replenishing groundwater, green infrastructure also promotes biodiversity, aesthetics, and in the case of a green roof, lowers energy costs. For residential settings, disconnecting downspouts and adding rain barrels, rain gardens, and permeable pavers are common approaches. Commercial applications are designed for larger volumes of runoff and include bioswales, green roofs, and permeable pavers. Let’s take a deep dive into the many shades of green infrastructure.

Beyond the Gutter

Many roof downspouts empty onto a hard surface such as a driveway or are directly piped to a storm drain. In both situations, rain becomes runoff that eventually reaches the nearest stream. Downspout disconnect is the simple, cost-effective practice of redirecting a gutter downspout away from a paved area or pipe system to an area where it can soak into the ground. The area where the downspout empties should be at least 5 feet away from the foundation of any building.

To disconnect your downspout, you will need a gutter downspout extension, a splash block, and possibly a tool like a hacksaw or metal snips to cut the downspout. Depending on the material and size you choose for the downspout extension and splash block, the typical cost to disconnect a downspout is $20-$50.

If you lack a lawn or planted area to direct water, a downspout planter or rain barrel may be a good alternative. Note that your planter should be large enough to hold the amount of water coming from your roof, otherwise you still need to plan for overflow events when rainfall exceeds the container’s capacity.

*Downspout with a planter attached. This example is from Philadelphia, PA.*

Harvest the Rain

Harvesting rainwater in a rain barrel prevents runoff and provides a free source of water for houseplants, lawns, and gardens. Rain barrels are typically connected to gutter downspouts, so keep in mind the potential pollutants your roof may introduce to the water. Do not drink collected water without filtration.

Rain barrels can be purchased at local garden stores and online; some local governments have cost-share programs, like this one in the Town of Hendersonville. Smaller rain barrels (less than 100 gallons) are typically used for residential sites, while larger barrels or tanks can be installed on commercial properties both above and below ground. A pump can be incorporated for use with irrigation systems. Rain barrel costs start at $75-$150 for 55-65 gallons of storage. You can also build your own for as little as $40.

To build a rain barrel, start with a food-grade plastic barrel that can be repurposed. A local source is M&M Steel Drum in Canton, N.C. Detailed instructions and a materials list can be found in the WaterRICH Rain Barrel Handout and instructional video.

Did You Know?

The average roof sheds about 1,000 gallons of water in a one-inch rain!

Plant the Rain

Rain gardens are bowl-shaped depressions that capture runoff and allow rainwater to soak into the ground. Filled with native plants, these gardens filter pollutants and create important habitats for pollinators and other wildlife. Rain gardens can be designed to fit a variety of sites, for both residential and commercial properties.

There are a few considerations before choosing a location. Plan for the rain garden to be at least 10 feet from a building and 25 feet from wellheads or septic systems. Start with a simple soil drainage test to ensure that the rain garden will drain in fewer than four days. This will ensure that mosquitoes are unable to breed in any standing water.

Constructing a rain garden consists of four major steps: 1) dig the basin; 2) build a berm; 3) construct an overflow path; then 4) add native plants and mulch. Find detailed instructions and plant lists in the WaterRICH Rain Garden Handout.

A Swale Approach

Bioswales, also known as bioretention swales, function like a long, narrow rain garden. Often used in commercial settings alongside roads or parking lots, bioswales can replace traditional curbs and stormwater drains. They add an aesthetically pleasing element that’s much cooler in summer compared to a typical parking lot.

For residential sites, a swale that follows the contour of the landscape is most commonly used to manage runoff. An on-contour bioswale runs parallel to the slope of the property and can be constructed on moderate slopes (up to 25% slope). Similar to a rain garden, on-contour swales can be planted with native and edible plant species. Multiple swales can be built on a single hillside and connected so that as one fills water, it overflows into the next swale.

For more information, see the WaterRICH Swale Handout.

The Space Between

Permeable pavers, unlike traditional asphalt or concrete, allow water to soak into the ground. Typically made of concrete or brick, permeable pavers are separated by spaces filled with pea gravel or sand that allow water to pass through, laid upon a base of washed stone. The versatility of permeable pavement allows for it to be used at many residential and commercial sites, although not every site will be suitable. Regular maintenance is required to prevent clogging. It is recommended to work with a design professional and experienced landscape contractor to ensure that permeable pavers are appropriate and installed correctly.
The average cost for permeable pavers depends on size and material, but ranges between $10-$30 per square foot for commercial sites and $8-$16 per square foot for a residential driveway. For more information visit the WaterRICH Guide (pg. 72).

*Image, courtesy of the Philadelphia Water Department shows the layers of permeable pavers to aid absorption.*

Raise the (Green) Roof

Green roofs consist of a waterproof membrane covered with a special lightweight soil mix and planted with drought-tolerant native plants. In addition to reducing roof runoff, green roofs provide pollinator habitat and have a cooling effect on the surrounding area, helping mitigate the urban heat island.

While green roofs are most commonly seen on commercial buildings, there is a growing trend of residential homes adopting this practice. It’s much easier to design buildings with green roofs in mind from the start rather than adding them later. On average, the cost of green roofs is $25-$30 per square foot.
Beyond environmental benefits, green roofs also offer economic savings.The vegetation insulates buildings reducing energy costs. Green roofs also extend the roof’s lifespan by over 40 years compared to conventional roofs. They typically achieve a return on investment in roughly six years. If you’re interested in implementing a green roof, check out Asheville-based company Living Roofs Inc.

*The Garage Apartments in Asheville, NC, image courtesy of Green Roofs for Healthy Cities*

Get Inspired with our local stormwater diaries

Resources

How Can You Help?

Ready to learn more? Head over to our Take Action page to learn more about simple ways you can reduce rain runoff at your residence or business.

TAKE ACtion

The Reduce Rain Runoff campaign was made possible by the generosity and support of The Community Foundation of Western North Carolina, The Duke Energy Foundation, The McClure Foundation and Land of Sky Regional Council.