When it rains, as it has so frequently over the past year, water nourishes our landscape. However, rain that falls on impervious surfaces–like rooftops, roadways, and compacted soils–runs downhill, gathering oils, grit, and other contaminants and transporting them directly into our waterways. In large volumes, like after a storm, runoff can be very powerful and damage roadways, overwhelm sewer systems, and erode creeks and rivers, and cause flooding.
Healthy landscapes with abundant plantings, rain gardens, and bio-swales slow the flow of runoff and allow the rainwater time to be infiltrate into the soil – ultimately filtering the water and replenishing our ground water aquifers. Besides the benefits to our water resources, these “working gardens” are also beautiful additions to the landscape.
Scott Scarfone, ASLA, PLA, is a practice builder at Kimley-Horn. He is a registered landscape architect in nine states and a certified professional horticulturist and author. He writes and teaches on various aspects of landscape architecture, including managing stormwater through the designed landscape.
Here, Scott answers four questions about stormwater management. You can learn more by attending Scott’s lecture Stormwater Ecology: A New Paradigm in Landscape Design at Mt. Cuba Center on Saturday, February 17 at 11 A.M. Register here.
Q: When we think about stormwater management, the images that pop to mind are French drains and retention basins. You propose that there’s a more holistic approach. How does this approach improve landscapes and stormwater management?
S: The ultimate objective of managing stormwater is to keep the water as close to the source as possible and to allow the water to infiltrate into the soil as quickly as possible. The old philosophy of putting water into a pipe and sending it away has been scientifically found to not support best environmental practices – however there are times when that must be done. The key is balance. Striving to infiltrate as much water into the ground closest to its source is the objective ultimately keeping as much water within a watershed or sub-watershed as possible.
Q: What kinds of naturally occurring landscapes inspire your designs?
S: I am an avid outdoorsman. Nature is our best model and being observant to how natural systems work is important. When hiking in various environments, I try to pay attention to how the land accommodates water, whether it be the very top of a watershed, following drainage channels through various types of topography, studying how a stream channel flows, or observing how wetland systems function and the plants that are there. I take time to notice where the water comes from, how it rests, and where it goes. These all inform me as how to be a better steward of the environment when I strive to manage water.
Q: Why is it important for private homeowners – even those who manage a small property – to think about where stormwater goes?
S: Every drop that can be managed adds up because downstream it is all cumulative. Water runs downhill! And it gathers velocity, speed, and potentially destructive power fast. Look at the Grand Canyon–water did all that. So strive to slow water down and keep it as close to the source as possible.
Q: What are your favorite plants to incorporate into landscape designs for stormwater ecology?
S: There is a common misperception that creating storm water infiltration facilities (bioswales, rain gardens, etc.) is the same as creating wetlands and therefore wetland plants are required. This cannot be further from the truth. In most instances many of these facilities are designed to only hold water for a brief period of time – 24-48 hours before the water infiltrates into the soil. The majority of the time the facilities are actually dry. So, plants required for these facilities must be able to accommodate only periodic inundation – they must be able to handle being submerged for short periods of time then being in relatively xeric, or dry, conditions. I select my plants based on these conditions as well as a plant’s ability to be tough. I am not trying to be horticulturally fancy or sophisticated here–I want plants that establish quickly and easily, live on their own with little assistance, have a long life, and multiply on their own. Other plants will certainly work but these are the plants I have found are the most reliable and durable. Some of my go-to plants are:
- Rushes (Juncus spp.)
- Sedge (Carex spp.)
- Blue flag (Iris versicolor)
- Eupatorium spp.
- Golden Ragwort (Packera aurea)
- Marsh Marigold (Caltha palustris)
- Turtlehead (Chelone glabra)
- Foxglove Beardtongue (Penstemon digitalis)
- Switchgrass (Panicum virgatum)
- Inkberry (Ilex glabra)
- Winterberry (Ilex verticillata)
- Black chokeberry (Aronia melanocarpa)
- Arrowwood (Viburnum dentatum)
- Black haw (Viburnum prunifolium)
- Swamp rose (Rosa palustris)
- Redosier dogwood (Cornus sericea)
Learn more about creating functional landscapes that slow and absorb stormwater at Scott’s lecture, Stormwater Ecology: A New Paradigm in Landscape Design on Saturday, February 16 at 11 A.M. Tickets are $20 and include refreshments after the lecture.