Sustainable Stormwater Solutions Through Landscape Design | Jay Archer for Turf Magazine Jay Archer recently contributed to Turf Magazine’s June edition — The Water Issue — with an article focused around managing stormwater. We are so thrilled that stormwater management and landscape drainage is becoming an integral part of all parts of the landscape industry. Below is Jay’s article in full, which details Green Jay Landscape Design’s approach to landscape drainage, improving the soil’s water-holding capacity, and a deep dive into three case studies that approach stormwater management with unique techniques. We hope you enjoy! Sustainable Stormwater Solutions in Home Landscapes by Jay Archer Stormwater is a natural byproduct of life-sustaining rainfall. But it can be greatly problematic when it hits a landscape whose soil and topography have been altered in a way that natural filtering, absorption, and water flow no longer exist. At Green Jay Landscape Design, we are dedicated to ecological practices and strive to find solutions to stormwater problems that work with the processes of nature, rather than combatting them. A rain garden designed for full sun in the Wainwright House front lawn. Rye, NY. As ecological landscape designers, we seek to enhance our clients’ quality of life AND to improve our local environment. Through thoughtful landscape design and construction, we draw our clients out into the natural world, where beneficial biology, fresh air, and outdoor activity boost mental and physiological health. Our predominantly native landscapes create vital habitat for pollinators and birds, while also sequestering carbon into the soil to combat climate change. Simultaneously, our landscapes actively work to combat erosion, manage stormwater, and restore biodiversity. When we encounter stormwater problems in the landscape, it’s usually a combination of factors that are contributing causes. Three primary considerations are: Existing infrastructure, particularly impervious space such as patios, walks, walls, driveways, etc; Surrounding watershed, including uphill sheet flow; and Soil surface, which is of critical concern. It may seem counterintuitive, but it’s key to address flow paths at the uppermost height of land. It presents an opportunity to infiltrate, absorb, and redirect stormwater before it gains velocity and volume—and options are often limited at the base or bottom of a slope. Watershed topography surrounding patios and driveways determines the direction of pitch and flow when designing the hardscape. This can be achieved by planting, bioswales, perimeter drains, or a combination of techniques. With infiltration and absorption of water onsite as the goal, planting native trees, shrubs, grasses, and perennials can go a long way to alleviating flooding and erosion problems. This rain garden is fed by piping stormwater from the gutters of the house, across the lawn to the garden. Case Study #1: Rain Garden Alleviates Flooding When we think of natural, ecological solutions, we start with the soil. In the case study here, we found the natural disposition of the developed suburban landscape presented frequent (or at least seasonal) issues with flooding in impounded or depressed areas. This is not uncommon. Looking over the fence and around the corner from the client site, we found the adjacent homes lacked dry wells connected to gutter/leader systems and had a serious absence of vegetation, particularly the type of plants that evapotransporate large volumes of water. Piping leads to the rain garden while also allowing some to passively irrigate the lawn. Our client also discharged stormwater onto the lawn within 10’ from the house by gutter/leaders. Compounding the problem, the soil was extremely compact clay. Our suspicion was that building material/fill constituted the sub grade material. (pH tests can sometimes indicate alkaline substrate due to natural causes or from construction.) Finally, the water table was astronomically high as a result of extraordinary rainfall over the last four to five seasons. The solution involved designing a comprehensive landscape plan for remediation based on site analysis, soil core, and pH tests. The first step of the design involved installing perforated PVC “drains,” with gravel and filter fabric, directing the flow to the corner of the property—which would feature a rain garden. Turf is removed and the rain garden soil is amended to a sandy fast-draining mix. Next, we aerated and amended the soil with gypsum, lime, compost, greensand, and a variety of bio-stimulants, including mycorrhizal inoculants. We seeded with seven seed mixes, dominant with turf type tall fescue. Applying a high-quality starter fertilizer and PennMulch seed accelerator were critical to the success of the new lawn. The second step was excavating to a depth of three and a half feet for the rain garden. The soil in that area was amended with sand and compost mix and blended with the existing soil. Placing plants for this mostly-native rain garden design in Hartdale, NY. Finally, the planting design featured predominately facultative native plants—those that can live under more than one specific environmental condition. Trees, shrubs, sedges, perennials, grasses, and ground covers were chosen for ecosystem function and landscape effect. A focal element is the Dawn Redwood tree. While not native, this tree will drink a lot of water, be lower maintenance than a weeping willow, and grow three to six feet a year! Case Study #2: Post-Hurricane Renovation This next project involved a landscape plan which featured bioengineering techniques requiring approval by an engineer, as well as local and state regulatory agencies. In projects like this, in addition to our ecological design plan of drawings and text (we use powerfully descriptive, sexy, pro-environmental restoration language), we find it helpful and expedient to also submit a ‘Letter of Intent’ with an Erosion and Sediment Control plan. This involves simple site detailing of the landscape installation, the site protection, and the erosion control devices to be used. Terraced hillside landscape for stormwater management and erosion control. At this client site, a steep slope had failed, leaving several layers of soil disposition exposed. We determined that, although located in a residential backyard, the slope was used as a dump site for mostly organic material (leaves, brush) over the course of many years. This resulted in an unstable condition and a lack of root development by the existing vegetation. It didn’t help that the few existing trees were buried above the root flare, smothering them! Before photo: storm damage from hurricane Ida caused this slope to collapse. We removed much of the remaining organic material which, now basically composted, was repurposed onsite but outside the area of disturbance. Starting mid-slope, we rebuilt the existing Unilock retaining wall with a proper footing. Stone steps and wood chip path make this steep slope and the river below it navigable. We also installed a locally-sourced fieldstone path on structural fill, leading to a cedar-mulched path which enables access to the river below. We retained the path with log water bars, which we found onsite. Where possible and practical—and if they meet our strict standards and specifications—we try to source all natural, Earth product materials (soils, compost, stone, mulch etc.) from the local area. Piping from gutters leads to underground flow wells. The five existing leaders were directed to NDS Flow Well kits to infiltrate the soil below the new landscape elevation. Working from just above the remaining trees on the slope, we installed Filtrexx Silt Socks and an uneven, interrupted terrace of rip rap boulders. We then began to backfill, regrade, and contour with engineered soil. The boulders protruded just above ground for stabilization and landscape effect. Stone terraces, filtrexx socks and jutte netting work together to stabilize the slope. The plant selection for this project consisted mostly of native three-gallon shrubs and two-gallon perennials. On the steepest parts of the slope, we planted directly into jute netting. Jute secures new plants to the slope as their root mass develops, and eventually biodegrades once the plants are established. For plant installation, we also use a combination of organic natural source products and fertilizers. They include Organic Mechanics BioChar Mix, Ocean Organics GBS, Plant Magic, Quantum Growth, and Yucca. Irrigation is installed before mulching for the cleanest order of operations. After planting and watering, we then soil drench with microbial and mycorrhizal inoculant, which helps reduce transplant stress, especially during high heat weather. And we add deer repellant! Case Study #3: Terraced Hillside for Erosion Control For the next project, we produced an ecological landscape plan which required review from the building department, the Lake Association, and a waiver for a wetland permit. In site analysis we determined that over the course of time (as many as a hundred years), the tree canopy grew to shade the slope completely, the deer ate the understory, and the soil eroded and washed down the hillside into the lake. A woodland path through the sloped terrace gardens on Lake Peekskill, NY. The scope of work included significant small tree removal and pruning to allow light to infiltrate. Next, lifting, filling, regrading, terraforming, and land contouring the slope was performed to create functional terraces with garden paths. This involved manually spreading soil and placing boulders, logs, and compost socks. The steepness of the slope required us to dig trenches so the boulders wouldn’t roll downhill. Fencing at the top of the slope was removed to allow for large-scale material delivery. The raw material included: 38 yards of large, natural stone boulders; 11 yards of triple-ground brown hardwood mulch; five yards of certified playground mulch (for garden paths); as well as silt fencing, hay bales, filter fabric, jute, and compost sox. The soil brought in included 60 yards of engineered soil fill (consisting of 80% mineral soil and 20% organic matter), and 30 yards of compost/topsoil blend. Two dry laid stone retaining walls, with a gravel and filter fabric backfill, created terraces at the steepest part of slope. This project required working around natural elements (ie, rock outcroppings) and repurposing natural materials found onsite. Tree wells for hemlock and viburnum were constructed (with onsite stone and wood) along the property border to provide screening. The series of paths were constructed using stone steps and logs as water bars to retain soil and mulch. Logs were also strategically repurposed along mulched pathways in a playground area. This level mid slope area for exercise and play was seeded with a no-mow ecoblend mix from North County Organics. Like the previous project, predominately native trees, shrubs, grasses, perennials and ground covers were planted in jute to aid stabilization. Today, a gravel apron along the front foundation enables access and ease of maintenance, while river rock bioswales conduct water cleanly from landscape to lake shoreline, without creating erosion. In all our work, we strive to not only rectify site problems, but create beautiful, successful, sustainable, and resilient landscape environments. Contact us to discuss your stormwater management project or any landscape design considerations. — Green Jay Landscape Design Where Design Meets Ecology 914.560.6570
