Landscape Drainage Solution: Rain Garden Design | Westchester County, NY We were hired to evaluate the landscape drainage issues at this Westchester County property, which proved to be complicated due to some peculiar construction from previous homeowners. Analyzing the Stormwater Problem The previous owners put an addition on the house and reconstructed the driveway to a grade that required an anti-gravity sump pump to re-route the stormwater. This complicated system often failed and led to flooding in our client’s basement and backyard. Half the backyard would have standing water for days after a large storm event. Furthermore, gutters and leaders from the large roof emptied out onto the lawn, which can only absorb so much water. Designing a Landscape Drainage Solution We knew that the problem had to be addressed before it reached the sump pump, to avoid system failure. If we could divert some of the stormwater runoff from the roof into the landscape to be absorbed, the engineered sump pump system could deal with a smaller amount of runoff overall. Diverting stormwater to a Rain Garden only works if the soil has appropriate drainage rates. Rain gardens are not bog gardens. Stormwater should drain within twenty-four hours. Not every site is compatible as a rain garden – the soil must have sufficient drainage capacity. Heavy clay soils hold water, and do not work as rain garden sites. We always perform percolation tests to test the soil characteristics, as part of our site analysis for a rain garden. In the photo above, Uziel tests the soil’s compaction level. In this case, the existing soil was highly compact with a high proportion of clay. We core aerated, vertical slice seeded and applied numerous soil amendments to the lawn area, to help relieve compaction and improve drainage capacity. To redirect stormwater away from the house and lawn, we connected two leaders from the roof into underground pipes. We directed the pipes toward the corner of the yard into the newly designed rain garden. The rain garden area itself was excavated and filled with topsoil with a high drainage capacity. The pipes leading to the rain garden are perforated at the bottom, allowing stormwater to seep out over a larger area, and come up through the pipe during periods of a higher water table. Once the water reaches the rain garden, it is dispersed and absorbed by plants’ roots. Rain Garden Design Facultative plants are found in mesic zones usually on slopes or in well drained spots, occasionally exposed to drought or flood conditions. Native & Non-Native Plants for Rain Gardens Many of our favorite native shrubs for wildlife also work in rain gardens: clethra, aronia, dogwood. Perennials in the rain garden can also create habitat: Eastern Red Columbine attracts hummingbirds, Blue Lobelia, Joe Pye Weed, and New York Ironweed are all pollinator magnets! In this design, we also planted a non-native Dawn Redwood. This fast-growing tree absorbs large amounts of water and grows fast; it will be extremely effective in this context. Start Your Landscape Drainage Solution If you have a consistently soggy landscape, there are likely improvements to be had. Check out our Stormwater Management page for a detailed look at stormwater solutions and Contact Us to schedule an on-site consultation. — Green Jay Landscape Design Where Design Meets Ecology 914-560-6570
