Rain Gardens and Bioswales
A rain garden is a lowered shallow planting area, designed to capture, hold and absorb rainwater. A bioswale is a shallow graded and planted flow path that slows, sinks and directs rainwater across the landscape. Both flood mitigation strategies depend on plants for proper function and offer us opportunities to manage stormwater in an attractive garden landscape.
Images capturing the construction of a bio-swale we designed for a Catskill landscape
How this works
Rain gardens act briefly as rainwater reservoirs. Often, only a few hours are required for water to disappear. Garden soils are typically much more pervious than compacted lawn and bare soil areas. This enhanced absorption is attributed to several factors: the permeability and water absorption qualities of organically rich soil, the ability of deeper-rooted plants to loosen compacted soils, and the increased transpiration rates of larger, healthier plants.
Bio-swales can be thought of as linear rain gardens with the added purpose of moving surface water across the landscape. This requires a slight grade across their length to ensure water flows. The larger area of bio-swales offers more absorption potential, supporting a goal shared with raingardens of recharging groundwaters. At the same time this larger area increases evaporative and plant transpiration potentials, moving water upward and outward.
An Adirondack rain garden we designed with native plants and site boulders
One of our Brooklyn rain gardens, designed with a boardwalk
Other benefits of rain gardens
Pollution Reduction: In New York City, a combined sewer system handles both storm water and sewage. Rain gardens intercept storm water and help reduce combined sewer overflows.
Clean water: Rain gardens remove sediment and pollutants from water by filtering and settling particles through plant roots and soil. The plants themselves absorb some of the pollutants in a process called nutrient cycling. Rain gardens help clean runoff before it enters nearby streams and other water bodies.
Biodiversity: Our rain gardens support diverse plant and animal species, and minimize the need for fertilizers due to using local adapted species.