When & Where To Install Bioswales

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In recent years, sustainable landscaping practices have gained significant traction among homeowners and environmental conservationists. One such practice gaining popularity is the inclusion of bioswales in urban areas and residential communities. These bold and innovative landscape features allow drainage systems to become both efficient and aesthetically pleasing. Come learn more about when and where bioswales should be added to decide if they are a good option for your property

What Is A Bioswale?

A swale, either naturally occurring or man-made, is a low-lying depression in the ground with sloped land on either side. A bioswale is a type of swale that is man-made and designed to serve as a channel for managing stormwater runoff. While swales are typically referred to as sloped land with a channel in the middle, bioswales include vegetation and other natural features in the channel to help remove pollutants from the stormwater and minimize flooding in the surrounding area. 

In more urban settings, bioswales are a great option for a drainage system that will filter groundwater before it is released to a storm sewer. As rainwater falls on an impervious surface, like a sidewalk or street, it trickles down the sloping sides of the bioswale and gets collected in the channel. Under the vegetative channel, there may be a perforated pipe surrounded by gravel that will feed the stormwater runoff back to the sewer system, helping prevent flooding and clearing debris from the water. 

Benefits Of Bioswales

Bioswales add greenery to urban settings, and they are a great way to utilize rainwater for plant life in a yard. Vegetation in a bioswale is relatively low maintenance, as it gets all the water it needs from runoff, making bioswales a great option for eco-friendly gardening. The vegetation on both the slopes and in the channel of a bioswale naturally filters the water, and the gradual slopes help reduce the velocity of the incoming runoff, which prevents overflow to the underlying drainage systems. 

  • Stormwater Management: Bioswales effectively capture, slow down, and filter stormwater runoff, reducing the volume and velocity of water entering drainage systems and water bodies.
  • Flood Mitigation: By intercepting and absorbing rainfall, bioswales help mitigate flooding by reducing peak flows and preventing excess water from overwhelming drainage infrastructure.
  • Water Quality Improvement: The vegetation and soil within bioswales act as natural filters, removing pollutants, sediments, and nutrients from stormwater runoff, thereby improving water quality in nearby water bodies.
  • Erosion Control: Bioswales help prevent soil erosion by stabilizing the ground with vegetation and slowing down the flow of water, reducing its erosive force.
  • Habitat Creation: The diverse vegetation within bioswales provides habitat and food sources for various wildlife species, contributing to biodiversity and ecosystem health.
  • Aesthetic Enhancement: Well-designed bioswales can enhance the visual appeal of landscapes, adding greenery, texture, and color to urban and suburban environments.

Bioswales vs. Rain Gardens

Bioswales and rain gardens are often confused with one another. Though they serve similar purposes and share many characteristics, there are some distinct differences. Bioswales are typically linear channels or depressions that follow the natural slope of the land, often positioned alongside roads, parking lots, or other impervious surfaces to capture and convey stormwater runoff. Rain gardens, on the other hand, are shallow, basin-like features that collect and retain rainwater on-site, usually integrated into landscaped areas such as yards, gardens, or parks. While bioswales prioritize conveyance and filtration of stormwater along a linear path, rain gardens focus on localized infiltration and storage, allowing water to slowly percolate into the soil. 

Perhaps the most significant difference between bioswales and rain gardens is that rain gardens utilize man-made drainage sources to redirect rainwater, such as gutters/downspouts, underground pipes, and more, to collect and use rainwater solely for irrigation. In contrast, bioswales use gravity via the natural (or sometimes excavated) slope of the land to collect water, which is then typically reintroduced to a larger water supply.

When To Install A Bioswale

Determining when to install bioswales requires careful consideration of various factors, including site characteristics, climate conditions, and stormwater management goals. Ideally, bioswales should be installed during the dry season or periods of minimal rainfall to allow for proper site preparation, excavation (if necessary), and planting. This timing ensures that construction activities are not disrupted by heavy precipitation and enables newly planted vegetation to establish root systems effectively. However, in regions with consistent rainfall throughout the year or mild climates, bioswales can be installed at any time with proper planning and construction techniques. 

Most importantly, bioswales should be installed when drainage systems are constantly flooded with excess water runoff. The slope of a bioswale helps distribute the water across the vegetation as it slowly makes its way to the channel, drastically reducing the amount of runoff that gets introduced to a drainage system at any given time. This functionality of bioswales is what makes them so efficient at managing excess water runoff. 

Where To Install A Bioswale

Bioswales are needed in various urban and suburban environments with slopes or natural drainage patterns where stormwater runoff tends to accumulate. One scenario where bioswales are particularly beneficial is in areas prone to flooding and erosion caused by excessive stormwater runoff. Areas like these that feature well-draining soil and naturally sloped land are prime candidates for bioswale installation. 

Bioswales are essential in regions experiencing urbanization and land development, where impervious surfaces such as roads, parking lots, and buildings contribute to increased runoff and pollution. Another critical application of bioswales is in neighborhoods and communities grappling with aging or inadequate stormwater management systems. Installing bioswales in these areas helps alleviate strain on traditional stormwater infrastructure and prevents pollutants from entering water bodies, thus safeguarding water quality and ecosystem health.

How To Install A Bioswale In Your Yard

Installing a small bioswale on your own property is a great way to ensure that your yard does not flood. The installation process can be as simple as planting some water-loving plants at the bottom of a natural slope in your landscape, but there are more advanced methods that can increase the efficiency of your new water-management system. Below are some key steps to keep in mind if you want to get the most out of your bioswale, but we recommend contacting a drainage and landscape specialist for the most effective and least invasive installation of a bioswale in your yard.

  • Step 1) Site Selection: Choose a location in the residential yard where stormwater runoff tends to accumulate or where it can be directed from impervious surfaces such as roofs, driveways, or sidewalks. Ensure the area has an existing natural slope for effective water flow.
  • Step 2) Trench Digging: Use a shovel or excavator to dig a trench in the selected area according to the desired dimensions of the bioswale. The trench should typically be 1-3 feet deep and 3-10 feet wide, depending on the available space and rainfall volume. The depth of your bioswale ditch should correspond to the amount of water absorbed by your soil in 24 hours.
  • Step 3) Underdrain Installation: If necessary, install an underdrain system at the bottom of the trench to facilitate water drainage and prevent waterlogging. Lay perforated drain pipes along the length of the bioswale, ensuring proper slope for water flow towards the outlet.
  • Step 4) Landscape Fabric/Lining: Line the bottom and sides of the trench with landscape fabric or geotextile liner to prevent soil erosion and ensure proper filtration of stormwater. Secure the fabric in place with stakes or anchors to prevent shifting during backfilling.
  • Step 5) Planting: Select a variety of native, deep-rooted plants suitable for wet conditions to plant along the length of the bioswale. Arrange the plants in a staggered pattern, spacing them according to their mature size to ensure adequate coverage and biodiversity. Dig planting holes slightly larger than the root balls of the plants and backfill with soil, ensuring proper compaction.
  • Step 6) Mulching: Apply a layer of organic mulch around the base of newly planted vegetation to retain moisture, suppress weed growth, and promote soil health. Spread the mulch evenly across the bioswale, leaving a gap around the stems of the plants to prevent rot and disease.