The Benefits of Bioswales and Bioretention in Stormwater Management

The Benefits of Bioswales and Bioretention in Stormwater Management

Table of Contents

Executive Summary

  • Bioswales and bioretention systems are simple green structures with plants and porous soil to contain and treat stormwater.
  • Bioswales and bioretention protect local waterways from contaminants, direct stormwater away from important infrastructure, and take stress off local stormwater management systems.
  • When developing a bioswale, there are a few best practices to follow to ensure they are efficient and effective at capturing stormwater.
  • Regular maintenance of bioretention systems is easy and helps to ensure the long-term effectiveness of the system.

You might not realize that some pleasant vegetation landscaping along the road or sidewalk actually serves a beneficial purpose for the surrounding infrastructure and local waterways. In developed areas, stormwater flows over hard surfaces like streets into storm drains, gathering pollutants along the way with no chance of filtration.

A bioswale or bioretention pond with native plants and porous soil collects, contains, and filters stormwater runoff, benefiting the environment and local structures by containing water and cleansing pollutants. When implementing a bioswale or bioretention system, there are a few best practices you should follow to make the most of their function.

What Are Bioswales and How Do They Work?

Bioswales are landscaped channels or depressions for collecting and draining stormwater runoff. These channels slow down, collect, and even filter stormwater, offering several environmental benefits.

The sloped construction of bioswales means water is directed to the system and pools in it before slowly being absorbed into the soil. This system is particularly beneficial in rainy environments, as it can redirect stormwater away from other areas to protect infrastructure against flooding. 

Bioswales work well in urban spaces like parking lots and along sidewalks and roadways, but they also work well in residential areas as a part of the landscaping. For example, rain gardens are a common type of bioswale.

What Is Bioretention and How Does It Work?

Bioretention is the practice of using landscaping depressions or basins to capture and naturally treat stormwater. The sloped construction of a bioretention system uses berms and a bowl-like shape to pull the water into the area and contain it. 

Once the water is contained in the system, the porous soil absorbs the water, and plants with long roots put the water to use. This process prevents the water from gathering on roadways and treats water before it enters storm drains.

How Does Bioretention Work with Bioswales?

Bioswales are one of the most popular types of bioretention systems. They are landscaped in a way that easily captures water and contains it. They are typically filled with soft, sandy soil that absorbs water easily and plants with long, fibrous roots that can use the water to grow. These plants and the soil absorb and filter the water, redirecting stormwater and preventing standing water from remaining in the system.

Advantages of Bioswales and Bioretention

Although the primary purpose of bioswales and bioretention systems is stormwater management, they serve many benefits. From improving the beauty of a space or landscape to protecting surrounding infrastructure, there are plenty of reasons to include a system on your property.

More Efficient Stormwater Management

The design of a bioretention system brings stormwater into a designated location instead of allowing it to pool on the ground or flow into streets uncontrolled. A bioretention system can effectively contain stormwater in areas that do not have a stormwater management system in place.

A bioretention system can also improve the efficiency of existing systems. Local governments are required to have stormwater management systems in place. However, treatment centers use energy and require maintenance.

Installing bioswales throughout an area helps to take stress off the local stormwater management system. By reducing the load of these systems, bioretention systems can also reduce the costs associated with energy usage and maintenance.

Higher Water Quality

Thanks to the inclusion of plants and porous soil, bioswales provide the first step of filtration from harmful contaminants before the water even makes it to retention centers. Plants and soil act as natural filters for the water that moves through bioswales, improving the quality of the water and protecting the surrounding environment.

Because bioswales can direct water away from sidewalks and roadways, they can also help prevent stormwater from collecting pollutants like oil, chemicals, and roadway salts in the first place. Altogether, bioswales take the stress off of the city’s water filtration systems and help protect the surrounding environment.

Minimize Flooding

Bioswales reduce the risk of flooding because of their increased soil infiltration. Water is directed to the landscaping instead of flowing across roadways or standing on other parts of the property. By minimizing flooding, these bioretention systems help to protect infrastructure, roadways, and landscaping.

Increases Biodiversity

In general, increased plant life and vegetation are great for the environment as they boost biodiversity, creating a safe space for butterflies, bees, birds, and beneficial insects. Plants also convert carbon dioxide into oxygen, serving multiple benefits for the life around them.

Bioswales can be used on residential properties and urban spaces alike, introducing native plant life to areas where it may not be present. This biodiversity beautifies areas, bringing flowers and plants to otherwise unused landscaping, which is more appealing to both locals and tourists. Using bioretention systems is far more attractive than concrete structures and stormwater washes.

Increased Environmental Well-Being

Stormwater runoff from urban centers can be harmful to local waterways, bringing contaminants into wildlife habitats. Bioswales mitigate this pollution as their plants naturally filter this water before it runs into nearby stormwater systems, creeks, rivers, and estuaries.

This promotes the environment’s health by minimizing the spread of pollutants, roadway salts, and more that can get into the water system and impact the health of local fish, plant life, and other animals.

Bioswales also retain water in the ground, benefiting surrounding plant life. Instead of water being directed away from an area, bioretention basins allow the water to be put to use by plants in a given location.

Realize the Benefits of Bioswales

Bioswales and bioretention systems are a great example of how green infrastructure can improve stormwater management. Alpha Environmental provides expert installation and maintenance to benefit your property and the environment.


How To Effectively Use Bioswales and Bioretention Systems

Bioretention systems are only effective if located in a place where they are helpful in redirecting and containing rainwater. Fortunately, with the right expertise and procedures, creating a system is not difficult.

To construct a bioswale or bioretention system, follow these steps:

  • Find the location. Consider at the bottom of a downslope or in a depression in the land. Choose a spot away from the root systems of trees.
  • Construct an inlet. Create an easy pathway for water to flow into the bioswale while creating a barrier between the system and a lawn or road.
  • Include a barrier. Including a system like rocks at the base of the inlet to slow the water flow and avoid overflowing the system.
  • Build a containment system. A berm or obstacle at the downhill end of the system will contain rainwater in the bioswale so it can be absorbed by the soil.
  • Test the soil infiltration rate. Ensure that the soil infiltration rate is high enough that the soil will absorb water quickly enough to avoid standing water.
  • Add mulch. Add 2-3 inches of mulch to keep out weeds, prevent erosion, and protect plant seedlings after the initial installation of a bioswale.

Sustaining Bioswales and Bioretention Systems

One of the most significant benefits of bioretention systems is that maintenance is relatively easy. Properly maintaining your system typically only takes a few hours each month. Taking small steps toward proper maintenance will ensure their long-term function and keep water from overflowing and defeating the purpose of the system.

To sustain the health and function of your bioswales, follow these steps:

  • Monitor the health of your system by watching to ensure it continues to drain within 48 hours and doesn’t overflow.
  • Tend to the plants with regular trimming.
  • Remove weeds to prevent them from stealing water from the plants – it’s best to do this weekly.
  • Regularly remove debris and sediment that accumulates in your system and the inlets and can block stormwater flow.
  • Water the plants during dry spells without rain.

Regular maintenance helps to ensure that the system works properly long-term. It also keeps the property healthy and looking nice.

Guidelines and Optimal Practices

Although the concept and function of a bioswale are relatively simple, there is a bit of nuance to its construction. Therefore, installation requires the right expertise and careful planning in order to maximize the function of the system.

Some best practices to follow when building a system include:

  • Install irrigation fabric, which helps to reduce soil erosion
  • Factor in biodiversity by planting intentional, beneficial plants
  • Consider how the vegetation used can improve the appearance of the landscape
  • Plant plants that are native to the area and avoid invasive species
  • Ensure the rainwater drains within 48 hours
  • Set the system away from the home or building by about 15 feet
  • Avoid shaded areas and areas above utilities like gas or electrical lines
  • Always check local regulations about where you can install your bioswale on your property

Why You Should Choose Bioswales and Bioretention Basins

Bioswales and bioretention systems are environmentally friendly methods for containing and filtering stormwater. Installing these systems offers an aesthetically pleasing way to improve the cleanliness of local water systems and reduce the stress placed on stormwater management systems.   

Whether you are looking for a bioretention system installation or are in need of regular maintenance, Alpha Environmental can help. With 21+ years of experience serving the Portland area, we can support you in installing and maintaining bioretention systems while following all best practices and local regulations.

Contact us today to learn more about bioswales and bioretention stormwater systems and to schedule an installation.

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