Bioswales and Rain Gardens: Sustainable Solutions for Positive Drainage

Executive Summary

• Bioswales and rain gardens are two green infrastructure solutions that can help manage stormwater runoff differently, ultimately reducing flooding and preserving water quality.
• Bioswales are intended to direct and filter water flow linearly, causing them to be placed along streets. In contrast, rain gardens focus on localized absorption, making them great for low areas near downspouts.
• These systems are gaining popularity throughout Portland due to their environmental sustainability, potential for aesthetic enhancements, and property value benefits.
• You can create a rain garden by selecting a low area, loosening the soil and adding compost, choosing native plants, mulching the area, and adding a berm or shallow trench; however, consulting environmental specialists is ideal.

Learning About Sustainable Solutions for Positive Drainage, like Bioswales and Rain Gardens

As urban expansion has continued throughout the Portland area, effective stormwater management has become crucial for reducing flood risks, preventing erosion, and safeguarding local water quality. Specifically, installing bioswales and rain gardens has become a popular, environmentally friendly way to manage stormwater runoff by slowing, filtering, and directing or absorbing excess rainwater.

Before property owners decide to implement bioswales and rain gardens, they must know their differences to determine which stormwater management system will work best for a specific situation. For instance, bioswales are deeper and are installed linearly, making them great for directing stormwater runoff along the side of a street. On the other hand, a rain garden is more shallow and is designed for absorption, making it ideal for low areas near a downspout.

This guide will help people in Portland, a place with historically heavy rainfall, learn about these green infrastructure solutions. However, contacting a trustworthy environmental specialist is the best way to get reliable guidance on implementing bioswales and rain gardens for positive drainage on your property.

What is a Bioswale?

A bioswale is a vegetated channel that slows, filters, and absorbs stormwater runoff. They are usually installed in linear patterns, allowing them to play a critical role in redirecting water away from areas vulnerable to pooling. While directing the rainwater, a bioswale can also naturally remove pollutants and debris, augmenting overall water quality.

Some examples of common bioswale placement options area:

• Along roads
• The edges of parking lots
• Near sidewalks or walkways
• Throughout playgrounds
• The perimeter of industrial sites

What is a Rain Garden?

Rain gardens are shallow, plant-filled depressions that collect and absorb rainwater. They are designed to reduce runoff and allow water to percolate into the ground. Unlike a bioswale that is meant to direct water flow, a rain garden’s main purpose is localized absorption. Therefore, most people place rain gardens within low areas near downspouts.

Some examples of spaces that rain gardens may benefit include:

• Residential yards or apartment complexes
• Near playgrounds
• Community spaces like public gardens
• Schools
• Commercial properties like office buildings

Knowing what bioswales and rain gardens can assist with is the first step in determining how these green infrastructure solutions may impact your property.

Functions of Bioswales and Rain Gardens

Bioswales and bioretention areas like rain gardens are multi-functional and may contribute to the following processes throughout your property. 

Stormwater Runoff Management

Both bioswales and rain gardens are known to slow down and absorb rainwater by forcing it to filter through vegetation and soil, simultaneously reducing the water runoff’s speed and volume. This natural process helps prevent excessive rainwater from overwhelming drainage systems.

Flood Mitigation

These green infrastructure solutions can minimize pooling throughout urban areas by absorbing or diverting excess rainwater away from impervious surfaces that could otherwise cause localized flooding.

Water Quality Improvement

These systems can also reduce erosion and sedimentation in nearby waterways by capturing and gradually absorbing stormwater. Therefore, bioswales and rain gardens can protect riverbanks and improve water quality by removing pollutants, such as oil, heavy metals, and debris.

Enhancing Biodiversity

By incorporating native plants into your living infrastructure systems, you may be able to attract pollinators and other beneficial wildlife, ultimately contributing to a healthier, more sustainable ecosystem.

Property Protection

Thanks to their absorption or redirection potential, bioswales and rain gardens can limit the risk of storm damage that can occur if polluted, debris-filled, or excessive amounts of rainwater sit on your property or reach vulnerable building materials.

Key Differences Between Bioswales and Rain Gardens

Although they can offer similar benefits as mentioned above, bioswales and rain gardens operate in unique ways, making some property owners opt for one over the other. You should consider the differences below to determine which green infrastructure solution will function best on your property. 

Design Considerations

Bioswales and rain gardens have distinct design traits. For instance, a bioswale offers water for conveyance, while a rain garden is designed for absorption. Moreover, a bioswale is usually deeper than a rain garden, even though it is still rather shallow. Bioswales also use engineered layers, while rain gardens rely on native soil and compost.

Ideal Locations

Due to their linear nature, bioswales are often placed along streets. This can keep excess water off of roads, protecting some vehicles from the risk of hydroplaning on pooled water. Conversely, rain gardens sit in low areas, making them ideal near downspouts, which can pump out excessive rainwater during Portland’s wet seasons.

Plant Selection

These green infrastructure solutions are suited for different plant types. For example, bioswales require erosion-resistant plants, such as:

• Switchgrass (Panicum virgatum)
• Blue sedge (Carex flacca)
• Red osier dogwood (Cornus sericea)
• Soft rush (Juncus effusus)

On the other hand, rain gardens allow for a greater variety of vegetation, giving property owners and the environmental specialists they are working with more freedom during the plant selection process.

Benefits of Implementing Bioswales and Rain Gardens

Although each property may experience unique advantages after installing one of these green infrastructure solutions, some examples of benefits of bioswales and rain gardens include:

• Environmental sustainability – These systems can reduce stormwater pollution by filtering contaminants, conserve water by facilitating ground infiltration, and support local wildlife by providing habitat and food sources.
• Aesthetic enhancements – Bioswales and rain gardens can add greenery and natural beauty to urban or residential landscapes, brightening the areas.
• Property value increases – In addition to improving curb appeal with their greenery, these sustainable drainage solutions may raise real estate value by showing buyers the property is safe from some water-induced threats.

Adding a bioswale or a rain garden to your property can open you up to the positive impacts above.

How is a Rain Garden Created?

To create a rain garden, a qualified individual should select a low-lying area that naturally collects water, preferably near a downspout. After choosing the best spot, they should evaluate the space to determine the appropriate size of the rain garden. The individual should consider runoff volume and soil absorption capacity during the evaluation process. 

Once your plans for sizing are fleshed out, the person should prepare the soil by gently loosening it with a tool like a rake. They may need to add compost if they are trying to improve drainage in that area. Once the soil is ready, the individual can pick native plants that can tolerate both wet and dry conditions.

Some examples of plants that may function well in a Portland-based rain garden are:

• Blue flag iris (Iris versicolor)
• Swamp milkweed (Asclepias incarnata)
• Red osier dogwood (Cornus sericea)
• Black-eyed Susan (Rudbeckia hirta)

The individual should arrange plants with taller, water-loving species in the center and drought-tolerant ones along the edges if possible. 

The rain garden creation process is usually finished by mulching and installing a berm or shallow trench to help direct water flow to the permeable area. Still, regular maintenance, such as weeding, mulching, and occasional replanting, is needed to keep the rain garden functional and thriving.

Alpha Can Augment Your Property’s Stormwater Management System

Depending on the setup of your Portland-based property, you may also be able to experience the benefits of bioswales and rain gardens. A bioswale can be installed in a linear fashion, directing water away from the flood-susceptible portions of your land while filtering the stormwater runoff along the way. Alternatively, a rain garden can sit in a low area and facilitate stormwater management through local absorption. Consult a reliable environmental company like Alpha Environmental for expert-level guidance on which stormwater management system is best for your property layout, budget, and aesthetic interests.

Alpha specializes in designing and implementing bioswales and bioretention systems for commercial and residential properties. Our team provides professional consultation, transparent pricing, and effective results. We are focused on helping our neighbors throughout the greater Portland area implement comprehensive stormwater management strategies that work best for them, whether it is a bioswale or dry well.

Contact Alpha Environmental to learn how to optimize stormwater management while improving your property’s resilience and aesthetics.