Exploring the Benefits of Rain Gardens

Published on June 25th, 2023 by Brett Knighton

A collage of native plant species from different regions.

5 Facts about Rain Gardens

  1. Compared to a traditional lawn, rain gardens contribute to water conservation efforts by allowing 30% more water to soak into the ground.
  2. Rain gardens should have an area about 20% the size of the roof, patio, or pavement area draining into it.
  3. A typical rain garden for a residential home or small building is between 100 and 400 square feet but even a small rain garden that's under 100 square feet can make a large impact.
  4. Rain gardens are used to reduce the amount of greenhouse gases that are emitted during the treatment of water at water treatment plants, which can help reduce the impact of climate change.
  5. Rain gardens are designed to drain within 12-48 hours, preventing the breeding of mosquitoes and other water-borne insects.

What if you could turn your front yard into a mini-ecosystem that benefits the environment, supports local wildlife, and looks beautiful all year round? Welcome to the world of rain gardens - a simple yet powerful tool for managing stormwater runoff, enhancing biodiversity, and beautifying our surroundings. In this article, we'll explore the benefits of rain gardens, showcasing how these sustainable landscaping options can significantly impact our environment and why they are an exceptional addition to any property.

What is a Rain Garden?

Rain gardens are shallow depressions incorporated into landscapes that are specifically designed to capture, filter, and infiltrate rainwater runoff from impervious surfaces like roofs, driveways, or sidewalks. These areas are strategically filled with deep-rooted native plants and grasses which, combined with the soil, work in tandem to filter out pollutants and make the water that seeps into our groundwater and surface water systems cleaner.

How Effective is a Rain Garden?

The effectiveness of a rain garden is impressive, particularly when considering their impact on environmental health and stormwater management. According to the Groundwater Foundation, rain gardens can remove up to 90% of nutrients and chemicals, and up to 80% of sediments from rainwater runoff. This is a significant contribution to improving water quality, especially in urban areas where stormwater runoff often carries pollutants from roads, roofs, and other impervious surfaces.

In the chart below, you can see a comparison of the effects of impervious surfaces on runoff and ground infiltration between natural ground cover like rain gardens and an area with 75-100% impervious surface. The chart is interactive, so feel free to click on it to explore the data in more detail.

Stacked bar chart showing the effects of impervious surfaces on runoff and infiltration

As you can see, impervious surfaces significantly increase runoff while decreasing both deep and shallow infiltration. This has important implications for urban planning and water management.

How Do Residential Rain Gardens Work?

Residential rain gardens are cleverly designed to utilize nature's natural water cycle efficiently within a compact space. They function using a series of steps that capture, cleanse, and reuse rainwater. Here is a simple breakdown of how they work:

  • Inflow from Drainage: When it rains, water is directed into the rain garden. This can be through gutters and downspouts on homes, or simply by designing the landscape so that runoff naturally flows into the garden.
  • Absorption: The rain garden is filled with a specific soil mix that is highly permeable, consisting of sand, gravel, and organic matter. This allows the rainwater that enters the garden to slowly soak into the soil.
  • Filtration: As the water seeps through the soil, it undergoes a process of natural filtration. The soil layers and the garden's plants work together to remove pollutants and sediments from the water, improving its quality.
  • Groundwater Recharge: The filtered water doesn't just disappear—it replenishes the groundwater. This is critical for maintaining a healthy water table and helps sustain the surrounding vegetation.
  • Evaporation and Transpiration: Some of the water in the rain garden will evaporate back into the atmosphere. Additionally, the plants in the garden absorb water through their roots and release it back into the air in a process called transpiration.
  • Overflow Management: In the case of excessive rainfall that the garden cannot hold, an overflow mechanism is typically included in the design. This ensures that any excess water is safely directed away from buildings or structures, preventing potential damage.

The Benefits of a Rain Garden

Rain gardens offer a wide range of benefits beyond their visual appeal. They demonstrate nature's ability to address environmental challenges and enhance our surroundings. Let's explore the many advantages of rain gardens:

  • Reduces Stormwater Runoff

    Rain gardens act as natural buffers, capturing and filtering stormwater runoff that would otherwise flow directly into sewer systems. This reduces the volume of runoff, minimizes erosion, and prevents the loss of valuable topsoil. By disconnecting impervious surfaces, such as roofs and driveways, rain gardens slow down the flow of stormwater, clean it, and help it soak into the ground.

  • Improves Water Quality

    The combination of plants and soil in rain gardens acts as a powerful filtration system, removing pollutants like heavy metals and excess nutrients from stormwater runoff. This natural filtration process significantly improves the quality of water that seeps into our groundwater and surface water bodies.

  • Protects Rivers and Streams

    By reducing the volume and speed of stormwater runoff, rain gardens play a crucial role in preventing erosion along local waterways like stream banks and river beds. The filtration process also prevents harmful pollutants from entering these water bodies, protecting aquatic life. Rain gardens contribute to clean water in your community.

  • Supports Local Wildlife

    Rain gardens create a welcoming habitat for various local wildlife, including birds, butterflies, and beneficial insects. Incorporating native plants in rain gardens provides food and shelter for the wildlife, promoting biodiversity. Rain gardens also provide habitat for pollinators and increase plant diversity, helping butterflies and bees pollinate crops and vegetables.

  • Water Conservation

    Rain gardens demonstrate the concept of "water wisdom." They capture and store rainwater, reducing the need for artificial irrigation and conserving water. This is particularly valuable in areas prone to drought or water restrictions. Rain gardens collect water, nutrients, and carbon with each rainfall, maintaining soil moisture even without extra irrigation during hot summers.

  • Flood Protection

    Rain gardens act as natural defenses against the risk of local flooding during heavy rain events. By absorbing large amounts of runoff, they help prevent flooding. The deep roots of plants in rain gardens also improve soil drainage, further aiding in flood prevention.

  • Addresses Drainage Issues

    Rain gardens can be placed strategically to intercept runoff from impervious surfaces, helping solve drainage problems. The design of the garden and the roots of the plants work together to improve soil permeability and promote water infiltration. Watershed Protection Departments have successfully installed rain gardens in parks with drainage issues, mitigating these problems effectively.

  • Beautification and Biodiversity

    Rain gardens enhance the aesthetics of landscapes with their attractive plants. Using native plants like flowering perennials, shrubs and grasses like switchgrass supports local biodiversity, contributing to a healthier ecosystem. By choosing plants that match the garden size and arranging them attractively, rain gardens become beautiful additions to any landscape.

  • Encourages Pollinators

    Native plants in rain gardens provide food and habitat for pollinators like bees and butterflies, encouraging their presence. This, in turn, benefits the wider ecosystem as pollinators play a crucial role in plant reproduction.

  • Improves Mental Well-being

    There's a growing body of research that suggests being around nature, including green spaces like rain gardens, can have a positive effect on mental health. The visual beauty and serenity of a rain garden can provide a calming effect, helping to reduce stress and anxiety. In urban environments, where concrete and asphalt dominate, rain gardens provide a peaceful haven in the midst of all the hustle and bustle. These gardens bring a touch of nature to the urban landscape, giving us a break from the concrete and noise.

  • A Low-Maintenance Landscaping Option

    Once established, rain gardens require minimal maintenance compared to traditional lawns. They are designed to thrive with natural rainfall and local climate conditions. Tasks such as mowing, fertilizing, and pest control are significantly reduced or even eliminated. Native vegetation in rain gardens does not require pesticides or fertilizers, although occasional watering during the first year and periodic weeding may be necessary.

  • Rebates and Incentives

    Some municipalities offer rebates or incentives to homeowners who install rain gardens, recognizing their positive impact on stormwater management and water conservation. These financial incentives can help offset the initial costs of installing a rain garden, making it a cost-effective choice for many homeowners. The overall cost of installing a rain garden is generally low, ranging from $3-5 per square foot for self-installation, while using professional landscaping companies may cost around $10-15 per square foot.

Why do we need Rainwater Gardens?

As urbanization continues to increase, the amount of pollution from stormwater runoff from impermeable surfaces has become increasingly urgent. It is a significant contributor to water pollution, accounting for approximately 30% of all water pollution, according to the U.S. Environmental Protection Agency.

Stormwater runoff pushing grass clippings into a storm drain.

In addition, various studies, including those published in ScienceDirect, have shown that stormwater runoff can carry high concentrations of heavy metals, nutrients, and pollutants. These contaminants pose serious threats to aquatic ecosystems, causing problems such as algal blooms and oxygen depletion, which can harm or even kill aquatic life.

Let's explore some specific negative impacts of stormwater runoff on aquatic ecosystems:

  • Oxygen Depletion: Stormwater runoff can cause oxygen depletion in aquatic ecosystems. This often occurs when organic matter (such as leaves and grass clippings) in the runoff decomposes in the water. Bacteria that break down the organic matter consume dissolved oxygen in the process, leading to oxygen levels that are dangerously low for aquatic life. This state, known as hypoxia, can kill fish and other aquatic organisms, leading to so-called "dead zones" where little or no aquatic life can survive.
  • Algal Blooms: The runoff often contains high levels of nutrients like phosphorus and nitrogen, often from fertilizers used in agriculture and landscaping. When these nutrients enter a body of water, they can stimulate the overgrowth of algae, resulting in algal blooms. These blooms not only block sunlight, hindering photosynthesis in aquatic plants, but when the algae die and decompose, they also consume a significant amount of oxygen, further exacerbating oxygen depletion and leading to conditions like eutrophication.
  • Toxicity to Aquatic Life: Stormwater runoff often contains pollutants such as heavy metals, oil, and other toxic chemicals that can be harmful or even lethal to aquatic life. These toxins can kill fish and other organisms outright or lead to long-term health problems, such as reproductive issues or increased susceptibility to disease. Even at low levels, these toxic substances can be harmful because they may bioaccumulate in organisms over time.
  • Disruption of Natural Processes: Stormwater runoff can disrupt natural processes in aquatic ecosystems in a variety of ways. For instance, the increased water flow can cause erosion and sedimentation, clouding the water and damaging habitats. It can also change the temperature and pH of the water, creating conditions that are unsuitable for certain species. Additionally, the runoff can carry invasive species into new environments, where they can outcompete native species.
  • Pesticide Contamination: Pesticides used in agriculture and gardening can be washed into aquatic systems through stormwater runoff. These chemicals can be harmful to non-target species, affecting everything from tiny plankton to large fish and amphibians. Some pesticides can disrupt the endocrine system of aquatic organisms, affecting reproduction and growth, while others can be directly toxic, causing death or illness.
  • Accumulation in the Food Chain: Many of the pollutants carried by stormwater runoff, such as heavy metals and certain organic chemicals, can bioaccumulate in the tissues of aquatic organisms. This means that these substances build up in the bodies of organisms over time, often reaching levels that are much higher than in the water or the organisms' food sources. These pollutants can biomagnify up the food chain, reaching particularly high levels in top predators. This can lead to serious health problems, including reproductive issues, immune system damage, and death. For instance, mercury is a common pollutant in aquatic ecosystems that can biomagnify, leading to high levels in fish and posing a risk to both wildlife and humans who consume these fish.

These severe consequences on aquatic ecosystems and potential risks to human health highlight the urgent need for solutions like rain gardens.

Urban Rain Gardens: A Solution for Cities

Incorporating rain gardens into our cities and towns is a proactive approach we can take to protect our water resources and safeguard our health and well-being. These gardens are often incorporated into public spaces like parks and roadside green spaces.

Urban rain gardens function similarly to residential ones but they often have to handle a larger volume of water due to the extensive impervious surfaces in cities, such as streets, parking lots, and buildings. Because of this, they are typically larger and may incorporate additional features like overflow channels and underdrains. Moreover, they can serve as educational tools, raising awareness about stormwater issues and the importance of sustainable practices.

What are the Common Mistakes to Avoid when Building a Rain Garden?

  1. Choosing the wrong site for a rain garden: It is important to choose a location that is not too close to the house or other structures, and that has good drainage. They should be placed at least 10ft away from a dwelling foundation to prevent water from entering the home. Avoid areas with steep slopes or areas that are prone to flooding.
  2. Not properly sizing the rain garden: A rain garden should have an area about 20% the size of the roof, patio, or pavement area draining into it. A typical rain garden for a residential home or small building is between 100 and 400 square feet. Make sure the garden is not too deep, as it should be no more than 6 to 12 inches deep.
  3. Not using the right plants: It is important to choose garden plants that are native to the area and can tolerate both wet and dry conditions. Avoid planting invasive species or plants that require a lot of maintenance.
  4. Not properly preparing the soil: The soil in the rain garden should be well-draining and free of debris. It may be necessary to amend the soil with compost or other organic matter to improve drainage.
  5. Not properly maintaining the rain garden: Once the rain garden is established, it is important to maintain it properly. This includes removing weeds, pruning plants, and removing debris that may accumulate in the garden.

Misconceptions about Rain Gardens

Despite all the advantages, misconceptions about rain gardens still linger. For example, many people mistakenly think they create a mosquito breeding ground or are filled with only water-tolerant plants. When built correctly, rain gardens are actually engineered to drain within a day or two, rendering them unable to sustain mosquito reproduction. Moreover, although some plants in these gardens can thrive in wet areas, a wide variety of plants that require different levels of moisture are included, including those that prefer dry environments.

Rain Garden Design Examples

Small Rain Garden

A small rain garden, often found in residential settings, is a perfect example of how you can make a significant environmental impact within a limited space. These gardens are typically designed to capture runoff from a single source, such as a downspout or driveway. Despite their size, they can be quite attractive, featuring a variety of native plants and grasses that not only thrive in the fluctuating moisture conditions but also provide habitat for local wildlife. The design of a small rain garden is often simple, focusing on the basics of rainwater capture and filtration.

A small rain garden located in the front yard.

Large Rain Garden

Large residential rain gardens are a step up in size and complexity. They are designed to handle larger volumes of runoff, often from multiple sources such as rooftops and driveways. These gardens can be quite gorgeous, featuring a wider variety of native plants and grasses. They may also incorporate features like stepping stones and benches, transforming the garden into a functional and attractive part of the landscape. Large residential rain gardens are a testament to how sustainable practices can be seamlessly integrated into residential design.

A large rain garden designed in the front yard.
Design and Photo by Terrain Landscape Architecture

Urban Rain Garden

Urban rain gardens are a crucial tool in managing stormwater in city environments. Often incorporated into public spaces like parks and roadside green spaces, these gardens provide a dual function of managing stormwater and providing green space in urban environments. Despite the challenges of urban conditions, these gardens can thrive and provide a much-needed touch of nature in the cityscape.

An urban rain garden strategically built next to a sidewalk and road to collect runoff.

Each of these rain garden examples showcases the versatility and effectiveness of this sustainable practice. Whether small or large, residential or urban, rain gardens play a crucial role in managing stormwater, promoting biodiversity, and enhancing our landscapes.

Overview

Rain gardens are great additions to your property and the environment, ranging from improved water quality to the creation of vibrant habitats for local wildlife. They are an environmentally-friendly and visually appealing addition to any landscape. By incorporating a rain garden on your property, you can actively contribute to a healthier environment while reaping the many benefits it provides.

FAQs

How much does it cost to build a rain garden?

The cost of building a rain garden can vary, driven by factors such as size, soil condition, and design. However, they are generally a low-cost solution for managing stormwater runoff. Some municipalities even offer rebates or incentives, promoting the installation of these eco-friendly features. These financial incentives can significantly reduce the overall cost, making rain gardens an affordable and sustainable choice for many homeowners.

How long does it take for a rain garden to start working?

A rain garden begins its work immediately after installation. It's designed to absorb and filter runoff from the very next rain event. This immediate functionality makes rain gardens a quick and effective solution for managing stormwater, improving water quality, and enhancing local biodiversity. Don't get discouraged if your rain garden has standing water in it after a storm. They are designed to slowly soak into the soil.

What types of soil are suitable for creating a rain garden?

While rain gardens can be built in most types of soil, they perform best in soils with good drainage. If your soil is heavy clay or compacted, you may need to amend it with compost or other organic matter to improve its drainage. This step ensures that your rain garden can effectively capture, filter, and infiltrate rainwater runoff, maximizing its environmental benefits.

How can I attract wildlife to my rain garden?

Incorporating native plants in your rain garden will naturally attract local wildlife. These plants provide food and shelter for various species, promoting local biodiversity. Additionally, you can enhance your rain garden's appeal to wildlife by adding features like bird baths or bee houses, creating a welcoming habitat in your own backyard.

What plants should you plant in a rain garden?

When selecting plants for a rain garden, it is important to choose species that are adapted to the local climate and soil conditions. Native plants are often a good choice because they are well-suited to the local environment and require less maintenance than non-native species.

Plants with deep roots are also beneficial because they help to absorb water and prevent erosion. It is also important to choose a mix of plants with different heights, textures, and bloom times to create a visually appealing garden that provides habitat for a variety of wildlife.



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