Rain garden

In recent years, there has been a growing concern over the adverse effects of stormwater runoff on the environment.

 

Traditional methods of stormwater management, such as underground piping and concrete channels, often lead to increased pollution, erosion, and the depletion of groundwater resources.

 

As a response to these challenges, the concept of “rain gardens” has emerged as an innovative and sustainable solution for managing stormwater. This text aims to explore the significance of rain gardens in stormwater management, their ecological benefits, and their role in creating more resilient urban landscapes.

What is a Rain Garden?

A rain garden is a shallow, planted depression designed to capture and filter rainwater runoff from impervious surfaces like rooftops, driveways, and roads. The primary objective of rain gardens is to mitigate the negative impacts of stormwater runoff by allowing the water to infiltrate into the soil, naturally replenishing the groundwater aquifers and reducing the flow of pollutants into nearby water bodies.

Functionality and Design

Rain gardens are carefully designed to optimize their functionality. They are usually located strategically in areas where stormwater runoff tends to accumulate, such as the bottom of slopes or at the end of downspouts. The soil in a rain garden is typically amended to improve infiltration rates, and a variety of native plants with deep root systems are selected to aid in water absorption.

 

As Douglas Tallamy, an entomologist and conservationist, emphasizes in his book Bringing Nature Home, “The importance of native plants in rain gardens cannot be understated. They provide essential habitat and food sources for local wildlife, including butterflies and native bees, promoting biodiversity within urban landscapes.”

Ecological Benefits

Rain gardens offer numerous ecological benefits that contribute to the overall health of the environment. Firstly, they act as natural water filters, reducing the levels of pollutants in stormwater runoff. A study by the Environmental Protection Agency (EPA) states that “Rain gardens have shown to be effective in removing various pollutants, such as sediment, nutrients, heavy metals, and hydrocarbons.”

 

Secondly, rain gardens help to recharge groundwater resources. As stated by the United States Geological Survey (USGS), “When rainwater infiltrates into the ground, it recharges aquifers, maintaining the base flow of streams and supporting the overall water balance in the region.”

 

Moreover, rain gardens can serve as crucial habitats for wildlife, particularly in urban settings where natural green spaces are limited. According to the National Wildlife Federation, “Rain gardens attract a diverse range of birds and beneficial insects, providing essential stepping stones for migratory species and supporting local biodiversity.”

Contributing to Resilient Urban Landscapes

In the face of increasing urbanization and climate change, creating resilient cities has become a priority. Rain gardens play a significant role in this context, as they help reduce the impacts of urban flooding, alleviate strain on aging stormwater infrastructure, and promote climate adaptation.

 

In the words of renowned architect and urban planner, Jane Jacobs, “Rain gardens are a testament to the idea of urban self-sufficiency and adaptability. By allowing cities to embrace natural systems, they contribute to the resilience of urban landscapes.”

Rain Gardens: Integrating Water Saving into Stormwater Management

Rain gardens are not only effective tools for stormwater management and promoting biodiversity but also play a crucial role in water saving. As the world faces increasing water scarcity due to climate change and population growth, it becomes essential to adopt sustainable practices that help conserve water. Rain gardens offer a unique opportunity to achieve this by harnessing the power of natural systems to preserve and efficiently use water resources. This text explores how rain gardens contribute to water saving and why they are an integral part of sustainable water management strategies.

1. Capturing and Reusing Rainwater

One of the key ways rain gardens save water is by capturing and reusing rainwater that would otherwise be lost as runoff. In conventional urban landscapes, rainwater typically flows off impervious surfaces and is directed into storm drains, carrying pollutants and wasting precious water resources. However, rain gardens act as natural sponges, intercepting this rainfall and allowing it to infiltrate the soil.
By enabling rainwater to percolate into the ground, rain gardens support groundwater recharge, maintaining the water table and preventing depletion. This stored water can then be used by plants and trees, reducing the need for additional irrigation and supplementing natural water sources during dry periods.

 

2. Reducing Irrigation Demands

Rain gardens, once established, consist of carefully selected native plants and vegetation with deep root systems. These plants have adapted to the local climate and require less water than traditional ornamental species. As a result, rain gardens significantly reduce the need for irrigation, especially during rainy seasons.

According to research published in the journal Landscape and Urban Planning, “Rain gardens have been found to reduce irrigation demands by up to 30%, leading to substantial water savings in urban landscapes.”

 

3. Minimizing Water Loss through Evaporation

Traditional stormwater management systems, such as concrete channels and underground pipes, often lead to increased evaporation of rainwater. On the contrary, rain gardens retain water in the soil, reducing surface exposure and evaporation losses. This conservation of water ensures a more efficient use of this valuable resource.

 

4. Combining Rain Gardens with Rainwater Harvesting

To maximize water-saving potential, rain gardens can be integrated with rainwater harvesting systems. These systems collect and store rainwater from rooftops and other impervious surfaces, directing it into rain gardens for natural filtration and storage. The stored water can then be used for non-potable purposes like irrigation, toilet flushing, and outdoor cleaning, further reducing the demand for treated drinking water.

Rain gardens are not only aesthetically pleasing and ecologically beneficial but also crucial components of water-saving strategies in urban landscapes. By capturing, reusing, and efficiently managing rainwater, they contribute to groundwater recharge, reduce irrigation demands, and minimize evaporation losses. When combined with rainwater harvesting systems, rain gardens become powerful tools in creating sustainable and resilient communities that prioritize responsible water management.

Species choice

Rain gardens are designed to be sustainable and low-maintenance, making them ideal for using native plants that are well-suited to the local climate and soil conditions. The main species used in rain gardens will vary depending on the region and specific environmental factors, but here are some common examples of plants that are commonly used in rain gardens and their general cultivation requirements:

 

Purple Coneflower (Echinacea purpurea): A perennial native to North America, the Purple Coneflower is well-known for its attractive pink-purple flowers. It thrives in full sun to light shade and prefers well-draining soils. Once established, it has good drought tolerance.

Switchgrass (Panicum virgatum): Switchgrass is a warm-season, clump-forming grass native to North America. It is excellent for erosion control and has deep roots that help with water absorption. It prefers full sun to partial shade and adapts to a wide range of soil types.

Bee Balm (Monarda spp.): Also known as Wild Bergamot, Bee Balm is a perennial plant with showy, aromatic flowers that attract pollinators. It thrives in moist to wet soils and prefers full sun to partial shade.

Sedges (Carex spp.): Sedges are grass-like plants that come in various species. They are well-adapted to wet conditions and help with soil stabilization. Some common varieties include Pennsylvania Sedge (Carex pensylvanica) and Fox Sedge (Carex vulpinoidea).

Swamp Milkweed (Asclepias incarnata): This perennial plant is native to North America and is an essential food source for Monarch butterflies. It prefers moist to wet soils and thrives in full sun to partial shade.

Blue Flag Iris (Iris versicolor): This native iris species is often found in wetland areas and rain gardens. It produces beautiful blue or purple flowers and prefers full sun to partial shade.

Cardinal Flower (Lobelia cardinalis): A striking perennial with bright red flowers, Cardinal Flower is an excellent choice for rain gardens with moist soils and partial shade.

Black-Eyed Susan (Rudbeckia hirta): Black-Eyed Susan is a popular perennial with yellow flowers and a high tolerance for different soil conditions. It prefers full sun.

Suggested readings

Alyaseri, I., Zhou, J., Morgan, S. M., & Bartlett, A. (2017). Initial impacts of rain gardens’ application on water quality and quantity in combined sewer: Field-scale experiment. Frontiers of Environmental Science & Engineering, 11, 1-12.

Asleson, B. C., Nestingen, R. S., Gulliver, J. S., Hozalski, R. M., & Nieber, J. L. (2009). Performance assessment of rain gardens 1. JAWRA Journal of the American Water Resources Association, 45(4), 1019-1031.

Autixier, L., Mailhot, A., Bolduc, S., Madoux-Humery, A. S., Galarneau, M., Prévost, M., & Dorner, S. (2014). Evaluating rain gardens as a method to reduce the impact of sewer overflows in sources of drinking water. Science of the Total Environment, 499, 238-247.

Bąk, J., & Barjenbruch, M. (2022). Benefits, Inconveniences, and Facilities of the Application of Rain Gardens in Urban Spaces from the Perspective of Climate Change—A Review. Water, 14(7), 1153.

Carpenter, D. D., & Hallam, L. (2009). An investigation of rain garden planting mixture performance and the implication for design. In Low Impact Development for Urban Ecosystem and Habitat Protection (pp. 1-10).

Lariyah, M. S., & Norshafa, E. N. (2012, November). Constructed Rain Garden for Water Sensitive Urban Design (WSUD) as Stormwater Management in Malaysia: A Literature Review. In Proceedings of the National Graduate Conference, Universiti Tenaga Nasional, Putrajaya Campus, Kajang, Malaysia (pp. 8-10).

Mehring, A. S., & Levin, L. A. (2015). Potential roles of soil fauna in improving the efficiency of rain gardens used as natural stormwater treatment systems. Journal of Applied Ecology, 52(6), 1445-1454.

Morash, J., Wright, A., LeBleu, C., Meder, A., Kessler, R., Brantley, E., & Howe, J. (2019). Increasing sustainability of residential areas using rain gardens to improve pollutant capture, biodiversity and ecosystem resilience. Sustainability, 11(12), 3269.

Nemirovsky, E. M., Lee, R. S., & Welker, A. L. (2015). Vertical and lateral extent of the influence of a rain garden on the water table. Journal of Irrigation and Drainage Engineering, 141(3), 04014053.

Osheen, & Singh, K. K. (2019). Rain garden—a solution to urban flooding: a review. Sustainable Engineering: Proceedings of EGRWSE 2018, 27-35.

Sharma, R., & Malaviya, P. (2021). Management of stormwater pollution using green infrastructure: The role of rain gardens. Wiley Interdisciplinary Reviews: Water, 8(2), e1507.

Somes, N., Potter, M., Crosby, J., & Pfitzner, M. (2007). Rain garden: Design, construction and maintenance recommendations based on a review of existing systems. Rainwater and Urban Design 2007, 1043-1050.