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Rain Garden

What is a rain garden?

The first rain garden's were copied off the natural versions before a building development in the area of Maryland, it was a developer who had the idea to replace the originals with a bio-retention area in 1990.

A "rain garden" is a planted depression, that improve's water quality by allowing rainwater run off from roofs, walkways, driveways, lawn area's and any other compacted urban area's the chance to be absorbed. A rain garden creates a "bio-retention area" by collecting the water runoff and storing it, and releasing it slowly into the soil. Basically rain garden's help cut down on pollution reaching our streams and creaks by up to 30%, by allowing the water to be absorbed by soil it alleviates flooding, water pollution and water erosion. A selection of native plants are ideal for rain garden's like fern's, wild flowers, rushes, and small trees as they don't need fertilizer, and are used to the water conditions, soil and climate.

When the water comes into contact with the soil and the roots of the shrubs and trees a filtering process takes place. The water filters through the soil layers and the root systems encourage infiltration and enhance moisture distribution. This process is the reason behind the improved quality of the water. The first rain shower collects like a pond in the depression of the rain garden, and contains the highest quantity of concentration of materials washed off urban surfaces like roads, walkway's, roofs, driveways and parking lots.

Backyard's Rain Garden

Who Needs to Create A Rain Garden?

Rain gardens are suitable for commercial, residential and industrial land use. The site for a rain garden should be in a strategic position to intercept the rain water and drain it straight into the depression area. This method will help to minimize the volume and improve the water quality that normally enters storm drains. creaks and streams. A rain garden is also a great opportunity for children to be involved in protecting our planet.

Ponding area

A grass buffer strip is usually created to slow the water entering the rain garden filtering the particles in the process. The particles in the material not filtered by the buffer is allowed to settle in the bottom of the depression. The deepest area of the rain garden should have a sufficient depth of 6 inches, and to avoid mosquito's breeding water should not pond further than four days.

For best results place rain gardens on a small slope about 10 feet from the building.

Components needed to create a rain garden

Mulch/Organic Layer

Apart from the decomposition of organic material, mulch plays a big part in the removal of metals. Applied properly mulch retains moisture by shading the soil from the hot sun therefore preventing evaporation. Mulch also evens out moisture levels so the plants enjoy the environment where the roots can spread as required. To reduce the amount of water needed for the plants to thrive it's recommended to use cedar mulch.

Weed Suppression

Planting Soil

The planting soil mixture has to provide water and nutrients for the plants to thrive. The recommended combination is 20% organic leaf mulch blended with 50% of sandy soil and 30% of top soil, this mixture will promote good drainage and help the breakdown of pollutants. Clay content will absorb heavy metals, and other pollutants, but it also inhibits drainage so do not exceed 10%.

Constructing a Rain Garden

Choosing a selection of plants

Your plants should be tolerant of the environment, soil, weather and add landscape value. Also bare in mind when choosing plants that there will be some dry periods. Your choice of plants should include plants nectar rich to encourage bees, butterflies and humming birds, and include flowers, berries, interesting leaves or bark. Groundcovers, shrubs, small trees and perennials like winter berry holly, and royal fern should be included in your plant design.

Garden Rain Flower

Rain Garden Placements

You should make each garden unique. The size of the garden will be influenced by the plant selection process, the drainage area, light, wind and temperature. The area for bio-retention is more important than the size of the garden and should be about 5/7% of the drainage area.

Resources for Creating a Rain Garden

An excellent resource for choosing which plants to put in your rain garden: Mason, Rich, and Hitchcock, Jason. Native Plants for Wildlife Habitat. Annapolis: U.S. Fish and Wildlife Service, 1995. www.fws.gov

What Is a Rain Garden? Virginia Department of Forestry. www.dof.virginia.gov.

Rain Gardens Organization, there you can search information about rain gardens process: www.raingardens.org

Used to build rain gardens, Center for Neighborhood Technology is a organization for urban sustainability: www.cnt.org/

Here you can find a manual for homeowners and a household way to improve water quality in your community: clean-water.uwex.edu/pubs/home.htm#rain