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Rain Gardens
Managing Stormwater in Annapolis Royal (Managing Water Resources in a Climate Changed World: An Annapolis Pilot Project) focused on demonstrating creative storm and rainwater runoff management techniques. One of the goals of this project was to improve the quality of storm water before it enters other watercourses. Another goal was to divert rainwater runoff from the storm water treatment system and use it effectively for lawn and garden irrigation.

Rain gardens are a unique approach to storm water management. The land has natural drainage patterns that develop through soil/rock composition, vegetation and climate. As a region is developed drainage patterns can change. Parking lots, roads, and roofs that do not absorb water can affect where water travels and how quickly (or slowly) water will drain. Some surfaces, like roads, can carry noxious substances (salt, motor oil, etc) and occasionally in high concentrations. The 'first flush phenomenon' describes the usually high concentration of pollutants in the first half-inch of runoff relative subsequent runoff. If this water is directed into a storm water sewer in Annapolis Valley it is going right out into the Annapolis River untreated.

A rain garden is an aesthetically pleasing collection of water loving plants that filter storm and rain water and allow it to infiltrate the ground. They are often situated to receive runoff from rooftops or impervious surfaces like driveways or parking lots. This allows water to slow down and debris to fall out of suspension. Rain gardens can be paired with vegetated swales or check dams to further reduce water velocity.

Native plants are recommended for rain gardens because they are adapted to our soils, climatic patterns and require little maintenance beyond the first year or so of planting. These plants encourage and support native biodiversity by offering cover, habitat and a source of food. An excellent candidate for a rain garden is the common cattail (typha latifolia). Not only does it thrive in wet environments but also its roots take up heavy metals and can sequester them for centuries if undisturbed. However, there are many attractive flowering plants such as turtlehead (chelone glabra) or marsh marigold (caltha palustris) that give a rain garden a more traditional look.

There are a variety of native plants that are suitable for a rain garden. This table includes species that are commercially available in Nova Scotia. The table describes natural habitats and soil preferences of each plant. More information such as bloom time, height and sun/shade preferences are readily available. Wild plant harvesting is not recommended unless performed by a professional botanist.

Normally, rain gardens are planted in a depression (usually it needs to be dug to appropriate depth) to receive overland run off flow. They are divided into three zones based on depth and moisture (Figure 1). The lowest area of rain garden is the wettest zone and is suitable for plants that can survive with submerged roots. The next zone is the slope of the rain garden. This is commonly a 3:1 slope ratio and is often still moist and rarely covered by standing water. The third zone is roughly level with the rest of the lawn and will be the driest part of the rain garden.


Figure 1. Schematic illustration of rain garden with three zones indicated.



























Aside from the obvious environmental benefits of improving water quality and more efficiently using water, potential effects of climate change are mitigated. In the report Historical and Projected Temperature and Precipitation Trends in the Annapolis Valley, Nova Scotia, Mehlman (2003) projected that there would be an increase in the number of warm and very warm days in the summer. The same amount of precipitation would fall but in fewer events. This would mean that more rain would fall in a single event, which could result in localized flooding. Rain gardens can aid in slowing floodwaters, filtering out pollutants and in some cases may also be able to absorb some of the excess water depending on plant composition. A good instruction manual on how to create your own rain garden can be found here.

Rain Barrels

Rain barrels are any sort of holding tank that collects water during a rain event. Rain barrels can be as simple as an old plastic drum fitted with a cover and spigot. An instruction manual on how to build your own rain barrel can be downloaded here. Most home hardware and home improvement centres sell rain barrels. Prices range from $70-$500. The styles, size and colours are incredibly diverse and can easily be integrated into your yard.

Not only do these rain barrels reduce water use costs but also they provide an important environmental service by reducing the use of potable water for outdoor use. Care is relatively simple. Keep openings covered to prevent mosquitoes, leaf litter and other animals out of the barrel. Keep the spigot and downspout clear of any debris. Take it out of operation in the winter. More in depth maintenance tips are available here.

Cisterns

Like rain barrels, cisterns are tanks designed to collect and store water. Cisterns tend to have a much greater capacity than rain barrels, some being 7500 litres or more. Cisterns require more elaborate installation than rain barrels and are suited for larger operations such as ornamental gardens, nurseries, municipalities with public gardens or planters and agricultural operations. Rainwater collected in cisterns is suitable for purposes such as irrigation and washing items such as cars, but it is unsuitable for consumption by humans or livestock without treatment.

Cisterns, like rain gardens and rain barrels, help reduce stormwater inputs and use of potable water for irrigation. Unlike rain barrels and rain gardens, they are large scale and generally require the services of a contractor or an engineer. They can be installed above ground and be gravity-fed, or they can be installed underground and use a pump to move water. Cisterns can be custom-built or purchased ready-made, and can be made out of a variety of materials. More information on cisterns can be found here.

Project Reports

Managing Water Resources in a Climate Changed World: An Annapolis Pilot Project


Project Information

How to Make Your Own Rain Barrel - Managing Water Resources in a Climate Changed World

Cisterns - Everything You Need to Know


Acknowledgements

This project has been made possible by the support and participation of:

Environment Canada's EcoAction Community Fund
Town of Annapolis Royal
Peter and Jane Nicholson
Joy Elliott Landscape Architectural Design
Annapolis Home Hardware
Annapolis Royal Historic Gardens
Lou Sullivan
Town of Annapolis Royal Department of Public Works
Staff of Clean Annapolis River Project

References

Evergreen Native Plant Database retrieved August 10-21, 2009 from http://www.evergreen.ca/nativeplants/

Mehlman S. (2003). Historical and Projected Temperature and Precipitation Trends in the Annapolis Valley, Nova Scotia. Retrieved on August 25, 2009 from http://www.annapolisriver.ca/downloads/climate_change_2003.pdf

Pennsylvania Department of Environmental Protection Stormwater Management Manual (2007). Recharge Garden/Rain Garden/Bioretention Garden. It was retrieved on August 25, 2009 from http://www.elibrary.dep.state.pa.us/dsweb/Get/Document-48477/07_Chapter_6.pdf

Washington State University Pierce County Watershed Stewards. Planting the Garden. Retrieved on August 25, 2009 from http://www.pierce.wsu.edu/Water_Quality/WSS/index.htm
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