This is a fantastic article about Rain Gardens. The article source is from Canada Mortgage and Housing Corporation (CMHC) and is very informative.

Rain Gardens: Improve Stormwater Management in Your Yard

Stormwater refers to rain and melted snow and ice. Stormwater runoff from your roof, driveway and other hard surfaces in your yard is typically directed towards the street and into the municipal storm sewer system. This stormwater runoff, which has picked up harmful substances such as road salt, heavy metals and oils, ends up in streams, lakes or other water bodies, where it can harm water quality and aquatic habitat. Meanwhile, water used for lawns and gardens is drawn from the local drinking water supply.

There are several ways that you can reduce runoff and better use stormwater in your yard while ensuring proper drainage. One relatively easy and attractive method is a rain garden (Figure 1).

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A rain garden is a planted or stonecovered bed specifically designed to receive stormwater and allow it to be slowly absorbed into the soil (infiltration). This About Your House provides information on designing and building a rain garden, as well as tips for improving stormwater management in your yard.

Let Nature Inspire You

In the natural hydrologic cycle, stormwater slowly infiltrates into the soil. There, it is naturally filtered and cleansed of some pollutants, is used by plants and replenishes the water table. Stormwater also falls directly into water bodies or gradually reaches them over land or through the shallow water table (Figure 2).

hydrologiccycle

 

 

 

 

 

 

 

 

 

 

 

 

 

 

In contrast, stormwater runoff in settled areas usually flows quickly from hard surfaces, such as roofs and driveways, into sewers that eventually empty into water bodies. The increased volume and frequency of high flows can cause erosion and related sedimentation in receiving lakes and rivers. Along the way, the water also picks up polluting substances, such as de-icing salt, grease and oil, animal wastes, excess sediments, pesticides and fertilizers. In areas with combined storm and sanitary sewers, the system can sometimes become overloaded, so that untreated sanitary sewage overflows into natural water bodies. All of these factors can harm water quality, habitat for aquatic species and the stability of shorelines and riverbanks. They also increase municipal costs to convey and treat stormwater.

There is a growing trend towards designing municipal stormwater systems to work with natural processes. These systems involve the use of wetlands and other methods that allow water to soak into the ground, filter pollutants and slow the flow of water before it enters water bodies.

Rain gardens are one way that you can reduce runoff and let stormwater soak slowly into the ground, as it does in nature, in your home landscape. Rain gardens are shallow depressions or lowlying areas that are designed to capture and absorb stormwater fairly quickly and dry out between rainfalls. When planted, they can also provide habitat for birds, butterflies and other fauna.

Steps in Designing a Rain Garden

Rain gardens are relatively easy and inexpensive to design and build, but there are a few considerations to ensure that they function effectively. The two most critical technical considerations are:

  1. Water must infiltrate and not stand in the bed for more than two days.
  2. Water should not create drainage problems on your property or neighbouring ones.

Beyond that, rain gardens can be naturalistic or more manicured, can include a variety of plants, and can be in various shapes.