Each time it rains, large quantities water flows off impermeable surfaces such as roofs, driveways and patios. On its way to nearest storm drain, it collects garden chemicals, oils, dirt and bacteria which in many cases end up directly in nearby rivers or other bodies of water. These chemicals can have a devastating effect on the organisms, fish and wildlife that call the river home. Rain gardens can prevent some of this water from reaching the storm drain in the first place, creating healthier waterways.
A rain garden is nothing like a water garden, pond or wetland, in fact the majority of the time it’s dry. Planted in a small depression, the garden contains native shrubs, perennials and flowers and is most often found on a natural slope. The garden only holds water for a short period of time during and immediately after it rains. The advantage of a rain garden is that it allows the collection of rainwater so that it can slowly percolate into the ground, recharging underground aquifers. The gardens have been proven effective at removing 90 per cent of chemicals from rainwater runoff and up to 80 per cent of sediments, neither of which we want flowing into our rivers and streams.
This excerpt is from a recent post on the St. Albert Leader's website. Go Here for the full article: http://www.stalbertleader.com/2013/05/02/rain-gardens-combine-form-and-function/
Also remember to check out Gravel-Lok for your stone scaping projects. It bonds natural stones in place but still allows water to pass through creating a beautiful, permeable surface.