Consumer Voice :: Sacred Groves

<<Back to index

“A little bit of Nature in the heart of the city”
WHAT ARE RAIN GARDENS???
A "rain garden" is a man-made depression in the ground that is used as a landscape tool to improve water quality. The rain garden forms a "bioretention area" by collecting water runoff and storing it, permitting it be filtered and slowly absorbed by the soil. The bioretention concept is based on the hydrologic function of forest habitat, in which the forest produces a spongy litter layer that soaks up water and allows it to slowly penetrate the soil layer. The site for the rain garden should be placed strategically to intercept water runoff.
A nutrient removal or "filtering" process takes place as the water comes in contact with the soil and the roots of the trees, shrubs and vegetation. This process accounts for the improved water quality. The first flush of rain water is ponded in the depression of the rain garden, and contains the highest concentration of materials washed off impervious surfaces such as roofs, roads, and parking lots.
Who Should Create A Rain Garden?
Rain gardens are suitable for any land use situation, residential, commercial and industrial. A rain garden should be placed so that impervious surfaces will drain into the depression area. Its purpose is to minimize the volume and improve the quality of water entering conventional storm drains and nearby streams. It is actually a form of water harvesting geared to garden needs. It is specially useful as there is very little soft-?? or soil open to the rain water.
Grass buffer strip
A grass buffer strip slows water as it enters the rain garden and its surface filters particulates from the runoff.
Ponding area
The depression area stores the water, provides for evaporation, and allows the particulate material, not filtered by the grass buffer, to settle to the bottom. The ponding area should have a depth of 6 inches, sufficient to provide adequate water storage, but should not pond in excess of four days (to avoid mosquito and other insect breeding).
Components of a Rain Garden

Mulch/Organic Layer
This material provides for the decomposition of organic material, and also plays an important role in the removal of metals. Shredded hardwood mulch is the preferred choice, since it allows for maximum surface area for binding and resists flotation/washout.