When the accumulation of rain flows over the parking lots and roads, it washes pollutants into bodies of water. How is the pollution classified?
Answers
One of the wide variety of soil-absorption/filter systems, a rain garden, also called a stormwater garden,[1] is a designed depression storage or a planted hole that allows rainwater runoff from impervious urban areas, like roofs, driveways, walkways, parking lots, and compacted lawn areas, the opportunity to be absorbed. The primary purpose of a rain garden is to improve water quality in nearby bodies of water and to ensure that rainwater becomes available for plants as groundwater rather than being sent through stormwater drains straight out to sea. In fact, it can actually reduce rain runoff by allowing stormwater to soak into the ground (as opposed to flowing into storm drains and surface waters which causes erosion, water pollution, flooding, and diminished groundwater)[2] and cut down on the amount of pollution reaching creeks and streams by up to 30%.[3]
The plants—a selection of wetland edge vegetation, such as wildflowers, sedges, rushes, ferns, shrubs and small trees—take up excess water flowing into the rain garden. Water filters through soil layers before entering the groundwater system. Deep plant roots also create additional channels for stormwater to filter into the ground. Root systems enhance infiltration, maintain or even augment soil permeability, provide moisture redistribution, and sustain diverse microbial populations involved in biofiltration.[4] Microbial populations feed off plant root secretions and break down carbon (such as in mulch or desiccated plant roots) to aggregate soil particles which increases infiltration rates. Also, through the process of transpiration, rain garden plants return water vapor to the atmosphere.[5]
A more wide-ranging definition covers all the possible elements that can be used to capture, channel, divert, and make the most of the natural rain and snow that falls on a property. Thus, the whole garden can become a rain garden, and each component of the whole can become a small-scale rain garden in itself.