Rain gardens are shallow depressions in the landscape that typically include plants and a mulch layer or ground cover. In addition to providing increased groundwater recharge, they are expected to provide pollutant treatment. Pollutant treatment in rain gardens has been attributed to adsorption, decomposition, ion exchange, and volatilization (Prince George's County Bioretention Manual, 2002). Rain gardens can be used in residential settings to accept runoff from a roof or other impervious surface. In a commercial setting, bioretention areas are similar to rain gardens, but are often larger, and have an engineered design.
Pollution is the undesirable state of the natural environment being contaminated with harmful substances, often as a result of human activity.
When stormwater (water that originated during precipitation events or from snow melt) moves over pavement, it picks up and carries with it fertilizer, pathogens, toxic contaminants, sediment and other pollutants before entering storm drains. These drains lead directly to waterways which lead to Long Island Sound. Polluted runoff can harm aquatic life and make the Sound unsuitable for fishing and swimming.
As a result of global climate changes, scientists predict that precipitation will increase in the Northeast U.S., leading to a greater volume of runoff. This presents a challenge, since more runoff means more pollution that can enter the Sound. Simply put, the more rain gardens, the less polluted runoff.