Land use in the United States has dramatically changed in the past 25 years. As natural areas are developed and turned into parking lots, driveways, and houses, more impervious surfaces are created, generating increased amounts of polluted runoff. This increased volume of runoff enters streams at a much faster rate than previously. In a natural setting, rain falls on vegetation and is either captured by plants or infiltrated into the soil. In a developed community, stormwater runoff can cause flooding that is known to scour streambanks and cause erosion. The water that runs over lawns, ball fields, roofs, parking lots, and golf courses collects and deposits pollutants such as oil, sediment, fertilizers, trash, debris, and chemicals into nearby waterways. Managing stormwater to prevent pollution and flooding is a key aspect of most development projects.*
The Importance of Stormwater Management
Stormwater management is the science of managing stormwater runoff to prevent adverse impacts on the environment. The main goal is to manage water quantity in addition to protecting water quality. For development in the last 20 to 30 years, the construction of stormwater management ponds (or basins) on the site has been the preferred stormwater management practice. Initially, the focus was on managing the rate of runoff from a development to prevent flooding and erosion. More recently, ponds were modified to address water quality issues in addition to quantity concerns. The concept is simple: convey stormwater runoff to a containment area where nonpoint source pollutants, such as sediment, can settle out. Clean water can then be slowly released into the nearest waterway. These facilities were typically one of three types: wet ponds, infiltration basins, and dry ponds. Recently, another category of stormwater management facilities has become widely used. They are collectively referred to as “green technology” and address water quality through more natural means such as infiltration.