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A retention basin is used to manage stormwater runoff to prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. Sometimes called a wet pond or wet detention basin, it is an artificial lake with vegetation around the perimeter, and includes a permanent pool of water in its design.〔(Water Environment Federation ), Alexandria, VA; and (American Society of Civil Engineers ), Reston, VA. ("Urban Runoff Quality Management." ) WEF Manual of Practice No. 23; ASCE Manual and Report on Engineering Practice No. 87. 1998. ISBN 1-57278-039-8. Chapter 5.〕〔U.S. Environmental Protection Agency. Washington, D.C. ("Preliminary Data Summary of Urban Storm Water Best Management Practices." ) Chapter 5. August 1999. Document No. EPA-821-R-99-012.〕 It is distinguished from a detention basin, sometimes called a "dry pond," which temporarily stores water after a storm, but eventually empties out at a controlled rate to a downstream water body. It also differs from an infiltration basin which is designed to direct stormwater to groundwater through permeable soils. Wet ponds are frequently used for water quality improvement, groundwater recharge, flood protection, aesthetic improvement or any combination of these. Sometimes they act as a replacement for the natural absorption of a forest or other natural process that was lost when an area is developed. As such, these structures are designed to blend into neighborhoods and viewed as an amenity.〔Mississippi State University. College of Engineering. (Stormwater Retention Basins. Chapter 4, Best Management Practices. )〕 ==Design features== Storm water is typically channeled to a retention basin through a system of street and/or parking lot storm drains, and a network of drain channels or underground pipes. The basins are designed to allow relatively large flows of water to enter, but discharges to receiving waters are limited by outlet structures that function only during very large storm events. Retention ponds are often landscaped with a variety of grasses, shrubs and/or wetland plants to provide bank stability and aesthetic benefits. Vegetation also provides water quality benefits by removing soluble nutrients through uptake.〔(Urban Drainage & Flood Control District ), Denver, CO. (Urban Storm Drainage Criteria Manual. Volume 3, Structural BMPs. )〕 In some areas the ponds can attract nuisance types of wildlife like ducks or Canada geese, particularly where there is minimal landscaping and grasses are mowed. This reduces the ability of foxes, coyotes and other predators to approach their prey unseen. Such predators tend to hide in the cattails and other tall, thick grass surrounding natural water features. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「retention basin」の詳細全文を読む スポンサード リンク
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