A
detention basin is a
stormwaterStormwater is a term used to describe water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt or runoff water from overwatering that enters the stormwater system...
management facility installed on, or adjacent to, tributaries of
riverA river is a natural watercourse, usually freshwater, flowing toward an ocean, a lake, a sea or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water...
s,
streamA stream is a flowing body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, kill, lick, rill, river syke, bayou, rivulet, or run...
s,
lakeA lake is a terrain feature , a body of liquid on the surface of a world that is localized to the bottom of basin and moves slowly if it moves at all. Another definition is, a body of fresh or salt water of considerable size that is surrounded by land...
s or
bayA bay is an area of water mostly surrounded or otherwise demarcated by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds....
s that is designed to protect against
floodA flood is an overflow or accumulation of an expanse of water that submerges land. In the sense of "flowing water", the word may also be applied to the inflow of the tide....
ing and, in some cases, downstream
erosionErosion is a gravity driven process that moves solids in the natural environment or their source and deposits them elsewhere...
by storing water for a limited period of a time. These basins are also called "dry ponds", "holding ponds" or "dry detention basins" if no permanent pool of water exists. Some detention ponds are also "wet ponds" in that they are designed to permanently retain some volume of water at all times.
A
detention basin is a
stormwaterStormwater is a term used to describe water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt or runoff water from overwatering that enters the stormwater system...
management facility installed on, or adjacent to, tributaries of
riverA river is a natural watercourse, usually freshwater, flowing toward an ocean, a lake, a sea or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water...
s,
streamA stream is a flowing body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, kill, lick, rill, river syke, bayou, rivulet, or run...
s,
lakeA lake is a terrain feature , a body of liquid on the surface of a world that is localized to the bottom of basin and moves slowly if it moves at all. Another definition is, a body of fresh or salt water of considerable size that is surrounded by land...
s or
bayA bay is an area of water mostly surrounded or otherwise demarcated by land. Bays generally have calmer waters than the surrounding sea, due to the surrounding land blocking some waves and often reducing winds....
s that is designed to protect against
floodA flood is an overflow or accumulation of an expanse of water that submerges land. In the sense of "flowing water", the word may also be applied to the inflow of the tide....
ing and, in some cases, downstream
erosionErosion is a gravity driven process that moves solids in the natural environment or their source and deposits them elsewhere...
by storing water for a limited period of a time. These basins are also called "dry ponds", "holding ponds" or "dry detention basins" if no permanent pool of water exists. Some detention ponds are also "wet ponds" in that they are designed to permanently retain some volume of water at all times. In its basic form a detention basin is used to manage water quantity while having a limited effectiveness in protecting
water qualityWater quality is the physical, chemical and biological characteristics of water. It is most frequently used by reference to a set of standards against which compliance can be assessed...
, unless it includes a permanent pool feature.
Functions and design
Detention basins are storm water
best management practicesBest Management Practices is a term used in the United States to describe a type of water pollution control. Historically the term has referred to auxiliary pollution controls in the fields of industrial wastewater control and municipal sewage control, while in stormwater management and wetland...
(BMPs) that provide general flood protection and can also control extreme floods such as a 1 in 100-year storm event. The basins are typically built during the construction of new land development projects including residential subdivisions or shopping centers. The ponds help manage the excess runoff generated by newly-constructed impervious surfaces such as roads, parking lots and rooftops.
A basin functions by allowing large flows of water to enter but limits the outflow by having a small opening at the lowest point of the structure. The size of this opening is determined by the capacity of underground and downstream
culvertA culvert is a conduit used to enclose a flowing body of water. It may be used to allow water to pass underneath a road, railway, or embankment for example. Culverts can be made of many different materials; steel, polyvinyl chloride and concrete are the most common...
s and
washesAn arroyo , also called a wash or draw, is a usually dry creek bed or gulch that temporarily fills with water after a heavy rain, or seasonally. As such, the term is similar to the word wadi. Arroyos can be natural or man-made. The term usually applies to a mountainous desert environment...
to handle the release of the contained water.
Frequently the inflow area is constructed to protect the structure from some types of damage. Offset
concreteConcrete is a construction material composed of cement as well as other cementitious materials such as fly ash and slag cement, aggregate , water, and chemical admixtures...
blocks in the entrance spillways are used to reduce the speed of entering flood water. These structures may also have
debrisDebris is a word used to describe the remains of something that has been otherwise destroyed. The singular form of debris is debris.Depending on context, debris can refer to a number of different things.- Geological :...
drop vaults to collect large rocks. These vaults are deep holes under the entrance to the structure. The holes are wide enough to allow large rocks and other debris to fall into the holes before they can damage the rest of the structure. These vaults must be emptied after each storm event.
Extended detention basin
A variant basin design called an
extended detention dry basin can limit downstream erosion and control of some
pollutantsWater pollution is the contamination of water bodies such as lakes, rivers, oceans, and groundwater. All water pollution affects organisms and plants that live in these water bodies and in almost all cases the effect is damaging either to individual species and populations but also to the natural...
such as
suspended solidsSuspended solids refers to small solid particles which remain in suspension in water as a colloid or due to the motion of the water. It is used as one indicator of water quality....
. This basin type differs from a
retention basinA retention basin, is a type of best management practice that is used to manage stormwater runoff to prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay...
, also known as a "wet pond," which includes a permanent pool of water, and which is typically designed to protect water quality.
While basic detention ponds are often designed to empty within 6 to 12 hours after a storm, extended detention (ED) dry basins improve on the basic detention design by lengthening the storage time, for example, to 24 or 48 hours. Longer storage times tend to result in improved water quality because additional suspended solids are removed.
See also
- Best management practice for water pollution
Best Management Practices is a term used in the United States to describe a type of water pollution control. Historically the term has referred to auxiliary pollution controls in the fields of industrial wastewater control and municipal sewage control, while in stormwater management and wetland...
- Retention basin
A retention basin, is a type of best management practice that is used to manage stormwater runoff to prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay...
- River reclamation
River Reclamation or River Restoration is a process to improve water quality and habitat conditions of rivers.The construction of new buildings and new roads increases the extent of impervious surfaces...
- Sustainable urban drainage systems
Sustainable Drainage Systems , sometimes known as Sustainable Urban Drainage Systems , are designed to reduce the potential impact of new and existing developments with respect to surface water drainage discharges....
External links