Detention basin

A detention basin or retarding basin is an excavated area installed on, or adjacent to, tributaries of rivers, streams, lakes or bays to protect against flooding and, in some cases, downstream erosion by storing water for a limited period of time. These basins are also called "dry ponds", "holding ponds" or "dry detention basins" if no permanent pool of water exists. Detention ponds that are designed to permanently retain some volume of water at all times are called retention basins. In its basic form, a detention basin is used to manage water quantity while having a limited effectiveness in protecting water quality, unless it includes a permanent pool feature.[1]

Dry pond
Detention Basin

Functions and design

Detention basins are storm water best management practices that provide general flood protection and can also control extreme floods such as a 1 in 100-year storm event.[2] 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 urban 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 culverts and washes to handle the release of the contained water.[3]

Frequently the inflow area is constructed to protect the structure from some types of damage. Offset concrete blocks in the entrance spillways are used to reduce the speed of entering flood water. These structures may also have debris 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.

New approaches

Research has shown that detention basins built with real-time control of the outflow from the basin are significantly more effective at retaining total suspended solids and associated contaminants, such as heavy metals, when compared to basins without control.[4]

Extended detention basin

A variant basin design called an extended detention dry basin can limit downstream erosion and control of some pollutants such as suspended solids. This basin type differs from a retention basin, also known as a "wet pond," which includes a permanent pool of water, and which is typically designed to protect water quality.[5][6][7]

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.[5]

See also

References

  1. ^ United States Environmental Protection Agency. Washington, DC."National Menu of Stormwater Best Management Practices." Fact Sheet: "Dry Detention Ponds."
  2. ^ Atlanta Regional Commission. Atlanta, GA. "Georgia Stormwater Management Manual." Archived 2008-04-10 at the Wayback Machine Section 3.4.1: "Dry Detention / Dry ED Basins." August 2001.
  3. ^ Dykehouse, Terry, P.E. Jones and Edmunds, Gainesville, FL."Retention Ponds and Detention Ponds, The Recovery Process." Archived 2008-04-10 at the Wayback Machine
  4. ^ "Ecohydraulic-driven Real-Time Control of Stormwater Basins" (PDF). Universite Laval. Retrieved 11 January 2015.
  5. ^ a b 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.
  6. ^ James Worth Bagley College. "Detention Basins." Chapter 4: Best Management Practices. Agricultural and Biological Engineering, College of Agriculture and Life Sciences.
  7. ^ Minnesota Pollution Control Agency. "Stormwater Detention Ponds." Archived 2008-04-10 at the Wayback Machine Chapter 5, Minnesota State Permit Guidance Document.

External links

Boeing Creek

Boeing Creek is a stream in the U.S. state of Washington, located in the city of Shoreline, just north of Seattle. It is about 1.6 miles (2.6 km) long and empties into Puget Sound. The creek is heavily modified along its course, and in many places has been diverted into culverts. The watershed of Boeing Creek is about 11.2 square miles (29 km2) in size, with two main tributaries aside from the mainstem. The creek takes its name from William Boeing, who built a mansion along the creek in 1913. Despite the river modifications and stormwater pollution, the creek supports a variety of riparian habitats, native animals and fishes.

Boneyard Creek

Boneyard Creek is a 3.3-mile-long (5.3 km) waterway that drains much of the cities of Champaign and Urbana, Illinois. It is a tributary of the Saline Branch of the Salt Fork Vermilion River, which is a tributary of the south-flowing Vermilion River and the Wabash River. The creek flows through the northern sections of the campus of the University of Illinois at Urbana-Champaign. The newsletter of the university's ACM chapter is Banks of the Boneyard, named after the creek.

Brays Bayou

Brays Bayou is a slow-moving river in Harris County, Texas. A major tributary of Buffalo Bayou, the Brays flows for 31 miles (50 km) from the western edge of the county, south of Barker Reservoir along the border with Fort Bend County, east to its convergence with the Buffalo at Harrisburg. Nearly all of the river is located within the city of Houston; it is a defining geographic feature of many neighborhoods and districts, including Meyerland, Braeswood Place, the Texas Medical Center, and Riverside Terrace.

As a result of its central route through Harris County, the Brays Bayou watershed is heavily urbanized. Over 700,000 people reside within its 129-square-mile (330 km2) drainage area, which contains 124 miles (200 km) of open-channel waterway, mostly from artificial drainage channels. This high level of development, combined with a relative lack of flood control infrastructure, means Brays Bayou is extremely prone to flash flooding events.

Clark County Regional Flood Control District

The Clark County Regional Flood Control District (CCRFCD) was created in 1985 by the Nevada Legislature allowing Clark County to provide broad solutions to flooding problems. The District has developed plans and so far successfully continued working on a 50-year program to eliminate most flooding from a 100-year flood in the populated areas for which the CCRFCD is responsible.

Flood bypass

A flood bypass is a region of land or a large man-made structure that is designed to convey excess flood waters from a river or stream in order to reduce the risk of flooding on the natural river or stream near a key point of interest, such as a city. Flood bypasses, sometimes called floodways, often have man-made diversion works, such as diversion weirs and spillways, at their head or point of origin. The main body of a flood bypass is often a natural flood plain. Many flood bypasses are designed to carry enough water such that combined flows down the original river or stream and flood bypass will not exceed the expected maximum flood flow of the river or stream.

Flood bypasses are typically used only during major floods and act in a similar nature to a detention basin. Since the area of a flood bypass is significantly larger than the cross-sectional area of the original river or stream channel from which water is diverted, the velocity of water in a flood bypass will be significantly lower than the velocity of the flood water in the original system. These low velocities often cause increased sediment deposition in the flood bypass, thus it is important to incorporate a mantaince program for the entire flood bypass system when it is not being actively used during a flood operation.

When not being used to convey water, flood bypasses are sometimes used for agricultural or environmental purposes. The land is often owned by a public authority and then rented to farmers or ranchers, who in turn plant crops or herd livestock that feed off the flood plain. Since the flood bypass is subjected to sedimentation during flood events, the land is often very productive and even a loss of crops due to flooding can sometimes be recovered due to the high yield of the land during the non-flood periods.

Floodgate

Floodgates, also called stop gates, are adjustable gates used to control water flow in flood barriers, reservoir, river, stream, or levee systems. They may be designed to set spillway crest heights in dams, to adjust flow rates in sluices and canals, or they may be designed to stop water flow entirely as part of a levee or storm surge system. Since most of these devices operate by controlling the water surface elevation being stored or routed, they are also known as crest gates. In the case of flood bypass systems, floodgates sometimes are also used to lower the water levels in a main river or canal channels by allowing more water to flow into a flood bypass or detention basin when the main river or canal is approaching a flood stage.

Infiltration basin

An infiltration basin (also known as a recharge basin or in some areas, a sump or percolation pond), is a type of device that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. It is essentially a shallow artificial pond that is designed to infiltrate stormwater through permeable soils into the groundwater aquifer. Infiltration basins do not release water except by infiltration, evaporation or emergency overflow during flood conditions.It is distinguished from a detention basin, sometimes called a dry pond, which is designed to discharge to a downstream water body (although it may incidentally infiltrate some of its volume to groundwater); and from a retention basin, which is designed to include a permanent pool of water.

Kanimbla, Queensland

Kanimbla is a suburb of Cairns in the Cairns Region, Queensland, Australia. In the 2016 census, the population of Kanimbla was 2,670 people.

Las Vegas Wash

Las Vegas Wash is a 12-mile-long channel which feeds most of the Las Vegas Valley's excess water into Lake Mead. The wash is sometimes called an urban river, and it exists in its present capacity because of an urban population. The wash also works in a systemic conjunction with the pre-existing wetlands that formed the oasis of the Las Vegas Valley. The wash is fed by urban runoff, shallow ground water, reclaimed water, and stormwater.The wetlands of the Las Vegas Valley act as the kidneys of the environment, cleaning the water that runs through it. The wetlands filter out harmful residues from fertilizers, oils, and other contaminants that can be found on the roadways and in the surrounding desert.

Near its terminus at Las Vegas Bay, the wash passes under the man made Lake Las Vegas through two 7-foot pipes.

Media filter

A media filter is a type of filter that uses a bed of sand, peat, shredded tires, foam, crushed glass, geo-textile fabric, anthracite, crushed granite or other material to filter water for drinking, swimming pools, aquaculture, irrigation, stormwater management, oil & gas operations, and other applications.

New Jersey stormwater management rules

The New Jersey stormwater management rules were organized in 1983 and updated in 2004. The rules restrict building within 300-foot of "high quality water"; and stormwater and parking lot runoff at new developments must be diverted to a retention basin or a detention basin that are used for groundwater recharge to replenish the aquifer. The detention basins have the added effect of filtering urban runoff from parking lots of motor oil and other chemicals that would end up in storm sewers and eventually rivers and streams.

Overton Park

Overton Park may also refer to the U.S. Supreme Court case, Citizens to Preserve Overton Park v. VolpeOverton Park is a large, 342-acre (138 ha) public park in Midtown Memphis, Tennessee. The park grounds contain the Memphis Brooks Museum of Art, Memphis Zoo, a 9-hole golf course, the Memphis College of Art, Rainbow Lake, Veterans Plaza, the Greensward, and other features. The Old Forest Arboretum of Overton Park, one of the few remaining old growth forests in Tennessee, is a natural arboretum with labeled trees along trails.

Retention basin

A retention basin, sometimes called a wet pond, wet detention basin or stormwater management pond, is an artificial lake with vegetation around the perimeter, and includes a permanent pool of water in its design. It is used to manage stormwater runoff to prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay.

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.In urban areas, impervious surfaces (roofs, roads) reduce the time spent by rainfall before entering into the stormwater drainage system. If left unchecked, this will cause widespread flooding downstream. The function of a stormwater pond is to contain this surge and release it slowly. This slow release mitigates the size and intensity of storm-induced flooding on downstream receiving waters. Stormwater ponds also collect suspended sediments, which are often found in high concentrations in stormwater water due to upstream construction and sand applications to roadways.

Sediment basin

A sediment basin is a temporary pond built on a construction site to capture eroded or disturbed soil that is washed off during rain storms, and protect the water quality of a nearby stream, river, lake, or bay. The sediment-laden soil settles in the pond before the runoff is discharged. Sediment basins are typically used on construction sites of 5 acres (20,000 m2) or more, where there is sufficient room. They are often used in conjunction with erosion controls and other sediment control practices. On smaller construction sites, where a basin is not practical, sediment traps may be used.Essential sediment abundance is prevalent in the construction industry which gives insight to future endeavors.

On some construction projects, the sediment basin is cleaned out after the soil disturbance (earth-moving) phase of the project, and modified to function as a permanent stormwater management system for the completed site, either as a detention basin or a retention basin.

Stormwater detention vault

A stormwater detention vault is an underground structure designed to manage excess stormwater runoff on a developed site, often in an urban setting. This type of best management practice may be selected when there is insufficient space on the site to infiltrate the runoff or build a surface facility such as a detention basin or retention basin.Detention vaults manage stormwater quantity flowing to nearby surface waters. They help prevent flooding and can reduce erosion in rivers and streams. They do not provide treatment to improve water quality, though some are attached to a media filter bank to remove pollutants.

Sustainable drainage system

Sustainable drainage systems (also known as SuDS, SUDS, or sustainable urban drainage systems) are a collection of water management practices that aim to align modern drainage systems with natural water processes. SuDS efforts make urban drainage systems more compatible with components of the natural water cycle such as storm surge overflows, soil percolation, and bio-filtration. These efforts hope to mitigate the effect human development has had or may have on the natural water cycle, particularly surface runoff and water pollution trends. SuDS have become popular in recent decades as our understanding of how urban development affects natural environments, as well as concern for climate change and sustainability, have increased. SuDS often use built components that mimic natural features in order to integrate urban drainage systems into the natural drainage systems or a site as efficiently and quickly as possible.

The Lakes, Copenhagen

The Lakes (Danish: Søerne) in Copenhagen, Denmark are a row of three rectangular lakes curving around the western margin of the City Centre, forming one of the oldest and most distinctive features of the city's topography. The paths around them are popular with strollers, bikers and runners.

Stormwater management structures
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