Detention basin is a empty excavated area near water bodies such as rivers, lakes and streams. It is also called retarding basin. These basins mostly remain dry. When it rains heavily, the basin get filled with water. Detention basins reduce the potential for flooding of surrounding areas. The detention basin is an empty pond. A basin that ...Opening a new coal mine—even one with a relatively modest A$2 billion price tag—is socially and environmentally irresponsible. Indian mining multinational Adani has announced that ...Bioretention practices, such as rain gardens, are landscaped depressions that treat on-site stormwater discharge from impervious surfaces such as roofs, driveways, sidewalks, parking lots and compacted lawns. They are used to collect stormwater and filter it through a mixture of soil, sand and/or gravel. The designs of bioretention practices ...q o = Outflow, or post-development peak discharge downstream of detention ponds; often the pre-development peak discharge is used as this value [L 3 /T]. V r = Runoff Volume [L 3]. V s = Detention Storage Volume [L 3]. SCS (1986) provides equations and a graph for V s / …Pond volume is critical for basins operate as plug flow systems; while the pond surface area is critical for sediment basins that operate as continuous flow systems. ... period—for example as a stormwater detention/retention system—then the location of the basin may in part be governed by the requirements of this final land feature.the detention basin, until it is emptied or restored to its designed pool level. Unlike most large federal flood control facilities, detention basins do not usually have adjustable gates or valves; the basins fill and empty based on the size of inlet and outlet channels and pipes. What is a detention basin? A stormwater detention basin (or pond ...There are two types of basins, dry detention ponds and wet detention ponds, also known as retention ponds. The biggest difference between the two is that a detention pond will remain dry until a storm occurs, and a retention pond will have a constant pool of water. Both dry detention and wet detention can be planned in a good …Detention Ponds will temporarily store a volume of stormwater runoff and discharge it at a regulated rate. Retention Ponds hold a consistent amount of water for the treatment of runoff in order to eliminate contaminants and sediments until it is discharged. Contact Everor Facility Management today to schedule a consultation on how to best ...The biggest difference between detention and retention ponds is how long they hold water. ... Different kinds of basins. In a retention pond, it has an orifice, or riser, level with the bottom of the basin, which allows all of …Shahrivar 11, 1399 AP ... Often these ponds are systematically fed runoff water from surrounding drainage systems. Detention ponds seek merely to check the surge by ... There are two primary types of basins, and with that in mind, let’s compare retention vs detention basin solutions. What Is a Retention Basin? Retention is the act of retaining, and a retention basin or pond is a man-made reservoir intended as a permanent pool of standing water. A retention pond can serve a number of purposes. Specific CSO retention methods include underground storage (e.g., tunnels), in-receiving water storage, and retention basins (RBs). RBs may be built in-line or off-line. Th is fact sheet describes near-surface, off-line RBs. CSO RBs capture and store some of the excess combined sewer flow that would otherwise be bypassed to receiving waters.Infiltration basins can be relatively cost-effective post- construction stormwater controls because their construction requires minimal infrastructure. Typical. construction costs, including contingency and design costs, can range from $55,000 to $85,000 per acre of impervious surface treated (King & Hagan, 2011).There are two types of basins, dry detention ponds and wet detention ponds, also known as retention ponds. The biggest difference between the two is that a detention pond will remain dry until a storm occurs, and a retention pond will have a constant pool of water. Both dry detention and wet detention can be planned in a good …Detention vs. Retention Stormwater Ponds: The Water Rights Implications. There are two types of stormwater ponds: detention ponds and retention ponds.Detention ponds only detain water for a short period of time, then release the water to a natural watercourse, while retention ponds retain the water for an indefinite period …Basins are generally used to collect stormwater and release it at a controlled rate to prevent flooding and erosion. Some basins can also filter some pollutants out of the water before it enters the storm drain system. Table 2.2.1 summarizes some common mitigation solutions that can improve the performance of these basins. Table 2.2.1.Mar 16, 2022 · Detention Ponds. A detention pond is a dry structure that has a riser located at the bottom of the basin. Whenever water flows into the detention pond, it is more likely to drain right out and stay dry. Detention ponds may have turf or wild grasses. Like retention ponds, they may require a large swathe of land to create one, but their main ... Bioretention practices, such as rain gardens, are landscaped depressions that treat on-site stormwater discharge from impervious surfaces such as roofs, driveways, sidewalks, parking lots and compacted lawns. They are used to collect stormwater and filter it through a mixture of soil, sand and/or gravel. The designs of bioretention practices ...Discharge rate of the treatment volume shall completely draw down between 2 and 5 days. 8. The average depth of the permanent pool shall be a minimum of 3 feet. The average depth shall be calculated as described in Figure 10-2b. 9. Permanent pool surface area shall be determined using Tables 10-1, 10-2, 10-3, and 10-4.As retention ponds need to hold back a constant level of water, highly permeable soils can be a drawback. If this is the case, clay blankets may be used to overlay or compact the existing soil and therefore make it less absorptive. Retention vs. Detention Basins. Retention basins are not to be confused with detention basins.Detention basin is a empty excavated area near water bodies such as rivers, lakes and streams. It is also called retarding basin. These basins mostly remain dry. When it rains heavily, the basin get filled with water. Detention basins reduce the potential for flooding of surrounding areas. The detention basin is an empty pond. A basin that ...The primary difference between detention basins and retention basins is whether there is always water in the basin or if the water is only ... By forming a pond ecosystem in a retention basin, ...extended detention basin (EDB). The 12-hour drain time helps to both better replicate pre-development flows for frequent events and reduce the potential for short circuiting treatment in smaller ponds. Retention ponds can be very effective in removing suspended solids, organic matter and metals through sedimentation, as well as Specific CSO retention methods include underground storage (e.g., tunnels), in-receiving water storage, and retention basins (RBs). RBs may be built in-line or off-line. Th is fact sheet describes near-surface, off-line RBs. CSO RBs capture and store some of the excess combined sewer flow that would otherwise be bypassed to receiving waters. Retention Basin. Author/Compiled by. Corinne Waelti (seecon international gmbh) Dorothee Spuhler (seecon international gmbh) Executive Summary. Retention …EXTENDED DETENTION (ED) POND VERSION 1.9 March 1, 2011 SECTION 1: DESCRIPTION An Extended Detention (ED) Pond relies on 12 to 24 hour detention of stormwater runoff after each rain event. An under-sized outlet structure restricts stormwater flow so it backs up and is stored within the basin.The first step in designing a farm pond is selecting the proper location. Soils and watershed quality are very important considerations. The Natural Resources Conservation Service (NRCS) is the agency to contact for their pond design and construction expertise. Gayla Speer District Manager, Johnson County Conservation …Retention Ponds. Retention ponds are built to catch stormwater and retain it at all times. These basins are built with a drain system positioned up higher. This drain …Bioretention practices, such as rain gardens, are landscaped depressions that treat on-site stormwater discharge from impervious surfaces such as roofs, driveways, sidewalks, parking lots and compacted lawns. They are used to collect stormwater and filter it through a mixture of soil, sand and/or gravel. The designs of bioretention practices ...Stormwater ponds and wetlands are generally either deep or shallow depressions with pretreatment basins and water level controls which provide storage and treatment for stormwater runoff. Stormwater ponds (Wet detention basins) have a permanent pool of water and native plant life. They can have a combination of permanent pool, extended …SJT: Get the latest San Juan Basin Royalty Trust Units of Benef.Int. stock price and detailed information including SJT news, historical charts and realtime prices. Indices Commodi...Feb 15, 2024 · A retention pond, also known as a retention basin or storage basin, is an engineered structure designed to manage excess stormwater runoff. Its key …Jul 10, 2019 · There are two types of basins, dry detention ponds and wet detention ponds, also known as retention ponds. The biggest difference between the two is that a detention pond will remain dry until a storm occurs, and a retention pond will have a constant pool of water. Both dry detention and wet detention can be planned in a good way to provide an ... Jul 10, 2019 · There are two types of basins, dry detention ponds and wet detention ponds, also known as retention ponds. The biggest difference between the two is that a detention pond will remain dry until a storm occurs, and a retention pond will have a constant pool of water. Both dry detention and wet detention can be planned in a good way to provide an ... Several hundred feet of 24-inch-diameter pipe leads from the detention basin to the treatment system. Because the elevation is considerably lower than the airfield, the water flows by gravity. A trash grate at the inlet to the detention basin keeps larger solids out of the basin. Check dams remove the first flush of sediment.Tir 9, 1386 AP ... A flood control detention basin temporarily stores excess storm runoff and then discharges it at a rate not to exceed the downstream channel ...Growing communities are at increased risk of flooding and erosion damage from excess stormwater runoff. Retention ponds are permanent structures designed to hold water flow for a short period of time, similar to a dam. In response to a storm, the pond’s water level fluctuates, reducing risk and saving the community from potential flood damage ...Dec 12, 2019 · This document provides design guidance and details for stormwater storage facilities, such as extended detention basins, retention ponds, and wetlands. It covers topics such as site selection, sizing, outlet structures, maintenance, and landscaping. It is part of the Criteria Manual Volume 3 by the Mile High Flood District, a public agency that manages flood risks and stormwater quality in the ... Bio Clean Catch Basin Inlet Filters; VortClarex Oil Water Separator; StormRax™ Racks and Debris Cages; Oil Stop Valve; ... Design Your Own Bridge Hydrodynamic Separator Detention or Infiltration System. Project Design Worksheets. Stormwater Pipe Armortec Bridges and Structures. MORE FROM CONTECH. Company. About Us Press Releases …Feb 17, 2021 · Take up less space. Often completely dry between storms. Detention basins are an inexpensive solution to stormwater management. They often …May 10, 2022 · Detention Basin Trash Racks. Maintaining proper water levels in detention basins, underground detention basins, and wet ponds is dependent on free-flowing outlet control structures (OCS). Water velocity and flow directs water to the outlet control structure where it leaves the basin at a controlled rate through an orifice or weir. Trash in detention ponds and waterways impacts water quality, can be harmful to aquatic life, and makes our local waterways look bad. 2. Sediment. Loose sediment from eroded shorelines and run-off can gather in the inlet and outlet structures, causing a blockage. If you notice shoreline erosion occurring along your stormwater …A look into the intricate world of how pilots navigate the transatlantic journey. The route between London and New York is the busiest in the world, with more than 30 flights a day...Two methods of managing stormwater are the utilization of retention ponds and detention ponds. While these terms are often used interchangeably, there are distinct differences between the two types of constructed basins. A main difference is the presence or absence of a permanent pool of water. Detention Pondsextended detention basin, including the volume in forebays, must be at least 120 percent or 1.2 times the WQv. Twenty percent of this volume is considered a sacrificial volume for sediment accumulation. Forebay(s) A forebay is a small basin or plunge pool located at the inlet to a practice, separate from the main pool, and readilyPond volume is critical for basins operate as plug flow systems; while the pond surface area is critical for sediment basins that operate as continuous flow systems. ... period—for example as a stormwater detention/retention system—then the location of the basin may in part be governed by the requirements of this final land feature.The main difference between a detention and a retention basin is whether or not it has a permanent pool of water – like a traditional “pond”. The water level is established by the low flow orifice. Most of the time the orifice is part of a metal or concrete structure called a riser.The equation for converting detention pond volume in mm over the watershed area, Vs, to m3, is: Vst = (10) (Vs) (A) m3. In S.I. units the runoff depth, Qb or Qa, can be calculated from known values for the peak runoff rate, time of concentration, and watershed area, with the equation: Q - 360 (qp tc/A).These basins are also called "dry ponds,” "holding ponds,” or "dry detention basins,” and are distinguishable from retention basins that are commonly known as “wet ponds” and designed to contain some water all-year-round. Detention basins may also be located underground in an array of pipe, chambers, concrete vaults, or otherponds used during the construction period, see WDNR Technical Standard 1064, Sediment Basin. This practice provides a method to demonstrate that a wet detention pond achieves the total suspended solids (TSS) reduction and peak flow control required by NR 151.12, Wis. A dm. Code, for post-construction sites. Pollutant loading models such asWhat is a Detention Pond? The main difference between a detention and a retention pond is whether or not it has a permanent pool of water. A detention pond is designed as a ^dry pond. Its purpose is to hold back flood waters and slowly release the water so that creeks and rivers do not become flooded. Are the ity of uda’s Retention ...May 10, 2021 · A detention pond — sometimes referred to as a “dry detention basin” or “dry pond” — is a sunken area (usually excavated) that stores water …The most confusing part of retention ponds or detention basins is the vocabulary. It’s an important distinction to avoid any confusion. In the case of today’s blog, we’ll use any one of the words below in talking about both retention and detention catchments: Ponds; Basins; Chambers; Catchments; Reservoirs; Watershed; DrainagePlanning & Zoning. Detention vs Retention Basin. The Difference Between a Detention and a Retention Basin. A detention basin/pond temporarily stores …Extended Wet Detention Basin - A wet detention basin that has been designed to increase the length of time that stormwater will be detained, typically between 24-40 hours. Retention Basin (Wet Pond) - A stormwater management facility designed to capture runoff that does not discharge directly to a surface water body.Trash in detention ponds and waterways impacts water quality, can be harmful to aquatic life, and makes our local waterways look bad. 2. Sediment. Loose sediment from eroded shorelines and run-off can gather in the inlet and outlet structures, causing a blockage. If you notice shoreline erosion occurring along your stormwater …Until now, the guards—employed by the private company that administers the detention center—were prohibited from using pepper spray. An ICE immigration detention center in South Fl...Retention ponds will help provide a treatment basin for pollutant removal, as well as serve as a collection area to keep in larger flows, which will help reduce the peak runoff rates downstream ...A detention basin is designed to detain or hold water for a specific time period, usually between 24 and 48 hours, before it is released downstream at a controlled rate. A retention basin, on the other hand, is designed to keep water on-site permanently. There are several reasons why you might need a detention tank. Managing stormwater is necessary for water management in the Atlanta metropolitan area. This is particularly important during storms to prevent flooding, ero... These detention basins are typically planted with a turf grass that is mowed on a regular basis. This creates large areas of habitat or resting places for nuisance wildlife such as Canada geese. Geese can defecate up to 1 ½ pounds of fecal material per day causing a mowed basin to become an increasing source of bacteria in the watershed.A rain garden is a type of basin that is designed to capture and infiltrate stormwater runoff. A shallow depression is lined with an easy-draining soil mixture of topsoil, sand, and compost. Hardy native plants are then planted in this basin. Stormwater runoff collects in the garden, is filtered through the soil, and is slowly released back ...Water quality best management practices (BMP) help protect water quality by removing pollutants from stormwater. Stormwater ponds–have a combination of permanent pool, extended detention or shallow wetland.; Stormwater wetlands–include significant shallow wetland areas to treat stormwater but often may also incorporate small permanent pools …There is often confusion between detention and retention basins, yet they are quite different. A detention basin is designed to mitigate flooding by temporarily storing stormwater and releasing it slowly into a stream or river. Conversely, a retention basin does both; storing water from … See moreShahrivar 11, 1399 AP ... Often these ponds are systematically fed runoff water from surrounding drainage systems. Detention ponds seek merely to check the surge by ...Algae is projected to become an important source of nutrition in the future. Check out future uses of the green stuff with HowStuffWorks. Advertisement Could algae be a solution to...Off-line storage refers to any arrangement where the storage is placed beside the main flow path, and water is diverted into the storage volume by an adjacent control structure, such as a catch basin and weir. The intent of this arrangement is generally to store all the inflow until the pond level reaches the weir or other overflow device.Mar 8, 2022 · Detention ponds are constructed for flood events and have shorter settling and retention times than retention basins. A retention basin stores water year-round, and the outfall structure contains an orifice at a higher elevation compared to a detention pond. In Ohio, we primarily see retention ponds surrounding developments due to the higher ... May 14, 2020 · Retention Pond vs. Detention Pond. Since a retention pond may be referred to as a wet detention pond, be careful not to confuse it with a detention pond or detention basin. Detention ponds are also known as dry ponds. This is a clue to the primary difference between the two stormwater management ponds: A retention pond is wet because it ... Bahman 14, 1399 AP ... Stormwater ponds (also referred to as retention ponds, wet ponds, or wet extended detention ponds) are constructed stormwater retention ...Learn how your customer success team can start having a direct impact on customer acquisition and retention with these real-world strategies. Trusted by business builders worldwide...Sediment basins are temporary pond structures that are used to remove coarse sediments from stormwater by reducing flow velocities to the settling velocity of the target sediment size. In this part two of GRT’s sediment basins articles, we reiterate the purpose of sediment basins: slow runoff velocity. retain coarse sediments from runoff.I share the details of my recent Amex Business Platinum retention offer and the reasons I turned it down even though it was a good offer. Increased Offer! Hilton No Annual Fee 70K ...But what are the main differences between detention and infiltration vs. harvesting and ... Stormwater detention is the storage of stormwater runoff within large or even small storage systems or retention ponds. After a set period ... This can be done by designing and building engineered underground storage vaults, basins or ponds.Bioretention practices, such as rain gardens, are landscaped depressions that treat on-site stormwater discharge from impervious surfaces such as roofs, driveways, sidewalks, parking lots and compacted lawns. They are used to collect stormwater and filter it through a mixture of soil, sand and/or gravel. The designs of bioretention practices ...There is often confusion between detention and retention basins, yet they are quite different. A detention basin is designed to mitigate flooding by temporarily storing stormwater and releasing it slowly into a stream or river. Conversely, a retention basin does both; storing water from … See moreAlso known as wet ponds, retention ponds are designed with a permanent pool of water to facilitate the treatment of stormwater. These ponds prevent ...A dry infiltration basin. Unlike a detention pond, an infiltration basin has an underground structure that helps water soak into the ground. A stormwater infiltration basin holds runoff and lets it soak into the ground. The basins are open facilities with grass or sand bases. They can either drain rapidly or act as permanent ponds where water ...Retention basins – or retention ponds are often referred to as a “wet ponds”, a “wet detention basin” or “stormwater management pond”. Moreover, retention basins are used to manage stormwater runoff which helps to prevent flooding, downstream erosion, and improve water quality that’s flowing from the basin to an adjacent river, stream, or lake.EXTENDED DETENTION (ED) POND VERSION 1.9 March 1, 2011 SECTION 1: DESCRIPTION An Extended Detention (ED) Pond relies on 12 to 24 hour detention of stormwater runoff after each rain event. An under-sized outlet structure restricts stormwater flow so it backs up and is stored within the basin. Get insights, news, tip & tricks delivered directly to your inbox. Categories. Bioretention; Treatment/Filtration; Detention; Infiltration Description. Retention and infi ltration basins are open, usually fl at, areas of grass that are normally dry. In heavy rainfall they are used to store water for a short time and so they fi ll with water. They are often multi use; for example, they can double as play areas. Retention basins can have local areas of wetland depending on the design.Detention ponds gradually release stormwater through an outlet structure to adjacent surface waters rather than through infiltration into the soils. Detention ponds can be designed as wet or dry. Wet detention ponds are constructed so that the pond bottom is below the SHWT elevation. Dry detention ponds set the pond bottom above the SHWT.Retention ponds, detention basins, constructed wetlands and bioretention cells have all been used to treat car park runoff. Veenhuis et al. (1989) monitored the performance of a dry detention basin, with a gravel base, receiving runoff from a 19 ha impermeable area associated with a shopping mall.These detention basins are typically planted with a turf grass that is mowed on a regular basis. This creates large areas of habitat or resting places for nuisance wildlife such as Canada geese. Geese can defecate up to 1 ½ pounds of fecal material per day causing a mowed basin to become an increasing source of bacteria in the watershed. The surface area of stormwater wetlands should make up at least 1 percent of the area draining to the practice. Wetlands should have a length-to-width ratio of at least 1.5:1. Making the wetland longer than it is wide ensures that water entering the wetland receives adequate treatment. underground detention Systems. Underground detention systems, or underground ponds, are often used on new development to hold and slowly release stormwater. As new development often converts a forest canopy to impermeable asphalt and rooftop, it is not fair to push the increased runoff into existing streams, rivers and downstream neighbors.
Feb 17, 2021 · Benefits of Detention Ponds. Inexpensive. Take up less space. Often completely dry between storms. Detention basins are an inexpensive solution to stormwater management. They often require less space than wet retention basins. Dry detention ponds use only a very gentle slope and often have plant life surrounding them to provide extra protection. . News west palm beach
The most significant distinction between a retention basin and a detention basin is whether a permanent body of water or pond is present. Retention ponds. These …With the combination pond, we have our detention storage volume in the dry portion of the pond and the wet portion, which serves as a water feature, a.k.a. wet/dry pond. Retention ponds, being constantly wet, don’t encounter the …Water quality best management practices (BMP) help protect water quality by removing pollutants from stormwater. Stormwater ponds–have a combination of permanent pool, extended detention or shallow wetland.; Stormwater wetlands–include significant shallow wetland areas to treat stormwater but often may also incorporate small permanent pools …The largest advantage of detention ponds are the cost efficiency. They are essentially large holes in the ground and can remain that way until a large storm. Similar to retention ponds, however, a large disadvantage to these ponds is that they require a lot of space to be useful. Detention ponds also can’t contribute to water retention ...A rain garden is a type of basin that is designed to capture and infiltrate stormwater runoff. A shallow depression is lined with an easy-draining soil mixture of topsoil, sand, and compost. Hardy native plants are then planted in this basin. Stormwater runoff collects in the garden, is filtered through the soil, and is slowly released back ...Detention Pond vs Retention Pond. Detention Pond releases water into the drainage system. Retention Pond does not release to a downstream system. Detention pond also refers to dry basins. However, Retention Ponds refer to wet basins. Detention ponds are designed to hold water by the process of underground pipes.Credit card retention offers can help you decide whether or not you want to keep a card open. Find out more about how to get these offers. We may be compensated when you click on p...Chylomicron retention disease is an inherited disorder that impairs the normal absorption of fats, cholesterol, and certain vitamins from food. Explore symptoms, inheritance, genet...Specific CSO retention methods include underground storage (e.g., tunnels), in-receiving water storage, and retention basins (RBs). RBs may be built in-line or off-line. Th is fact sheet describes near-surface, off-line RBs. CSO RBs capture and store some of the excess combined sewer flow that would otherwise be bypassed to receiving waters.Now there is a better way. TRUEGRID Permeable Paver parking lot installation at the North Houston Bike Park, in Houston, TX. Read the case study to learn how TRUEGRID was used to eliminate a large detention pond while gaining 100 extra parking spaces and adding over 58,000 cubic feet of storm water detention in a flood prone area.. Put your storm water …Here’s a look at why retention and detention pond maintenance is crucial. Retention vs. Detention: What’s the Difference? A common method for managing stormwater is to build a pond, or basin. There are two different kinds: retention and detention. Retention ponds are pools of water that fluctuate in response to rain and runoff. 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. [7] [8] [9] 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 ... Detention basins are engineered to temporarily hold stormwater and release it at a pre-determined rate, usually through an outlet structure. The key difference from dry ponds is that detention basins are specifically built to delay the discharge rather than to dry out completely, and can incorporate controlled releases to local waterways.Call Dare provides retention basin maintenance & cleaning services in New Jersey. Call our team today if you need help with your retention pond! New Clients: 800-881-1469 Existing clients: 800-694-1199 Human Resources: 800-582-4649 ... The Difference Between Detention & Retention Ponds.Discharge rate of the treatment volume shall completely draw down between 2 and 5 days. 8. The average depth of the permanent pool shall be a minimum of 3 feet. The average depth shall be calculated as described in Figure 10-2b. 9. Permanent pool surface area shall be determined using Tables 10-1, 10-2, 10-3, and 10-4.A retention pond or "wet pond" is designed to hold water continuously, and only partially drains any incoming surge of storm water. A detention pond is designed purely to capture the surging storm water, and to release it to a water management system at a manageable pace, and with storm debris cleaned out, etc - subsequently becoming a "dry pond" until …DESCRIPTION. Wet detention ponds are storm water control. structures providing both retention and treatment of. contaminated storm water runoff. A typical wet. detention pond design is shown in Figure 1. The. pond consists of a permanent pool of water into. which storm water runoff is directed. Managing stormwater is necessary for water management in the Atlanta metropolitan area. This is particularly important during storms to prevent flooding, ero... The high abstraction in summer causes water scarcity. Therefore, water retention ponds are recommended to satisfy agricultural water demand and maintain ecological flow, as required in the Po River Basin District's Water Management Masterplan (AdBPo, 2015). Water retention ponds are built mostly by excavation.Detention vs. Retention Stormwater Ponds: The Water Rights Implications. There are two types of stormwater ponds: detention ponds and retention ponds.Detention ponds only detain water for a short period of time, then release the water to a natural watercourse, while retention ponds retain the water for an indefinite period ….