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==Overview==

==Overview==

[[Enhanced swales]] are gently sloping vegetated open channels featuring a parabolic or trapezoidal cross-section and check dams, designed to convey and treat stormwater runoff (i.e., rainwater or snowmelt from roofs or pavements). The [[grading]], [[Check dams]] and [[vegetation]] spreads out and slows down the flow of water, allowing suspended sediment and floatables (e.g., trash, natural debris, oil and grease) to settle out. A portion of the flowing water soaks into the soil and replenishes groundwater or is taken up by plant roots and evaporated back to the atmosphere. Runoff water is delivered to the practice through [[inlets]] such as [[curb cuts]], [[Curb cuts: Gallery|spillways]] or other concrete structures, sheet flow from pavement edges, or [[pipes]] connected to [[Pretreatment|catchbasins]] or [[Downspout disconnection|roof downspouts]]. The [[Plant lists|planting bed]] and side [[slopes]] are typically covered with [[grasses]] or a mixture of flood tolerant, [[erosion]] resistant [[vegetation]] and [[stone]]. They do not feature [[filter media]] soil and [[underdrains|sub-drains]] like [[bioretention]] or [[bioswales]] do. Water not ponded behind check dams or absorbed by the planting bed is conveyed to an adjacent drainage system (e.g., municipal storm sewer or other BMP) at the lowest downstream point by an [[Overflow|outlet structure]] (e.g., ditch inlet catchbasin, culvert). Key components of this feature are described in further detail below. <br>

[[Vegetated filter strips]] (a.k.a. buffer strips and grassed filter strips) are gently sloping, densely vegetated areas that treat runoff as sheet flow from adjacent impervious areas. They slow runoff velocity and filter out suspended sediment and associated [[Pollution prevention|pollutants]], and provide some [[infiltration]] into underlying soils. Originally used as an agricultural treatment practice, filter strips have evolved into an urban SWM practice. [[Vegetation]] may be comprised of a variety of [[trees]], [[shrubs]] and native [[plants]] to add aesthetic value as well as water quality benefits. With proper design and maintenance, filter strips can provide relatively high pollutant removal benefits. Maintaining sheet flow into the filter strip through the use of a [[level spreaders|level spreading device]] (e.g., pea gravel diaphragm) is essential. Using vegetated filter strips as [[pretreatment]] practices to other best management practices is highly recommended. They also provide a convenient area for snow storage and treatment, and are particularly valuable due to their capacity for snowmelt infiltration.  

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Properly functioning enhanced swales reduce the quantity of pollutants and runoff being discharged to municipal storm sewers and receiving waters (i.e., rivers, lakes and wetlands). In addition to their SWM benefits, enhanced swales provide aesthetic value as attractive landscaped features.

Properly functioning vegetated filter strips and [[Soil amendments|soil amendment]] areas reduce the quantity of pollutants and runoff being discharged to municipal storm sewers and receiving waters (i.e., rivers, lakes and wetlands). In addition to their SWM benefits, they provide aesthetic value as attractive landscaped features.  

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{{textbox|Key components of [[Enhanced swales]] to pay close attention to are the:  

{{textbox|Key components of [[Vegetated filter strips]] to pay close attention to are the:  

*[[Inlets]]

*[[Inlets]]

*[[Turf|Vegetated Slopes]]

*[[Turf|Vegetated Slopes]]

*[[Enhanced swales: Specifications|Slope & Channel Design]]

*[[Soil amendments]]

*[[Vegetated filter strips#Design|Slope & Channel Design]]

*[[Overflow|Overflow outlets]]}}

*[[Overflow|Overflow outlets]]}}

Trash, debris and sediment builds up at these locations and can prevent water from flowing into or out of the practice.

Trash, debris and sediment builds up at these locations and can prevent water from flowing into or out of the practice.

*'''[[Swales: Gallery|Grass Swales]]''': A parabolic or trapezoidal-sized bottom, swale that contains grassed sloping sides and a filter media bottom to both convey overland flow and provide water treatment, and are often subject to more frequent maintenance. They generally contain an outlet structure at the lowest point for water to be sent to another LID BMP or the storm system; sometimes referred to as a roadside ditch. Does not contain check dams.

*'''[[Swales: Gallery|Grass Swales]]''': A parabolic or trapezoidal-sized bottom, swale that contains grassed sloping sides and a filter media bottom to both convey overland flow and provide water treatment, and are often subject to more frequent maintenance. They generally contain an outlet structure at the lowest point for water to be sent to another LID BMP or the storm system; sometimes referred to as a roadside ditch. Does not contain check dams.

*'''[[Swales]]''': Swales are linear landscape features consisting of a drainage channel with gently sloping sides. Underground they may be filled with engineered soil and/or contain a water storage layer of coarse gravel material. Two variations on a basic swale are recommended as low impact development strategies, although using a combination of both designs may increase the benefit.

*'''[[Swales]]''': Swales are linear landscape features consisting of a drainage channel with gently sloping sides. Underground they may be filled with engineered soil and/or contain a water storage layer of coarse gravel material. Two variations on a basic swale are recommended as low impact development strategies, although using a combination of both designs may increase the benefit.

*'''[[Bioswales]]''' are sometimes referred to as 'dry swales', 'vegetated swales', or 'water quality swales'. This type of BMP is form of [[bioretention]] with a long, linear shape (surface area typically >2:1 length:width) and a slope which conveys water and generally contains various water tolerant [[vegetation]]

*'''[[Bioswales]]''' are sometimes referred to as 'dry swales', 'vegetated swales', or 'water quality swales'. This type of BMP is form of [[bioretention]] with a long, linear shape (surface area typically >2:1 length:width) and a slope which conveys water and generally contains various water tolerant [[vegetation]].