A swale is a long, gently sloping, landscaped depression that collects and cleans stormwater. When. it rains, water runs over pavement and other hard surfaces, picking up pollutants along the way. Much of this polluted stormwater runoff goes to storm drains and into our rivers and streams.
Swales follow the contours around the base of a natural or created slope, redirecting storm water and filtering runoff as it sinks into the soil, instead of keeping it in one place, like a rain garden. Plants suck up the water along a swale’s gently sloping banks and sometimes down the center of the channel.
The swale is vegetated with flood tolerant, erosion resistant plants. The design of grassed swales promotes the conveyance of storm water at a slower, controlled rate and acts as a filter medium removing pollutants and allowing stormwater infiltration.
Bioswales are storm water runoff conveyance sys- tems that provide an alternative to storm sewers. They can absorb low flows or carry runoff from heavy rains to storm sewer inlets or directly to sur- face waters.
Bioretention swales are shallow, vegetated, landscaped depressions with sloped sides. They are designed to capture, treat and infiltrate stormwater runoff as it moves downstream.
Vegetated swales are most effective on soils that allow infiltration. If infiltration is desired, the underlying soil drainage rate should exceed 0.5 inches per hour. Amended topsoil can be installed to improve infiltration and retention of runoff.
Swales are not appropriate on steep landscapes. Any area with more than a fifteen-degree slope (about 1:3.75) isn’t appropriate for installing swales, as the water saturation may cause slides, which could be dangerous.
Bioswales reduce flooding by their decreased elevation and connected channelization, which guide water towards them. Additionally, their increased surface area and the permeability of their soil and stone components both slow the force and drain the volume produced in a rain event.
Bioswales are typically less costly to construct than curb and gutter or underground storm sewer systems for residential and commercial applications.
Bioswales are typically vegetated, mulched, or xeriscaped. They consist of a swaled drainage course with gently sloped sides (less than 6%). Bioswale design is intended to safely maximize the time water spends in the swale, which aids the collection and removal of pollutants, silt and debris.
To put it simply, a ditch is made to carry water away and a swale is made to collect and slowly release water into the landscape.
Six- to 12-inches deep
There are no hard rules about the size of a swale, but the bigger it is the more water it can absorb during a rainstorm. Six- to 12-inches deep and 3- to 4-feet wide are typical dimensions. Smooth out the shape of the berm with a hard metal rake to form a planting bed.Nov 17, 2015
Generally speaking, Vegetated Swales cost between $4.50 and $8.50 per linear foot when vegetated from seed, and $15 to $20 per linear foot when vegetated from sod. Annual maintenance costs will be around $1 per linear foot (seed) and $2 per linear foot (sod).
Concrete swale on a commercial site conveys stormwater to a drain inlet. DESCRIPTION. An A/C swale is a man-made drainage channel designed, shaped, and lined to convey surface runoff in a non-erosive manner downstream to a treatment and/or infiltration system.
Definitions of drainage ditch. a ditch for carrying off excess water or sewage. type of: ditch. a long narrow excavation in the earth.
If you plan to build out a rain garden or bioswale, costs will vary. Estimated cost for a rain garden is $3–5 per square foot if labor is donated • Estimate $200–4,000 for a 200m2 bioswale.
Bioswales are not recommended in locations with low infiltration rates because standing water, localized flooding, and other issues can cause problems within the street and sidewalk in an urban environment.
For this reason, bioswales work best when installed in parking lots, along roadways and sidewalks or as an Benhancement to natural or existing drainage swales; however they may be constructed in any location provided there is a mild slope (no greater than five percent).
Bioswales typically are located along a roadway. These stormwater BMPs need regular maintenance, similar to other landscaped areas, including: weeding, removing trash and debris, pruning, and mulching.
Bioretention is an important technique that uses soil, plants and microbes to treat stormwater before it is infiltrated or discharged. Bioretention “cells” are shallow depressions filled with sandy soil, topped with a thick layer of mulch, and planted with dense vegetation.
According to the American Society of Landscape Architects (ASLA), a 4-meter bioswale can reduce about 25% the of total rainfall runoff. The effectiveness of bioswales extends to their ability to filter stormwater naturally.
The main difference is that the bioswale moves water to somewhere else in the garden, while also allowing some (but not all) of it to infiltrate. A rain garden is specifically meant to increase infiltration. Bioswales are often used to convey water to a rain garden.
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