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Landscape swale design and management
Landscape swales are a simple, but highly effective means to manage stormwater runoff and provide some measure of protection to valuable and sensitive soils. Swales should be constructed with an adequate amount of native vegetated area and a natural edge to enhance the swale as a stormwater management tool and preserve the existing land use.
Swales can be effective in reducing stormwater runoff. Swales are often used in low-impact development and urban areas as an effective method for managing the water in the swale that drains into the roadway. Some swales include a rain garden or an existing grassy area that allows for rainwater to filter through the root zone of plants and vegetation. When designing landscape swales in urban areas, developers must be cautious of not creating a “parking lot” that can affect the ability to maintain stormwater quality.
Swales and rain gardens can be considered stormwater best management practices in many states throughout the U.S. These practices can be particularly beneficial to new developments and those in areas with high groundwater tables. The swale concept has a more extensive history in Europe. Its use in urban areas in the U.S. is now increasing as the practice becomes more recognized. Swales can be combined with rain gardens, or built directly into paved areas.
Landscape swales may be constructed as either permanent features or temporary structures (e.g., designed to be removed after the rainy season). The following information describes various landscape swale design considerations.
A permanent swale will require little to no maintenance. A permanent swale should be designed to fit into the landscape where the runoff flows. Permanent swales can be a simple slope or a series of shallow trenches.
A permanent swale is often considered a stormwater best management practice in some states, like New Jersey, if constructed at a minimum depth of 1 foot. If a permanent swale is to be used, one should select the material with the greatest amount of infiltration, usually clay. Clay will also hold runoff longer than other materials. In general, the best design would be to make a series of shallow trenches at least 1 foot deep.
Temporary swales can be used for situations where the property owner plans to remove the swale after the rain. In many states temporary swales must be planted with grasses (e.g., Bermuda, zoysia) or shrubs. It is also important to plant shallow grasses to filter pollutants.
Temporary swales can be placed in paved areas to keep cars and trucks from tracking in the water or the swale.
In areas with low rainfall, a permanent swale can be placed in areas prone to water runoff (e.g., right of way, landscaping areas). This would be a low-maintenance swale.
Stormwater Planning Checklist
Make sure all landscaping (shrubbery, grass, trees) is placed to drain and is in alignment with your existing stormwater drainage system.
Be sure to test your system and drainage outlets to make sure they drain properly.
The more open a site is to the weather the more runoff your site will experience. Sites that face street stormwater runoffs need to be especially vigilant and well-managed to keep sediment and pollution from being transferred into the watercourse.
All streets in the country (both town and country) should be planted and drained so that water is drained away from properties.
Stormwater runoff that is not properly drained will cause pollution. It will also cause erosion, blockages and water shortages.
Stormwater Ponds and Bioswales
Stormwater ponds are a form of green infrastructure. This is an important feature in many parts of the United States. Stormwater ponds have a wide array of uses such as retention ponds, wetlands, and infiltration ponds.
They also serve as a type of a habitat for aquatic life.
In addition to their ability to be used for habitat, stormwater ponds can be used for stormwater runoff mitigation.
They also work as a filtration system that will filter out pollutants.
They can also be used to retain soil and pollutants that would otherwise be going into the water table and streams.
Stormwater ponds can be beneficial to a surrounding area since they can capture rainwater runoff. These ponds can provide a good source of water for aquatic species as well as human consumption.
They can also help with water supply during drought conditions.
Stormwater Ponds can also be installed along roads and at road medians.
In some cases, stormwater ponds can be a large part of a stormwater management system.
In order for stormwater ponds to be successful, they need to be properly managed.
Stormwater Ponds are different from other types of green infrastructure because they are designed to perform a specific function.
Stormwater ponds can be considered an engineered form of natural water supply. They also work to remove pollutants that would otherwise flow into streams, rivers and lakes.
This helps in promoting a healthy and thriving environment.
Stormwater Ponds and Bioswales
Bioswales are defined as areas where soil and plant material have been incorporated into the ground. They are similar to the landscape design element called a swale.
A bioswale is a more open and less defined structure than a stormwater pond. It can still filter water through soil and plant matter.
The benefits of a bioswale include, water filtration, erosion prevention, and pollution control.
They can also be used to add natural beauty and habitat to a community.
In terms of stormwater management, bioswales can be thought of as shallow, self-contained stormwater storage tanks.
Stormwater Ponds vs. Bioswales
Stormwater ponds and bioswales are both very similar in nature.
The only significant difference between the two is that a stormwater pond has a roof and is covered whereas a bioswale does not have a roof and allows for some natural precipitation to run off.
Stormwater ponds can be designed to be larger than bioswales, but a larger stormwater pond may not be suitable for a community of any size.
Both of these structures are considered to be effective stormwater management systems.
In order to choose the most appropriate type of green infrastructure in your stormwater management system, you should first determine what is necessary for your location.
If you have existing vegetation that has already filled in your pond, it may be necessary to remove that vegetation in order to completely fill the pond.
This may be done to control the size of your pond, or to add to its aesthetic value.
Your municipality may be able to help determine whether you need a stormwater pond or a bioswale.
They will be able to help you with a stormwater management plan that is appropriate for your location.
In areas where your municipality does not have a stormwater plan or where the stormwater plan they do have is out of date, it may be necessary for you to complete an application for a permit to construct a green infrastructure system.
An example of a stormwater plan is one that has regulations for how much impervious coverage can be constructed in a location.
The area also needs to have a green infrastructure system and a waterway system.
This area must also have infrastructure to support the green infrastructure such as a system to transport water and to reduce the volume of the water run-off that would come from an impervious surface.
There must be an education