What is a swale in drainage?
Swales are shallow, broad and vegetated channels designed to store and/or convey runoff and remove pollutants. They may be used as conveyance structures to pass the runoff to the next stage of the treatment train and can be designed to promote infiltration where soil and groundwater conditions allow.
How deep should a drainage swale be?
Six- to 12-inches deep
Step Two: Dig It 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.
What is purpose of a swale?
Today, swales not only convey stormwater but also help to treat runoff to reduce pollutants. Like ditches, swales collect stormwater from roads, driveways, parking lots and other hard surfaces. Unlike ditches, swales are not deep with straight sides. They have gently sloping sides and are wider than they are deep.
How do you make a drainage swale?
- Step 1: Evaluate the Slope. Construction of a swale begins with analyzing the slope of the yard and water runoff patterns to plan the route for the swale ditch.
- Step 2: Lay Out the Swale.
- Step 3: Excavate the Swale Ditch.
- Step 4: Lay Gravel and Drain Tile.
- Step 5: Finish the Swale.
What is the difference between a French drain and a swale?
French drains have a more functional purpose, as they are intended to keep water away from the foundation. Swales, on the other hand, are often recommended by landscapers as a general-purpose drain. Swales are sometimes not an option in urban areas because they require large lots to shape properly.
How do you build a drainage swale?
How are swales calculated?
The runoff above every swale but the top one will be given by the formula: Runoff Volume (litres) = C • ACatchment (m2) • Vrain (mm), where C = Coefficient of Runoff (which is percent runoff ÷ 100), ACatchment is the area of the catchment in m2, Vrain is the volume of a large rain event in mm, and the ACatchment is the …
Where do you put swales?
So, ideally, a swale will be installed at the highest point possible but still low enough, downslope, to catch water run-off. From here, spread the water out on level plain by extending the swale on contour for as long as possible, that way water can absorb evenly into the land downhill.
How far apart should swales be?
Decide on the distance between the swales This will depend on your site goals and rainfall and runoff conditions, but the overarching rule of thumb is: the greater the runoff, the closer the swales should be spaced. In general, it will be 5 – 20 m (15 – 65 feet). But again, the greater the runoff the closer the swales.
What is the best drainage system?
Landscaping plants can be a great drainage solution for areas with a small amount of excess water. Red-twig dogwoods, willows, and many native plants in each region are well-adapted to periodic bog conditions. French drain. A French drain is the most well-known type of outdoor drainage system.
How far apart should Swales be?
How much water can a swale hold?
With these dimensions, the swale has the capability to hold 15gals. of water for every foot of length. For a 100 ft frontage lot with one driveway would result in 1275 gals of water storage. A typical city block of 400 ft should be able to store about 10,000 gals.
How do you make a proper swale?
Do swales hold water?
In this way, the swale fulfills three important functions: it carries water from the ditch to fill the dam, it rehydrates the landscape, and it prevents the dam from overflowing by acting as a channel back to the ditch.
What are the two types of drainage systems?
There are two main types of drainage system options: surface drains and french drains. Surface drainage systems consist of a few ground-level areas drains that are connected to PVC piping. When it rains, water flows down the drains, into the piping, and is transferred away from the house.