Why would you need a Swale? Landscapes often develop natural depressed areas that are channeling out as rainfall finds its way down slopes. Sometimes the natural water paths are in inconvenient areas and sometimes they create unwanted areas of erosion. In addition, manmade structures can funnel water in new directions that create swampy areas or new areas of erosion.
Building a Swale is a way to decrease erosion or ponding of water and controlling where water goes so that it is naturally absorbed into the ground where it can enhance the plants of the landscape and avoid entering the storm water drains leaving the property without the benefit of the naturally occurring water.
A Swale is a channel that is situated to capture rushing water and slow it down. When the water is slowed, it can be absorbed into the ground rather than rushing downhill creating the flooding problems.
Manmade Swales are designed by first identifying the starting point of the rushing water and then designing a natural fall area that includes switchbacks and rock and other natural elements to slow the water as it travels the channel. Swales are never paved or “rip-wrapped,” which only increases the speed of the water flowing through it. Natural plantings along the Swale edges, grasses and other water loving plants will help keep the Swale healthy and doing its job.
To determine whether a Swale is a good solution for your property, put on a pair of boots and a rain jacket and watch the rain water during the next storm event. You can then get an idea of where your Swale will need to start.
The depth of the Swale should be about 12 inches and it should be about 2 ½ feet wide, but can also include wider areas. You should plan for the Swale to extend about 20 feet, creating a natural area and then maybe creating a second Swale if needed. It is important to remember that you are not building a trench to channel water, you are building to slow the water down an allow it to absorb and filtrate into the ground.