In many regions, water management by changing the terrestrial structure is a necessary task. Large influxes of water have the capacity to flood, erode, and damage crops and buildings. Utilizing methods such as swale permaculture can help minimize any negative impact water can have, while also preserving or directing it to needed sites. There are many swale landscaping ideas that will also beautify the garden and help manage run-off.
Land stewardship requires a holistic approach to manage elements that can cause damaging changes. Large amounts of water deposited by flooding waterways, torrential rains, or other events may necessitate installing a swale. Such structures will slow the movement of water, direct it intentionally, and spread it out to minimize damage.
Swales are simply ditches that catch water and allow it to percolate slowly into the earth. They may be bare in the case of diversion ditches, but the usual structure is a vegetated swale where plants can receive necessary moisture. The ditches may be straight or contoured depending upon the purpose for the water.
Types of Swale Gardening
A swale is a shallow ditch or channel that directs water. It has gentle hills bordering it and relies upon gravity to move water. Swales do not need to be deep to be effective. In essence, they are a depression whose depth is determined by the amount of water that will need to be channeled. In the home garden, a depth of a couple shovels-full usually suffices. A diversion channel will need a grade of at least one percent to move water away from structures, fields, and other items. The water will go to a storage site or into drainage.
With a contoured swale, the sinuous curves are based on a level bottom. The curves keep water movement slow while it takes it away from areas of concern. Either type is generally lined with river rock or vegetation. The liner should allow some percolation of the moisture for maximum effectiveness. The berms along the edges need to be tall enough to contain the moving water.
How to Build a Swale
The first step is determining the direction of water movement. The area should have gentle sloping to direct the flow down and away. Where possible, observe the natural movement during a rainstorm and mimic this movement, but in a controlled way. If water collects around a building naturally, use the swale to send it away from the foundation. Avoid constructing swales where there is a steep slope. This will cause water to rush quickly and can cut into the soil and cause erosion.
The ideal site has less than two percent grade. A laser level or the use of stakes and twine can help determine the grade and location for the swale. Swales should be at least 5 feet (1.5 m) from buildings, away from septic sites, and away from large tree roots. If planting a vegetative swale, the site should also be in at least partial sun. Once the site has been gauged, it is time to dig. Dig the channel about 6 inches (15 cm) deep consistently all the way to the end point.
Plants for a Vegetated Swale
The best choices for a vegetated swale are native riparian and aquatic species. Many types of grass are ideal such as fescue and sedges. These are planted on the berms to stabilize the slope and acquire moisture naturally. Rushes can be planted in the depression itself.
Whatever you choose, make sure the plant can tolerate periods of dry and rainy season wet. Deer grass is also a species tolerant of swale conditions. Around the edges of the berms use plants like buckwheat, Santa Barbara Daisy, dogwood, willow, chokeberry, and buttonbush. Many perennials will thrive on the banks of a swale such as meadowrue, ironweed, and vervain.