How to Landscape Drainage Swales

Table of Contents

What is a Drainage Swale?
Can I Fill a Swale to Level it Out?
Can I Dig a Swale?
What to Avoid When Landscaping Drainage Swales
How To Landscape Drainage Swales

What is a Drainage Swale?

Let’s start with the dictionary definition of swale, which is — according to Merriam-Webster — “a low-lying or depressed and often wet stretch of land.”

Swale Uses

• Guide water away from homes and roadways
• Direct water to gardens
• Prevent flooding
• Capture rain water for reuse

Swales can be part of an area’s natural landscaping, or they can be created to help ensure proper drainage, minimize runoff or capture storm water. In simple terms, they are generally shallow ditches that have gently sloping sides. Depending on their function, they may run along the contour lines of a hillside and may have a berm on the downhill side of the ditch. They rely on gravity to move water and are designed to direct the water where we want it to go.

In areas that receive more annual rainfall than we do here in sunny Southern California, swales are considered a more efficient way to capture rainwater than rain barrels. They are a popular choice among eco-minded homeowners in these areas who use them to direct water to flower or vegetable gardens, to limit runoff, and to trap silt and pollutants in surface runoff.

Locally, swales can be used for this purpose, but they are more often an integral part of the drainage plan for residential, commercial and municipal properties. More commonly referred to by laypeople as ditches or gutters, swales are often found along sloping driveways, adjacent to roads and parking areas, incorporated into golf courses, winding along the contours of hills on farms and in backyards, or along curbs to guide water away from roadways and into storm drains. The primary purpose of most swales in dry climates is to protect structures and to slow down or divert water.

While it might seem like our drought-prone state would not need much in the way of excess water management, drainage swales are a critical part of flood prevention and help keep our ground water cleaner. And even though we do not get as much rain as folks who use swales as part of their irrigation system in wetter climates, we can still maximize our use of the rainfall we do receive by strategically including swales in our landscape design.

Can I Fill in a Swale to Make It Level with My Lawn or Other Landscaping?

The short answer for this one is no.

Some homeowners consider swales unsightly and would rather have a nice, level lawn or a smooth surface along their driveway. The issue is, a manmade swale on your property was put there for a reason, and natural swales are serving a necessary water-carrying service as well, or it would not have naturally formed.

If you really hate the look of your swale or would like to landscape your yard in a way that does not easily accommodate an existing swale, you may have some options available to you.

For example, if you have a swale on your property that is no longer necessary because your property’s drainage plan has changed, you may be able to fill in your swale. It may also be possible to create another swale in a less offensive location to make your current swale obsolete. Depending on your particular situation, it may also be possible to install a French drain, which many people find more attractive.

The most important thing to keep in mind is that swales serve a very important purpose, and no homeowner without an engineering degree or years of experience in grading and groundwork should mess with the swales on their property without calling in the professionals.

Also keep in mind that a swale on your property might not necessarily be protecting your home; it might be there to prevent runoff from your yard from entering your neighbor’s property and causing damage to structures. So just because it looks like the hillside in your backyard is sloped in a manner that does not put your home in danger, this does not mean that the swale directing water coming from that hillside is not necessary. That swale could be saving your neighbor’s house from flooding and saving you from a lawsuit.

Can I Dig a Swale to Direct Water on My Property?

You can add a swale to your property, but — again — you really should not do anything that changes the drainage on your property without the help of professionals.

Landscape architects, engineers and contractors who specialize in grading and groundwork can survey your property and determine the best ways to enhance drainage and direct water while keeping structures and landscaping safe, making sure you abide by local ordinances and ensuring that your neighbors will not bear the brunt of poor drainage decisions.

Additionally, governmental agencies are getting more serious about any type of residential or commercial landscaping changes that could affect groundwater. This means that you may need a permit or there may be ordinances with which you must comply aside from those already tied to your property’s drainage plan.

If you work with professionals, they can also help you make sure you comply with any laws or ordinances affecting your property. If you have existing landscaping, you may be able to work with your landscape architect to add a swale to your current design.

If you are in the process of designing your landscaping from scratch and have sloping areas in your yard, work with your landscape architect to ensure swales or other drainage options are included to divert water away from outdoor living areas and structures and to incorporate these drainage options into the design as seamlessly as possible.

What to Avoid When Landscaping Drainage Swales

Before we dive into some of the many options you have when landscaping swales, we should first address a few things to avoid.

Most importantly — and, hopefully, obviously — you do not want to introduce anything to the swale that will impede the flow of water.

For example, if you need to put a solid fence across a swale, you need to make accommodations to allow the water to flow either below or through that section of fencing unobstructed.

If you have swales with berms, trees can do quite well when planted on the berms or below the swale, but should not be planted in the swale, since this can also impede water flow.

If you plan to plant inside the swell, you will need to be careful not to significantly change the grading, unless the swale is now obsolete, and your intention is to fill it.

How to Landscape Drainage Swales

While it may seem like these utilitarian trenches are completely unusable or impossible to landscape in an attractive way, swales actually provide some great landscaping opportunities, including some that are particularly well suited for drought prone areas.

Here are just some of the options you can consider for attractively landscaping your swales:

1. Natural Grass

If you have one or more swales running through a natural grass lawn (and plan on keeping your natural grass), seeding or laying sod in your swale is a great way to quickly landscape it and make it less noticeable.

If the sides are not particularly steep, this is an easy option that can enhance the visual appeal of your yard, but you will need to make sure children and pets can safely use the area, since the similar appearance could mean that they will not notice that the ground is not level.

2. Artificial Grass

If you have a swale running through an area where you would like to install an artificial grass lawn, this should not be an issue. Talk to your landscape designer or synthetic turf installer about your particular situation to make sure this is a good choice for you.

Artificial grass is a great choice for sloping areas and can be used to help control erosion, so it is an easy choice for the sloping sides of swales. Again, the similar appearance may make it difficult to see that the ground is not level so supervise pets and children to ensure their safety when playing around the swales.

3. Gravel

This is one of the most common choices for swale landscaping, and it is a great way to manage runoff, limit erosion, slow water flow and allow rainwater to more efficiently infiltrate into the soil.

Gravel is also an attractive option that is inexpensive and can be used in just about any situation, which makes this a good choice for most homeowners. However, it can give your swale an even more utilitarian look and can emphasize that you have a swale running through your landscaping.

4. Turfstone

Turfstone pavers are a type of permeable paving stone that can bring stability to gently sloping swales.

The lattice-like design allows you to plant grass or other living ground cover options in the open spaces, or you can fill these spaces with gravel. This durable, attractive option can help you avoid runoff and erosion and can help filter water as it infiltrates the soil.

Homeowners who choose this option for their swales often appreciate the visual appeal of grass or other living ground covers but want to avoid erosion on the sides of their swales and may want to use their swales for other purposes — such as walkways.

5. Create a Walkway

Shallow swales, or even deeper swales with wide bases, can be used as seasonal walkways in arid climates. In areas like Southern California where our swales are usually dry, we can design swales as multifunctional landscaping features that serve as water management systems and as walkways. As long as you do not impede the flow of water, you can line your swale with gravel and place stepping stones along the base to create a walkway.

Alternatively, in a shallow swale, you can install a durable, attractive, paving stone walkway. Mulch, bark, wood chips and similar walkway materials are not as good of an idea, since they will wash away with a heavy rain and could end up in storm water drains.

6. Design a Dry Creek Bed

This one is really where I think most Southern California homeowners will find the most inspiration.

The movement towards xeriscaping and other drought-tolerant styles of landscape design definitely have most of us using more rocks, gravel and native plants in our designs. Swales are particularly well suited for this type of landscaping, especially if you are interested in including a water-free water feature in your yard.

Dry creek beds are increasingly popular these days, particularly because they bring the look and feel of a water feature into your landscape design without actually wasting any water in the process.

By using river rocks of various sizes to create what looks like a natural creek bed, you can bring an entirely unique look and texture to your landscaping design to enhance the overall visual appeal of your yard, while maintaining the function of your swale.

7. Plant a Garden Along the Edge

If your swale has a berm, this is a great place to plant flowers, trees or a vegetable garden. If not, you can plant along the sides of the swale to take advantage of soil moisture that will be present whenever the swale is performing its primary function of capturing and directing water. As the water seeps into the soil, it will hydrate your plants, which allows you to save water — at least when it rains.

Drought-tolerant, native species are the best bet and the most environmentally responsible choice, particularly due to our lack of rain, which means you cannot rely solely — or even primarily — on your swale to water your garden.

8. Plant a Rain Garden

Our constant state or drought may make a rain garden seem like an idea better suited for our friends in the Pacific Northwest, but small swales, such as those that move water from house gutters to drains or dry wells, can make great rain gardens.

Once established, native plants can do well with little water between rainfall, which makes rain gardens with native species a possibility for Southern California homeowners.