Can a swale include plants?

Yes, a swale can include plants that tolerate changing soil moisture and help hold the soil in place. Plant choice should match sunlight, drainage, and maintenance needs.

What site detail changes a swale design?

The intended water outlet strongly affects the design. A swale needs enough slope to move water, but its flow must not erode soil or drain toward a structure.

Does a swale always hold standing water?

No, a swale usually carries water during runoff and then drains or dries. Persistent standing water may signal compacted soil, poor grading, or an undersized outlet.

Glossary

What Is a Swale?

A swale is a shallow, sloped channel that guides and slows stormwater across a landscape. It may be covered with grass, planted with water-tolerant species, or finished with rock. Unlike a buried drain, a swale works at the surface, where soil and plants can help filter water before it leaves the site.

Last reviewed: October 29, 2026Reviewed by Adam Gorski

Quick Facts About Swale

Key Takeaways About Swale

A swale is broad and shallow, not a deep ditch.
Its slope directs water toward a safe outlet.
A swale is not the same as a French drain.

How Swale Works

A sketchbook page shows the word “SWALE,” a pencil drawing, a ruler, and a pencil on a desk

A swale moves stormwater along a planned surface path. Its gentle shape spreads flow across the channel, which slows runoff and gives water time to soak into the soil. Grass, native plants, stone, or other surface materials can protect the channel from washing away.

Related glossary terms: Berm, Bioswale, Erosion Control.

Designers set the swale's direction, slope, width, and outlet to match the site. The outlet may lead toward a planted area, a drainage structure, or another approved part of the landscape. Soil type affects how quickly water can soak in, while heavy clay may keep water moving along the channel.

Surface Drainage Compared With Buried Drainage

A swale stays visible and can become part of the planting plan. A French drain carries water below the surface through a gravel-filled trench and perforated pipe. Some sites use both systems when surface flow and underground water need separate paths.

Two hands measure a landscape plan with a tape measure and pen on a worktable

Expert Note

When we plan a swale, we study where water starts, how the ground slopes, and where flow should end. We also check soil, erosion risk, nearby structures, and planting conditions. Our team shapes the channel so drainage works with the existing landscape instead of creating a new low spot.

Swale in Practice: A Real-World Example

A sloped Issaquah yard may send roof and driveway runoff toward a lawn. A swale can guide that flow through a planted strip, slow it down, and direct excess water toward a suitable drainage point.