Hi Frank, thanks for your question about vegetative swales.

What Is a Swale?

Swales are soil depressions, usually manmade, that filter and collect runoff water. Vegetated swales, or bioswales, are planted with vegetation, which serves as a filtration tool and controls erosion.

The vegetation planted in these swales should be native plants that are suitable to variable moisture ranges. The swales can be different sizes and designs depending on how much runoff they are going to catch.

Stormwater Runoff: Why Are Bioswales Green?

Swales are “green” because the bioswales reduce runoff water, which is the number one cause of non-point source pollution. They do this by providing a permeable surface through which water can percolate, which replenishes underground reservoirs.

Also, vegetated make an important contribution to the ecosystem because they provide transition borders between two different environmental areas (say a dryer soil and another more humid one), which are zones of very high biological activity and diversity.

Vegetated Swales and LEED

ince swales capture and treat stormwater, they can help to earn points for a LEED project. According to the LEED for New Construction rating system, they may qualify for Sustainable Sites (SS) Credit 6.2: Stormwater Design – Quality Control.

If the swales are planted with native vegetation on a previously developed site, they could contribute to SS Credit 5.1: Protect or Restore Habitat.

Swales may also have some indirect benefits to LEED.

For example, swales reduce the heat island effect. Building swales may reduce the amount of hardscape that you need to treat for heat island effect (SS Credit 7.1: Heat Island Effect – Nonroof).

In addition, given that these vegetative swales are going to maintain a more or less humid area, it is possible that the plants that could obtain its water supply only from the moisture that accumulates in the swale area. This would reduce the demand for irrigation water, which could make Water Efficiency (WE) Credit 1: Water Efficient Landscaping easier to achieve.

Related Advice:

• Stormwater Runoff Products: What's Recommended in Areas of High Traffic?



• Xeriscaping Ideas: Going with Native or Drought Tolerant Plants



• What is Xeriscaping?: Water Efficient Landscaping for LEED