Naturalized Swales and Berms

What is it?

A Naturalized Swale, or naturalized drainage way, is a constructed stormwater conveyance tool that consists of a system of gently-sloped depressions that uses gravity to collect and direct stormwater. Similarly, Naturalized Berms are used to extend the flow path of water before entering a wetland or other water body.


Both are considered types of ‘green conveyance’ which contain natural materials and vegetation, follow natural or constructed contours, and can connect to wetlands. And both slow the flow rate of stormwater, allowing water to be infiltrated into the ground, mitigating flood events, preventing erosion, and capturing sediments.

How can municipalities use it?

Municipalities can use Naturalized Swales and Berms as a part of their stormwater management. Best practice and design manuals can include specifications for Naturalized Swales and Berms to guide municipal staff in development approval decisions, and to guide developers on potential stormwater management technologies.

What are the advantages?

The advantages of Naturalized Swales and Berms include:

  • Can result in much lower costs for managing stormwater

  • Improves water quality

  • Slows peak stormwater flow rates, preventing erosion and sedimentation

  • Increases stormwater infiltration, adding to the ground water supply and supporting natural hydrologic processes

  • Use of native vegetation provides habitat, as well as contributes to clean air and water

  • Adds aesthetic value to stormwater infrastructure

What should you watch out for?

No tool is a silver bullet. The following should be considered when utilizing Naturalized Swales and Berms as a natural infrastructure solution:

  • Traditional engineering practices do not include Naturalized Swales or Berms, so planners and developers may be slow to adopt them

  • Must be designed to fit the unique characteristics of a site

  • Cannot be implemented in areas of flat topography

  • Periodic inspections are required during establishment and after severe storm events

  • Installation of naturalized swales or berms may require authorization under the provincial Water Act

How can it help maintain natural infrastructure?

Naturalized Swales and Berms protect the natural infrastructure system by allowing the natural hydrological cycle to be maintained. They encourage infiltration, and reduce erosion and sedimentation, protecting water quality. Further, the use of native vegetation contributes to clean air, and habitat creation and connectivity. Ultimately, Naturalized Swales and Berms are tools that can help ensure the natural infrastructure system can function and its benefits are realized.

Resources

Naturalized Drainage Ways Fact Sheet – Prepared by the City of Edmonton, this fact sheet gives a basic overview of naturalized drainage ways.


City of Edmonton The City of Edmonton has several examples where the use of naturalized drainage ways are used as a stormwater conveyance feature. The link includes photos of the examples.


Combatting Canada’s Rising Flood Costs: Natural infrastructure is an underutilized option – This document provides a case study on assessing the value of a naturalized channel in the town of Oakville, Ontario. In summary, the naturalized channel provides stormwater conveyance and flood attenuation benefits, which would otherwise cost Oakville $1.24 million to $1.44 million under current and intensified land use conditions, respectively.

Did we miss something?

If you know of a resource that should be on this list - or your municipality has a sample or case that should be here, please let us know!