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Swale: a shallow, sloped ditch which is often a wet tract of land;  used to direct surface runoff towards a City right-of-way (lane or street).

Minimum slopes for drainage swales:
At least + 1.5% for a grass drainage swale and + 0.75% for a concrete drainage swale

Internal and common property drainage swales are graded to meet the requirements of the approved lot grading plan. Swales must provide a minimum unobstructed width of 15 cm within each property and a minimum depth of 10 cm and a minimum 1.5% slope to direct surface runoff towards a City right-of-way. 

The following diagrams and pictures illustrate how the swales help drain the runoff away during the rain:


Typical Common Property Drainage Swales between lots



During Heavy Rain

After Light Rain

After Average Rain

Final Grade Swale



For lots that drain from rear to front, a swale is located in the back yard where the forward slope of the lot meets the rearward slope of the foundation grading. The rear internal swale directs surface drainage to one, or both, of the side lot swales.



This Rear to Front Surface Drainage diagram shows how the swales direct water away from the properties


For Split Drainage Lots, swales are necessary to convey surface drainage from the highest points to the nearest street or lane.



This Split Surface Drainage diagram shows how the swales convey water to the front and back

Common Property Drainage Swale grading must provide a minimum of 15 cm of unobstructed width within each property.


This is an example of a Common Property Drainage Swale which maintains at least 15 cm of unobstructed width within the property.

If decorative rocks or wood chips are used, the rough grade must be raised to final grade to maintain the function of surface drainage.

Placing decorative rock on the clay (rough grade) will create a place for ponding

Improper grading generates a chance for ponding



Raising the base to final grade before placing decorative rock will minimize or eliminate ponding

Acceptable final grade base



Lot-to-lot drainage may be approved due to the topographic conditions of the developing areas.

On some lots, an easement or right-of-way is registered to allow a concrete or grass drainage swale construction. Easements or rights-of-way shown on approved Lot Grading Plan must be displayed on Lot Grading Certificate.

Note: There is a 1.5% of minimum slope requirement for grass drainage swales, and a 0.75% for concrete drainage swale.


This lot-to-lot drainage directs surface water from one lot to the other

This grass swale is marked with a string line as a guide.



Grass Swale on Easement/Right-of-way

Concrete Swale on Easement/Right-of-way

Common Property Concrete Drainage Swale between lots


For More Information

Development Services, Lot Grading

2nd Floor, Edmonton Tower
10111 104 Avenue NW
Edmonton, AB

T5J 0J4



Fax 780-496-2865

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