Property Drainage and Grading

As a property owner, you are responsible for maintaining your property’s grading and surface drainage.

Homeowner maintenance

Any work you carry out that changes the original approved grades or the historically existing grades, must not impair the land’s ability to drain properly.

Typically, your drainage is contained on your property and directed to an approved outlet such as the municipal sewer or ditch, a rear lot catchbasin, or creek. Rainwater and melted snow flow across your property to approved outlets or focused flow in swales (shallow ditches).

Landscaping changes that impact properties could result in numerous issues: negative feelings with your neighbours, costly repairs, and possible involvement of the Town of Oakville and/or charges under the town’s by-laws.

Who to call when doing work

Site alterations

If you or your neighbour have a site alteration permit or are performing site alteration work, and the work resulted in drainage issues on your or your neighbour’s property, you may contact ServiceOakville at 905-845-6601, and the town’s engineering department may be able to provide guidance.

No site alterations

If there is no site alteration work, but there are drainage and flooding issues resulting from raised flower beds or walkways or a misdirected downspout, you may need to take corrective action on your property, speak with your neighbour about corrective action on their property, or consult an engineer or other licensed contractor.


Often issues arise that have a negative impact on neighbour relations but no by-law has been broken. 

In cases where mediation may assist in resolving the issue, visit the Community Conflict Resolution Services of Halton (CCRS Halton) website or phone 905-844-5414 for information on how to resolve conflict or Halton Regional Police Service at 905-825-4777 if the issue becomes heated or you are experiencing harassment from neighbour(s), 

Ensure a well-drained lot

  • Be sure plantings, fences, landscaping, pools, etc. do not alter the drainage and impact your neighbours’ or other properties.
  • Inspect your property, including the area around your home (1-2 metres from the foundation) and ensure that the ground drains away from your house.
  • If any settlements have occurred adjacent to your house or elsewhere on your property, fill them back to the original grade with topsoil.
  • Ensure that downspouts discharge onto splash pads or a hard surface directing water away from your house. If they discharge to the ground without a splash pad, there is the chance that the water will penetrate the ground beside your foundation wall and cause basement issues.
  • Do not extend downspouts or other pipes to the property line or onto your neighbour’s property.
  • Do not fill swales or change the direction of sheet drainage on your property. 
  • Ensure that all swales and rear lot catchbasin covers are free of debris and leaves on a regular basis, especially in the fall and early spring.
  • Discharge from pools, either periodic or in preparation for winter must be directed to the front of your property, to the road gutter or ditch to avoid impacting your neighbours.
  • If you are planning a backyard skating rink, be aware of spring drainage issues that may arise on your own property or your neighbour’s.
  • Talk to your neighbours on a regular basis about drainage maintenance issues.

Landscaping tips

Any grading along a mutual property line must be carried out to meet the existing grades. Your property should not be higher or lower than the elevation at the property line. If you are proposing a higher elevation than that of the property line, you need to maintain the existing elevation at the property line. You may need a retaining wall to be constructed entirely within your property or grade your property to contain your property’s surface drainage.

Before constructing property line fencing, or when replacing existing fencing, it’s best to discuss the location, style and finances with your neighbours. Fencing along a property line where fence posts are located in the middle of a swale, may decrease the capacity of the swale. Additionally, if the fence cladding extends right to the ground, it may further challenge the functionality of the swale. To reduce the negative effects, remove any earth spoil from the fence post holes and keep all cladding materials min 1 inch from the ground.

You may want to consult:

Retaining walls are used to transition from one elevation to another, like steps. The alternative is a slope or hill. Walls can be made from wood landscape ties to two-ton armour stone. Regardless of what material you use and the height, there should always be a drainage system behind the wall to allow ground water to exit and not build up pressure that may cause the wall to fail. All retaining walls are to be confined to the property that they are constructed for (including tie-backs) and must be a minimum of 0.3 meters (1 foot) from the property line to allow proper drainage.

Encroachment refers to any work that you do or item that you place outside the limits of your property lines. This also applies to any easement within your property. All of your work (landscaping or other) should remain on your property. 

Your property may have an easement on it. To find out, please check your legal survey or contact the Registry Office. Easements on your property would typically be for drainage, sewers, rear lot catchbasin, utility wires, etc. crossing from one side to the other. Where there is a drainage, sewer or catchbasin easement, you are prohibited from filling or covering within the width and length of the easement.  

Irrigation systems are an option for keeping everything green; however, they need to be maintained. A leaking irrigation system can cause drainage issues on your property and on your neighbours’. Town property is used for many utilities and neither the town nor the utilities will be responsible for damaged irrigation systems. Any irrigation system placed on town property, is there at your own risk. 

Plants and gardens are a great way to improve the look and feel of your property. However, gardens can also become a source of issues with grading and drainage of your and your neighbour’s property, if planting beds are placed right beside the property line or fence. Water flow in the swale may become blocked and then pond on your property or your neighbour’s property. When placing gardens, planting beds and trees, please review your grading to see where water is directed and make sure you don’t block the flow. 

Grading and drainage terms and definitions

Municipalities and the construction industry use many terms that are unique to describing and detailing how grading and drainage works. The following are some of the more common terms used and their definitions:

Apron swale

An apron swale is a swale that is formed across the rear yard of a front draining lot, approximately five metres from the house, which collects water from the rear yard and directs it to the side property line swales.


A catchbasin is typically a square concrete chamber in the ground with a slotted iron lid which allows surface water to be collected and then directed into a storm  sewer. They may be found along the edges of a road or in rear corners of private yards. 

Focused flow

Surface drainage that has been collected or concentrated in one area or outlet. 


Grade typically indicates the level (height) of the ground. It can be measured from a known point or in comparison to the ground level at a previous/ future time.

High point

Is a location on the ground from where water flows away. Typically it is a starting point of a swale or the top of a sloped area.

Property line swale

A swale located along a property line, where half of the swale is located on each abutting property

Rear to front drainage

Rear to front drainage is where the rear property line is the highpoint. All surface drainage on the property flows to the front of the property via an apron swale in the rear of the property that directs the water around the house to the side lot swales (located on the property line) on either  side of the house and then out to the street.

Split drainage 

Split drainage is where a high point is established at approximately the mid-point of the property. The surface drainage from the front of the property drains toward the road; and the rear of the lot drains towards the rear lot line where a swale collects the water and directs it to an outlet. e.g. a rear year catchbasin or adjoining property line swale.

Sheet flow

Sheet flow refers to surface drainage that is not collected or focused, but allowed to flow over a wide area in a specific direction. 


The amount of inclination or angle up or down that a surface (the ground) has from a flat or horizontal surface. 

Surface drainage

Surface drainage is the removal of excess surface water as a result of rain, snow melt, downspout discharge, etc., by the use of sloped ground and swales. 


A swale is a shallow ditch approximately 150 to 300 millimetres in depth and typically 1 to 2 metres in width and having side slopes no greater than 3:1, which is sloped along its length to convey surface drainage from one point to another.