Drainage and Grading



Lot Grading and Drainage Patterns

With modern Subdivision Design and Construction, drainage from private properties (lots) are generally directed to public roads/infrastructures or maintain its current pre-development drainage patterns in order to protect homes and properties from flooding. 

Types of Drainage Patterns:

Generally, all lot drainage types can be categorized into two different patterns; rear to front drainage and split drainage. For split drainage lots, the front of the lot is drained to the municipal road fronting the property while the rear of the lot is drained towards the rear of the property. This usually means that a portion of the rear drainage will enter onto neighbouring properties that use rear to front drainage. For rear to front draining lots, the entire lot is drained to the municipal road fronting the property. As mentioned above, this may include flows from properties backing onto the lot. It is important to note that rear to front drainage lots will typically handle higher volumes of water due to flows from neighbouring lots. The drainage design is shown on Engineering Plans and lot drainage is conveyed by sheet drainage and/or connected swales.

Diagram of a property with rear to front drainage

  • Image credit - City of Winnipeg, Water and Waste Department

Apron Swales:

In a rear to front draining lot, there will be an apron swale which is usually 3 to 5 meters from the back wall of the house on the lot. This swale runs parallel to the back wall of the house across the width of the property and connects to side yard swales which direct flows to the road.

Diagram of a property with split drainage

  • Image credit - City of Winnipeg, Water and Waste Department

Sheet Drainage:

All lot surfaces are designed and constructed to convey drainage in a particular direction away from the house, this is known as the slope or grade. Sheet drainage allows for rainwater to flow to a lower elevation with the ground absorbing some of rainwater as it flows, this is known as infiltration.

Photo of property with sheet drainage

  • Above photo shows a property with sheet drainage

Connected Swales:

For urban subdivisions the lot sheet drainage is typically directed to swales on the common property line.  A swale is a shallow "V" shaped channel in the ground that collects the sheet drainage flows and efficiently directs the flows to an appropriate outlet, whether it be a public road or other infrastructures such as rear yard catchbasins.

Most swales run along the entire distance of shared property lines and usually extend about 60 centimeters onto each side of the property line.  On larger subdivision lots, the use of swales may not be necessary if the property can drain effectively by use of sheet drainage alone.

Photo of properties with connected swales

  • Above photo shows a property with connected swales

Eavestroughs and downspouts:

In the Town of Whitby, front downspouts are typically connected to the storm sewer system while rear downspouts are drained to splash pads.  Exceptions are in place for townhouse units where the rear downspouts are also connected, or when special requirements are necessary for the subdivision, such as water balance requirements. Rainwater and melted snow falling on the roof of a home is collected by the eavestroughs and directed to the ground by downspouts. Downspouts may be connected into the storm sewer or may drain directly onto the property. If downspouts are not connected to the storm sewer, they should run into an extension pipe and/or splash pad to keep water moving away from the home.

Photo of downspout draining to splash pad

  • Above photo shows a downspout draining onto a splash pad

Townhouse Drainage:

In new townhouse developments, typically all downspouts are connected to the storm sewer system. For drainage, townhouses use split drainage, with rear yard swales which direct water to rear yard catchbasins. In townhouse developments, it is particularly important that residents do not alter the swales on their properties and maintain the original drainage patterns.

How to Protect Your Home and Property from Rainwater

As noted above there are two methods of conveying lot drainage, sheet drainage and connected swales.  The drainage measures designed for a property are sensitive and need to be protected and maintained.   Changes to the drainage conveyance measures designed for a lot can cause a big impact for not only one property, but also those properties in the surrounding area, as storm drainage can become blocked and cause flooding. 

Below, please find some general tips to remember to help protect drainage conveyance measures and to protect homes from rainwater:

  • Avoid disturbing or altering the ground near property lines as this area is usually where drainage swales are located. Common mistakes made by homeowners include building gardens, retaining walls and sheds along the edges of their properties. Gardens, walls and structures near property lines can block or eliminate swales, which may lead to ponding water and flooding. The Town recommends that property owners do not place any materials or make any changes to their properties within 60 centimeters of a property line. Should you need to make changes to this portion of your property, you should hire a reputable landscaper or a Professional Engineer for advice.
  • Regularly cut, trim and rake grass and weeds along the edges of your property. Swales that are filled with long grass, weeds or discarded grass clippings can become less effective and in large rain events may become overwhelmed by the volume of rainwater. Swales filled with long grass and weeds tend to remain saturated for long periods of time.
  • If you are considering a large construction project on your property such as a raised patio or swimming pool, make sure you speak with your contractor about lot grading and drainage and ensure they understand the drainage patterns on your property and those on your neighbour's properties. If you are unsure about the drainage pattern for your lot, you may contact the Town's Public Works Department, Engineering Services at 905.430.4307 or engineering@whitby.ca to obtain drainage pattern information for your area. If a construction project interferes with drainage patters and causes ponding on a neighbouring property, the drainage provisions in the Town's Property Standards By-law may be enforced by the Town's By-law Services Division.
  • If your property contains low spots that are prone to ponding, consider filling these areas with additional soil. If you decide to add soil to your property, you should consult with a reputable landscaper or a Professional Engineer and ensure that adding soil won't obstruct or block the drainage pattern on your property or a neighbour's property.

Individual House Siting Plan

For all new subdivision draft plans that are approved by Council after 2016, it will be the Developer's responsibility to provide a copy of the approved individual house siting plan to the homeowner/purchaser prior to closing. For subdivisions approved prior to 2016, homeowners may request a copy of their own house siting from the Public Works Department via e-mail: engineering@whitby.ca and include the following information:

  • Your name (you should be the registered property owner)
  • Your address

Concerns about a Neighbour's Lot Grading and/or Drainage

The Town's Property Standards By-law states that every property owner shall ensure that the grading on their property prevents the excessive, recurrent ponding of water, prevents water from damaging structures, and does not interfere with drainage patterns.

It is important to note that homeowners are allowed to make changes to their yards, including changes to grading and elevations, provided these changes do not result in water ponding on their property or on a neighbour's property, and provided that the overall drainage patterns in the neighbourhood remain as designed.

Should you have a concern with a grading change that your neighbour has made to their property which has resulted in water ponding on your property, you are encouraged to follow the steps below:

  • Discuss the concern directly with your neighbour and let them know how the change is affecting you and your property. Suggest that you and your neighbour work together to find a solution.
  • Review the condition of your own property and take into account any conditions on your property such as gardens, retaining walls and low spots that may be contributing to the problem. Sometimes property owners are able to resolve minor drainage concerns through small changes on their own properties (please review the above section, "How to Protect your Home and Property from Rainwater" for more information). 
  • If you've attempted the above steps with no success, take detailed photos of your property, including photos of water ponding on your property and then contact By-law Services at bylaw@whitby.ca or complete the By-law Services Online Complaint Form to file a formal complaint.

All complaints, including emails, must contain the complainant's name, address and phone number. Please note that all personal information about complaints is kept confidential.

Upon receipt of a complaint, By-law Services staff will review the photos of your property to assess the extent of the drainage concern. Should staff confirm that the photos show significant ponding of water, staff will review the drainage plan for your neighbourhood. After reviewing the drainage plan, staff may conduct an in person inspection of your property and that of your neighbours.

Should the inspection find that your neighbour has made a grading change which has resulted in water ponding on your property, staff will work with your neighbour to solve the concern and reinstate an acceptable drainage pattern.