Drainage and Grading

This area is often where drainage swales are located so altering this area could impact your drainage. Some common mistakes made by properties include adding the following elements near your property lines:

• Gardens
• Retaining walls
• Sheds

These elements can block or eliminate drainage swales leading to flooding on your property. We recommend that you don't make any changes to your property within 60 cm of the property line. If you do want to make changes to this area, you should contact a professional landscaper or engineer.

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. If you are unsure about the drainage pattern for your lot, you may contact us or give us a call at 905-430-4307. We can provide you with drainage pattern information for your area.

All construction projects need to meet the drainage provisions within the Town's Property Standards By-law. Failure to comply could result in a fine.

If your property contains low spots that may cause ponding, you may want to fill those spots with soil. Before adding soil, you should consult with a professional landscaper or engineer to make sure that adding soil won't obstruct or block the drainage pattern on your property or a neighbour's property.

In a rear to front draining lot, there will be an apron swale, which is usually 3 m to 5 m 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.

Photo Credit: City of Winnipeg, Water and Waste Department

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 rainwater to flow to a lower elevation with the ground absorbing some of rainwater as it flows. This process is known as infiltration.

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 catch basins.

Most swales run along the entire distance of shared property lines and usually extend about 60 cm 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.

In the Town of Whitby, front downspouts are typically connected to the storm sewer system while rear downspouts are drained to splash pads. There is an exception 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 eaves troughs 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.

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 catch basins.

In townhouse developments, it is particularly important that you don't alter the swales on your properties and maintain the original drainage patterns.