Stormwater Management

Understanding how stormwater is managed and who is responsible.

Stormwater is water from rain, snow melt, and other precipitation that runs off roofs, streets and other surfaces and drains into ditches, storm drains, local creeks and Lake Ontario.  

It is important to make sure runoff travels away from homes and buildings to protect private and public property from flooding during storm events.

Managing stormwater

Rain and melted snow from your property is manage through two types of storm systems:

The minor storm system refers to the network of smaller pipes, drains, and localized drainage structures that manage stormwater runoff from smaller rainfall events or areas with lower drainage requirements. It typically handles runoff from regular rainfall events with a shorter duration and lower intensity.

The minor storm system is designed to collect runoff from individual properties, streets, parking lots, and smaller catchment areas. It includes smaller pipes and inlets that mvoe the water to the major system or directly to natural water bodies, such as streams or rivers. 

The minor system helps prevent localized flooding, ensures proper drainage in neighbourhoods, and contributes to overall stormwater management.

The major storm system refers to the primary infrastructure designed to handle larger and more significant storm events. It is made up of larger pipes, channels, detention ponds, and other storage structures capable of managing large volumes of stormwater runoff. The purpose of the major system is to control and move runoff from major storms, typically defined as storms with a return period of 10 to 100 years or more. The return period of a storm is the likelihood of a storm of that size occurring within that specific time frame.

The major storm system is responsible for collecting stormwater from a large catchment area, such as multiple neighbourhoods or a significant portion of the town. It transports the collected runoff to designated retention or detention facilities, which can include large ponds, underground storage, or open channels. This is done by overland flow routes like swales and the road itself. These facilities help to temporarily store the excess stormwater and release it at a controlled rate to prevent downstream flooding and reduce the impact on receiving water bodies.

Oakville's stormwater infrastructure


Jurisdiction over the different types of stormwater infrastructure and natural assets is shared:

Homeowners own the pipe called the sewer lateral that connects from main sewer pipe at the property line to the home, and responsible for lot grading around the property  

Halton Region manage sanitary sewer mains that carry sewage (wastewater) from the homes to treatment plants.  

Sanitary sewer mains may become submerged during overland flooding events, which can cause backups (surcharging) of the mainline system.

We maintain the various infrastructure that helps direct runoff water underground (storm sewer pipes) and above ground (roadways, catch basins, ditches, swales, road culverts and storm ponds) within the public right-of-way.  

The town also helps maintain creek and shoreline embankments.

Conservation Authorities regulate the creek floodplains to help protect communities from natural hazards such as flooding.