FAQs

A floodplain is an area of land near water bodies (rivers, lakes, etc.) that is often flooded when the water body is too full.  Examples of floodplains include low lying lands that are flooded/inundated with water when a river spills over its banks or when lake levels rise due to storm surge, or significant precipitation.  Floodplains are natural features that allow flow to spread across the landscape, limiting flooding and erosion potential.  

Knowing which areas will be inundated by flood waters is an important tool for land use planning and emergency management. This knowledge helps guide sensitive land use away from high-risk areas, and for areas where historical development has already occurred, helps us identify ways to mitigate flood risk, all with the aim of better protecting people, property, and the resilience of our city for generations to come.

The regulatory flood plain is the approved standard used in a particular watershed to define the limit of the flood plain for regulatory purposes. This standard is defined by the Ontario Ministry of Natural Resources and Forestry. Within TRCA’s jurisdiction, the regulatory flood plain is based on the more severe of the Regional Storm (Hurricane Hazel), or the 100 year storm; whichever is greater.  For most of our jurisdiction, it is Hurricane Hazel. A hydrology model simulates the effect of this amount of rainfall as if it were over each watershed, taking into account the topography, soil type, land-use, and other characteristics to determine how much water would end up in our rivers and streams. A hydraulic model then looks at where this water would go, and what areas would be inundated. The inundated area for the regulatory storm is called the regulatory flood plain.

To check if your house is in the new floodplain, please visit https://camaps.maps.arcgis.com/apps/webappviewer/index.html?id=181c780107b94448a7ba4f41f0f1f74a.