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There are two components to the regulatory flood plain feature service. The floodplain layer is a polygon feature that is the extent of the regulatory flood plain, and the floodline layer is a line feature that represents spills, spill screening area and undefined flood plain locations. Please download both layers for the complete regulatory flood plain.
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 Northern Development, Mines, 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.
Please note: this layer includes both engineered and estimated flood data. Proponents seeking detailed site specific information* should contact TRCA.
* The flood plain remains but one criterion for our regulation, other regulatory criteria may apply. For more information about planning and permits please click here FAQ's - Planning and Permits. Click this link for the TRCA Regulated Area Search page.
A flood plain spill area exists where flood waters are not physically contained within the valley or stream corridor and exit into surrounding lands. As a consequence, the limit and depth of flooding are difficult to determine. Flood spill areas occur naturally or can occur as a result of downstream barriers to the passage of flood flows such as undersized bridges or culverts. Please refer to TRCA’s Living City Policies for further information on flood plain spills.
The flood plain spill screening area is a defined area where properties may be within the flood plain, or within a flood plain spill, and the corresponding sections of the Living City Policies may apply. Model information, or minimum floodproofing elevation requirements, may be available, or further studies may be required to determine if this property is impacted by a spill. Please contact TRCA for further information.
Undefined flood plain areas are identified where the extent of the flood plain is beyond the boundary limits of the topographical map that was available at the time the flood plain map was created.
Areas adjacent to spill and undefined flood plain locations may be within the flood plain, however, at the time the flood plain map was developed, there was insufficient information to accurately define the extent of the flood plain in these areas.
For more information on the areas adjacent to the undefined flood plain or spill areas, please contact TRCA’s Planning and Development staff, and for additional FAQ's please visit our website : TRCA Website - Flood Plain FAQ's