Is a Whitchurch-Stouffville address in a regulated flood area, and whose map says so?

The Town's Official Plan says natural hazard lands in the town fall under the jurisdiction of two conservation authorities, the Lake Simcoe Region Conservation Authority and the Toronto and Region Conservation Authority, and that the Town requires the authority's approval for new development and site alteration within its Flood Plain Area overlay. The Toronto and Region authority's own table puts 43% of the town's population inside its jurisdiction, and the Lake Simcoe Region authority's planning page lists the Town of Whitchurch-Stouffville in its jurisdiction. The Toronto and Region authority's Regulated Area Search takes an address or postal code, and the Lake Simcoe Region authority's interactive regulation map viewer shows whether a property is regulated; the first says a feature or hazard does not have to be mapped to be regulated, and the second that the regulation's description prevails over its mapping, which it reviews every year.

A permit from the authority is needed for development in its regulated area, such as building, site grading or placing fill. Neither permit replaces the Town's: the Toronto and Region authority says the municipality cannot legally issue a building permit until its permit or clearance has been obtained, and the Lake Simcoe Region authority says the municipality may require its own permit. A regulated-area result governs permits for work near water, such as additions, decks and grading; it is not a forecast that a home will flood, and a home outside the mapped area can still take water through a basement. Under the Conservation Authorities Act as amended in 2026, the Toronto and Region authority is to join the Central Lake Ontario Regional Conservation Authority, and the Lake Simcoe Region authority the Lake Huron Regional Conservation Authority, on 1 February 2027 or a later date set by regulation.

• Official Plan, 2025 (consolidated July 2026): the Town's Official Plan, with its two conservation authorities and the Flood Plain Area policies (PDF)
• About TRCA: jurisdiction: the authority's watersheds and the share of each municipality's population inside them
• TRCA Regulated Area Search: the address search for the Toronto and Region Conservation Authority's regulated area
• TRCA: building a new home: the authority's permit and the municipality's building permit
• LSRCA: planning: the Lake Simcoe Region authority's municipalities and its permits under Ontario Regulation 41/24
• LSRCA: for realtors: the authority's property lookup and what regulated land means
• LSRCA: do I need a permit: the authority's permits under Ontario Regulation 41/24, its mapping updates and its note that the municipality may require a permit
• Bill 97, Plan to Protect Ontario Act (Budget Measures), 2026: Schedule 3 amends the Conservation Authorities Act; the transition date is 1 February 2027 or a later date set by regulation
• Regional conservation authority boundaries (ERO 025-1257): the Province's decision of 10 March 2026 on which authority joins which of the nine regional authorities
• Ontario Regulation 41/24: Prohibited Activities, Exemptions and Permits, the regulation behind every conservation authority's regulated area

Conservation-authority regulated-area and flood plain checks are not currently included in our reports, so for a Whitchurch-Stouffville home the authorities' own maps are the place to look. The full report's water and flooding group does cover past floods seen by satellite, nearby creeks, rivers and ponds, and mapped wetlands for any Whitchurch-Stouffville address.

What we cover, city by city See the sample report