Is an East Gwillimbury address in a regulated flood area, and whose map says so?

The Lake Simcoe Region Conservation Authority's planning page lists the Town of East Gwillimbury among the municipalities in its jurisdiction; the Toronto and Region authority's table of municipalities doesn't name it. The authority's lookup shows whether a property is regulated, with staff to answer by phone or email; it says regulated land may be prone to flooding or erosion, have a watercourse through it, abut a shoreline or have wetland features, that it reviews its mapping every year, and that the regulation's description prevails over the map. The Town's Official Plan says buildings in the floodplain of the Holland Marsh Specialty Crop Area are flood-proofed to the authority's satisfaction and that permits are needed from both the Town and the authority before development there.

A permit from the authority is needed for work such as building, additions, site grading or placing fill in a regulated area, and the authority says the municipality may require its own permit as well, so it doesn't replace the Town's building permit. A regulated-area result governs permits for work near water; 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 Lake Simcoe Region authority is to join the Lake Huron Regional Conservation Authority on 1 February 2027 or a later date set by regulation.

• 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
• About TRCA: jurisdiction: the authority's watersheds and the share of each municipality's population inside them
• Official Plan (October 2018 consolidation): the Town's policies for the Holland Marsh Specialty Crop Area floodplain (PDF)
• 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 an East Gwillimbury home the authority's own map is 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 East Gwillimbury address.

What we cover, city by city See the sample report