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

Two authorities share the town. The Toronto and Region Conservation Authority lists Ajax among its participating municipalities, with 86 per cent of the town's population inside its jurisdiction, which takes in the Carruthers Creek and Duffins Creek watersheds. Its Regulated Area Search shows whether an address falls in its regulated area, and its Flood Plain Map Viewer shows a generalized riverine flood plain, which the authority says is not the regulatory flood plain map. The Central Lake Ontario Conservation Authority counts Ajax among its municipal partners; its regulation area mapping, endorsed by its board in November 2025, names parts of Ajax on sheets such as Lakeshore Ajax, Audley Road North and Northeast Ajax, and it publishes a Floodplain Mapping Tool for property owners.

The Toronto and Region authority says filling, changing grade or building in its regulated area needs its permit, and that under the Building Code Act that permit comes before the Town's building permit; the Central Lake Ontario authority says new or enlarged structures, additional dwelling units, fill and grading near a stream or wetland may need its permit before the work. The Town's zoning also leans on these records: no accessory dwelling unit is permitted on land the authority determines to be hazardous. 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 Toronto and Region authority and the Central Lake Ontario authority are to join the Central Lake Ontario Regional Conservation Authority on 1 February 2027 or a later date set by regulation.

• TRCA Regulated Area Search: the authority's address lookup for its regulated area
• TRCA apply for a permit: what needs a permit, and its place before the building permit
• TRCA Flood Plain Map Viewer: a generalized view of the riverine flood plain
• About TRCA: the authority's watersheds and participating municipalities
• CLOCA regulation area mapping: the authority's regulated area map sheets, updated November 2025
• CLOCA flood protection and prevention: the authority's Floodplain Mapping Tool
• About CLOCA: the watershed and the authority's municipal partners
• 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 Ajax 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 Ajax address.

What we cover, city by city See the sample report