Is a Richmond Hill address in a regulated flood area, and whose map says so?

The Toronto and Region Conservation Authority's jurisdiction takes in the Don, Humber and Rouge river watersheds, and its own table puts 99% of Richmond Hill's population inside it. Its Regulated Area Search takes an address or postal code and says whether a property falls inside the area regulated under Ontario Regulation 41/24, which covers land subject to flooding or erosion, wetlands, shorelines and watercourses; the authority says not every regulated area is mapped. The City's additional unit page asks for the authority's approval for properties in its regulated area.

The Lake Simcoe Region Conservation Authority's watershed map shows its southern boundary near Bloomington Road, at the city's northern edge, and the authority notes that watershed lines don't follow municipal boundaries, so some towns are regulated by two authorities. A home near that edge can be looked up in its regulation map viewer too. 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 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.

• TRCA Regulated Area Search: the address search for the Toronto and Region Conservation Authority's regulated area
• About TRCA: jurisdiction: the authority's watersheds and the share of each municipality's population inside them
• LSRCA: for realtors: the Lake Simcoe Region authority's property lookup and its note on watershed boundaries
• Lake Simcoe watershed map: the authority's watershed and its southern boundary (PDF)
• Ontario Regulation 41/24: the regulation behind every conservation authority's regulated area
• 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

Conservation-authority regulated-area and flood plain checks are not currently included in our reports, so for a Richmond Hill 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 Richmond Hill address.

What we cover, city by city See the sample report