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

Newmarket sits in the East Holland River watershed, and its Official Plan names the Lake Simcoe Region Conservation Authority as the authority for the floodplain: it says the floodplain is also subject to the authority's regulations and that the authority's regulation mapping, which combines the floodplain and other hazard lands, is the detailed mapping to use. The authority's lookup shows whether a property is regulated, with staff to answer by phone or email; it says its regulated area takes in land prone to flooding or erosion, watercourses, shorelines and wetlands, and that a permit may be needed for work there.

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. The authority also says the municipality may require its own permit for the same work. 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: 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
• Official Plan, August 2025 consolidation: the Town's floodplain and hazard land policies (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 Newmarket home the authority's own lookup 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 Newmarket address.

What we cover, city by city See the sample report