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

The City of Stratford is one of the 17 member municipalities that appoint the Upper Thames River Conservation Authority's Board of Directors. The authority's regulated area maps are online at maps.thamesriver.on.ca and can be seen at its Watershed Conservation Centre, and it says the regulated area represents the greatest extent of the combined current hazards or features plus an allowance: hazardous lands, wetlands, river or stream valleys, shorelines and areas within 30 metres of a wetland. The City's Zoning By-law shows the authority's regulated area as an overlay on its Schedule A and says those lands are susceptible to flooding or erosion hazards. Under Ontario Regulation 41/24 the flood standard for the Upper Thames watershed is the 1937 flood on the Thames River, which the regulation estimates as equivalent to a 1-in-250-year flood.

A permit from the authority is needed before building, grading, placing or removing fill, or changing a watercourse or wetland in its regulated area. The authority says any municipal Planning Act approvals must be in place before an application, and that it is the applicant's job to make sure the City has a copy of its permit where one is needed to support a building permit application under the Ontario Building Code; the authority's permit is not the City's building permit. A regulated-area result governs permits; 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 Upper Thames River authority is to join the Western Lake Erie Regional Conservation Authority on 1 February 2027 or a later date set by regulation.

• UTRCA: regulated area maps: the authority's online map of its regulated area and how it is drawn
• UTRCA: Conservation Authorities Act regulation (section 28): what the regulated area covers and what needs a permit
• UTRCA: how to apply for a permit: the steps, the Planning Act approvals first, and the permit's copy for a building permit
• UTRCA: Board of Directors: the 17 member municipalities, the City of Stratford among them
• Zoning By-law 10-2022: section 2.5.5 on the authority's regulated area overlay (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, with the 1937 Flood Event Standard for the Upper Thames

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

What we cover, city by city See the sample report