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

The Grand River Conservation Authority regulates river and stream valleys with their floodplains and slopes, wetlands and the Lake Erie shoreline, and its Map Your Property tool lists Guelph among its municipalities: look up the address and see whether it falls within the 'Regulation Limit (GRCA)' layer. The authority says not every regulated area may be mapped, and that the regulation applies whether an area is mapped or not. In the Grand River watershed the floodplain is set by the greater of the Hurricane Hazel storm and the 100-year flood, which the authority calls the Regulatory Flood.

A permit from the authority is needed for development in a regulated area, such as a new house, an addition, a garage, a swimming pool, a septic system or a driveway, and it doesn't replace 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 Grand River authority is to join the Eastern Lake Erie Regional Conservation Authority on 1 February 2027 or a later date set by regulation.

• GRCA Map Your Property: the Grand River Conservation Authority's map of its regulated area, by municipality
• GRCA permits: what needs a permit in a regulated area, and how to ask staff
• GRCA flooding: the Regulatory Flood, the authority's dams and dikes, and floodplain mapping updates
• Eastern Lake Erie Regional Conservation Authority transition: the authority's page on the merger planned for 1 February 2027
• 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 a Guelph home the authority's own map tool 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 Guelph address.

What we cover, city by city See the sample report