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

The Central Lake Ontario Conservation Authority counts the Town of Whitby among its municipal partners; its watershed runs from Lake Ontario north to the crest of the Oak Ridges Moraine. Its regulation area mapping, endorsed by its board in November 2025, shows hazardous lands such as valleylands, wetlands, watercourses, flood and erosion areas and the Lake Ontario shoreline on 28 sheets, many of them in Whitby, from Southwest Whitby and North Whitby to Brooklin and Myrtle; it also publishes a Floodplain Mapping Tool for property owners. The authority says new or enlarged structures, additional dwelling units, fill and grading near a stream or wetland may need its permit before the work starts.

The Town's building permit page lists a CLOCA permit among the documents an application may need, and the Town's zoning bars additional dwelling units in hazard lands as determined by the authority, including the regulatory flood limits. 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 Central Lake Ontario authority is to join the Central Lake Ontario Regional Conservation Authority on 1 February 2027 or a later date set by regulation.

• CLOCA regulation area mapping: the authority's regulated area map sheets, updated November 2025
• CLOCA inquiries and permits: what may need a permit, and how to ask staff
• CLOCA flood protection and prevention: the authority's Floodplain Mapping Tool
• About CLOCA: the watershed and the authority's municipal partners
• Building Permits: the Town's list of what a building permit application includes
• 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 Whitby 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 Whitby address.

What we cover, city by city See the sample report