London Ontario Floodplain Bylaws & Building Rules

Land Use and Zoning Ontario 4 Minutes Read · published February 12, 2026 Flag of Ontario

In London, Ontario, building in floodplains is regulated by municipal zoning rules and by conservation authority permits. Property owners and developers must consult City of London hazard guidance and maps to identify regulated hazard lands and follow the Upper Thames River Conservation Authority permit process for works near watercourses and wetlands. City of London hazard lands and flood information[1] and the conservation authority controls are the starting points for legal compliance.Upper Thames River Conservation Authority permits[2]

Check both the city zoning and conservation authority requirements before designing foundations or elevations.

Overview

London’s municipal planning framework, together with conservation authority policies, restricts certain types of development in mapped floodplain and hazard lands. The City’s Zoning By-law and planning review identify permitted uses, elevation and grading requirements, and when a development application or variance is required. City of London Zoning By-law (Z.-1)[3]

Penalties & Enforcement

Enforcement is shared between the City of London (planning, building and by-law enforcement divisions) and the conservation authority for regulated watercourse and hazard permits. Specific monetary fines, escalation schedules and many administrative penalties are not specified on the cited municipal or conservation authority pages and therefore must be confirmed on the applicable enforcement page or by contacting the responsible office.

  • Monetary fines: not specified on the cited pages; contact enforcement for current fines and ticket amounts.
  • Escalation: first, repeat and continuing offences procedures are not specified on the cited pages.
  • Non-monetary sanctions: stop-work orders, orders to restore or remove structures, and court prosecutions may be used by enforcement authorities.
  • Enforcers: City of London Building and By-law Enforcement divisions and the Upper Thames River Conservation Authority enforce respective rules; complaints are routed through official contact pages.
  • Appeals and review: appeal routes and time limits are not specified on the cited pages; applicants should request written reasons and follow the appeal directions provided with orders or permit decisions.
Record and photograph any site communications and orders to support appeals or compliance responses.

Applications & Forms

The most common applications and permits relevant to floodplain work are:

  • Conservation authority permit: required for development, interference with wetlands, and alterations to shorelines and watercourses; application details and submission instructions are on the conservation authority permits page.Permits and application information[2]
  • Municipal planning/building applications: site plan, building permit and minor variance applications where zoning or elevations conflict with floodplain restrictions; check City of London planning and building pages for forms and fee schedules.
Permit applications often require engineered floodproofing or elevation drawings prepared by a professional.

Fees, submission addresses, processing timelines and specific form numbers are not fully listed on the cited pages and can vary by project; always confirm current fees and required attachments with the approving office before submitting.

Mitigation and Design Considerations

When development in or near a floodplain is allowed, typical mitigation measures include raised finished floor elevations, floodproofing of utilities, geotechnical assessment, erosion control, and design to avoid increasing downstream flood risk. Work in regulated areas often requires engineered drawings and monitoring during construction.

  • Elevate habitable spaces above the regulatory flood elevation.
  • Provide drainage and erosion control measures that meet municipal and conservation authority standards.
  • Use flood-resistant materials below the required elevation to minimize damage and facilitate cleanup.

Action Steps

  • Confirm whether your property lies in a mapped hazard/floodplain using City of London mapping and conservation authority resources.[1]
  • Contact the Upper Thames River Conservation Authority for permit pre-consultation if works affect watercourses or wetlands.[2]
  • Apply for required building permits and zoning approvals with the City of London; obtain any variances before construction begins.[3]

FAQ

Do I need a permit to raise my house or add fill on my lot?
Possibly; adding fill or changing elevations on a property in the floodplain typically requires municipal and conservation authority review—check both City of London hazard maps and the conservation authority permit requirements.
What happens if I build without a permit in a floodplain?
Unauthorised work can lead to stop-work orders, restoration orders and prosecution; specific fines are not specified on the cited pages and must be confirmed with enforcement authorities.
Where do I start for technical floodproofing standards?
Begin with the conservation authority’s permit guidance for site-specific elevation and erosion-control requirements, and consult the City of London building department for construction standards.

How-To

  1. Confirm floodplain status: review City of London hazard maps and property records.
  2. Pre-consult: contact the Upper Thames River Conservation Authority for permit guidance and the City of London planning/building staff for zoning and permit requirements.
  3. Prepare documentation: gather site plans, elevation drawings, floodproofing details and professional reports as requested.
  4. Submit applications: file conservation authority permit and municipal building/zoning applications with required fees and attachments.
  5. Follow conditions: complete any required mitigation works, inspections and final approvals before occupancy.

Key Takeaways

  • Both City of London bylaws and the conservation authority can restrict development in floodplains.
  • Permits and engineered floodproofing are commonly required for work near watercourses.

Help and Support / Resources

  1. [1] City of London hazard lands and flood information
  2. [2] Upper Thames River Conservation Authority permits
  3. [3] City of London Zoning By-law (Z.-1)

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