Flood Plain Mapping

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Regulatory Context

Natural systems such as flood plains are regulated under the Conservation Authorities Act and implemented by local conservation authorities.

There are 3 Conservation Authorities within the City of Ottawa: South Nation Conservation, Rideau Valley Conservation, and Mississippi Valley Conservation.

  • Conservation authorities create flood plain maps based on the applicable ‘design flood’ event standard established by the Province. In Eastern Ontario the design event is the 100 year storm. This is the event that has a one per cent chance of occurring in any year.
  • Mapping is reviewed every five years and updated on an as needed basis.
  • A permit from the conservation authority is required prior to any development or site alteration within the flood plain.
  • Development is prohibited where flooding may compromise the ability to deliver essential services, where flooding may cause unacceptable risk of property damage, or where chemical, hazardous or toxic substances could contaminate potential flood waters.

In order to reduce the potential for public costs, risk of injury, loss of life, property damage, or economic or social disruption that may result directly or indirectly from development and other activities in flood plains, municipalities also incorporate the flood plain mapping produced by the conservation authorities into their Official Plan policies (Section 4.8.1) and Zoning By-law policies (Section 58).

The City’s Official Plan separates flood risk areas into two categories: Flood Plain, and Two-Zone Flood Plain: Floodway and Flood Fringe. Each of these categories contain specific policies for the regulation of development. Two-zone flood plain areas may permit a wider range of development than Flood Plain areas, where flood risk is reduced due to flood mitigation infrastructure or other similar features.

Purpose of the Flood Plain Overlay

The City of Ottawa Flood Plain Overlay is a set of zoning provisions that regulate development within areas of potential flooding. To acknowledge reduced flood risk in areas with flood mitigation infrastructure or other similar features, there are two zoning overlay categories:

  • Flood Plain: Development not permitted other than limited additions to existing buildings. Intensification is generally not supported.
  • AreaSpecific Flood Plain: Limited development is permitted subject to flood proofing, protection works, and access standards. Intensification in these areas is not encouraged. Despite the underlying zoning, severances in these areas are not supported under Official Plan policies.

Mapping Updates - Flood Plain Overlay

The City of Ottawa keeps flood plain overlay mapping as up to date with the Conservation Authorities mapping as possible . The most recent round of updates have been divided into 4 phases:

Phases 1 and 2 - May 2016 and July 2018, affecting:

  • Constance Creek;
  • Huntley Creek; Feedmill Creek;
  • the Rideau River from the Ottawa River to Burritt’s Rapids;
  • watercourses within a large portion of the South Nation Conservation Authority watershed;.
  • the Ottawa River shoreline;
  • portions of the Carp River; Poole Creek;
  • Green Creek;
  • Cardinal Creek;
  • John Boyce Municipal Drain, and;
  • Osgoode Garden/Cedar Acres Municipal Drain.

Phase 3 – October 2019, affecting:

Mississippi Valley Conservation Authority

  • Constance Bay/Ottawa River 
  • Shirley’s Brook and Watt's Creek / Kizell Drain  – additional updates still ongoing
  • Various locations along Feedmill Creek and Carp River

Rideau Valley Conservation Authority

  • Flowing Creek and Hobbs Drain 
  • Kings Creek 
  • Nichols Creek 
  • Various locations along Poole Creek (Ward 6, 21) and Carp River 
  • Stevens Creek 
  • Becketts Creek

South Nation Conservation

  • South Bear Brook River 
  • McKinnon’s, East Savage and McFadden Creeks 
  • Middle Castor River, Buckle’s Creek and Ebber’s Creek 

Phase 4 - updates are scheduled for 2021, following completion of the consultation process being conducted by local conservation authorities.

Below is a list of areas that are currently being reviewed:

Mississippi Valley Conservation Authority

  • Mississippi River 
  • Harwood Creek
  • Carp River 
  • Casey Creek

Rideau Valley Conservation Authority

  • Van Gaal Drain
  • Mud Creek 
  • Bilberry Creek 

South Nation Conservation

  • North Castor River/Findlay Creek 
  • Shaws Creek 
  • South Castor River 
  • South Bear Brook River 


For general inquiries regarding floodplain provisions, conservation authority regulation limits, or to confirm the zoning of your property, please contact a Development Information Officer (DIO) at 613-580-2424, ext. 23434 or dioinquiry@ottawa.ca.

To sign up for flood plain engagement opportunities or to stay up to date on conservation efforts in your area, please contact your local conservation authority:

Rideau Valley Conservation Authority
613-692-3571 | 1-800-267-3504 (toll-free)
Fax: 613-692-0831
Email: info@rvca.ca

Mississippi Valley Conservation Authority
Fax: 613-253-0122
Email: info@mvc.on.ca

South Nation Conservation
613-984-2948 | Toll free: 1-877-984-2948
Fax: 613-984-2872
Email: info@nation.on.ca

For further information please contact the undersigned:

Marika Atfield, Planner II
Ottawa City Hall
110 Laurier Avenue West, 4th floor
Ottawa,Ontario K1P 1J1
613-580-2424, ext. 41488
fax: 613-580-2459
email: marika.atfield@ottawa.ca