Photo: Harleyd613 · CC BY 4.0Ottawa is on Canada’s flood inventory: 28 listed, led by South Nation Conservation
Little of the land around Ottawa has burned: 0% within 25 km since 1986, or 0.001% a year. Seismic risk runs high: $0.15 of expected damage per $1,000 of buildings a year, the typical town $0.030. Radon is about average around Ottawa: 6.2% of tested homes in the survey area topped the guideline, against 6.6% for the typical town.
What stands out about Ottawa’s hazards
For Ottawa, from NRCan’s seismic model, Health Canada’s radon survey, the national burned-area record and the flood map inventory.
What Ottawa faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Hazard risk in Ottawa: the grade is still to come
Two inputs always count for Ottawa, earthquakes and radon; the third, wildfire, counts only against a town.
How sure: Earthquake losses are a model’s expectation over many years, not a forecast for any one. The radon share rests on 64 home tests in the survey area, so a few homes move it. The burned-area record misses fires under about 10 ha and most grass and farm fires.
Wildfire is rare near Ottawa: 0% of the land within 25 km burned since 1986, 0.1% within 5 km
Past fire around Ottawa’s homes, from the national burned-area record, with the fuel within 5 km.
Ottawa burns at 0.001% a year, low against 0.000% for the typical Canadian town.
Forest fuel is spread evenly around Ottawa: 9.9% within 5 km, 14% within 25 km.
Shares of land within 5 and 25 km of populated blocks: burned at least once in 1986–2025 (CWFIS burned-area composite), forest fuel and grass (fire behaviour fuel types, 2026, 250 m grid).
Burn rate a year, towns in Ontario · highest of 872
In the top quarter in Ontario: Ottawa ranks 83rd of 872 at 0.001% a year, with Sioux Lookout first at 0.16%.
Each bar: the yearly average share of land within 25 km of a town’s homes that burned, 1986–2025 (CWFIS); the seven highest towns of 2,500 people or more.
7.5% of Canada’s 2,610 towns burn fast enough to rank moderate or above; Ottawa stays low, with 92%.
Bands of the yearly burn rate: low under 0.05%, moderate under 0.25%, high under 1%, very high 1% or more; towns of 2,500 people or more.
Fire danger and active fires (CWFIS)
Canadian Wildland Fire Information System: National Burned Area Composite 1986–2025 and fire behaviour fuel types (2026), Natural Resources Canada. Measured within 25 km and 5 km of each populated dissemination area; past fire, not a forecast.
Flooding around Ottawa is mapped in 28 studies, the newest by South Nation Conservation
What Canada’s Flood Map Inventory lists for Ottawa: who studied flooding and where to see their maps.
South Nation Conservation and others have studied flooding in areas that include Ottawa: 28 studies, the latest from 2025.
| Study | By | Year | Status |
|---|---|---|---|
| Delineating Flood Hazard and Associated Impacts in the Quaile Creek Watershed | South Nation Conservation | 2025 | final · not public |
| Bear Brook Flood Mapping | South Nation Conservation | 2024 | under review · not public |
| Castor River Flood Mapping | South Nation Conservation | 2024 | under review · not public |
| Jock River Flood Risk Mapping from Richmond Road to Ashton Station Road | Rideau Valley Conservation Authority | 2021 | final |
| Lower Mississippi River Flood Plain Mapping Study | Mississippi Valley Conservation Authority | 2019 | final · not public |
| Mud Creek | Rideau Valley Conservation Authority | 2019 | final |
| Buckles Creek Flood Risk Mapping | South Nation Conservation | 2019 | final · not public |
| Billberry Creek | Rideau Valley Conservation Authority | 2019 | final |
20 more studies on the inventory touch Ottawa.
Towns with a flood study on file
Its flood study puts Ottawa with 69% of towns in Ontario; Canada’s share is 58%.
NRCan Canada Flood Map Inventory: a study footprint touching the town’s boundary; towns of 2,500 people or more.
Mapping around Ottawa began in the 1970s; the 2010s saw the most work (16 of 28 studies), the latest in the 2020s.
Study dates as the NRCan inventory lists them, one count per study touching Ottawa.
Nothing here counts toward Risk; the studies are pointers to the maps their owners keep for Ottawa.
The inventory’s own caution (NRCan): “The Canada Flood Map (CFM) does not include every flood hazard map in Canada and may be incomplete or contain inaccuracies. It should not be relied upon as the official source of flood mapping information. Furthermore, if a map appears to be missing, this does not necessarily mean that the area has never been mapped. For the official version of a map, updated information, or confirmation of applicable regulations, please contact the local authority responsible for flood mapping.”
Natural Resources Canada, Canada Flood Map Inventory; links go to each study’s owner.
High seismic risk in Ottawa: $0.15 per $1,000 of buildings a year
Expected yearly building losses from earthquakes, from Natural Resources Canada’s model.
The typical town loses $0.030 a year to shaking; Ottawa loses $0.15, 5 times as much.
Shaking damage a year per $1,000 of building value
At $0.15, Ottawa is above the typical town in Ontario ($0.043); Alexandria has the most at $0.21.
NRCan seismic risk model (2022): mean yearly building loss per $1,000 of value; medians of towns of 2,500 people or more.
Ottawa sits above most of Canada’s 2,611 towns on earthquake risk; 15% are higher.
Each column: the share of Canada’s towns of 2,500 people or more in that range of yearly loss per $1,000 (NRCan, 2022).
For Ottawa the model prices shaking damage to buildings, nothing more.
Natural Resources Canada, Canada’s Seismic Risk Model (2022), by census subdivision (2016 boundaries; a few 2021 subdivisions take their residents’ mean).
Some radon around Ottawa: 6.2% of area homes over the guideline
Long-term radon tests in homes across the survey area, against Health Canada’s guideline.
Near the middle for radon: Ottawa’s area 6.2%, the typical Canadian town 6.6%.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
The median in Ontario is 4% over 200 Bq/m³; the survey area around Ottawa has 6.2%.
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
Ottawa is in the 5–10% band with 37% of Canada’s 2,611 towns; 26% have more.
Each bar: the share of Canada’s towns of 2,500 people or more whose survey area had that share of tests over 200 Bq/m³.
Neighbouring homes in Ottawa can differ a lot; only a long-term test tells you about yours.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011). · Radon tests published for the City of Ottawa Health Unit, not by town
Where to get warnings in Ottawa
Environment and Climate Change Canada issues the weather alerts for Ottawa; Alert Ready carries the urgent ones to phones, radio and TV.
| Alert | What it means |
|---|---|
| Warning | Severe weather is happening or about to: act now. |
| Watch | Conditions favour severe weather: be ready. |
| Advisory | Weather that is less severe but could disrupt the day. |
| Special weather statement | Unusual weather worth knowing about. |
| Special air quality statement | Poor air, often wildfire smoke. |
Smoke and fire warnings for Ottawa come through Environment Canada and Alert Ready; the fire map is CWFIS’s.
Weather alerts (ECCC) · Alert Ready · Fire danger and active fires (CWFIS)
Hazards in the places around Ottawa
Wildfire band, earthquake risk, radon and flood studies for each place nearby.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Ottawa | Low | $0.15 | 6.2% | Yes |
| Carleton Heights-Courtland Park 8,621 · 0.6 km | Low | $0.15 | 6.2% | Yes |
| Borden Farm - Fisher Glen 11,100 · 1.2 km | Low | $0.15 | 6.2% | Yes |
| Fisher Heights 6,451 · 1.2 km | Low | $0.15 | 6.2% | None listed |
| Riverside Park - Mooneys Bay 4,692 · 2.0 km | Low | $0.15 | 6.2% | Yes |
| Riverside Park South - Revelstoke 3,030 · 2.3 km | Low | $0.15 | 6.2% | Yes |
| Carlington 16,354 · 2.6 km | Low | $0.15 | 6.2% | None listed |
Fire is no heavier anywhere nearby than around Ottawa (low), with Carlington next at low.
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Ottawa faces
What to do about the hazards Ottawa faces, and what to ask before you buy.
- Test for three months in winter.
- Over 200 Bq/m³: fix it.
- Kits are cheap; pros test too.
- Never drive through floodwater.
- Move papers and medicines upstairs.
- Ask whether your street is mapped.
- Drop, cover and hold on.
- Strap the water heater down.
- Keep 72 hours of supplies.
- Has it had a radon test?
- Check the address on the flood map.
- Are flood and wildfire insured?
- Is earthquake cover included?
What this data can and can’t tell you
- Flood studies aren’t flood zones. NRCan’s inventory says where flood mapping exists, not where water goes; the map’s owner is the authority for Ottawa.
- Radon is a survey. About 14,000 homes were tested across Canada in 2009–2011, and the share over the guideline for Ottawa is its health region’s, the survey’s design unit.
- Earthquakes are modelled. The earthquake figure is an expected loss, not a forecast, worked out by NRCan for each census subdivision, Ottawa’s included.
- Wildfire counts one way. Burned land within 25 km of where people live, averaged over 1986–2025 and checked for fuel near homes, is the measure; it looks back, not ahead, and only ever counts against Ottawa.
Questions about flooding and hazards in Ottawa
How is Ottawa’s Hazard risk Grade worked out?
Not yet: Canada’s grades come with its first grading run, when Risk will weigh earthquakes and radon in Ottawa, with wildfire able only to lower it.
Is Ottawa at risk of wildfire?
Fire has reached 0% of the land around Ottawa since 1986 (last in 2025); at low, it neither helps nor hurts the grade.
Is radon a problem in Ottawa?
Around Ottawa, 64 survey homes were tested and 6.2% came in over 200 Bq/m³, a guide to the area, not to any one home.
How big is the earthquake risk in Ottawa?
NRCan’s model expects shaking to cost buildings in Ottawa $0.15 a year for every $1,000 of their value, on average over many years.
Does Ottawa flood?
There is flood mapping for Ottawa on the national inventory, each study linked to its owner’s map, none of them graded.
Seismic risk: Natural Resources Canada. Radon: Health Canada. Wildfire: Canadian Wildland Fire Information System. Flood studies: Natural Resources Canada, Canada Flood Map Inventory. Contains information licensed under the Open Government Licence – Canada.
Sources: NRCan, Canada’s Seismic Risk Model 2022 · Health Canada, Cross-Canada Survey of Radon Concentrations in Homes · CWFIS, National Burned Area Composite and FBP fuel types · NRCan, Canada Flood Map Inventory. Under the Statistics Canada Open Licence.
Adapted from Statistics Canada (Census of Population 2021, population estimates 2025, 2021 census boundaries) under the Statistics Canada Open Licence; this does not constitute an endorsement by Statistics Canada. Neighbourhood names in some cities © OpenStreetMap contributors (ODbL).