Photo: P199 · CC BY-SA 3.0A flood study covers Chelsea: 2 on the national inventory, the newest from Ville de Gatineau
Little of the land around Chelsea has burned: 0% within 25 km since 1986, or 0.001% a year. Shaking is a bigger worry than in most places, at $0.081 a year per $1,000 of building value ($0.030 typical). In Health Canada’s survey, 13% of homes tested in the area exceeded 200 Bq/m³ (6.6% typical). Hazard risk gives Chelsea a grade of C−, from earthquakes and radon alone.
What stands out about Chelsea’s hazards
For Chelsea, from NRCan’s seismic model, Health Canada’s radon survey, the national burned-area record and the flood map inventory.
What Chelsea faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Hazard risk in Chelsea: C−
Risk averages earthquakes and radon; wildfire joins only where it pulls the average down, so a town like Chelsea with little fire nearby would get no credit for it.
Its place: #412 of 507 in Quebec and #2,396 of 2,589 Canadian towns.
How sure: The seismic figure is a long-run average from NRCan’s model, not a prediction. The radon share rests on 63 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.
Little of the land around Chelsea has burned: 0.1% within 5 km, 0% within 25 km since 1986
Fires mapped since 1986 around where Chelsea’s residents live, and the fuel next to their homes.
Next to the typical Canadian town (0.000% a year), Chelsea’s 0.001% is in the low band.
16% of the land within 5 km of Chelsea is forest fuel, close to the 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 Quebec · highest of 513
At 0.001% a year, Chelsea ranks 136th of the 513 towns in Quebec; Mistissini leads at 0.31%.
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; Chelsea 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.
2 flood studies cover Chelsea, the newest from Ville de Gatineau
Flood studies whose area touches Chelsea, from NRCan’s inventory, each linked to its owner.
For Chelsea the inventory points to 2 studies, most recently Ville de Gatineau’s in 2014.
| Study | By | Year | Status |
|---|---|---|---|
| Ville-de-Gatineau | Ville de Gatineau | 2014 | final |
| Farmers-Hull | Gouvernement du Québec | 1978 | final |
Towns with a flood study on file
Flood maps are thinner in Quebec, 45% of towns against 58% nationally, but Chelsea has one.
NRCan Canada Flood Map Inventory: a study footprint touching the town’s boundary; towns of 2,500 people or more.
No single decade dominates: 2 studies for Chelsea between the 1970s and the 2010s.
Study dates as the NRCan inventory lists them, one count per study touching Chelsea.
The grade leaves flood out, since a study area says nothing about how many of Chelsea’s homes are at risk.
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.
Earthquakes cost buildings in Chelsea $0.081 per $1,000 a year
NRCan’s seismic risk model: the damage shaking is expected to do to buildings each year, on average over many years.
The typical town loses $0.030 a year to shaking; Chelsea loses $0.081, 2.7 times as much.
Shaking damage a year per $1,000 of building value
The typical town in Quebec expects $0.14 a year in shaking damage; Chelsea expects less, $0.081, and La Pocatière the most, $0.48.
NRCan seismic risk model (2022): mean yearly building loss per $1,000 of value; medians of towns of 2,500 people or more.
More earthquake risk than most: only 28% of Canada’s 2,611 towns are above Chelsea.
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).
Only shaking damage to buildings in Chelsea is counted; landslides, liquefaction, tsunami and fire after a quake aren’t.
Natural Resources Canada, Canada’s Seismic Risk Model (2022), by census subdivision (2016 boundaries; a few 2021 subdivisions take their residents’ mean).
13% of homes tested around Chelsea are over the radon guideline
Health Canada’s survey of long-term home tests: the share above the 200 Bq/m³ guideline. · Area-wide: radon tests, counted over the Outaouais health region
Radon runs above the typical Canadian town (6.6%) in Chelsea’s area, at 13%.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Around Chelsea, 13% of tests were over 200 Bq/m³ and 4.8% over 600, against a median of 8.2% in Quebec.
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
Chelsea is in the 10–20% band, with 22% of Canada’s 2,611 towns; only 4.6% are higher.
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.
A low area share in Chelsea doesn’t clear a house, nor does a high one condemn it: test.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011).
Where to get warnings in Chelsea
Environment and Climate Change Canada issues the weather alerts for Chelsea; 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 Chelsea 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 Chelsea
The same four hazards for the places next door.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Chelsea | Low | $0.081 | 13% | Yes |
| Cantley 12,291 · 5.2 km | Low | $0.080 | 13% | Yes |
| Hautes-Plaines 6,353 · 8.5 km | Low | $0.12 | 13% | Yes |
| Les Rapides 15,090 · 8.7 km | Low | $0.12 | 13% | Yes |
| Mont-Bleu 21,636 · 11 km | Low | $0.12 | 13% | Yes |
| Du Plateau 29,234 · 12 km | Low | $0.12 | 13% | None listed |
| La Cité 30,930 · 12 km | Low | $0.12 | 13% | Yes |
Cantley (low) has the heaviest fire record of Chelsea’s neighbours, and Chelsea (low) matches or beats it.
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Chelsea faces
What to do about the hazards Chelsea 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.
- Clear needles and wood nearby.
- Keep a grab-and-go bag ready.
- In smoke, stay in; filter air.
- Has it had a radon test?
- Check the address on the flood map.
- Are flood and wildfire insured?
What this data can and can’t tell you
- Wildfire counts one way. For Chelsea, wildfire means how much nearby land burned in the past forty years, a one-way input that can pull Risk down and nothing more.
- Earthquakes are modelled. Seismic risk is NRCan’s model of yearly building losses from shaking, averaged over many years and given for Chelsea’s census subdivision (a neighbourhood shows its city’s).
- Radon is a survey. Radon figures pool the survey’s home tests by area: postal areas once their boundaries arrive, the 2007 health region around Chelsea until then.
- Flood studies aren’t flood zones. Flood studies cover areas of every size, which is why the page lists them for Chelsea without grading them.
Questions about flooding and hazards in Chelsea
How big is the earthquake risk in Chelsea?
Expected earthquake damage in Chelsea comes to $0.081 a year for each $1,000 that buildings are worth.
How is Chelsea’s Hazard risk Grade worked out?
Chelsea’s Hazard risk grade is C−, built on earthquakes and radon with a one-sided wildfire input.
Does Chelsea flood?
A flood study covers Chelsea on Canada’s Flood Map Inventory; open the owner’s map to check a street, since flood isn’t graded.
Is radon a problem in Chelsea?
Around Chelsea, 63 survey homes were tested and 13% came in over 200 Bq/m³, a guide to the area, not to any one home.
Is Chelsea at risk of wildfire?
Fire has reached 0% of the land around Chelsea since 1986 (last in 2021); at low, it neither helps nor hurts the grade.
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).