Photo: Veillg1 · CC BY-SA 4.0Wildfire low, radon 10%: how Grenville stands on hazards
Little of the land around Grenville has burned: 0% within 25 km since 1986, or 0.001% a year. Shaking is a bigger worry than in most places, at $0.12 a year per $1,000 of building value ($0.030 typical). Hazard risk gives Grenville a grade of C−, from earthquakes and radon alone.
What stands out about Grenville’s hazards
For Grenville, from NRCan’s seismic model, Health Canada’s radon survey, the national burned-area record and the flood map inventory.
What Grenville faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Hazard risk in Grenville: C−
Two inputs always count for Grenville, earthquakes and radon; the third, wildfire, counts only against a town.
How sure: The seismic figure is a long-run average from NRCan’s model, not a prediction. The radon share rests on 78 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 Grenville: 0% of the land within 25 km burned since 1986, 0.1% within 5 km
Past fire around Grenville’s homes, from the national burned-area record, with the fuel within 5 km.
Fire claims 0.001% of the land around Grenville each year, a low band, with the typical Canadian town at 0.000%.
Forest fuel is spread evenly around Grenville: 7.8% within 5 km, 11% 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 514
At 0.001% a year, Grenville ranks 136th of the 514 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.
Grenville is in the low band with 92% of Canada’s 2,610 towns; 7.5% sit in moderate or higher.
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.
The flood map inventory lists nothing for Grenville
What Canada’s Flood Map Inventory lists for Grenville: who studied flooding and where to see their maps.
Nationally, Grenville has no listed flood study; the municipality is the place to ask.
Towns with a flood study on file
Only 45% of towns in Quebec have a flood study, short of Canada’s 58%, and Grenville is not among them.
NRCan Canada Flood Map Inventory: a study footprint touching the town’s boundary; towns of 2,500 people or more.
Flood mapping is shown for Grenville to be opened and checked, never turned into a grade.
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.”
High seismic risk in Grenville: $0.12 per $1,000 of buildings a year
Expected yearly building losses from earthquakes, from Natural Resources Canada’s model.
At $0.12 per $1,000, Grenville carries roughly 3.9 times the typical Canadian town’s earthquake risk ($0.030).
Shaking damage a year per $1,000 of building value
Grenville’s $0.12 is close to the median in Quebec, $0.14; La Pocatière is highest at $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 24% of Canada’s 2,611 towns are above Grenville.
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 Grenville 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).
Test for radon in Grenville: 10% of area homes were over the guideline
Long-term radon tests in homes across the survey area, against Health Canada’s guideline. · Area-wide: radon tests, counted over the Laurentides health region
the typical Canadian town has 6.6% over the guideline; Grenville’s area has 10%.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Around Grenville, 10% of tests were over 200 Bq/m³ and 1.3% 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.
One test in ten or more tops the guideline around Grenville, as in 22% of Canada’s 2,611 towns; 4.6% go 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 Grenville 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 Grenville
Alerts for Grenville come from Environment and Climate Change Canada and, for emergencies, Alert Ready.
| 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. |
Evacuation orders for Grenville come from the municipality or the province, while CWFIS maps fire danger every day.
Weather alerts (ECCC) · Alert Ready · Fire danger and active fires (CWFIS)
How Grenville’s neighbours compare on hazards
Wildfire band, earthquake risk, radon and flood studies for each place nearby.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Grenville | Low | $0.12 | 10% | None listed |
| Hawkesbury 11,451 · 2.6 km | Low | $0.16 | 6.1% | Yes |
| Grenville-sur-la-Rouge 3,040 · 4.1 km | Low | $0.093 | 10% | None listed |
| Vankleek Hill 9,321 · 8.3 km | Low | $0.16 | 6.1% | Yes |
| East Hawkesbury 3,787 · 14 km | Low | $0.20 | 6.1% | None listed |
| Brownsburg-Chatham 8,466 · 15 km | Low | $0.12 | 10% | None listed |
Nowhere around Grenville burns more: Hawkesbury, the closest rival, is low to its low.
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Grenville faces
What to do about the hazards Grenville 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?
- Ask the municipality for flood maps.
- Are flood and wildfire insured?
- Is earthquake cover included?
What this data can and can’t tell you
- 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 Grenville.
- Earthquakes are modelled. The earthquake figure is an expected loss, not a forecast, worked out by NRCan for each census subdivision, Grenville’s included.
- 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 Grenville until then.
- Flood studies aren’t flood zones. Flood studies cover areas of every size, which is why the page lists them for Grenville without grading them.
Questions about flooding and hazards in Grenville
Does Grenville flood?
Nothing is listed for Grenville on the national inventory (0); local maps may still exist with the municipality.
Is Grenville at risk of wildfire?
Less than most of Canada: 0% of the land within 25 km of Grenville has burned since 1986, the last in 2024, a low band that leaves Risk alone.
How is Grenville’s Hazard risk Grade worked out?
Hazard risk gives Grenville C−, weighing earthquakes and radon and counting wildfire only against it.
How big is the earthquake risk in Grenville?
In NRCan’s seismic model, Grenville’s buildings lose $0.12 per $1,000 of value in an average year.
Is radon a problem in Grenville?
In Health Canada’s survey, 10% of 78 homes tested in Grenville’s area were above 200 Bq/m³, though only a test tells you about one house.
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).