Photo: MatildaMars · CC0Flood mapping exists for Delson: 2 on record, latest by MRC Roussillon
For Delson, wildfire history is close to nil: 0% of nearby land since 1986, 0.001% a year. Seismic risk runs high: $0.21 of expected damage per $1,000 of buildings a year, the typical town $0.030. Radon around Delson is ordinary for Canada: 8.2% of tested homes over the guideline (6.6% typical). Delson grades C− for hazard risk; wildfire is low here, so it earns no credit.
What stands out about Delson’s hazards
For Delson, from NRCan’s seismic model, Health Canada’s radon survey, the national burned-area record and the flood map inventory.
What Delson faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Delson grades C− for hazard risk
The grade weighs Delson’s seismic risk and radon equally, and wildfire is one-sided: a high band counts against a town, a low one earns nothing.
Its place: #378 of 507 in Quebec and #2,356 of 2,589 Canadian towns.
How sure: The seismic figure is a long-run average from NRCan’s model, not a prediction. The burned-area record misses fires under about 10 ha and most grass and farm fires.
Wildfire is rare near Delson: 0% of the land within 25 km burned since 1986, 0% within 5 km
Fires mapped since 1986 around where Delson’s residents live, and the fuel next to their homes.
The land within 25 km of Delson burns at 0.001% a year on average, the low band; the typical Canadian town: 0.000%.
Delson’s homes have had no fire within 5 km since 1986; the closest was 5.8 km away.
Land that isn’t forest covers nearly all the ground around Delson: forest fuel is 0.6% within 5 km and 0.6% 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
Delson burns at 0.001% a year, 136th of 513 towns in Quebec; the leader, Mistissini, reaches 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.
Low, like 92% of the country’s 2,610 towns: the land around Delson burns, but slower than in the 7.5% above it.
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 Delson, the newest from MRC Roussillon
Flood studies whose area touches Delson, from NRCan’s inventory, each linked to its owner.
MRC Roussillon and others have studied flooding in areas that include Delson: 2 studies, the latest from 2001.
| Study | By | Year | Status |
|---|---|---|---|
| Roussillon-St-Régis-St-Pierre-Portage | MRC Roussillon | 2001 | final |
| Roussillon-Tortue | MRC Roussillon | 2000 | final |
Towns with a flood study on file
Flood maps are thinner in Quebec, 45% of towns against 58% nationally, but Delson has one.
NRCan Canada Flood Map Inventory: a study footprint touching the town’s boundary; towns of 2,500 people or more.
Flood is shown here, never graded: a study says where a map exists, not how many of Delson’s homes stand in a flood zone.
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 Delson: $0.21 per $1,000 of buildings 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; Delson loses $0.21, 7.1 times as much.
Shaking damage a year per $1,000 of building value
At $0.21, Delson is above the typical town in Quebec ($0.14); La Pocatière has the most 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.
Delson is in the top tenth of Canada’s 2,611 towns for earthquake risk; 7.7% rank 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).
Only shaking damage to buildings in Delson 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).
Some radon around Delson: 8.2% of area homes over the guideline
Health Canada’s survey of long-term home tests: the share above the 200 Bq/m³ guideline. · Radon tests for the Monteregie health region
At 8.2% over the guideline, the area around Delson is about level with the typical Canadian town’s 6.6%.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Around Delson, 8.2% of tests topped the guideline, about the same as the typical town in Quebec (8.2%).
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
A middling share of high tests puts Delson with 37% of Canada’s 2,611 towns, below 26% of them.
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.
Health Canada advises testing every home, Delson’s included, whatever the area’s figure.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011).
Where to get warnings in Delson
Environment and Climate Change Canada issues the weather alerts for Delson; 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 Delson 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 Delson
The same four hazards for the places next door.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Delson | Low | $0.21 | 8.2% | Yes |
| Sainte-Catherine 17,782 · 1.9 km | Low | $0.22 | 8.2% | Yes |
| Saint-Constant 32,124 · 2.5 km | Low | $0.22 | 8.2% | Yes |
| Candiac 24,920 · 2.9 km | Low | $0.20 | 8.2% | Yes |
| Saint-Philippe 8,674 · 6.4 km | Low | $0.18 | 8.2% | Yes |
| La Prairie 27,159 · 6.5 km | Low | $0.21 | 8.2% | Yes |
| Sault-Saint-Louis 47,270 · 7.6 km | Low | $0.20 | 6.8% | None listed |
Fire is no heavier anywhere nearby than around Delson (low), with Sainte-Catherine next at low.
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Delson faces
What to do about the hazards Delson 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
- Earthquakes are modelled. The earthquake figure is an expected loss, not a forecast, worked out by NRCan for each census subdivision, Delson’s included.
- Radon is a survey. The radon share comes from about 14,000 long-term home tests in 2009–2011, pooled for now by the 2007 health region Delson sits in.
- 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 Delson.
- Flood studies aren’t flood zones. A study’s area can be a whole watershed or province, so being on the inventory says a map exists, not that a home in Delson floods.
Questions about flooding and hazards in Delson
Does Delson flood?
Delson’s area has been studied for flooding, and the owner’s map shows which streets lie in a zone; the grade leaves flood out.
Is Delson at risk of wildfire?
Fire has reached 0% of the land around Delson since 1986 (last in 2025); at low, it neither helps nor hurts the grade.
Is radon a problem in Delson?
Around Delson, 110 survey homes were tested and 8.2% came in over 200 Bq/m³, a guide to the area, not to any one home.
How big is the earthquake risk in Delson?
Expected earthquake damage in Delson comes to $0.21 a year for each $1,000 that buildings are worth.
How is Delson’s Hazard risk Grade worked out?
Delson’s Hazard risk grade is C−, built on earthquakes and radon with a one-sided wildfire input.
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).