Photo: Verne Equinox · CC BY-SA 3.0High radon around Dorchester: 20% of homes tested in the area exceed 200 Bq/m³
Burn scars are few around Dorchester, with 0.2% of the land within 25 km touched by fire since 1986 (0.006% a year). For earthquakes Dorchester is middling, $0.020 a year per $1,000 against $0.030 for the typical town. Dorchester grades C for hazard risk, with wildfire counted against it.
What stands out about Dorchester’s hazards
Four national sources, each read for Dorchester: earthquakes, radon, past fires and flood studies.
What Dorchester faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Dorchester grades C for hazard risk
Seismic risk and radon set Dorchester’s grade, wildfire can drag it down, and flood mapping stays out of it.
How sure: Earthquake losses are a model’s expectation over many years, not a forecast for any one. Small fires and grass fires are largely missing from the national burned-area record.
Little of the land around Dorchester has burned: 0% within 5 km, 0.2% within 25 km since 1986
Fires mapped since 1986 around where Dorchester’s residents live, and the fuel next to their homes.
Around Dorchester fire takes 0.006% of the land in a typical year, the typical Canadian town 0.000%, which is low.
The closest burn since 1986 lies 18 km from Dorchester’s homes, none within 5 km.
Within 5 km of Dorchester, 58% of the land is forest fuel; widen the ring to 25 km and it is 65%.
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 New Brunswick · highest of 61
Dorchester sits mid-table in New Brunswick: 24th of 61 towns, at 0.006% a year, well behind Tracadie (0.28%).
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.
Some fire is mapped around Dorchester, but not enough to leave the low band, where 92% of Canada’s 2,610 towns are; 7.5% rank 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.
Service New Brunswick - GeoNB has mapped flooding for Dorchester (1 study)
Flood studies whose area touches Dorchester, from NRCan’s inventory, each linked to its owner.
The flood study touching Dorchester is Service New Brunswick - GeoNB’s, dated 2020; its own map shows the zones street by street.
| Study | By | Year | Status |
|---|---|---|---|
| Inland Flood Mapping in New Brunswick and Updated Sea-Level Rise and Flooding Estimates for New Brunswick Coastal Sections 2020 | Service New Brunswick - GeoNB | 2020 | final |
Towns with a flood study on file
Its flood study puts Dorchester with 93% of towns in New Brunswick; 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.
The grade leaves flood out, since a study area says nothing about how many of Dorchester’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 Dorchester $0.020 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.
Nothing unusual about Dorchester’s ground: $0.020 against a typical $0.030, 0.7 times.
Shaking damage a year per $1,000 of building value
Earthquake risk in New Brunswick peaks in St. Stephen ($0.16); Dorchester, at $0.020, is below the median of $0.036.
NRCan seismic risk model (2022): mean yearly building loss per $1,000 of value; medians of towns of 2,500 people or more.
Middle of the pack: 64% of Canada’s 2,611 towns have more earthquake risk than Dorchester.
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).
The loss is to Dorchester’s buildings alone, from ground shaking; infrastructure and secondary hazards are left out.
Natural Resources Canada, Canada’s Seismic Risk Model (2022), by census subdivision (2016 boundaries; a few 2021 subdivisions take their residents’ mean).
Radon runs high around Dorchester: 20% of tested homes over the guideline
Health Canada’s survey of long-term home tests: the share above the 200 Bq/m³ guideline. · Measured across the Region 1 health region: radon tests
A higher share than most: 20% of tested homes around Dorchester, the typical Canadian town 6.6%.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Ordinary for towns in New Brunswick at 20% over 200 Bq/m³ (20% is the median), the area around Dorchester had 3.7% over 600.
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 Dorchester, 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.
The share describes the area, not a house: in Dorchester as anywhere, test to be sure.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011).
Weather and fire alerts for Dorchester
Environment and Climate Change Canada issues the weather alerts for Dorchester; 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 Dorchester come through Environment Canada and Alert Ready; the fire map is CWFIS’s.
Weather alerts (ECCC) · Alert Ready · Fire danger and active fires (CWFIS)
How Dorchester’s neighbours compare on hazards
The same four hazards for the places next door.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Dorchester | Low | $0.020 | 20% | Yes |
| Memramcook 5,616 · 9.4 km | Low | $0.021 | 20% | Yes |
| Sackville 1,286 · 9.8 km | Low | $0.028 | 20% | Yes |
| Sackville 6,572 · 11 km | Low | $0.028 | 20% | Yes |
| Hillsborough 1,414 · 12 km | Low | $0.022 | 20% | Yes |
| Hillsborough 1,569 · 14 km | Low | $0.022 | 20% | Yes |
Sackville (low) has the heaviest fire record of Dorchester’s neighbours, and Dorchester (low) matches or beats it.
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Dorchester faces
Practical steps for Dorchester’s hazards, most pressing first.
- 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. Wildfire is read from the national burned-area record around Dorchester’s homes since 1986, a history of fire that may lower Risk but never raises it.
- Radon is a survey. About 14,000 homes were tested across Canada in 2009–2011, and the share over the guideline for Dorchester is its health region’s, the survey’s design unit.
- Earthquakes are modelled. NRCan models what earthquakes would cost buildings each year on average, subdivision by subdivision; Dorchester’s figure is its subdivision’s.
- 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 Dorchester.
Questions about flooding and hazards in Dorchester
Does Dorchester flood?
There is flood mapping for Dorchester on the national inventory, each study linked to its owner’s map, none of them graded.
How is Dorchester’s Hazard risk Grade worked out?
Hazard risk gives Dorchester C, weighing earthquakes and radon and counting wildfire only against it.
How big is the earthquake risk in Dorchester?
About $0.020 a year per $1,000 of building value, NRCan’s long-run expectation for Dorchester.
Is Dorchester at risk of wildfire?
Some, but Dorchester’s low band (0.2% of nearby land burned since 1986, latest 2017) is short of the level that counts.
Is radon a problem in Dorchester?
The area’s survey found 20% of 107 tested homes above Health Canada’s guideline, so a three-month test is worth doing in Dorchester.
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).