Photo: Rub-a-dub Hedgehog · CC BY 4.0Radon is Chatham’s main hazard: 17% of tested homes in its area top Health Canada’s guideline
Wildfire is rare near Chatham: 0% of the land within 25 km has burned since 1986, a burn rate of 0.001% a year. Earthquake risk in Chatham is ordinary: NRCan’s model puts building losses at $0.021 a year per $1,000 of value, close to the typical town’s $0.030. Chatham grades C for hazard risk; wildfire is low here, so it earns no credit.
What stands out about Chatham’s hazards
For Chatham, from NRCan’s seismic model, Health Canada’s radon survey, the national burned-area record and the flood map inventory.
What Chatham faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Chatham grades C for hazard risk
Risk averages earthquakes and radon; wildfire joins only where it pulls the average down, so a town like Chatham with little fire nearby would get no credit for it.
Its place: #833 of 866 in Ontario and #2,068 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 Chatham: 0% of the land within 25 km burned since 1986, 0% within 5 km
Past fire around Chatham’s homes, from the national burned-area record, with the fuel within 5 km.
The land within 25 km of Chatham burns at 0.001% a year on average, the low band; the typical Canadian town: 0.000%.
Around Chatham the forest is thin or far off: 0.2% of the land within 5 km and 0.8% within 25 km is forest fuel.
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 871
Chatham ranks 83rd of the 871 towns in Ontario for burn rate, at 0.001% a year; Sioux Lookout leads with 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.
Beside 2,610 Canadian towns, Chatham reads low, with 92% of them; only 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.
Chatham is on the flood map inventory: 2 studies, latest by Essex Region Conservation Authority / County of Essex
What Canada’s Flood Map Inventory lists for Chatham: who studied flooding and where to see their maps.
Essex Region Conservation Authority / County of Essex and others have studied flooding in areas that include Chatham: 2 studies, the latest from 2024.
| Study | By | Year | Status |
|---|---|---|---|
| Essex Region | Essex Region Conservation Authority / County of Essex | 2024 | final |
| SCRCA Floodplain Estimation Study for Ontario Regulation 171-06 | St. Clair Region Conservation Authority | 2009 | final · not public |
Towns with a flood study on file
Chatham is one of the 69% of towns in Ontario with a flood study on file; across Canada it is 58%.
NRCan Canada Flood Map Inventory: a study footprint touching the town’s boundary; towns of 2,500 people or more.
Flood mapping around Chatham has come in steps: 2 studies from the 2000s to the 2020s.
Study dates as the NRCan inventory lists them, one count per study touching Chatham.
Nothing here counts toward Risk; the studies are pointers to the maps their owners keep for Chatham.
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.
Expected shaking damage in Chatham: $0.021 a year per $1,000
Expected yearly building losses from earthquakes, from Natural Resources Canada’s model.
With $0.021 of shaking damage a year per $1,000, Chatham is about even with the typical $0.030 (0.7 times).
Shaking damage a year per $1,000 of building value
Chatham’s $0.021 sits under the median in Ontario, $0.043, and well under Alexandria’s $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.
Middle of the pack: 63% of Canada’s 2,611 towns have more earthquake risk than Chatham.
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 Chatham 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).
Radon runs high around Chatham: 17% of tested homes over the guideline
Long-term radon tests in homes across the survey area, against Health Canada’s guideline.
More homes than usual test high around Chatham: 17% against 6.6% for the typical Canadian town. Chatham doesn’t get its own radon tests figures; the ones here come from the Chatham-Kent Health Unit.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Chatham’s area, at 17%, is above the median in Ontario (4%), and 3% of its tests passed 600 Bq/m³.
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
4.6% of Canada’s 2,611 towns have a higher share of homes over 200 Bq/m³ than Chatham, in the 10–20% band with 22%.
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 Chatham 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 Chatham
Environment and Climate Change Canada issues the weather alerts for Chatham; 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. |
In fire season, check CWFIS for danger and active fires around Chatham, and listen to local authorities for orders.
Weather alerts (ECCC) · Alert Ready · Fire danger and active fires (CWFIS)
Get ready for what Chatham faces
What to do about the hazards Chatham 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. 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 Chatham.
- Earthquakes are modelled. The earthquake figure is an expected loss, not a forecast, worked out by NRCan for each census subdivision, Chatham’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 Chatham sits in.
- 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 Chatham floods.
Questions about flooding and hazards in Chatham
Is Chatham at risk of wildfire?
Less than most of Canada: 0% of the land within 25 km of Chatham has burned since 1986, the last in 2025, a low band that leaves Risk alone.
How big is the earthquake risk in Chatham?
In NRCan’s seismic model, Chatham’s buildings lose $0.021 per $1,000 of value in an average year.
Is radon a problem in Chatham?
In Health Canada’s survey, 17% of 201 homes tested in Chatham’s area were above 200 Bq/m³, though only a test tells you about one house.
How is Chatham’s Hazard risk Grade worked out?
Chatham’s Hazard risk grade is C, built on earthquakes and radon with a one-sided wildfire input.
Does Chatham flood?
Chatham’s area has been studied for flooding, and the owner’s map shows which streets lie in a zone; the grade leaves flood out.
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).