Photo: SimonP · CC BY-SA 3.0Alderwood is on Canada’s flood inventory: 1 listed, led by Toronto Regional Conservation Authority
No wildfire is mapped within 25 km of Alderwood’s homes since 1986 (0% of the land, 0.000% a year). Shaking is about as much of a worry in Alderwood as in most places, at $0.043 a year per $1,000 of building value ($0.030 typical). Fewer homes than usual carry radon here, 2.7% over the guideline where the typical town has 6.6%. Hazard risk gives Alderwood a grade of A−, from earthquakes and radon alone.
What stands out about Alderwood’s hazards
Four national sources, each read for Alderwood: earthquakes, radon, past fires and flood studies.
What Alderwood faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Alderwood grades A− for hazard risk
Two inputs always count for Alderwood, earthquakes and radon; the third, wildfire, counts only against a town.
Its place: #285 of 866 in Ontario and #700 of 2,589 Canadian towns.
How sure: The seismic figure is a long-run average from NRCan’s model, not a prediction. Only 74 homes were tested in the survey area, so the radon share is rough. Small fires and grass fires are largely missing from the national burned-area record.
Little of the land around Alderwood has burned: 0% within 5 km, 0% within 25 km since 1986
Fires mapped since 1986 around where Alderwood’s residents live, and the fuel next to their homes.
Around Alderwood fire takes 0.000% of the land in a typical year, the typical Canadian town 0.000%, which is low.
Little near Alderwood’s homes can carry a forest fire; only 0% of the land within 5 km is forest fuel, and 0.5% 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 Ontario · highest of 871
Little or nothing burns around Alderwood in a typical year; 638 of the 871 towns in Ontario share that, and Sioux Lookout leads at 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.
92% of Canada’s 2,610 towns are in the low band and 7.5% above it; Alderwood is among the many where the yearly burn rate rounds to zero.
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.
Alderwood is on the flood map inventory: 1 study, by Toronto Regional Conservation Authority
Flood studies whose area touches Alderwood, from NRCan’s inventory, each linked to its owner.
The flood study touching Alderwood is Toronto Regional Conservation Authority’s, dated 2021; its own map shows the zones street by street.
| Study | By | Year | Status |
|---|---|---|---|
| Toronto Floodline Consolidation | Toronto Regional Conservation Authority | 2021 | final |
Towns with a flood study on file
Alderwood 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 is shown here, never graded: a study says where a map exists, not how many of Alderwood’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.
Expected shaking damage in Alderwood: $0.043 a year per $1,000
NRCan’s seismic risk model: the damage shaking is expected to do to buildings each year, on average over many years.
At $0.043 per $1,000, Alderwood’s earthquake risk is about the typical Canadian town’s ($0.030; 1.4 times).
Shaking damage a year per $1,000 of building value
Neither high nor low in Ontario: Alderwood’s $0.043 sits by the median of $0.043, while Alexandria reaches $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.
Neither high nor low for Canada: 36% of the 2,611 towns expect more damage than Alderwood.
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).
Roads, pipes and bridges aren’t in Alderwood’s figure, nor landslides or tsunami: it is buildings and shaking.
Natural Resources Canada, Canada’s Seismic Risk Model (2022), by census subdivision (2016 boundaries; a few 2021 subdivisions take their residents’ mean). · Not measured by town: earthquake risk (the city of Toronto)
Little radon around Alderwood: 2.7% of area homes over the 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 City of Toronto Health Unit
At 2.7% over the guideline, the area around Alderwood is under the typical Canadian town’s 6.6%.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Alderwood’s area, at 2.7%, is below the median in Ontario (4%).
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
The quietest radon band, under 5%, holds 37% of Canada’s 2,611 towns and Alderwood; 63% sit 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 survey sample isn’t a map: any home in Alderwood can be high, and a three-month test is the only way to know.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011).
Weather and fire alerts for Alderwood
Environment and Climate Change Canada issues the weather alerts for Alderwood; 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. |
For fires near Alderwood, the national fire information system maps danger and active fires daily; local authorities give any evacuation order.
Weather alerts (ECCC) · Alert Ready · Fire danger and active fires (CWFIS)
How Alderwood’s neighbours compare on hazards
The same four hazards for the places next door.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Alderwood | Low | $0.043 | 2.7% | Yes |
| Long Branch 11,400 · 1.6 km | Low | $0.043 | 2.7% | Yes |
| New Toronto 11,502 · 2.8 km | Low | $0.043 | 2.7% | None listed |
| Dixie 3,749 · 2.9 km | Low | $0.040 | 0% | Yes |
| Lakeview 21,789 · 3.1 km | Low | $0.040 | 0% | Yes |
| Etobicoke City Centre 23,856 · 3.5 km | Low | $0.043 | 2.7% | Yes |
| Mimico-Queensway 18,207 · 3.9 km | Low | $0.043 | 2.7% | Yes |
Long Branch (low) has the heaviest fire record of Alderwood’s neighbours, and Alderwood (low) matches or beats it.
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Alderwood faces
What to do about the hazards Alderwood 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
- 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 Alderwood sits in.
- Earthquakes are modelled. Shaking damage is modelled from the ground, the buildings and the odds of each quake, and published for whole subdivisions such as Alderwood’s.
- Wildfire counts one way. The wildfire figure is the share of land within 25 km of Alderwood’s homes burned each year from 1986 to 2025, past fire rather than a forecast, and it can only lower Risk.
- 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 Alderwood floods.
Questions about flooding and hazards in Alderwood
Is Alderwood at risk of wildfire?
Very little by the national record: Alderwood’s band is low, with 0% of the land within 25 km burned since 1986, so wildfire doesn’t change its grade.
Is radon a problem in Alderwood?
Around Alderwood, 74 survey homes were tested and 2.7% came in over 200 Bq/m³, a guide to the area, not to any one home.
How big is the earthquake risk in Alderwood?
Expected earthquake damage in Alderwood comes to $0.043 a year for each $1,000 that buildings are worth.
How is Alderwood’s Hazard risk Grade worked out?
Hazard risk gives Alderwood A−, weighing earthquakes and radon and counting wildfire only against it.
Does Alderwood flood?
Alderwood’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).