Photo: James O'Brien · CC BY-SA 4.0Earthquake risk in Lake Cowichan runs 28 times the typical Canadian town’s: $0.85 per $1,000 a year
Fire seldom reaches Lake Cowichan: since 1986, 0.3% of the land within 25 km has burned (0.008% a year). In Health Canada’s survey, just 0.9% of homes tested in the area exceeded 200 Bq/m³ (6.6% typical). Hazard risk gives Lake Cowichan a grade of B−; its wildfire band pulls it down.
What stands out about Lake Cowichan’s hazards
For Lake Cowichan, from NRCan’s seismic model, Health Canada’s radon survey, the national burned-area record and the flood map inventory.
What Lake Cowichan faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Lake Cowichan grades B− for hazard risk
Two inputs always count for Lake Cowichan, earthquakes and radon; the third, wildfire, counts only against a town.
Its place: #166 of 254 in British Columbia and #1,702 of 2,589 Canadian towns.
How sure: Earthquake losses are a model’s expectation over many years, not a forecast for any one. The burned-area record misses fires under about 10 ha and most grass and farm fires.
Few fires near Lake Cowichan: 0.1% within 5 km, 0.3% within 25 km
Fires mapped since 1986 around where Lake Cowichan’s residents live, and the fuel next to their homes.
Forty years of fire maps put Lake Cowichan at 0.008% a year, low next to the typical Canadian town’s 0.000%.
Near or far, forest fuel covers a similar share around Lake Cowichan: 81% within 5 km and 82% 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 British Columbia · highest of 255
Lake Cowichan burns at 0.008% a year, 104th of 255 towns in British Columbia; the leader, Oliver, reaches 0.98%.
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 Lake Cowichan, 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.
Ministry of Environment and Climate Change Strategy has mapped flooding for Lake Cowichan (1 study)
Flood studies whose area touches Lake Cowichan, from NRCan’s inventory, each linked to its owner.
A 1984 study by Ministry of Environment and Climate Change Strategy covers Lake Cowichan, and its map, not the inventory, shows the zones.
| Study | By | Year | Status |
|---|---|---|---|
| Cowichan Lake Floodplain Mapping | Ministry of Environment and Climate Change Strategy | 1984 | final |
Towns with a flood study on file
Flood maps are common in British Columbia: 76% of towns have one, against 58% nationally, and Lake Cowichan is among them.
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 Lake Cowichan’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.
Shaking is Lake Cowichan’s costliest hazard: $0.85 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.
The typical town loses $0.030 a year to shaking; Lake Cowichan loses $0.85, 28.3 times as much.
Shaking damage a year per $1,000 of building value
Lake Cowichan’s $0.85 tops the median in British Columbia, $0.36, though Duncan reaches $1.33.
NRCan seismic risk model (2022): mean yearly building loss per $1,000 of value; medians of towns of 2,500 people or more.
Lake Cowichan is in the top tenth of Canada’s 2,611 towns for earthquake risk; 0.2% 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 Lake Cowichan 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 low around Lake Cowichan: 0.9% of tested 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 Central Vancouver Island health region
Lake Cowichan’s survey area reads 0.9% over the guideline, under the typical Canadian town’s 6.6%.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
The median in British Columbia is 1.8% over 200 Bq/m³; around Lake Cowichan it is 0.9%.
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
Lake Cowichan is in the lowest band, with 37% of Canada’s 2,611 towns: under 5% of tests over the guideline, while 63% have more.
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, Lake Cowichan’s included, whatever the area’s figure.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011).
Where to get warnings in Lake Cowichan
Environment and Climate Change Canada issues the weather alerts for Lake Cowichan; 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 Lake Cowichan, 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 Lake Cowichan’s neighbours compare on hazards
The same four hazards for the places next door.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Lake Cowichan | Low | $0.85 | 0.9% | Yes |
| Electoral Area F, Cowichan Valley 1,837 · 5.3 km | Low | $0.59 | 0.9% | Yes |
| Electoral Area I, Cowichan Valley 1,521 · 12 km | Low | $0.54 | 0.9% | Yes |
Among its neighbours Lake Cowichan has the most fire on record (low); Electoral Area I, Cowichan Valley follows (low).
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Lake Cowichan faces
What to do about the hazards Lake Cowichan 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
- Radon is a survey. About 14,000 homes were tested across Canada in 2009–2011, and the share over the guideline for Lake Cowichan is its health region’s, the survey’s design unit.
- 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 Lake Cowichan.
- Earthquakes are modelled. Seismic risk is NRCan’s model of yearly building losses from shaking, averaged over many years and given for Lake Cowichan’s census subdivision (a neighbourhood shows its city’s).
- Wildfire counts one way. For Lake Cowichan, wildfire means how much nearby land burned in the past forty years, a one-way input that can pull Risk down and nothing more.
Questions about flooding and hazards in Lake Cowichan
Does Lake Cowichan flood?
There is flood mapping for Lake Cowichan on the national inventory, each study linked to its owner’s map, none of them graded.
How big is the earthquake risk in Lake Cowichan?
About $0.85 a year per $1,000 of building value, NRCan’s long-run expectation for Lake Cowichan.
Is radon a problem in Lake Cowichan?
Around Lake Cowichan, 109 survey homes were tested and 0.9% came in over 200 Bq/m³, a guide to the area, not to any one home.
Is Lake Cowichan at risk of wildfire?
Fire has reached 0.3% of the land around Lake Cowichan since 1986 (last in 2025); at low, it neither helps nor hurts the grade.
How is Lake Cowichan’s Hazard risk Grade worked out?
Lake Cowichan grades B− for hazard risk, from earthquakes and radon, with wildfire counted only where it lowers the grade.
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).