Climate Hazards

• Extreme Heat

  

  Extreme heat is a growing climate hazard that affects people, communities, and natural systems. Heatwaves can also make other hazards worse, such as poor air quality, drought, and wildfire.

  Heatwaves are long periods of unusually high temperatures. They are often caused by slow moving weather systems that trap hot air over an area. Local conditions like urban development, loss of trees, lower elevation, and distance from the coast can increase heat severity. Coastal and higher elevation areas are generally cooler.

  What Was Assessed and Key Findings

  This assessment examined how heatwaves are changing by looking at how often they occur, how long they last, and how severe they are. Climate data from 1981–2010 was compared with projections for the 2050s.

  Results show that:

  • Lower elevation and more populated areas face higher heat risk
  • Heatwaves are expected to become more frequent, longer, and more severe
  • The hottest days may increase from about 28°C to 32°C

  By the 2050s, heatwaves are projected to occur three to four times per year, last longer, and affect a much larger area.

  Why This Matters

  These changes are expected to begin within the next 5 to 10 years. Extreme heat is becoming more dangerous and increases risks to health, infrastructure, and the environment.

  Interactions with Other Hazards

  Extreme heat often occurs with other climate hazards. It can worsen droughts and wildfires and may happen at the same time as windstorms, flooding (coastal, river, and stormwater), and extreme precipitation. In summer, extreme heat is often linked to strong rainstorms caused by warm air rising.

  

  Emergency Management Considerations

  • Use climate pattern forecasts, such as El Niño, to anticipate periods of extreme heat
  • Monitor local weather forecasts for heat warnings
  • Prepare cooling spaces that can be opened quickly, are easy to access, and are available across the area

  Complete Extreme Heat Hazard Description from the Climate Hazard Mapping and Assessment Overview Report PDF

  

• Extreme Cold

  

  Extreme cold can cause snowstorms and blizzards that affect travel, public safety, water systems, and the environment. It usually occurs when very cold Arctic air moves into the area, influenced by large weather patterns such as El Niño and La Niña.

  Local conditions like elevation, valley landscapes that trap cold air, surrounding land and watersheds, and distance from the ocean affect how cold it gets. Higher areas are generally colder, but cold air can also settle in low‑lying areas.

  Key Findings

  This assessment examined how often extreme cold occurs, how long cold events last, and how severe they are, using climate data comparing 1981–2010 with projections for the 2050s.

  Results show that:

  • The coldest conditions occur at higher elevations in less populated areas
  • Extreme cold is expected to become less frequent and less severe
  • Cold spells are likely to be shorter and warmer

  By the 2050s, many lower‑elevation areas may no longer experience extreme cold, with fewer blizzards, less snowfall, and smaller snowpacks.

  Interactions with Other Hazards

  Extreme cold often happens at the same time as other weather hazards. It affects whether precipitation falls as snow or rain. Extreme cold can also occur during drought conditions and strong wind events, such as Arctic outflow winds.

  Other than its effect on precipitation type, no strong links were found between extreme cold and the other climate hazards assessed.

  Emergency Management Considerations

  • Use climate pattern forecasts, such as La Niña, to anticipate colder conditions
  • Monitor local weather forecasts for extreme cold events
  • Prepare warming or shelter spaces that can be quickly opened when needed

  Complete Extreme Cold Hazard Description from the Climate Hazard Mapping and Assessment Overview Report PDF

  

• Extreme Precipitation

  

  Extreme precipitation includes sudden heavy downpours or long periods of intense rain. These events can increase flooding and make other hazards worse.

  They are mainly caused by large weather systems, such as atmospheric rivers in fall and winter, and intense summer rainstorms. Local factors like mountains, watersheds, and elevation affect how much precipitation falls. At higher elevations, heavy precipitation may fall as snow.

  Key Findings

  This assessment used climate data to compare conditions from 1981–2010 with projections for the 2050s.

  Results show that:

  • Higher‑elevation areas receive more precipitation
  • Very wet and extreme precipitation events are becoming more frequent and severe
  • Total rainfall during very wet days is expected to increase by about 30%

  These changes are expected to begin within the next 5 to 10 years, meaning extreme precipitation is a growing risk.

  Interactions with Other Hazards

  Extreme precipitation often causes or worsens other hazards. It directly triggers river flooding, stormwater flooding, and landslides. It can also happen at the same time as coastal flooding, windstorms, or extreme cold when precipitation falls as snow or ice.

  Heavy rainfall can end droughts, but it may also be followed by periods of extreme heat. Extreme precipitation is often linked to heatwaves, when warm conditions create intense rainstorms.

  

  Emergency Management Considerations

  • Use climate forecasts, such as La Niña conditions, to anticipate higher rainfall and hazard risk
  • Follow weather alerts and local forecasts to track heavy rainfall
  • Monitor Nanaimo weather forecasts for changing conditions

  Complete Extreme Precipitation Hazard Description from the Climate Hazard Mapping and Assessment Overview Report PDF

  

• Riverine Flood

  

  Flood risk increases when water is deeper or moving faster.

  River flooding is mainly caused by heavy or long‑lasting rainfall and rapid snowmelt during warm weather. Atmospheric rivers are a major cause of extreme rainfall events. Flood severity is also affected by local factors such as watershed size and shape, slope, soil type, land use, and infrastructure like dams and dikes.

  What Was Assessed

  Flood hazard mapping from existing studies was used for the Nanaimo River and Millstone River. The maps show flooding from a rare, large event (a 200‑year flood) under current conditions and future climate conditions, including increased river flows and sea level rise. Smaller rivers and creeks were not fully assessed.

  Key Findings

  • Parts of the Millstone River, including East Wellington and Buttertubs Marsh, are prone to flooding
  • The Nanaimo River estuary is especially vulnerable, affecting nearly half of several nearby reserve areas
  • Flooding can also occur along smaller rivers and tributaries, though data is limited

  Climate Change Outlook

  By 2100, increased winter rainfall and sea level rise are expected to worsen river flooding. Flood‑prone areas are projected to expand along both major rivers, with notable increases in park and estuary areas. These changes are expected to begin within the next 5 to 10 years, meaning river flood risk is increasing over time.

  Interactions with Other Hazards

  River flooding often occurs with other hazards and can make them worse. It can increase coastal flooding, especially in estuaries, and trigger local stormwater flooding. River flooding frequently happens during heavy rainfall and windstorms.

  Flood risk can also be higher after wildfires or when landslides block rivers or add debris. After flooding, periods of extreme heat or drought may follow if rainfall decreases.

  

  Emergency Management Considerations

  • Use rainfall and climate forecasts, such as La Niña, to anticipate flood risk
  • Link precipitation forecasts with river gauges and flood maps for earlier warnings
  • Use existing flood maps to plan actions before a flood
  • Monitor local river gauge stations

  Complete Riverine Flood Hazard Description from the Climate Hazard Mapping and Assessment Overview Report PDF

  

• Coastal Flood

  

  Coastal flooding can damage buildings, roads, utilities, and natural areas near the shoreline. Flood risk increases with higher water levels and stronger waves, which can also cause shoreline erosion and loss of land.

  Coastal flooding is caused by storm surges from large weather systems, high tides, and rising sea levels. Sea level rise from climate change is steadily increasing coastal water levels. Local conditions such as shoreline slope, ocean depth, natural barriers and coastal structures also affect how far flooding spreads.

  What Was Assessed

  Existing coastal flood maps were used to show a large, rare flood event (a 200‑year flood) under current conditions, the 2050s, and 2100. Areas at risk from coastal erosion were also identified. The mapping does not show all possible flood sizes or frequencies.

  Key Findings

  • Coastal flood risk currently affects areas such as Departure Bay, Downtown Nanaimo, Duke Point, Saysutshun Island, and Protection Island.
  • Flooding is widespread in the Nanaimo Estuary and nearby reserve areas.
  • Some areas, such as North Slope, also face erosion and slope instability.

  Climate Change Outlook

  By 2100, sea level rise is expected to:

  • Worsen flooding in areas already at risk
  • Expand coastal flood areas by about 13%

  These trends are expected to begin within the next 5 to 10 years, meaning coastal flooding risk is increasing over time.

  Interactions with Other Hazards

  Coastal flooding often happens together with other hazards and can make them worse.

  When coastal flooding is the main event, it can:

  • Increase river and stormwater flooding by pushing water back upstream
  • Occur at the same time as windstorms that create storm surge
  • Cause or worsen coastal erosion and cliff failure
  • Be followed by periods of extreme heat or drought

  When coastal flooding happens as a secondary hazard, it is often:

  • Made worse by river flooding
  • Linked to heavy rainfall and stormwater flooding
  • Triggered or intensified by strong windstorms

  In some cases, underwater landslides can also trigger or worsen coastal flooding, such as during tsunami events.

  

  Emergency Management Considerations

  • Use storm surge forecasts and existing flood maps to improve early warnings
  • Use flood maps to identify location‑specific actions before a forecasted flood event

  Complete Coastal Flood Hazard Description from the Climate Hazard Mapping and Assessment Overview Report PDF

  

• Stormwater Flood

  

  Stormwater flooding happens when heavy rain overwhelms local drainage systems. It can flood low‑lying urban areas, damage homes and businesses, and make roads and trails unsafe.

  This type of flooding is mainly caused by intense rainfall. Large weather patterns, such as fall and winter atmospheric rivers, can increase the chance of heavy rain. Local conditions also affect flood risk, including:

  • Urban development, which creates hard surfaces that prevent water from soaking into the ground
  • Local slope and soil conditions
  • The design and condition of stormwater pipes and drains

  Flooding can occur when drainage systems are blocked or cannot handle the volume of water.

  What Was Assessed

  Because information is limited, the assessment focused on existing stormwater studies and known problem areas. The map shows:

  • Areas covered by stormwater models and drainage studies
  • Locations where City staff have observed flooding concerns

  Projections for future extreme rainfall were also reviewed and are summarized with the extreme precipitation hazard.

  Key Findings

  • About 55% of the LSA has been studied using stormwater models or drainage plans
  • Most known problem areas are within locations already studied
  • Many flooding concerns occur close to streams or lakes and may also be affected by river flooding

  Future Trends

  Stormwater flooding risk is expected to increase due to:

  • More intense rainfall events, especially longer storms
  • A projected increase of over 20% in one‑day rainfall intensity
  • Ongoing urban growth, which may increase hard surfaces from 65% to 80% by 2046

  Recent modelling has begun to include climate change, which may help reduce future risk. However, without careful planning and maintenance, stormwater flooding is expected to worsen over the next 5 to 10 years.

  Interactions with Other Hazards

  Stormwater flooding is mainly caused by heavy rainfall. It can also be made worse when rivers or coastal waters back up into storm drains. Landslides or debris can increase flooding by blocking drains.

  Stormwater flooding often follows drought at the start of the rainy season. Flooding events may also be followed by periods of extreme heat.

  

  Emergency Management Considerations

  • Use climate forecasts, such as La Niña, to anticipate higher rainfall and flood risk
  • Follow weather alerts and local forecasts to track heavy rain
  • Continue to monitor known flood‑prone areas

  Complete Stormwater Flood Hazard Description from the Climate Hazard Mapping and Assessment Overview Report PDF

  

• Drought

  

  Water is essential for people, the economy, and the natural environment. Drought happens when there is too little rainfall over time or when high temperatures increase water loss. Large‑scale climate patterns and local factors like soil type, land use, and water storage affect how drought develops.

  What Was Assessed

  The assessment looked at both natural water supply (rainfall, rivers, and climate projections) and human water management (future demand and drinking water system capacity).

  Key Findings

  • The local water supply depends mainly on rainfall in the Upper Nanaimo River watershed
  • Droughts appear to be lasting longer and occurring later in summer
  • Future water availability depends on temperature and rainfall changes
  • The drinking water system is strong, with conservation measures in place

  Most drinking water comes from Jump Lake Dam, which is expected to meet demand until at least 2061.

  Future Trends

  By the 2050s, temperatures are expected to increase, with less summer rain and more rain in other seasons. Because of uncertainty in climate impacts and water use, drought risk over the next 5–10 years is unclear and should continue to be monitored.

  Interactions with Other Hazards

  Drought increases the risk of extreme heat and wildfires. It can also weaken soils and vegetation, making landslides more likely. Drought is often followed by heavy rainfall, which can cause flooding.

  

  Emergency Management Considerations

  • Use climate forecasts, such as El Niño, to anticipate drought risk
  • Monitor the BC Drought Information Portal
  • Regularly review risks to the drinking water system

  Complete Drought Hazard Description from the Climate Hazard Mapping and Assessment Overview Report PDF

• Windstorm

  

  Windstorms can damage trees, powerlines, and other critical infrastructure. Their impacts can be widespread.

  Windstorms are caused by strong differences in air pressure, often due to temperature differences between land and ocean. Local features such as hills, valleys, forests, urban areas, and open coastlines affect how strong winds become.

  Key Findings

  • Strong winds are more common near the coast and over the Salish Sea
  • Extreme wind events vary widely by location and season
  • Most extreme winds occur in winter and spring
  • Some areas are sheltered by islands, while more exposed areas, such as North Slope, are at higher risk

  
  

  Climate Change Trends

  Data is limited, but average wind speeds may be increasing slightly. There is low confidence in changes to extreme winds, but this trend may continue over the next 5 to 10 years.

  Interactions with Other Hazards

  Windstorms often occur with other hazards, including:

  • Extreme cold
  • Heavy rainfall and flooding
  • Coastal flooding from storm surge

  During dry or warm periods, windstorms can worsen drought, spread dust, and increase wildfire risk.

  

  Emergency Management Considerations

  • Improve monitoring of extreme wind speeds across the area
  • Focus on reducing risk and increasing resilience to windstorm damage, especially in exposed locations

  Complete Windstorm Hazard Description from the Climate Hazard Mapping and Assessment Overview Report PDF

  

• Wildfire

  

  Wildfires can harm:

  • Homes and infrastructure
  • Wildlife habitat and ecosystems
  • Human health

  Wildfires start when an ignition source, such as human activity or lightning, meets dry vegetation. Risk is higher during hot, dry weather with low humidity. Large‑scale climate patterns affect how often these conditions happen.

  Fire behaviour is influenced by:

  • Type and amount of vegetation
  • Past logging, insect damage, or previous fires
  • Slope and terrain
  • Fire suppression efforts

  A wildfire assessment used local climate data, terrain, and fuel types to model fire spread, intensity, and how difficult fires may be to control, including areas outside the local boundary where fires could spread from.

  Key Findings

  • About half of the study area has moderate or high wildfire hazard
  • Forested land along the western edge poses the highest risk
  • A fire starting in this area could spread quickly toward nearby communities if not controlled

  Climate Change Trends

  Wildfire risk is expected to increase with more extreme heat and longer dry periods. Conditions suitable for wildfires are likely to happen more often, and burned areas are expected to increase.

  These trends are expected to begin within the next 5 to 10 years, meaning wildfire risk is growing.

  Interactions with Other Hazards

  Wildfires often happen during extreme heat and drought, which dry out vegetation and make fires easier to start and spread. Strong winds can also increase wildfire spread.

  After a wildfire, burned areas are more likely to experience river flooding, stormwater flooding, and landslides because vegetation is lost and soils are weakened. Heavy rainfall can reduce wildfire activity by putting fires out.

  

  Emergency Management Considerations

  • Use climate forecasts, such as El Niño, to anticipate higher wildfire risk
  • Plan for limited water supply during drought, which can affect firefighting
  • Focus on wildfire education, prevention, and preparedness
  • Use tactical response plans to help contain wildfires during severe conditions

  Complete Wildfire Hazard Description from the Climate Hazard Mapping and Assessment Overview Report PDF

  

• Mass Movement Geohazards

  

  Mass movement geohazards happen when soil, rock, or debris moves downhill. These events can occur suddenly and damage buildings, roads, and utilities.

  They are caused by heavy or long rainfall, rapid snowmelt, freeze‑thaw cycles, earthquakes, and local land conditions such as steep slopes, soil type, land use changes, and human activities.

  What Was Assessed

  Four types of unstable slope hazards were identified:

  • Rockfall
  • Rock‑topple
  • Coastal slides
  • Slope instabilities in drainage areas

  These hazards were mapped using modeling techniques and professional judgement. The results show areas with minor, moderate, and high likelihood of slope instability.

  Key Findings

  • Most areas have a minor or moderate likelihood of instability and require management.
  • A small coastal area has a high likelihood of instability and is not suitable for development without further study.
  • Maps are approximate and based on desktop analysis only.

  Interaction with other Hazards

  Mass movement hazards (such as landslides and debris flows) often occur alongside flooding. They can worsen river, coastal, and stormwater flooding by blocking rivers and drains, adding sediment, eroding coastlines, or even triggering small tsunamis. Extreme rainfall is the main driver of these hazards, while flooding, wildfires, and drought can increase the risk of future mass movements.

  

  Climate Change Outlook

  By the 2050s, climate change is expected to increase slope instability due to higher rainfall, warmer temperatures, and sea level rise.

  Hazard events are likely to become more frequent over the next 5–10 years.

  Complete Mass Movement Geohazards Description from the Climate Hazard Mapping and Assessment Overview Report PDF