Pacific Northwest Flooding

Unprecedented rainfall causes flooding across the us-canada border, november 2021

The Canadian province of British Columbia and the US state of Washington experienced significant and widespread flooding after a powerful storm brought record rainfall to the Pacific Northwest.

The rainfall has been described as the worst to hit the region in a century, with impacts significantly greater than expected (Washington Post, 2021). At least two fatalities have been reported due to flooding and landslides.

Our specialist Event Response team has produced a flood footprint for the event, estimating extents and depths for the areas affected. Sign up using the form at the bottom of the page to receive it straight to your inbox, or email for access.


The Pacific Northwest has received unusually heavy rainfall between September and November after a series of storms occurred in the region, with the storms linked to an atmospheric river, or a narrow corridor of concentrated moisture in the atmosphere (Guardian 2021a).

This rainfall reached a peak during the most recent storm, from 13-15 November, when the region saw over a month’s worth of rainfall in just two days in some places, much of which fell on already saturated ground (NASA EO, 2021).

Areas east of Vancouver received nearly 600mm (23.6 inches) of rain between 14 and 15 November (Guardian, 2021b) – over double the average November rainfall for Vancouver of around 200mm (7.9 inches) (Weather Statistics, 2021).

Bellingham International Airport in Washington State recorded 141mm (5.57 inches) of rainfall in two days, compared to the average rainfall for the whole of November of 132mm (5.2 inches) (AP News, 2021). Western Washington has received almost relentless rain since Mid-October, with some areas reaching 1.01m (40 inches) in 30 days (Washington Post, 2021).

Much of the rainfall reported in the region has broken historical daily and two-day records (NASA EO 2021).

Impacts in Canada

The Premier of British Columbia issued a state of emergency on Monday 15 November, with military personnel deployed to help evacuation and rescue efforts (Guardian 2021b) and restrictions expected on resources, travel and supplies (Vancouver Sun, 2021).

At least one fatality has been confirmed in British Columbia at the time of writing, with several more reported missing (Guardian 2021c) and thousands of people affected by flooding and landslides throughout the region (Guardian 2021b).

The city of Vancouver, supply links to Vancouver port, and the surrounding areas, including Squamish, were cut off by floodwaters, with road and rail links inundated with floodwater and mudslides (Guardian 2021b).

In Merritt, all 7,000 residents were placed under mandatory evacuation after a bridge collapsed into the Nicola river. Further south in Princeton, 290 homes were evacuated as the Tulameen River breached its banks and inundated properties within the town (Saanich News, 2021).

In the city of Abbotsford, which sits on the low lying plain of the former Sumas Lake, 180 residents were evacuated due to fears of local pump stations failing. The pump stations divert water from the former lake at half a million gallons a minute (Guardian 2021b). Residents in Chilliwack worked to protect its local pump station, including building a wall of sandbags, after parts of the town were placed under evacuation orders (Global News, 2021).

While the pump stations have held so far, water levels continue to rise in Fraser Valley, with the Nooksack River from Washington State pushing water north and further rain expected (Toronto Star 2021b). The mayor of Abbotsford has stated an urgent need for repair of broken dikes in Fraser Valley (Toronto Star 2021b). Surrounding areas of Fraser Valley, including Chilliwack, continue to be at risk of rising water levels.

Several major roads have been damaged or destroyed, with parts of Coquihalla highway and the Trans-Canada highway washed away, and Highway 99 damaged by a landslide (Guardian 2021b).

The effects of the flooding are not solely confined to human impacts. Thousands of farm animals have died or were trapped by flood waters, largely in British Columbia’s central agricultural region of Abbotsford (Guardian 2021c).
Over 120 farms in the Abbotsford area were under evacuation orders on Tuesday 16 November (Guardian 2021c), with many farm buildings seen to be flooded in aerial imagery.

Impacts in US

Washington State has borne the brunt of the storm in the US, with thousands of residents impacted by floodwaters. On Monday 15 November, Governor Jay Inslee declared a severe weather state of emergency in 14 counties (AP News 2021).

One fatality has been recorded near Everson after an individual was reported missing following being swept off the road (Washington Post 2021; AP News 2021).

At the height of the storm, over 150,000 people were without power in western Washington, with more than 30,000 still cut off on Tuesday 16 November (AP News 2021).

In the border town of Sumas, 1,600 people were without power and a reported 75% of homes in the town had some level of water damage (Guardian 2021b; AP News 2021). In Ferndale, residents and businesses were urged to evacuate in an area near the Nooksack River as water levels rose (AP News 2021).

Interstate 5, the US west coast’s main north-south highway, was temporarily shut due to landslide debris with further work expected to fully restore the road, while trains in Sumas and wider western Washington stopped until tracks could be inspected and repaired (AP 2021).

Flood warnings were in place for several rivers around western Washington, with four rivers reported to have reached record levels (Washington Post, 2021). A flood wall constructed in 2016 on the Skagit River, south of Bellingham, however, was deemed a success for holding back water levels (AP News 2021).

Financial losses and historical events

Due to the severity of infrastructure damage and the inclement weather of winter months, repairs are expected to take weeks, if not longer (Washington Post, 2021; Toronto Star, 2021a).

Economic impacts are expected to grow as supply chains continue to be disrupted, including huge amounts of agricultural produce in Abbotsford that is unable to leave the province (Toronto Star 2021a; Vancouver Sun, 2021).

Steve Bowen, Head of Catastrophe Insight at Aon, estimates that losses could be a minimum of hundreds of millions USD, with the potential to pass the billion-dollar threshold (Washington Post, 2021).

This estimation places the most recent flooding in line with some of the most significant floods in recent history in the region (Table 1).

Table 1: Historical events in the Pacific Northwest region in recent history. Sources: National Weather Service 2021; CBC News, 2003; The Globe and Mail, 2003.

Climate change and land use change

Scientists and agriculturalists are already pointing to climate change and changes in land use as major factors contributing to the severity of this event.

The effects of the region's summer heatwaves in 2021 are still being felt, with scientists analysing the heatwaves finding that climate change made extreme weather “at least 150 times more likely” (Guardian, 2021a).

Wildfires caused by extreme heat means that land already suffering from deforestation caused by logging becomes stripped of vegetation, with nothing to stop surface water travelling rapidly into valleys and rivers (Guardian, 2021a).

The abrupt change from extreme dry to extreme wet conditions, a phenomenon known as ‘precipitation whiplash’, is expected by scientists to increase with climate change in parts of western North America. In fact, it is believed that these dry-to-wet precipitation events could increase by 25 to 100 percent in California (Washington Post, 2021).

When seen in conjunction with the lengthening and widening of atmospheric rivers – long, narrow regions in the atmosphere that transport most of the water vapour outside of the tropics (NOAA, 2015) – and slope instability caused by wildfires and the over-felling of forests, the autumn floods in Canada and the USA are an example of a “compound climate disaster” (Guardian, 2021a).

Our specialist Event Response team has produced a flood footprint for the event, estimating extents and depths for the areas affected. Sign up using the form below to receive it straight to your inbox, or email for access.

It’s vital that organisations act now in response to flood risk. We offer flood mapping and probabilistic flood modelling worldwide, including for the US and Canada, which provides flood risk insights at any location globally. This can help re/insurers, financial organisations, and the International Development sector to better understand and manage flood risk.

To find out more about our flood data and how it can help you, get in touch with the team.

This report is covered by JBA’s website terms – please read them here.


AP News. 2021. Northwest storm: ‘devastating’ flood damage, 1 dead in BC. AP News. [online] 17 November 2021. Available at: [Accessed 19 November 2021].

CBC News. 2003. B.C. hit with more rain, flooding forces 800 to flee homes. CBC News. [online] 21 October 2003. Available at: [Accessed 23 November 2021].

Global News. 2021. B.C. flooding: Chilliwack downgrades evacuation orders for Yarrow, Majuba Hill. Global News. [online] 17 November 2021. Available at: [Accessed 19 November 2021]

The Globe and Mail. 2003. Search called off for B.C. flood victims. The Globe and Mail. [online] 23 October 2003. Available at: [Accessed 23 November 2021].

The Guardian. 2021a. How bad is the British Columbia and Pacific north-west flooding and what caused it? The Guardian. [online] 18 November 2021. Available at: [Accessed 19 November 2021].

The Guardian. 2021b. Military deployed as British Columbia grapples with devastating floods. The Guardian. [online] 18 November 2021. Available at: [Accessed 19 November 2021].

The Guardian. 2021c. Canada floods leave thousands of farm animals dead and more trapped. The Guardian. [online] 18 November 2021. Available at: [Accessed 19 November 2021].

NASA Earth Observatory. 2021. Severe Flooding in the Pacific Northwest. NASA Earth Observatory. 14 November 2021. [online] Available at: [Accessed 19 November 2021].

National Weather Service, National Oceanic and Atmospheric Administration. 2021. Flooding in Washington. 2021. [online] Available at: [Accessed 23 November 2021].

National Oceanic and Atmospheric Administration. 2015. What are atmospheric rivers? 2015. [online] Available at: [Accessed 22 November 2021].

Saanich News. 2021. 290 homes in Princeton under evacuation as flooding causes chaos. Saanich News. [online] 15 November 2021. Available at: [Accessed 19 November 2021].

Toronto Star. 2021a. B.C storm disrupts supply chain, could have lasting impacts on economy: experts. Toronto Star. [online] 17 November 2021. Available at: [Accessed 19 November 2021].

Toronto Star. 2021b. Essential access only on some B.C highways but major infrastructure to be rebuilt. Toronto Star. [online] 18 November 2021. Available at: [Accessed 19 November 2021].

Vancouver Sun. 2021. B.C. floods: floodwaters recede in Abbotsford for now as state of emergency declared. Vancouver Sun. [online] 17 November 2021. Available at: [Accessed 19 November 2021].

Washington Post. 2021. First fires, now floods: British Columbia and Washington reeling from atmospheric river. Washington Post. [online] 18 November 2021. Available at: [Accessed 19 November 2021].

Weather Statistics. 2021. Total precipitation – monthly data for Vancouver. 2021. [online] Available at: [Accessed 19 November 2021].