What is Sumas Lake? 100 years ago, Abbotsford had a 134 sq km lake (PHOTOS)

Nov 17 2021, 6:58 pm

On a typical day, 80,000 vehicles drive along the Fraser Valley stretch of Highway 1 between the Whatcom Road interchange in Abbotsford and the Yale Road interchange in Chilliwack.

But almost a century ago, this 10 km highway segment, roughly following the southeastern perimeter of the base of Sumas Mountain, was the shoreline of the vast Sumas Lake. The agricultural and livestock areas that stretch from Sumas Mountain in the northwest to Vedder Mountain in the southeast are on a low-lying area that was previously the bottom of a lake.

Depending on the source, the estimated size of the former Sumas Lake greatly varies, but there was consensus that this was a significant body of water that greatly fluctuated in size as the seasons changed.

In its surveys following the region’s 1990 flood, the United States Army Corps of Engineers estimated the dormant lake’s maximum extent, reaching across the border at times, was about 80 sq km — equivalent to over 20% the geographic size of the City of Abbotsford today or 70% of the City of Vancouver. Put another way, Sumas Lake was 13 times larger than Cultus Lake or 20 times larger than Stanley Park.

The provincial government’s records of estimated springtime rainfall and snowmelt into the Chilliwack and Vedder rivers grew the lake’s size from about 40 sq km to up to approximately 134 sq km, equivalent to the size of Vancouver, New Westminster, and the University of British Columbia’s Point Grey campus combined.

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Map of the baseline size of the former Sumas Lake (outlined in dotted blue) and the historical extent of the lake from freshet (outlined in dotted black). (Sean Moore)

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Map of the Sumas Lake area. (City of Vancouver Archives)

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Historic map of the former interurban railway system in the Lower Mainland, including a depiction of Sumas Lake, circled in red. (UBC)

The ever-changing lake shoreline was highly problematic for European farmers in the late 1800s and early 1900s, who saw their crops frequently destroyed by the lack of predictability in the size of the water body from seasonal freshet. However, there was opposition to the approach from local Indigenous populations, who depended on the lake as a source of food and their way of life. In 2013, the descendents of the Sumas First Nation contemplated pursuing compensation for historic losses from the disappearance of the lake.

But European settlers in the early 1900s also made their case for draining the lake by pointing out that it created a mosquito population nightmare during the flood season. Research by Abbotsford’s The Reach Gallery Museum states the mosquitoes were such a problem to the extent that it forced schools to close, with children kept indoors for up to six weeks. As well, farmers reported that unprotected young livestock died from the loss of blood.

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Panorama of Sumas Lake, 1922. (The Reach Gallery)

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Sumas Lake, early 1900s. (The Reach Gallery)

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Sumas Lake, early 1900s. (The Reach Gallery)

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Sumas Lake, early 1900s. (The Reach Gallery)

According to a 1996 UBC thesis by Caroline Berka on the Sumas River watershed, the lake was drained and reclaimed in 1925 with the completion of the Vedder Canal and Sumas Pump Station, which diverted the Sumas River along four creeks. As well, 40 km of flood protection dikes were also built at the time.

Within a few years, tens of thousands of acres of farmland were added to the Lower Mainland, becoming the Sumas Prairie of quilted, pristine green fields. This area of the former lake bed became some of the most productive farmland in Canada.

BEFORE; Sumas Lake before the 1924 drainage:

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Sumas Lake, early 1900s. (The Reach Gallery)

AFTER; Sumas Prairie, previously Sumas Lake, after the 1924 drainage:

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Sumas Lake after drainage and reclamation, 1920s. (The Reach Gallery)

Almost exactly 60 years later in 1984, the Sumas Pump Station was replaced with the Barrowtown Pump Station — a modernized, higher-capacity water pump to keep the Sumas Prairie dry by moderating the water levels of the Sumas River. With its high dikes, the Chilliwack River-fed Vedder Canal naturally flows into the Fraser River from gravitational pull as it is on a higher elevation. On the other hand, the pump station moves water from the lower elevation Sumas Canal to the other side of an earthfill dam that leads into the Fraser River.

Following the historic rainstorm that swept across much of BC earlier this week, this entire intricate system that prevents the Sumas Lake from reforming is on the verge of collapse. Officials with the City of Abbotsford sounded the alarm Tuesday evening over the imminent failure of the Barrowtown Pump Station that prevents excess water from entering the Sumas Prairie.

Excess water was already an issue from the Fraser River and other channels spilling their banks from the incredible rainfall recorded from Sunday through early Tuesday, and then funnelling into the low-lying areas of the Fraser Valley. These conditions have proven to be too much for the Barrowtown Pump Station.

City officials in their immediate evacuation notice of the Sumas Prairie went as far to say that “the event is anticipated to be catastrophic.”

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Barrowtown Pump Station in Abbotsford (Google Maps)

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Barrowtown Pump Station in Abbotsford (Google Maps)

“The Barrowtown Pump Station serves as a critical piece of infrastructure to ensure the Sumas Lake does not reform,” stated the city in Tuesday night’s release.

“With the failure of this key piece of infrastructure, water within the Sumas Prairie will not be able to be pumped out and water from the Fraser River will begin entering the already flooded Sumas Prairie area.”

In a scenario without a fully operational Barrowtown Pump Station, there is no telling when the currently flooded Sumas Prairie and Highway 1 segments, along with the reformation of Sumas Lake, could be drained. The lake would likely quickly re-emerge within days of the pump station’s failure, with water cascading from the Fraser River into areas below sea level.

However, by Wednesday morning, it became clear that disaster in the Sumas Prairie was narrowly averted for now, thanks to the efforts of about 300 people, including firefighters, contractors, farmers, and volunteers, who worked throughout the night to protect the pump station from floodwaters.

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Sumas Lake, early 1900s. (The Reach Gallery)

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Sumas Lake, early 1900s. (The Reach Gallery)

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Sumas Lake, early 1900s. (The Reach Gallery)

Devastating images of dozens of kilometres of the Fraser Valley submerged may seem eery and unfamiliar, but flooding to such an extent has happened before. It is a well-known and researched fact that the region’s low-lying areas are at risk for a major flooding event.

According to the Fraser Floods Research Group project by Simon Fraser University students in 2018, the 1894 event was the largest flood ever recorded in the Lower Mainland, driven by an above average winter snowpack and hot spring conditions. Flooding began on May 25 and reached a peak on June 10, with flooding stretching from Harrison to Richmond. Low-lying areas such as Annacis Island were entirely under water.

The same flood-inducing conditions were repeated again in May 1948. While the extent of the flooding was not as extreme as the 1894 event, the flood of 1948 still inundated tens of thousands of agricultural acres in the Fraser Valley, including the Sumas Prairie. The flood was comparatively smaller but far more destructive, given that the region had at this point seen more urban development through settlement. Over 2,300 homes were destroyed, and 16,000 people had to evacuate, leaving their farm-based livelihoods behind.

The 1948 event severely damaged the railways in the region, marking the first time Vancouver was cut off by land from the rest of the country since the railways were built. With wartime resources still fresh, the federal government was able to quickly mobilize the military to assist with evacuations, performing engineering work on dikes, and cleaning up.

In November 1990, the Sumas Prairie and the adjacent segment of Highway 1 flooded after the Nooksack River in Washington State overflowed its banks from heavy rainfall. Thousands of people were evacuated on both sides of the border, and two people died. The waters receded after about a week.

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1990 flood vs. 2021 flood at Highway 1’s Whatcom interchange in Abbotsford. (BC Archives/City of Abbotsford)

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Flooding in Abbotsford on November 16, 2021. (City of Abbotsford)

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Flooding in Abbotsford on November 16, 2021. (City of Abbotsford)

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Flooding in Abbotsford on November 16, 2021. (City of Abbotsford)

Environment Canada meteorologists have stated that the contributing factors of November 2021’s floods were a combination of heavy rainfall — totalling an entire month’s worth of precipitation in some areas — and the rapid melt of the season’s early snowpack from the elevated freezing levels high above the mountains. This was a moisture-laden system that accumulated its strength from tropical waters.

It is unclear when floodwaters in the Fraser Valley will peak; Tuesday night’s bulletin from the City of Abbotsford warned additional water flow down from Sumas Mountain was creating further flooding in the Sumas Prairie. The storm’s rainfall and snowmelt water from the mountains deep in the BC interior is still making its way towards the Lower Mainland from the Fraser River.

A 2016 study by the Fraser Basin Council on the Lower Mainland’s flood management strategy estimated that a repeat of the severity of the 1894 flood would currently cost about $23 billion in damages, including $9 billion in losses to residential, commercial, public, and institutional buildings; $7.7 billion in interrupted cargo shipments; $4.6 billion in infrastructure losses; and $1.6 billion in agricultural losses.

The Lower Mainland also faces a risk of flooding from the volcanic eruption of Mount Baker, which is just across the border, southeast of Sumas Prairie. Geologists have deemed lahars — the term for destructive mudflows with the consistency of wet concrete — to be Mount Baker’s greatest threat.

The potential for lahars is significant as Mount Baker has an estimated 1.8 cubic km of glacial ice – more than all of the other volcanoes on the Cascade Volcanic Arc combined, excluding Mount Rainier. Within hours of an eruption, lahars and flooding could occur in the Fraser Valley and parts of eastern Metro Vancouver.

Mount Baker Fraser Valley

View of Mount Baker from the Fraser Valley. (Shutterstock)

Kenneth ChanKenneth Chan

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