The Volcano and The River

You can blame insufficient dikes for the flooding of the Sumas Valley. You can also blame various levels of government or Mother Nature.

Or, if you would rather blame something a little more sturdy, you might cast your eye toward the big volcano to the south. Because the Nooksack River would not have turned into a raging torrent last week were it not for the mountain that feeds it.

Understanding the Nooksack River is critical as discussions turn to how to protect Sumas Prairie in the decades to come. But to understand the Nooksack, you need to understand Mt. Baker, the volcano where most of its water originates. And you need to realize how things are changing on the mountain at a rapid pace.

This isn’t your grandpa’s volcano anymore.

Borne of mountains

The Nooksack we have seen spilling its banks may appear to be a meandering river that winds its way through farmland towards the Pacific Ocean. Over thousands of years, the Nooksack’s waters have shaped the valley bottoms and the prairies. It seems to materialize from a narrow valley, then charts a northerly course for 10km before entering Everson, where flood waters spilled over the bank two weeks ago.

But before the Nooksack tumbles onto the vast northern Washington floodplain, its waters collect on the mountains and, specifically, Mt. Baker.

It’s Baker, the giant volcano looming over the Pacific Northwest, that feeds the three-forked monster that has spilled north into Canada and re-filled Sumas Lake.

Mt. Baker is obviously big. But in a region of large mountains, its height and size can be under-estimated. Baker is nearly 3,300m tall. That’s almost double the height of Cathedral Mountain, one of the most prominent North Shore mountains. Mt. Cheam is 2,100m tall—more than a kilometre shorter than its partner mountain. (For the Stó:lō people who have lived in its shadow for millenia, Baker is called Kulshan and is the estranged husband of Lhilheqey—Cheam. When Kulshan is angry, he may express that displeasure with volcanic fury.)

When tropical storms race across the Pacific Ocean and slam into British Columbia, the clouds rise, cool, and then start dropping their moisture in the form of rain or snow. Much of that falls on Vancouver Island, the North Shore mountains, and the Olympic Peninsula in Washington State. But Mt. Baker is taller than any mountain in those areas. The clouds that climb its slope dump huge amounts of snow and rain on the volcano and surrounding area.

Its height and ability to trap moisture has helped Baker lay a claim to being the snowiest place on earth: its ski area holds the world record for the largest snowfall in a single season.

Photo courtesy by Randy Small Photography

The forks

All that water, whether it falls as rain or melts as snow, flows downhill into a creek or tributary, and then collects in one of the three forks: The South Fork, or Nuxw7íyem (“always clear water”) in the Nooksack language; the Middle Fork, or Nuxwt’íqw’em (“always murky water”); and the North Fork, or Chuw7álich (“the next point”). All three get their water from Baker, though the North also collects water from Mt. Shukshan.

Each fork is a unique river unto itself that has carved a valley for dozens of kilometres, draining some of the wettest terrain in North America. They sit at the bottom of valleys they have helped shape over thousands of years.

The South Fork, Nuxw7íyem, starts the lowest and winds its way through 50km of dense, wet forest. The Middle Fork, Nuxwt’íqw’em, is the shortest, running due west from the very bottom of Baker’s southeast glacier. And the final fork, Chuw7álich or the North Fork, is the longest. The main reach of the North Fork actually begins at the base of Mt. Shukshan, a mountain that sits in the shadow of Baker, 10km to the east and nearly as tall. As the North Fork passes below Baker’s northern flanks, it is fed by streams and creeks that originate on Baker’s receding glaciers.

Two confluences bring all three forks together in a short stretch valley in Baker’s western foothills, about 25km west of the peak. From there, it dives through one more valley it has carved over the years, and exits the mountains onto a broad floodplain.

The Nooksack has been moving quickly downhill until this point. But here, as it enters flatter territory, it slows. And as it loses energy, it begins to drop material—sand, gravel, and volcanic ash—it has been carrying from upstream. That material shapes the banks of the river and helps guide it north. (Left to its own devices, it also over time reshapes the river and influences its current and erosion patterns.) Shortly after leaving the mountains it arrives in Everson, its waters almost entirely originating from the slopes of Baker. And here it makes a choice.

Today, it chooses to run to the Pacific Ocean. In the distant past, it had chosen to go north. And because it remains so close to its old path—basically on the other side of a short road—when it swells and spills its banks, that water finds itself in another watershed—that of the Sumas River. From there it goes north.

When that happens, disaster can occur. And it all comes back to Mt. Baker and its watershed.

But understanding the nuances is critical not to understand just where all the water on Sumas Prairie has come from, but to figure out how to stop a repeat of the ongoing disaster.

The rain and the snow

Floods have always taken place on the river. It has spilled its banks dozens of times, affecting Canada on multiple occasions. But as time passes, one can expect Baker to fill the Nooksack past its brim much more often. But unlike some climate science that takes years of study to fully comprehend, the danger is fairly simple to understand.

First: the warming. Between 1950 and 1979, the average temperature in Abbotsford, just north of the volcano, was about 9.5 C. Between 1990 and 2019, the average temperature was around 10.7 C. The thermometer doesn’t lie: the valley and its surroundings have clearly warmed, and a mass of evidence—which has linked that warming to human activity—says the trend will continue.

Warmer temperatures—even by a degree or two—are a big problem for Mt. Baker, the Nooksack, and the communities threatened by its periodic flooding.

The problem here is simple. The Nooksack tends to flood in the winter (or near-winter) during and after rain storms. The more gradual release of snowmelt (when not combined with a winter storm) is less problematic. So lots of rain: bad. Lots of snow: not so bad. There are more complex issues at work of course. But the rain-and-snow mix is the general thrust of the problem: when warmer temperatures cause more rain than snow to fall, that’s bad news for potential flooding.

This problem exists across North American mountain ranges. But it’s especially acute on Mt. Baker because of its vast geography. Large portions of the mountain are located right on the freezing mark, where snow can finally stick to the ground. Increase the temperature by just one degree, and the snow level rises roughly 150 metres. Any rain that falls in that band quickly makes its way downhill into a creek, and then in the Nooksack. Which, as we’ve learned in the past two weeks, is bad.

Photo courtesy by Randy Small Photography

The professorThe rising snow level has already had an effect on peak stream flows. And Robert Mitchell, a professor at Western Washington University who has studied the Nooksack for more than a decade, says it will continue to do so.

“As the climate gets warmer, that snow line is going to increase in elevation, meaning that more landscape is going to be getting rainfall rather than snowfall,” Mitchell told The Current last week. “And that rainfall runoff gets to a stream much quicker than if it was snowpack on a landscape.”

There are a range of other, more complex factors related to climate change that are altering the severity and frequency of storms in general, across the region and the globe. But the rain/snow dynamic in the Nooksack basin is one that clearly means there is a higher chance of large floods today than there was 70 years ago, when temperatures were cooler.

As Mitchell says: even if the same amount of precipitation falls on Mt. Baker, warmer weather will mean that precipitation will hit the ground as rain rather than as snow.

“We’re going to be seeing the same annual amounts of precipitation, but more of it’s going to be coming as rain on those landscapes, and more of it’s going to be coming in these atmospheric rivers we experienced last week.”

Mitchell said that last Wednesday. Four days later, another atmospheric river slammed into BC. Another one is forecast to hit the region Tuesday, with temperatures well above historic averages.

“We anticipate going forward, later in the century, on average, at least a 25% increase in the magnitude of floods,” Mitchell said. “So imagine what we just had this past week and increase that by 25%.”

Mt. Baker throws other curveballs too. The volcano has massive glaciers that are expected to shrink dramatically over the next century. All that water from the west-facing glaciers will end up in the Nooksack, at one point or another. Fortunately, most of it won’t melt during the winter. But their disappearance still has an effect: glaciers and other patches of established snow or ice on the ground can help slow the rapid rise of water in streams, creeks, and the Nooksack. When rain hits a snow or ice patch, it takes a while for that water to filter through to the ground. Without that dampening effect, the impact is more immediate and concentrated.

Researchers looking at other rivers to the south of the Nooksack have seen similar results. When they ran climate simulations to gauge the effect of climate change on rivers in King County, the results consistently showed rivers will swell higher in the winter, and shrink more in the summer.

They also found the biggest changes were those with the largest annual snowpacks, which is bad news for a mountain that might be the snowiest place on the whole planet; in 1999, 30 metres of snow fell at Mt. Baker Ski Area, setting a world record. The snowmelt from the ski area all drains into the Nooksack’s North Fork. More of it falling as rain is trouble, and previous research suggests the average temperatures in the region will increase by between 4.1 C to 6.7 C over the next 80 years.

The president, the prime minister, and the student

Mitchell is now working with a graduate student to measure how, precisely, warming will affect the Nooksack in particular. But the work being done by him and his students isn’t focused on the human effects and flood risk. Instead much of his research has been driven and financed by those trying to understand the effects on the salmon that rely on the research. (The Nooksack First Nation is one major financier.)

Analyses by the City of Abbotsford have used the research by Mitchell and his students to gauge the Nooksack’s flood risk. They helped planners come to the conclusion that, with climate change, a flood that previously occurred every 200 years will now happen about every 128 years. With our present flood protections and waterways, that translates to an extra cataclysmic, Sumas Lake-filling flood every 400 years.

Still, the studies are imperfect, and not designed to evaluate the potential for extreme floods. That, in part, is what one of Mitchell’s students has begun doing. Evan Paul is now looking to model peak flows on the Nooksack. The basics, he wrote, are already known: peak flows are projected to increase because of more intense rain and less snowpack. But figuring out just how much the Baker and its river are changing would be helpful, wrote Paul.

After the first flood, two weeks ago, President Joe Biden and Prime Minister Justin Trudeau began talking about the Nooksack and its propensity to flood Canada. And as we publish this on the morning of Nov. 29, water from the Nooksack is again filling Sumas Prairie. It will take weeks to drain it, if not longer. It has become clear to a continent that there is a river problem that needs solving, a volcano feeding it, and a future to prepare for.

Five months ago, Paul wrote that his project would help prepare for that future by providing “Nooksack Tribe officials and Whatcom County river and flood managers with the information necessary to improve salmon habitat restoration efforts and mitigate future flood risk by improving flood infrastructure and updating flood maps.”

Paul’s thesis is due next June. No pressure.

More of our in-depth coverage of the 2021 Fraser Valley floods:

• Our groundbreaking story on the history of Sumas Prairie, Sumas Lake, and the Nooksack River

• Our story on how to get, and give, help during this crisis

• Our investigation into the failure of the Sumas dike, and the reasons other levees are doomed to fail in the event of an even worse flood from the Fraser

• Our comprehensive story on the challenges Fraser Valley dairy farmers are facing