How Sumas Prairie is more protected than two years ago

Photo: City of Abbotsford

This is the first of a three-part story. You can read the second part, on the vulnerabilities that remain, here. The third part, on the future and political present, of the prairie, can be found here. Members can read all three stories as a single feature. Become a member and support our journalism for just $2/week here.

Two years after 2021’s devastating floods and landslides, the region is better prepared for a future event. But it’s not prepared enough.

In recent months, FVC readers have questioned whether our region is just as vulnerable as in 2021. This month, The Current is going to try to answer those questions, using public documents, responses from governments, and our own eyes.

In three stories this week, we’ll focus on the Nooksack River and Sumas Prairie—the site of one of Canada’s most-expensive natural disasters.

We’ve catalogued the work that has been done the last 24 months, the projects that are planned and proposed but not yet funded, and the governmental and climactic uncertainties that complicate the situation. We will be publishing three separate stories in The Current’s daily newsletter.

Today, we are looking at the ways in which Sumas Prairie is better prepared and protected than two years ago—even if some protections in the United States are unlikely to ever happen. Tomorrow, we will examine all the work that must still be done. And Friday, we will consider the state of Sumas Prairie as a whole.

Insider Members can read the three stories as a single comprehensive piece. Just check your newsletter for the member-specific link. New members will find the link in your welcome email.

Next week we will look at other places that were affected by 2021’s atmospheric rivers, including Hope, Clayburn Village, and the Fraser Canyon.

The River

There is no doubt that the Fraser Valley and local, provincial and national governments are better prepared to deal with another Nooksack River flood than in 2021.

But that’s not really saying much, given the lack of awareness and various failures that occurred during and following the first atmospheric river.

In Canada, there is significantly more awareness of the Nooksack’s threat than immediately before its floodwaters crossed the US border two years ago. We also know much more about the ability—or lackthereof—of the Fraser Valley’s dikes, pumps, and water systems to deal with flooding from the south.

Over the last two years, there have also been modest but very real infrastructure improvements to address the most obvious, easily fixed problems identified during the 2021 disaster.

At the same time, nobody is suggesting that enough has been done to prevent a repeat of the 2021 flooding in Sumas Prairie.

To understand what’s been improved, and what vulnerabilities remain to be addressed, we’re going to follow the Nooksack from the foothills of Mt. Baker to the Fraser River.

When the rain comes

To understand or evaluate the work that has been done, and that which is still needed, one needs first to consider how and why the Nooksack River floods Sumas Prairie every 30 years.

We’ll start with all that damn rain and water. The Nooksack flooded after epic amounts of rain fell on the slopes of Mount Baker, from which almost all the river’s water originates. (You can read all about that relationship here.) The water barreled down Mt. Baker, breached the banks of the Nooksack near Everson, Wash., and from there flowed downhill north to Canada and Abbotsford, where it filled Sumas Prairie and the old Sumas Lake bed. Eventually the water was pumped out of that artificial basin into the Sumas Canal, from which it flowed north to the Fraser River and, finally, to the Pacific Ocean.

The resulting flood is now considered a one-in-100-year event. That means that roughly every year brings a 1% chance of such an event. Smaller floods are more common—in 1990, the Nooksack spilled its banks and flooded the western portion of Sumas Prairie but not the eastern, lakebed section.

Larger Nooksack floods are less likely, but still possible in any one given year. Climate change is altering these odds in unpredictable ways. We’ll have more on that in the third part of this story.

Capacity

The rain and volume of water isn’t the only factor deciding whether, and how much, water will pour out of the Nooksack basin and into Canada.

The other is the capacity of the river in Everson, Wash., where, just before a bridge crossing the river, the Nooksack occasionally fills to the brink, then pours north into the basin of the Fraser.

American farmers have been calling for years for the river to be dredged to increase the volume of water that the river’s banks can hold. They say that every year, the river fills with more sediment, which decreases its capacity and increases the likelihood of flooding.

But that work brings with it implications for fish populations.

Over the last two years, one project has been completed near the bridge to provide extra room for high water.

According to the county: “Preliminary analysis suggests that increased flow down this side channel could lead to a modest increase in local river flow conveyance and an associated reduction in the volume and rate of flow that overtops the river’s right bank during large flood events, thus potentially reducing the severity of flooding in the Everson overflow corridor.”

But the change is, indeed, modest. It also doesn’t address the main choke point that causes the river to overflow.

The Everson dike (or lack thereof)

The Nooksack floods into Canada are partially a result of geography and a legacy of the time when the river flowed north, not west. And they are partially the result of a decision to not build a relatively small dike at Everson. As The Current has reported, American officials have repeatedly decided not to build a dike that could prevent the river from flooding north because retaining the water in the Nooksack basin would aggravate flooding in Washington State communities downriver of Everson.

Officials from governments in Canada and the United States continue to talk about both that flow split and other ways to address Whatcom County flooding. But there still seems to be little appetite on the part of the Americans to build a dike at Everson.

There has been some progress: the Americans have placed temporary sandbags along Emerson Road, the key crossing point between the Sumas and Nooksack basins. Slightly raising that road’s level will reduce the frequency and scale of flooding within the United States, particularly in Sumas, Wash. However it isn’t expected to do much for Canada, given the scale of the flood events that cross the border.

US flood storage

Some of the work south of the border could have an impact on Canadians.

The United States has mapped out a “floodway” between Everson and the Canadian border where water naturally flows when it escapes the Nooksack’s banks and starts to flow north. Within this floodway, the Americans are buying out property owners, or providing money so that homeowners can raise their houses to minimize damage during future flood events.

The Americans are also looking at increasing flood “storage” within the floodway area. Such storage areas are essentially pockets—largely farmland—where water can be allowed to sit while it waits to flow north toward the Fraser. The Nooksack’s progression through existing fields has been likened to an ice cube tray: water enters at one end and—after moving from one module to the next—escapes through the other.

Increasing the flood storage would essentially see those cube modules deepened and able to accept more water. Doing so could slow the progression of water and reduce its level, in the same way that a wide, short glass can accommodate the same amount of water as a taller, narrow glass.

But there’s still only so much impact such work can have on floods of the scale that impact Canada. The vast majority of flood prevention work south of the border concerns either reducing flooding during relatively frequent modest events—like one that occurred in 2020—that threaten American communities but not Canada.

When it comes to larger floods, the Americans’ goal is to route the water away from populated areas and directly to Canada. One document suggests a plan for a dike that would route northbound floodwaters to the east of Sumas, Wash.

So water from the Nooksack will one day again flow north into Canada, Abbotsford and Sumas Prairie.

If that were to happen again this November, Sumas Prairie and Yarrow would be better prepared in some key aspects—but still vulnerable in many other ways.

Completed Improvements

Awareness

Perhaps the most important change from 2021 is the simple fact that residents and, especially, governments are actually aware of the Nooksack’s flood threat and the potential damage it can cause.

The Nooksack had flooded in 1990, closing Highway 1, and a task force had been set up in the wake of that event. But it went dormant and, with it, so too seemingly did the awareness of the river by BC transportation and emergency preparedness authorities.

The Nooksack task force is now a cautionary tale of how international “frameworks” and “agreements” don’t mean much if they don’t actually lead to action.

It’s hard to overstate the manner in which the Nooksack flood seemed to take most Canadians by surprise.

A full 24 hours after the 2021 atmospheric rivers hit, local and provincial authorities still seemed unaware that a flooding American river could cause one of Canada’s most expensive natural disasters.

By the Monday morning following the storm, multiple BC highways had been closed and the Nooksack had already breached its banks. Water was flowing towards Abbotsford and The Current warned that morning that the river could pose a threat to Fraser Valley residents. But Canadian governments seemed caught off guard even as water began crossing the border.

Despite the fact that it took more than 12 hours for water from the Nooksack to reach Canada, residents were given little notice they may have to leave their homes until the moment many evacuation orders were issued. Commuters between Chilliwack and Abbotsford were given less than an hour’s notice that Highway 1 was likely to be closed. Similarly, farmers were left scrambling to evacuate livestock as water filled barns and fields.

On the Tuesday following the storm, the water in Sumas Prairie continued to rise, overtopping and eventually destroying a key section of dike. In one of the most surprising and dramatic turns, high waters threatened to overwhelm the Barrowtown Pump Station prompting a dire warning from the City of Abbotsford; only a community-driven volunteer effort to create a makeshift barrier saved the station. If it had been swamped, the resulting flood could have made it dramatically harder to drain the newly-reformed Sumas Lake.

The awareness of the Nooksack’s threat is undoubtedly higher today than in 2021 and should bring an improved response in the event of a flood—if the awareness be maintained.

The importance of flood awareness, and the improved response it enables, could be seen when a new series of storms bore down on the region just two weeks after the first 2021 atmospheric river hit. At that time, the province and local cities took much more substantial action to prepare.

In addition to repeatedly and vocally warning the public and landowners, sandbags were placed in vulnerable areas like the Huntingdon neighbourhood near the US/Canada border and along key dikes. Most visibly, a tiger dam was erected across Highway 1 at the Sumas River to try to address a key low point in the dike separating the western portion of Sumas Prairie from the eastern, lakebed portion.

That dam illustrated that the government had the tools and ability to take short-term action to address a key flaw in the region’s flood defenses—if had the knowledge of those weaknesses to begin with.

The second-storm response suggest that improved awareness is likely to lead to short-term work to prevent some of the consequences of a future flood, especially if the Nooksack were to breach its banks in the next couple years.

The City of Abbotsford is also buying equipment and training more staff to improve its capabilities in the case of another flood.

But maintaining the awareness and levels of preparation is difficult and can’t be taken for granted. It’s common for both governments and the public to turn their attention elsewhere as a disaster recedes into history. The flooding in 2021 was not unprecedented, but came after previous lessons had been forgotten. This time the hope will be that the 2021 disaster won’t be so quickly forgotten. But only time will tell.

Infrastructure

Since the 2021 floods, the City of Abbotsford has undertaken a series of projects to both fix damage caused during the disaster and try to bolster local flood defences.

The most substantial improvement is the construction of a 150-metre-long concrete spine to a portion of dike that collapsed two years ago. The City has also worked to raise the height of dikes on either side of the Sumas River, albeit to varying degrees and often in a manner that is temporary, rather than permanent.

Specifically, the dikes were raised between Atkinson Road and Barrowtown, north of Highway 1, in areas where they were particularly low. In some areas, the same large white sandbags that were used near Everson south of the border were installed along the dike. The sandbags aren’t a permanent solution, but rather a makeshift improvement while the city works towards a billion-dollar-plus comprehensive plan to remake the region’s flood protections.

Raising the dikes in vulnerable locations is important because a dike is only as strong as its lowest, weakest point. Dikes aren’t made to accommodate water overtopping them. They become extremely susceptible to collapse and erosion once water starts to flow over their top.

Capacity

Like in the Nooksack, the depth of the Sumas River and its tributaries influences how much water they can hold before they begin to flood. In natural systems, rivers drop sediments as they slow. That sediment influences the course of a river or creek over time, prompting it to shift and meander over years and decades. But creeks and rivers that are bound by human activity can’t move to find new routes around the sediment they deposit. Instead, that sediment ends up on the bottom of river beds. And as the level of that sediment rises, it gradually reduces the capacity of waterways.

Historically, authorities have dredged rivers to maintain their carrying capacity. But recent years have seen an increased awareness of the harm that can cause to populations of fish that lay eggs in the sand and gravel at the bottom of those waterways.

So there are increasing rules governing, and often prohibiting, sediment removal, with oversight by federal and provincial regulatory bodies. Over the last two years, sediment removal has been undertaken in Kilgard Creek, McKay Creek and Sumas Canal, all of which are near the highway bridge over the canal. This fall, debris is also being removed from Saar Creek and Arnold Sough. Work is also anticipated soon on Sumas River sediment traps, though fish migration patterns could halt that activity.

Imminent improvements

In addition to the dredging and debris removal that has already been completed, Abbotsford will be removing sediment from the canal that carries water across the Sumas Lake bottom to the Barrowtown Pump Station.

It is also installing a backup power generator at Barrowtown to keep the pumps going in case of a power failure, as well as repairing seals, bearings, and recoating impellers (basically a spinning fan that propels the water). That work is being done gradually because it requires the removal of pumps during a small window of time each year.

Crucially, the city is also working to prevent a repeat of one of the most stunning moments from 2021, when rising waters threatened to inundate the very pump station needed to remove water from Sumas Prairie. Abbotsford is looking to build a “flood wall” that can protect the city in cases of high water on the Fraser. The province has already provided $3.2 million for such work, but Abbotsford is seeking another $5 million. The city says if it gets the money soon, the wall can be completed before next fall.

Abbotsford is also planning more work to stabilize several portions of the Sumas River dike. That work had been awaiting permits from the province and federal governments. Federal sign-off for one of the three sites was received in late September.

The city will also install new cameras and sensors to monitor water levels in Sumas and Matsqui prairies. However, those plans don’t include the installation of an audible warning system, like that which exists just south of the border.

The City of Sumas operates a flood warning system that sounds an alert when water begins to cross into the Sumas watershed at Everson. The siren signals to residents that water is on its way. That siren could be heard in Abbotsford in 2021, though the city didn’t—and still does not—have a similar audible alert that can warn residents that flooding is imminent.

The hard work

The last two years worth of dike fixes, dredging, and awareness-building may help mitigate damage the next time the Nooksack floods. 

But no one is pretending they are enough to avert another major disaster. Indeed, the scope of the challenge and the practical realities of planning and funding large flood management projects mean that the largest, most-consequential works needed to protect the prairie may not be completed for years—or decades.

In the second part of this series, we’ll look at the work that still needs to be done to prevent a repeat of 2021. Make sure you’re subscribed to The Current’s daily newsletter to ensure you get it in your email inbox Wednesday morning. Or become a Fraser Valley Current Insider Member to read the rest of this story right now.