Abbotsford mulls the creation of floodways and buyouts on Sumas Prairie

We have collected all our past coverage—including in-depth stories on the history and geography of Sumas Lake, Sumas Prairie, and the Nooksack River—in one location. Find it here.

Moving nine million gallons of American water through Sumas Prairie isn’t easy, cheap, or painless.

Unless the Americans bolster the banks of the Nooksack, the river can be expected to flood north once again in the coming decades. And as Abbotsford considers how to prepare for and lessen the damage of the next flood, much of the focus will be on the creation of potential floodways to get that water through Sumas Prairie as quickly as possible.

What a “floodway” in the Fraser Valley means, and how one is created on Sumas Prairie, will have a huge bearing on the future of the area and the families that currently call it home. It is also likely to affect commuters, elementary school students, golfers, and even residents south of the border.

What is a floodway?

Some floodways are mostly paper exercises: a series of lines on a map and regulations in building codes and bylaws. That’s largely the case just south of the border, where a federally designated floodway has long identified areas where the Nooksack’s waters can be expected to go when they breach their banks. There, certain rules apply to properties located within the designated floodway. Usually, they forbid the building of non-agricultural structures that aren’t raised above the projected height of floodwaters.

The system in Washington is overseen by the US federal government, and is part of a nationwide system of floodways. Communities are required to regulate development to allow water to move through floodway areas. Like unclogging a bathtub’s drain, it allows the water to smoothly flow downhill, relieving pressure on upstream areas experiencing flooding.

Following November’s floods, American officials plan to significantly increase the size of the Nooksack’s floodway. The changes are likely to result in the government buying out many property owners who find themselves in a future flood’s path. (You can read our story on that decision here.)

Although managed floodways do exist north of the border, Canada has nothing comparable on a federal level. Instead, most flood management systems in BC are overseen and designed by local governments. That has left the province with a patchwork of flood protection systems based on municipal boundaries and jurisdictions. But floods don’t respect human-created boundaries. The province has vowed to change the system, but for now Abbotsford is taking the lead to come up with Nooksack protections. So all its planning only involves potential actions within its borders.

While the city hopes to have the Vedder dike beefed up, it hasn’t commented on what work would be needed for Chilliwack-managed parts of the dike that protect Yarrow.

Abbotsford’s floodway options borrow elements from the American system, but expand on them by suggesting the creation of new dikes that would funnel water towards the Barrowtown floodgates, where the city hopes to build a new $700 million pump station. (We wrote about those plans last week.)

The geography of Sumas Prairie requires dikes to ensure that Sumas Lake—which was drained a century ago—does not re-form. The lake bed sits around sea level, far lower than the surrounding waterways. A dike currently splits the prairie into two, guiding water away from the lake bed and toward the Barrowtown floodgates. (You can read more about that geography here.)

Abbotsford’s floodway plans would increase the height of the dike that divides the prairie to prevent a breach like that which occurred in November. It would also reposition much of that dike. Other dikes would also be built in the west, north, and along Highway 1 between the Cole Road exit and the Vedder Canal.

The configuration of those dikes is still to be decided upon. Officials have stressed that the options are only a starting point for discussions. But the final details could determine which homes, businesses, farms, and schools remain and which may have to be abandoned. They will also determine the future of homes on the old bed of Sumas Lake, where buyouts may also occur.

Floodways and “flood storage”

Click here for a larger version of the map above and the City of Abbotsford’s description of this floodway concept

One of two floodway options designed by the city and its engineers would leave the western portion of Sumas Prairie largely unprotected, as it is now. But it would be, by design, a “flood storage” area. Notably, a cap would be placed on just how high the water would be allowed to rise. At some point, water would be allowed to escape through a designated area to the Sumas Lake bed.

A complex dike system would be designed to corral most flooding from the Nooksack. A western dike would protect Huntingdon and Highway 11; another would protect the Sumas First Nation land. In the east, a dike would trace the eastern bank of Saar Creek, then run eastward along the border to the base of Vedder Mountain. Along Highway 1, east of the Cole Road exit, a dike would keep floodwaters north of the highway and away from the Sumas lake bottom, squeezing water toward Barrowtown.

There are two key aspects to highlight.

First, a “designated floodway” would be in effect east of Cole Road and north of Highway 1, extending to Barrowtown. In that area, there would likely be restrictions on building. (We’ll have more on that aspect later in this story.)

The area in the west would not be a floodway—at least in the preliminary designs. Instead, homes and buildings in this area would “rely on private local floodproofing.” That area would fall short of full floodway status because of one key feature: an escape hatch in a Saar dike that would be used to allow water to escape into the former bed of Sumas Lake in the event of a flood exceeding the one-in-200-year threshold.

The controlled overflow would allow the lake bottom to act as a flood storage area to mitigate some of the impacts on the western prairie. While some water would flow into the lake bottom, the goal would be for water to escape at an even-more-rapid rate through the Barrowtown choke point.

The scale of how much lake bottom area is under water would depend on both the construction of the overflow area and the scale of a flood. But the design would supposedly protect much of the Sumas Lake bed against a one-in-200-year flood. It would definitely be an upgrade on the protection that currently exists.

Council was recently told that property owners in flood storage areas would be “made whole financially,” meaning they would likely be eligible for buyouts. Any areas where flood protection didn’t meet the one-in-200-year threshold* could be bought out and would be used to grow “flood-resistant crops” that could rebound after being underwater for a significant length of time (as opposed to plants like blueberries, that take years to grow and needed to be removed in the wake of November’s disaster.)

*Estimates vary as to the return period of last year’s flood: Braun said it was a one-in-100-year event, while provincial officials have said it exceeded one-in-200-year levels. Given climate change and uncertainties as to how quickly the weather will warm, it’s probably impossible to say much more than such floods are expected to increase in scale and frequency in the coming century.

A border-to-pump floodway

Click here for a larger version of the map above and the City of Abbotsford’s description of this floodway concept

There is a second floodway option. It would protect the largest number of properties out of all the suggestions, according to Abbotsford staff. But it also has the largest floodway—and could potentially create ramifications for property owners south of the border.

That option would essentially create two large dikes along the length of the meandering Sumas River. A dike would be created near, or along, Highway 1 northeast of the Cole Road exit. Another long dike would extend along the border, leaving an opening only at the site where the Sumas River crosses into Canada. Limited overflow would be permitted to enter the Sumas Canal, but there would be no designated lake bottom storage area, with areas there expected to have greater than one-in-200-year flood protection.

By penning the floodwaters within a narrowed Sumas River basin, the dikes would significantly increase the flood levels within that corridor south of Highway 1. The city says property owners in areas with substandard flood protection would financially be “made whole,” and fields could be farmed with flood-resistant crops.

Within the floodway, dozens of homes may need to be bought out and new building permits are unlikely to be granted. The concepts are still very much a discussion-starter. Funding is still uncertain, and the design and locations of the floodway and dikes are subject to change. But a range of non-agricultural facilities sit in close proximity to the Sumas River and potentially within the floodways. They include Upper Sumas Elementary School, Fraser Glen Golf Course, and the Abbotsford Fish and Game Club.

Any extended dike along the border could also have ramifications for residents south of the border.

Previously, Abbotsford Mayor Henry Braun said a full flood-stopping border dike would need to be 18-feet tall, and was therefore impractical. The new border dike concept would still allow the Nooksack’s waters to flow north into Canada and toward the Fraser River. But by reducing the flood storage capacity in Sumas Prairie, creating a narrow floodway, and beefing up dikes along the border, it’s possible the dike could also increase the duration and scale of flooding in the United States. (It’s unclear what, if any, engineering work or modelling has been done on the impact of the dike to the United States.)

The Sumas River basin is shaped like a funnel, with Nooksack floodwaters waiting to exit into the Fraser through the Barrowtown floodgates (or future pump station). Currently, much of that water sits in Sumas Prairie. Reducing flood storage in Sumas Prairie could push the mouth of that funnel further into the United States, potentially leaving properties in Sumas, Wash., under water for considerably longer.

That could create friction south of the border. But it could also help spur work along the Nooksack’s banks that could prevent flooding in the first place. American officials are hesitant to add dikes along the Nooksack, in part because of concerns that it could exacerbate flooding downriver in Whatcom County.

(Asked about whether Abbotsford has considered the ramifications south of the border, a city spokesperson wrote: “More specific modelling still needs to be done and will be done as we move forward with a preferred option. We recognize the importance of understanding the impacts of each option to the United States, and will be having discussions with our partners across the borders as we move closer to a preferred option.”)

What a buyout would mean

Finding one’s property in a floodway does not mean that it would suddenly be flooded each year. In fact, properties could go decades without seeing much water beyond the usual pooling in fields.

The most immediate change, though, could be the ability of property owners to improve or change their home or farm.

“You can still farm that land and grow crops,” Braun told The Current about life in a floodway. But, he warned, “we probably as a city will end up in a place where we would say, if you’re in that floodway, you’re not getting a building permit for a new house, for any new barns.”

The concept is one called “managed retreat,” where people gradually pull back from flood-prone areas to both minimize future damage and leave more room for nature to take its course.

But managed retreat can have very real emotional and financial tolls. Braun says the loss of a property’s value is one that shouldn’t be borne by individuals left out to dry by shifting lines on a map.

“Somebody is going to lose some value and they have to be made whole,” he said. Braun said that would require funding from senior levels of government while Abbotsford oversees and handles the process.

Different Sumas Prairie residents may make different choices about how to proceed, he said.

“Some might say, you know, ‘I can live with [a floodway], my house is 50-60 years old, I was thinking of building a new house, I’m going to build that new house on higher ground that’s not in the floodplain and I will stay there.’ Others may say, ‘OK, no: buy us out.’”

A starting point

The city has developed four different options for new flood protection works on Sumas Prairie.

Floodways only feature prominently in the two costliest plans (which also offer the highest-degree of protection).

The first does little to add any additional flood protection, save for improvements in Clayburn Village. (The concept also includes previously made funding requests to improve water resiliency and upgrade the dike protecting Matsqui Prairie.)

A second option includes the above requests, and adds the need for a new Barrowtown pump station. (That station is needed to move water out of the prairie when the floodgates would otherwise have to be closed and is required for both floodway plans.)

The city is most interested in the two options involving floodways. The price tag for each is relatively similar, given the scope of all the work ($2 billion versus $2.3 billion, not including the other infrastructure asks). Braun has stressed the two concepts are a starting point for discussions. He has also noted that Abbotsford’s plans are liable to change depending on plans south of the border. If the Americans commit to bolstering the Nooksack’s banks, that could change the calculations.

But for now, he says there is urgency to get the plans solidified soon, so that Abbotsford can convince the federal and provincial governments that it needs and deserves a sizable share of the billions in recovery funding that have been offered.

Braun knows that actually completing the work will take time. A new Barrowtown pump station is likely the simplest to act upon, though the $700 million cost is steep. Work involving dikes and floodways could take five years to come together, he said. History suggests it could all take longer than that. But a course of action needs to be agreed upon soon. Otherwise, Braun and others have warned that the attention of governments is likely to stray and the money may dry up.

“We will end up, if we’re not careful, with the status quo,” Braun said. “Maybe with a new pump station, but the rest will be the same and that still doesn’t solve our problem.”