Abbotsford says taming Nooksack River could cost up to $2.8 billion

Click here for all our previous coverage of last November’s disasters, and the aftermath.

Abbotsford residents will be asked to weigh in on four options to mitigate the future threat of the Nooksack River overflowing its banks.

The cheapest of the four options would cost $209 million and offer little new protection for Sumas Prairie residents. The cost for the other options range from $1.3 billion to $2.8 billion. All plans also include protections for residents in Clayburn Village; three include improvements to bolster the dike protecting Matsqui Prairie from a Fraser River flood.

The plans were released Friday and will be discussed by Abbotsford council at its Monday meeting. Information direct from the city can be found here.

In 2020, the City of Abbotsford signed off on a mitigation strategy to address the Nooksack flood threat. That strategy focused on encouraging the Americans to undertake a cost/benefit analysis that, Abbotsford hoped, would prove the value of upgrading the Nooksack’s dikes.

The Nooksack, as residents were reminded last November, is a sleeping American giant of a river that can, and has, cause devastation to thousands of homes in Canada. That threat is more complex than most rivers, created by a historic mix of geography, politics, and human hubris. And reducing the threat will be just as complicated.

On the American side of the border, officials continue to weigh the downriver consequences of stopping the river from flowing north, into the Fraser River’s basin, when it floods.And on the Canadian side, the legacy of a natural lake that was drained a century ago continues to leave its mark. A dike currently protects the former lake basin, but as seen in November, it’s not built to provincial standards and is liable to fail when waters rise as high as they can.

Raising it creates more complications. In the same way that Canada serves as a release valve for the Nooksack when it spills its banks in the US, flooding subsides in the western part of Sumas Prairie when the waters breach the dikes and flow into the eastern part of the prairie and the former bed of Sumas Lake. Raising the dike complicates the situation in the western prairie.

On top of all that, November’s flood showed the weaknesses of the Barrowtown floodgates. If the water on the Fraser River side of the floodgates is too high, water cannot be drained from the western prairie. Instead, it backs up, rising to the point at which it overtops the dikes.

In 2020, the City of Abbotsford signed off on a mitigation strategy to address the Nooksack flood threat. That strategy focused on encouraging the Americans to undertake a cost/benefit analysis that, Abbotsford hoped, would prove the value of upgrading the Nooksack’s dikes. Now, post-2020, the city is focusing on what it can do on its own land.

On Friday, the city unveiled the following four plans.

All four options include $32 million to increase the resiliency of Clayburn Village. Plans 2, 3, 4, also include $388 million to bolster the dike protecting Matsqui Prairie.

The plans

Plan 1: Status quo, with upgrades to Barrowtown Pump Station. Estimated cost: $209 million.

This cheapest option “would not meet minimum flood protection guidelines in BC [and] not provide an enhanced level of protection,” according to the city. It would only protect against a one-in-35-year flood event. (November’s flood is believed to have been at least a one-in-200-year event.)

Map and details from city

Plan 2: Status quo on dikes, with Barrowtown upgrades and new Sumas River pump station. Estimated cost: $1.3 billion.

This option would still not meet minimum provincial guidelines, but would offer some additional flood protection for residents. The new Sumas River Pump Station would be built to move water from the western part of the prairie to Fraser River levels. Currently, only floodgates allow gravity to drain water from the western prairie. When the Fraser is too high, the water cannot leave the prairie and continues to rise, as occurred in November. This option would also protect the Sumas Prairie lake bottom from flood levels expected to occur every 50 to 100 years. It would leave the western part of the prairie unprotected. (The current Sumas Prairie dike splits the prairie into two halves. The upper, western part of the prairie drains via the Sumas River. Water in the eastern part of the prairie must pumped out through the Barrowtown Pump station.)

Map and details from city

Plan 3: New floodway and water storage area in western Sumas Prairie, with Barrowtown upgrades and a new Sumas River pump station. Parts of the Sumas and Vedder dikes would be raised, as well as an extended stretch of Highway 1. Estimated cost: $2.5 billion.

This option would meet minimum provincial standards for flood protection by creating three new dikes. It would offer nearly one-in-200-year protection for the Sumas lake bottom, but would still leave the western part of the prairie unprotected.

Map and details from city

Plan 4: New floodways in Sumas Prairie, five different pump stations, controlled overflow zone and more. Estimated cost: $2.8 billion.

This option would expect to protect against flood events exceeding a one-in-200 year level. It would add five different new pump stations, along with an upgrade for Barrowtown. Highway 1 would be raised for a considerable stretch across the prairie, as would the Southern Railway of BC. Several dikes would be raised. It would offer the greatest protection, particularly for those in the western part of Sumas Prairie.

Map and details from city

The city plans to begin consultations with residents this month. The final plan for the region is likely to be largely influenced by the provincial and federal governments and their willingness to contribute the huge sums needed to reduce the flooding risk to the area. It will also likely be impacted by flood plans south of the border and what, if any, improvements American governments make to prevent water from escaping the Nooksack’s course in the first place.

In 2021, and in previous years that the river has flooded Canada, the Nooksack has breached its banks near Everson. The Americans have previously balked at raising the Nooksack’s banks in that location, fearing that doing so would increase flooding downriver to the west. You can read our story on the American discussion around that topic.