The Nooksack and Sumas Transboundary Flood Initiative

Who’s involved

The nine partners to the collaborative framework are:

• Sumas First Nation (Semá:th)
• Leq’á:mel First Nation
• Matsqui First Nation (Máthxwi)
• Nooksack Indian Tribe
• Lummi Nation
• City of Abbotsford
• Whatcom County
• Province of British Columbia
• State of Washington

The Initiative’s nine partners are committed to jointly:

• Advancing flood risk reduction and ecosystem restoration strategies
• Sharing data
• Leveraging funding opportunities to support flood mitigation projects in the transboundary area 

The State of Washington and the Province of British Columbia help to facilitate and coordinate the work of the Initiative. The TFI partners signed the Collaborative Framework (the framework) in October 2023. The framework will remain in effect for an initial period of four years. The partners anticipate renewals as solutions are advanced.

Planned initial work of the TFI is:

• Updating and aligning hydraulic models and improving flood forecasting
• Understanding flood risk and impacted communities on both sides of the border
• Understanding uncertainty and factors affecting flood risk throughout the Nooksack and Sumas watersheds
• Developing joint values and objectives that communicate the varied interests and shared goals represented by the Initiative
• Looking for solutions that advance ecosystem restoration and mitigate flood risk
• Incorporating Traditional Ecological Knowledge into solutions where appropriate
• Creating durable solutions for adapting to climate change

"Meeting together and spending time on the land is an opportunity for First Nations to share knowledge, and it’s also an opportunity for the respective partners to have their technical and policy folks, and decision makers to exchange ideas. Sharing that time together helps us to articulate the challenges, issues and opportunities for managing floods and restoring habitat."

 — Murray Ned, Semá:th First Nation Advisor

"There are many agencies involved in transboundary flood issues and things become difficult when you start bringing a lot of people into the room, especially with varying levels of government. TFI has helped us collectively establish working relationships and begin complicated work."

— Justin Laslo, Leq’á:mel First Nation

"TFI provides an opportunity for governments on each side of the border to understand others’ priorities and objectives. The members of the TFI are coordinating complex data across the international border, improving flood warning systems, and eventually will design projects to reduce risks while protecting the environment. We have made tremendous progress over the first two years of the initiative, and I look forward to building on that success to benefit the communities we serve."

— Tom Buroker, Washington State Department of Ecology
 

During the December 2025 atmospheric river event, emergency managers used improved cross-border flood forecasting and warning systems, including real-time data from new flood gauges and cameras, to issue earlier alerts and warnings and refine evacuation areas. Flood engineers and planners found the improved hydraulic models were helpful in predicting water depths and timing of flood waters — critical information for both managing emergencies and designing flood management projects.

TFI partners continue to meet regularly to coordinate local work plans and share information. These strong, collaborative relationships remain a priority and have continued to grow, even as broader Canada–U.S. relations have faced challenges in 2025. 

In 2025, TFI streamlined coordination and review of several projects, including: 

• A joint habitat assessment project in the Sumas Watershed 
• Replacement of the SR 544 overflow structure near Everson 
• Whatcom County sediment modeling work 

Joint habitat assessment in the Sumas Watershed 

The TFI partners, led by Semá:th First Nation and Nooksack Tribe, are working together on a project to understand and improve aquatic health in the Sumas Watershed. The project looks at water quality, fish habitat, streamside areas, fish passage, cultural site access, land connections and species at risk to set priorities for restoration in the watershed. Partners are also collecting DNA samples from Sumas River salmon, as part of the first assessment of salmon populations. 

The team is starting with a pilot study in the Saar and Arnold sub-watersheds, which cross the U.S.-Canada border. They are using data and aerial photos to map streamside conditions and find areas for restoration. This study will help guide plans to include nature-based flood solutions in local projects.

To move this work forward, Canadian TFI partners hosted a tour of key sites on the north side of the watershed, including Barrowtown Pump Station, Sumas River Floodboxes, the former Sumas Lake (Semá:th X̱ó:tsa), and the Semá:th fish weir.

The event gave First Nation partners a chance to share knowledge about their traditional lands and let all partners see the area in person. Seeing these issues and challenges helps everyone build a shared understanding and adds real-world context to the technical work. This will lead to better flood and habitat solutions for everyone. 

Replacement of the SR 544 overflow structure 

Protecting critical infrastructure is a key flood planning priority. An example of critical infrastructure is State Route (SR) 544, which crosses the Nooksack River at the city of Everson. On the south side of the main bridge, there is an arched culvert that carries extra water during a flood. The culvert was damaged in the November 2021 floods and received an emergency repair. 

The Washington State Department of Transportation (WSDOT), which manages SR 544 and its crossings, plans to construct a permanent fix in 2026. WSDOT will replace the culvert with a new bridge to allow more floodwaters to flow through the area. This is intended to help protect the existing bridge and reduce flooding. The TFI Technical Table reviewed and provided feedback on design plans in June 2025.

Whatcom County sediment modeling work 

Understanding how and where sediment accumulates in the Nooksack River is a major factor in effective flood management. According to the U.S. Geological Survey, the Nooksack River carries nearly a million tons of sediment every year. 

Sediment in the Nooksack does not behave like rocks placed in a bucket of water. It is much more complex. The river bottom is constantly changing with floods and long-term climate patterns, which makes modeling and predicting sediment dynamics challenging.

Sediment is not deposited uniformly along the river’s length. As the river flows to the ocean, more gravel moves along the riverbed at Everson, WA, than it does at Ferndale, WA. Coarser sediment tends to settle out of the river between Deming and Everson, where the land becomes flatter and the river slows down. Sediment can also build up faster where levees and revetments (structures to protect against bank erosion) confine the river. These changes in the riverbed can make flood impacts difficult to predict.

Whatcom County developed models to better understand how sediment moves along the river at different water levels and how it affects flooding. The models looked at current and future conditions to provide important information for project planning. A summary of this work is in the “Everson Corridor Sediment Modeling Investigation Report” (2025), on Whatcom County’s website. 

One of the Initiative’s goals is to create a common technical understanding on both sides of the border, using shared data on conditions, land use, priorities, and risks. This common understanding will provide a framework for local decision making, guiding projects that will integrate flood management and habitat restoration approaches. 

Technical milestones reached in the first year of the Initiative include:

• Alignment of the US and Canadian hydraulic models – These computer models predict where floodwaters will go and what their impacts may be. Previously they did not reflect information from the other side of the border, and did not use the same data. They are now consistent with each other and are able to share data and projections.
• Improved flood warning – The Nooksack River is a very dynamic river due to the large amount of sediment carried from its headwaters in the North Cascades. The depth of its riverbed is constantly changing, making it a challenge to accurately forecast floods. The National Weather Service worked with Initiative partners on both sides of the border to improve the flood forecasting protocols, resulting in new flood impact statements and flood warning bulletins for the Everson Overflow Corridor.  

The framework includes three tables that work at different levels to develop solutions. Each table works together to address flooding concerns and ecosystem restoration. The three tables are:

• Leadership Table
• Technical Table
• Policy Table 

The three tables work collectively to advance:

• Policy recommendations
• Values-based discussions
• Technical solutions

Leadership Table 

The Leadership Table includes elected leaders or representatives of government agencies from each of the nine parties. This table:

• Provides high-level coordination of priorities and needs
• Directs the Policy and Technical Tables to investigate topics 
• Provides guidance to the Policy and Technical Tables when issues arise 
• Meets two to three times per year

Policy Table

The Policy Table includes policy or department staff from each of the nine partners. This table:

• Discusses values-based issues and develops solutions to bring to the Leadership Table
• Requests more information from the Technical Table as needed
• Meets every other month

Technical Table

The Technical Table is made up of flood managers, scientists, and subject-matter experts. The table:

• Discusses technical information, such as sediment and river modeling and climate change data 
• Works collaboratively with the Policy Table 
• Receives direction from the Leadership Table to develop reports and plans
• Fosters collaboration between the Floodplain Integrated Planning work group in Whatcom County and the Sumas River Watershed Flood Mitigation Plan work group in B.C.
• Meets every other month 

The TFI is just one aspect of work to build flood resilience and restore habitat on both sides of the border. Local initiatives within the Sumas and Nooksack watersheds develop proposals and on-the-ground projects for flood risk reduction and habitat restoration, and TFI provides a venue for signatory parties to pursue greater alignment of these local initiatives and maximize benefits throughout the watershed.

These proposals and other on-the-ground projects are being developed in parallel, using shared data about flood management priorities and risks to reduce conflicts among the projects. They are led by local partners, First Nations, and Tribes:

• Sumas River Watershed Flood Mitigation Planning
  • Participants include the B.C. Government, Semá:th, Leq’á:mel and Máthxwi First Nations, and the Cities of Abbotsford and Chilliwack.
• City of Abbotsford flood response
  • Project planning for Barrowtown Pump Station is underway following a $76.6 million investment from the Province of B.C. for completion in 2027. One of the components is a floodwall to protect the Barrowtown Pump Station, and this work starts in early 2025.
  • A backup power generator is being installed at Barrowtown Pump Station, to maintain pumping operations and increase flood resiliency in the event of a power failure. Installation is expected to be complete by the end of 2024.
  • Bank stabilization and dike erosion repairs along Sumas River have been completed.
• Nooksack River Floodplain Integrated Planning (FLIP)
  • Participants include the Whatcom County Flood Control Zone District, Lummi Nation, Nooksack Indian Tribe, Ag Water Board, the cities in the Nooksack River floodplain, and Ecology.
  • A storymap about the FLIP process was published this year.
• Whatcom County River and Flood Division
  • The River and Flood Division has secured grants for voluntary property buyouts and home elevations in areas at high risk of repeated flooding, including $9.4 million for 12 acquisitions and $2.4 million for 12 home elevations.

• October 20, 2023 news release jointly issued by the State of Washington and the Province of B.C.
• Collaborative Transboundary Flood Management Framework
• Technical Table Status Report, September 2024
   

If you have feedback on the Transboundary Flood Initiative, please reach out to the First Nation or municipality where you live.