Flood Zones in Whatcom County, Washington: The Nooksack River Corridor

Two severe floods, four years apart

The lower Nooksack River, particularly around Sumas and Everson near the Canadian border, has experienced two major flood disasters in recent years: November 2021, which damaged the Nooksack River culvert at State Route 544 near Everson and caused widespread flooding across the Sumas Prairie area on both sides of the border, and again in December 2025. County flood-risk data indicates this isn't a coincidence of two unrelated severe-weather events -- flooding along the lower Nooksack has grown measurably more frequent, longer-lasting, and more damaging over the past several decades, a trend that has accelerated since the 1990s. For a land buyer, that means recent flood history in this corridor should be read as an indicator of an ongoing, worsening pattern, not a freak occurrence unlikely to repeat.

A real, formal cross-border response

Because the Nooksack River's flooding affects communities on both sides of the Canadian border -- the Sumas Prairie area extends into Abbotsford, British Columbia -- addressing it required a genuinely cross-jurisdictional response. In October 2023, representatives from the State of Washington, the Province of British Columbia, local Tribes and First Nations, Whatcom County, and the City of Abbotsford formally signed the Nooksack and Sumas Transboundary Flood Initiative, committing to jointly develop longer-lasting flood-risk solutions rather than each jurisdiction acting alone on its own side of the border. This is a real, documented, dated agreement -- not an informal or aspirational statement -- and it's the institutional framework behind the specific mitigation planning described below.

The county's active 2026 mitigation planning: levee setbacks and buyouts

As of February 2026, Whatcom County staff working on flood-risk mitigation were focused on a specific technical strategy: widening the river itself by setting back the levees and armored banks that have artificially constricted the Nooksack for decades, restoring its natural ability to move sediment and reducing flood heights and flow velocities during high-water events. This Floodplain Integrated Planning (FLIP) process, underway since 2017 as an ongoing collaborative effort among the county, tribes, and other stakeholders, also includes targeted sediment management where buildup has reduced channel capacity, side-channel and wetland restoration to recreate natural flood storage while improving salmon habitat, and voluntary property buyouts in the highest-risk areas to permanently remove structures from harm's way. This isn't purely theoretical: in February 2022, the county's River and Flood Division sent letters to more than 700 property owners in flood-prone areas inviting them to express voluntary interest in either a buyout or elevation assistance, and more than 100 property owners responded, with county staff evaluating eligibility and submitting FEMA Hazard Mitigation Assistance grant applications on their behalf.

For a buyer considering land in the lower Nooksack corridor, this active planning cuts both ways. On one hand, a parcel identified as part of a future levee-setback or floodplain-reconnection project could face real future land-use restrictions or a county buyout offer down the road -- worth knowing before you buy, not after. On the other hand, the same activity signals real, funded, ongoing investment in reducing flood risk for the corridor overall, which could improve conditions over time for parcels outside the highest-risk buyout zones. Either way, the only way to know where a specific parcel stands is to ask the county's River and Flood Division directly, rather than relying on general awareness that flooding happens in this area.

What to check before buying in the Nooksack corridor

1. Ask Whatcom County's River and Flood Division whether the specific parcel is within a currently mapped FEMA floodplain, and separately whether it falls within an area under active consideration for a levee setback, buyout, or elevation-assistance program under the FLIP process.
2. Check whether the parcel or a neighboring parcel was among the 700+ properties contacted in the county's 2022 buyout/elevation-assistance outreach, and if so, what came of that inquiry.
3. Confirm current flood-insurance requirements and estimated premium costs for the parcel given its specific mapped flood zone -- this can be a material ongoing cost independent of any future mitigation project.
4. If buying for agricultural use, ask about the compound effects of flood risk on that specific use, since Whatcom County's own flood-risk planning materials explicitly reference protecting farms alongside cities and infrastructure as a FLIP goal.