The River Forecast Centre expanded its streamflow bulletin on Dec. 10, 2025, adding Flood Watches for the Ashnola and Similkameen rivers and upgrading the Tulameen advisory — a change that kept large parts of the South Coast and Vancouver Island, including West Shore watersheds such as Millstream Creek and the Goldstream/Colwood drainage, on alert because heavy rain and rising freezing levels could push rivers up quickly. The initial RFC bulletin was posted at 11:45 a.m. PST on Dec. 10, and the centre issued an update the next morning (7:45 a.m. Dec. 11) that upgraded some reaches of the Similkameen and Tulameen to Flood Warnings. (See the River Forecast Centre bulletin.)
The shift matters locally because the RFC kept a Broad High Streamflow Advisory in place for Vancouver Island and the South Coast, meaning island rivers and creeks that drain through the West Shore are being watched for rapid rises and unstable banks. The RFC uses real‑time models — its 10‑day CLEVER forecasts and 5‑day COFFEE forecasts — along with weather observations to predict which stations may approach or exceed bankfull.
The watch levels are worth a quick translation. The RFC’s definition for a High Streamflow Advisory is: “High Streamflow Advisory: River levels are rising or expected to rise rapidly, but that no major flooding is expected. Minor flooding in low‑lying areas is possible.” A Flood Watch means river levels are expected to approach or may exceed bankfull, and a Flood Warning means flooding is occurring or imminent. EmergencyInfoBC also urges caution: “Stay clear of these fast‑flowing rivers and potentially unstable riverbanks.”
Environment and Climate Change Canada and media reports say the driver is an atmospheric river that arrived Dec. 9–10, bringing heavy rain and warm air that raised freezing levels and increased snowmelt. As CBC reported quoting ECCC: “Warm air with the system will cause freezing levels to rise and snowmelt combined with the already saturated ground and heavy rain, will likely result in high streamflows and localized flooding.” Local officials in the Similkameen area pre-activated emergency operations out of concern the system could push across the mountains; regional reporting noted the RFC forecasts had the potential to exceed “once‑in‑10‑year to once‑in‑20‑year levels.”
On the West Shore, the creeks most likely to respond quickly are Millstream Creek and the Goldstream/Colwood drainage network, plus smaller Colwood-area gullies and culvert-fed streams. Local stewardship groups such as the Peninsula Streams Society keep long experience of which channels flood first and where banks erode; provincial park information describes Goldstream’s steep, flashy watershed behaviour.
For now, local emergency services are watching river gauges and weather forecasts closely and advising people to avoid riverbanks, secure property where possible, and sign up for municipal alerts.
