BC Glacial Outburst Flood Moves Into Rapid Draw‑down Phase – Highest Flows Expected Monday

Early Tuesday morning officials confirmed that the glacial lake outburst that began late Monday night in the Squamish‑Lillooet Regional District is now "well into" a rapid draw‑down phase. Water levels in the downstream river are falling, but the deluge hasn’t yet peaked. According to the BC Ministry of Water, Soil and Climate Change, the highest flows are still expected on Monday, roughly 36 hours after the initial breach.

Scientists say the outburst was triggered by a sudden collapse of ice at the margins of a high‑altitude lake perched above the Mamquam River watershed. When the ice gave way, a torrent of meltwater surged down the valley, swelling the river to well‑above flood‑stage. The resulting surge scoured riverbanks, swept away a few debris piles, and forced the closure of a short stretch of Highway 99.

“We’re seeing the water level drop at a faster rate than we anticipated,” explained Dr. Alisha Khan, a hydrologist with provincial emergency management. “That’s a good sign, but the river is still carrying a massive volume of water. The peak flow curve is projected to crest Monday afternoon before it begins a steadier decline.”

In response, BC Wildfire Service crews, along with local fire‑lookout volunteers, have been stationed at key bridge crossings and low‑lying farms to monitor water heights in real time. Residents of the small communities of Brackendale and St‑Ives are being reminded to keep an eye on flood‑watch alerts issued by Environment Canada and to avoid driving across washed‑out sections of the road.

Emergency services have not ordered any evacuations yet, but a precautionary advisory remains in effect for homes within the 100‑metre floodplain. “If you hear the sirens or see the river rising faster than expected, get to higher ground,” said Squamish‑Lillooet RCMP spokesperson Sergeant Marco Diaz. “We’re prepared to move quickly if conditions worsen.”

The outburst follows a series of similar events across western Canada this summer, all linked to abnormally warm temperatures that are accelerating glacial melt. The provincial government is urging residents to stay tuned to the official alert system and to report any new signs of flooding, such as unexpected water movement on roads, railways, or near the river’s edge.

Authorities will continue to release updated flow forecasts throughout Monday. By Tuesday, they expect water levels to return to near‑normal conditions, assuming the rapid draw‑down proceeds as planned. In the meantime, the public is asked to be patient, stay informed, and avoid unnecessary travel in the affected corridor.