About 30,000 cubic metres of debris from the Chilcotin River landslide was successfully caught by a debris trap in the Fraser River near Hope.
It was a momentous moment for the partnership between the province and Shxw’ōwhámél First Nation.
"Overnight success at the Fraser River Debris Trap!" said Minister Bowinn Ma on Aug. 6 via a post on Twitter/X. "It trapped 30,000 cubic metres of woody debris from the Chilcotin landslide. Huge thanks to the facility operator for sharing this update. Gratitude to Shxw’ōwhámél First Nation, who co-manage this debris trap with the Province."
The debris — which mainly consisted of logs — was successfully caught by the trap on Aug. 6 after water overflowed the dam, formed by the landslide, on Aug. 5.
Shxw’ōwhámél signed the Fraser River Debris Trap Co-Management agreement with the B.C. government back on June 17, 2023. The agreement, which was the first of its kind, formally recognized Shxw’ōwhámél’s role in overseeing containment barriers on the Fraser River; the trap is located in the community's territory, between Hope and Agassiz, and the agreement gave them “a role in the stewardship of the operation of the trap."
Government officials said the water began pouring over the blockage southwest of Williams Lake last Monday, around 9 a.m., where it began picking up speed every hour. The landslide, which took place from July 30 to July 31, dammed the Chilcotin River near Farwell Canyon or 18 kilometres southeast of Hanceville. At the time it was estimated to be 1,000 metres long, 600 metres wide and 30 metres deep.
A lake also began forming due to there being "minimal seepage" behind the dam that extended several kilometres. Water levels rose steadily during this time, with a rate of 22 centimetres per hour on Aug. 3 and then a rate of 18 centimetres per hour on Aug. 4.
The dam also caused higher water levels upstream. Prior to the landslide, a high stream flow of 200 cubic metres per second was recorded at the river. By July 31, "data from the WSC station Fraser River at Big Bar Creek (08Md013) indicated that flows declined by over 150 cubic metres per second."
On Monday by 1:30 p.m. Connie Chapman, the B.C. water management executive director, said that the lake built up behind the landslide was dropping at 1.3 metres per hour and the surge of water coming out of it was travelling at about 750 cubic metres per second. Though this flow was lower than what is seen during a spring snowmelt, it was still significantly faster than the river's normal flow.
The province predicted that the river at Lytton, Boston Bar, and Hope would be affected by the surge at various points throughout the day. They estimated that by 7:30 a.m. Lytton would be impacted, with water estimated 3.3 metres above normal; Boston Bar would see river levels rise 2.6 metres by 11 a.m.; and Hope would see water rise about one metre around 3:30 p.m.
While debris, such as logs, was seen at Lytton by Tuesday morning, and at Hell's Gate (near Boston Bar) by Tuesday afternoon, Hope did not see any debris until late Tuesday evening. High and fast waters were seen, however, by 3:30 p.m.
During this time, a flood watch and high streamflow advisory were issued for the Hope area. As of last Wednesday (Aug. 7), both the watch and advisory were lifted.
"Flows along the Chilcotin River have now returned to pre-event levels," Ma said on Aug. 7 via her Twitter/X post. "Crews continue to monitor for the risk of additional landslides and bank erosion along the Chilcotin River valley. Please continue to follow instructions issued by your local government or First Nation."
In operation for over 40 years now, the Fraser River Debris Trap reduces the volume of woody material flowing into the lower reaches of the Fraser River and Salish Sea. Without the debris trap, this material would pose a danger to human safety, navigation and downstream infrastructure. The debris trap also keeps B.C. clean by intercepting other waste, such as plastics, propane tanks, abandoned boats and other floating debris.
It is estimated that the trap prevents millions of dollars in damages each year related to the cleanup, repair and maintenance of boats, docks, bridges, riverfront infrastructure and wetlands habitat.
In fact, according to the province, as much as 100,000 cubic metres of wood debris – about 2,000 logging truck loads – is collected annually. This is done mostly during the high-water period of the spring runoff and during periods of excessive rainfall. After the atmospheric river events of November 2021, additional debris collected included recreational vehicles and large portions of residential sundecks.
The wood collected by the trap will eventually be repurposed. Some options considered includes converting it to bioenergy, selling it as salvageable timber, and even building a longhouse. Meanwhile, the non-wood debris is recycled.
