Massive landslide blocks Chilcotin River, triggers evacuations and flood concerns, Canada

A landslide in Farwell Canyon, British Columbia, Canada on July 30, 2024, caused a large section of earth to collapse, creating a 1 000 m long (3 281 feet) debris mound that obstructed the Chilcotin River. As water pooled behind the blockage, authorities issued urgent flood warnings and evacuation orders.

A significant landslide occurred along the south bank of the Chilcotin River in Farwell Canyon, British Columbia, on July 30. The landslide caused a large piece of earth to drop more than 50 m (164 feet), resulting in a debris mound 1 000 m (3 281 feet) long, 600 m (1 969 feet) wide, and 30 m (98 feet) deep, which blocked the river and halted its flow.

Water had started pooling behind the landslide, forming a long, narrow lake by August 1, as captured by the OLI-2 on Landsat 9. Local authorities quickly issued flood warnings for upstream areas and evacuation orders for downstream areas due to the risk of destructive outburst floods, according to Robert Emberson from NASA’s Landslides research team.

Water began to breach the natural dam on August 5, causing downstream water levels to rise rapidly and carry debris down the river. Preliminary modeling from British Columbia’s River Forecast Center indicated that water levels would surge above typical spring flooding levels on the Chilcotin River.

Officials from the Ministry of Emergency Management and Climate Readiness (EMCR) warned that the water would have greater momentum and force than usual spring floods. Fraser River water levels peaked at 3 640 m³/s (128 600 ft³/s) on August 6.

The Chilcotin River, although sparsely populated, has agriculture downstream that could be affected by the flooding. The Tšilhqot’in National Government expressed concern about the blocked movement of Taseko sockeye salmon, an endangered population critical to the area. They called on various levels of government and fisheries to take measures to conserve the salmon.

The event took place about 100 km (62 miles) southwest of Williams Lake, in an area known as Nagwentled by the Tšilhqot’in. Daniel Shugar, a geomorphologist at the University of Calgary, noted that the terrain shows signs of ancient landslides.

Authorities are monitoring the situation using helicopters, uncrewed vehicles, satellites, and other remote sensing technologies. One person was partially buried by the initial landslide and had to be rescued by a resident, according to the Canadian Broadcasting Corporation.

References:

¹ Landslide Dams the Chilcotin River – NASA/EO – August 7, 2024