Earth from space: Massive landslide dams Canadian river, trapping endangered fish on the wrong side

Striking new satellite imagery shows a Canadian river quickly swelling in size after a massive landslide completely dammed the waterway. The obstruction may have also doomed an endangered salmon population by preventing the individuals that survived the sudden damming from reaching their spawning grounds upriver.

The massive landslide occurred late on July 30 near Farwell Canyon on the southern bank of the Chilcotin River — a 150-mile-long (240 kilometers) tributary of the Fraser River. The landslide took place around 14 miles (22 km) upstream from where the Chilcotin joins the Fraser, dumping roughly 640 million cubic feet (18 million cubic meters) of earth and rock across the waterway and completely blocking its flow, according to an emergency statement from the British Columbia government.

Within less than 48 hours, the river had swelled significantly, breaking its banks at several points and forming a debris-filled lake behind the blockage, images from NASA's Earth Observatory show. The stretch of the Chilcotin between the landslide and the Fraser River was left almost completely dry.

Regional authorities quickly issued evacuation orders for residents living close to the banks downstream of the blockage, fearing that the rocky dam would eventually break and release a surge that could cause flash flooding or trigger further landslides downstream. It is unclear how many people were evacuated.

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On Aug. 5, part of the dam finally broke, unleashing a torrent of water that violently raced through the previously emptied riverbed. Despite the water flowing at more than 12,000 cubic feet (3,500 cubic meters) per second, the surge of water did not cause any major damage.

However, the landslide will likely have a major impact on the river's resident sockeye salmon (Oncorhynchus nerka), most of which were likely downriver of the landslide when it occurred, according to a statement from the Tŝilhqot'in Indigenous nation.