NAVWARN details

•         A large landslide occurred on the Chilcotin River 30 km upstream of the Fraser River confluence at approx. 11pm on July 30, 2024. Additional smaller landslides have occurred during the evening of August 3 and the morning of August 4, originating from the top of the primary landslide failure. The new smaller landslides are contained primarily to the right side of the channel and preliminary reports show this has not changed the minimum overtopping elevation.

•         The landslide blockage was approximately 1000 m long (along the channel) and 600 m wide.

•         The river was completely blocked 16 km upstream on August 4.

•         As of August 4, slope instabilities and other minor landslides had been noted in the upstream flooded area.

•         This morning water has begun actively flowing over the landslide blockage of the Chilcotin River. At 8:50 August 5 water reached the downstream edge (toe) of the blockage.

•         At 9:50 am, the flow has increased to in the range of few hundred cubic meters per second. Downcutting of the landslide blockage is occurring and the overflow channel width was estimated at 15 m wide.

•         At 10:00 am the leading edge of the breach water had reached approximately 3km downstream. Note that the leading-edge water indicated the start of water level rise and is not representative of the peak breach height.

•         There is woody debris being mobilized in the channel, and the leading edge of the water does contain woody debris.

•         There is potential for the debris to travel the entire length of the Fraser River, from the confluence with the Chilcotin River all the way to the Pacific Ocean.

•         The actual debris volume that will make it past the debris trap is unknown.

•         All Mariners should use caution navigating, especially at night.

•         Recreational craft of all types should avoid navigating Fraser River and its Delta until conditions clear.

•         Mariners navigating in the Salish Sea should expect debris on and below the surface.