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Slesse and Ranger Slides

Last updated on March 1, 2024

Image of Ranger slide

Area: Chilliwack

Due to the scale of these two landslide sites, geotechnical assessments are necessary to evaluate the stability of the area, comment on the probability of a large volume slide in the future, and explore potential impacts of future flooding events.

Slesse Park Slide is a large landslide complex located just upstream of the Slesse Park subdivision on the north bank of the Chilliwack River. The Slesse Park landside is approximately 2,000,000 meters in volume with a long-documented history of landslide movement and the occasional partial blockage of the Chilliwack River. A previous attempt to mitigate deposition of landslide material into the Chilliwack River and provide erosion protection along the riverbank consisted of a toe berm located at the base of the slide along the Chilliwack River. This was damaged by several landslides and then heavily eroded during the November 2021 ARE.

The Ranger Run Slide is a landslide located approximately 17.5 km east of Vedder Crossing on the north bank of the Chilliwack River. It is 6 km upstream and due west of the Slesse Park Slide. The Ranger Run Slide is 400 meters wide and located on an outside bend on the Chilliwack River upstream of the Slesse Park Slide. The site has experienced at least two large debris slides in the past 60 years which blocked the Chilliwack River. 

Project Details

Total Budget:

$600,000

Projected Completion Date:

TBD

Community & Taskforce Members

 

Slesse Slide Map

 

Ranger Slide Map

Images

Above image: Slesse Slide along the Chilliwack River from January 2024 site tour

​Above image: Slesse Slide bank erosion from January 2024 site tour

​​Above image:Slesse Slide along the Chilliwack River. 

​Above image: Chilliwack River on the way to Slesse Slide from January 2024 site tour

​Above image: Ranger Slide along the Chilliwack River. 

Risk Evaluation

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Public Health and Safety

Ranger

There is no immediate risk to public safety from the previous slide; however, a large burst outflow after a larger future slide could have significant impacts to the public downstream of the slide location. Additional investigation is required to determine the potential slide volume and probability in order to determine a more reliable assessment of potential public hazard consequences.

Slesse

A large landslide leading to a large outburst flood could have catastrophic safety impacts to downstream residents and the public. This risk may extend to the Fraser River but is dependent on a number of unknown parameters.

 

River Capacity

Ranger

The current river capacity does not appear to be significantly impacted, but further slides have the potential to have significant impacts.

Slesse

A large slide at this location would block the river valley and impound river flows. A rapid failure of a large river valley blockage, referred to as an outburst flood, would result in peak flows that greatly exceed an extreme flood event.

 

Environmental

Ranger

As the fine-grained material deposited from the previous slide migrates downstream, it could impact fish habitat. Future slides can be expected to have further impacts to both fish habitat and recreational sites downstream.

Slesse

A large slide of fine-grained material is expected to have negative impacts to both fish habitat and recreational sites downstream.

 

Infrastructure

Ranger

There is no immediate risk to infrastructure from the previous slide; however, there is the possibility of a burst of outflow from a future slide that could generate high flows with significant debris that would be expected to impact downstream infrastructure.

Slesse

A large outburst flood would impact infrastructure and private property for a significant distance downstream.

 

Contact information

Information Officer
sec.info.epd@gov.bc.ca