British Columbia’s emergency management ministry says water is expected to start moving over the top of the massive landslide site currently blocking the Chilcotin River within hours.
The ministry says in a statement area modelling suggests water is expected to start moving over-top of the landslide site late Sunday or early Monday and enter the riverbed below the slide area.
The statement says minimal seepage from the slide site is being observed, but the water level behind the dammed area continues to increase at about 18 centimetres per hour.
The ministry statement says the most likely scenario to occur in the coming hours involves the trapped water moving through the slide area over 12 to 24 hours and resulting in flows downstream at the Fraser River resembling typical spring runoff, but higher peak water flows along the Chilcotin River.
The ministry says a worst-case scenario could involve a rapid draining of the slide site, which could result in a 21-metre rise of the Chilcotin River near the Farwell Canyon Bridge, but typical spring freshet flows downstream along the Fraser River.
A massive landslide Wednesday at Farwell Canyon located about 22 kilometres south of Williams Lake dammed the Chilcotin River and created a lake about 11 kilometres long behind the slide.
The ministry says people are urged to keep out of the Chilcotin River valley between Hanceville and the confluence of Fraser River
It says an evacuation order issued by the Cariboo Regional District remains in place.
People are also advised to stay away from the banks of the Fraser River.
The ministry says risks to public safety include the potential for further landslides upstream of the natural dam and downstream of the dam once water begins to flow past it.
The ministry says it is preparing for all possible outcomes since modelling does not provide guarantees.
Emergency Management Minister Bowinn Ma said at a news conference Saturday dangers still remain and people should heed evacuation orders and alerts and stay away from the river areas.
The ministry says it has set up a new web portal for Chilcotin River landslide information, visit: https://gov.bc.ca/landslide.
