B.C. (CP) – Authorities in British Columbia have issued an evacuation order for an area just north of where the Chilcotin River meets the Fraser River because of the danger of flooding caused by a landslide.
In a news release Sunday night, officials with the Cariboo Regional District told residents to leave “immediately” and that people who choose to stay do so at their own risk. The evacuation order covers 3.5 square kilometres.
A massive landslide last week 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.
Sean Leslie, spokesman for the ministry of water, land and resource stewardship, said in a statement Monday that water trapped behind the natural dam has not yet reached the top, although levels rose overnight. Leslie said that the height of the trapped water is similar to what is witnessed during the spring thaw but is expected to move more quickly and with greater force.
Experts expect water will reach the top of the natural dam and start flowing into the riverbed in the next several hours, he added.
The Tsilhqot’in First Nation said in a social media post that as of Sunday morning the slide was holding back 61 million cubic metres of water, equalling “24,400 Olympic swimming pools.”
British Columbia’s Emergency Management Department said on Sunday that water was expected to start moving over the top of the massive landslide site 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.
The department urged people to stay away from the Chilcotin and Fraser rivers because of the threat from the landslide.
The River Forecast Centre issued flood warnings for the Chilcotin River upstream and downstream of the landslide near Farwell Canyon.
A flood watch is in effect for the Fraser River from the Chilcotin River confluence downstream to Hope, B.C.
