The BC River Forecast Centre has upgraded the high streamflow advisory for the South Thompson River to a flood watch, joining the North Thompson River in that category.
The centre said the South Thompson at Chase is flowing at 1,180 cubic metres per second as of June 19, which is just past a five-year flow rate. The centre said the river is expected to continue to rise, with a 10-year flow rate possible this week.
The North Thompson at McLure is flowing at 1,940 cubic metres per second (between a two- and five-year flow rate) and could reach above 2,500 cubic metres per second (between a 20- and 50-year flow rate) this week due to a rainy forecast.
It is that upcoming rain that has led to upgraded advisories from the BC River Forecast Centre.
“Rivers in the region are flowing very high for this time of year and are extremely vulnerable to a heavy rainfall event,” the centre’s bulletin states.
“An upcoming major concern is the weather forecast for a potential long‐ lasting rain event in the headwaters of the South Thompson, North Thompson and Cariboo Mountains beginning late Tuesday (June 21) through Wednesday. Uncertainty remains high for rainfall totals and spatial extent. If widespread heavy rainfall occurs, rivers will reach the highest level of the season and it’s possible for significant flooding to occur.”
The City of Kamloops will present a flood risk update during a press conference in Riverside Park on Tuesday morning.
What the terms mean
• A high streamflow advisory means river levels are rising or expected to rise rapidly, but that no major flooding is expected. Minor flooding in low-lying areas is possible.
• A flood watch means river levels are rising and will approach or may exceed bankfull. Flooding of areas adjacent to affected rivers may occur.
• A flood warning means river levels have exceeded bankfull or will exceed bankfull imminently and that flooding of areas adjacent to the rivers affected will result.
As always, the public is advised to stay clear of the fast‐flowing rivers and potentially unstable riverbanks during the high‐streamflow period.