Mission Creek slowing its roll into the lake

After weeks of steady increases, flow velocities in Mission Creek have begun to drop slightly.

Kelowna's main waterway was flowing at the rate of 58 cubic metres per second on Monday, but it began slowing on Tuesday morning and as of Wednesday afternoon the flow was 55 cubic metres per second.

An average flow for Mission Creek is late May is about 30 cubic metres per second, Dave Campbell, of the BC River Forecast Centre, said Wednesday.

Still, he cautioned the slight downward trend in flows seen over the past two days does not necessarily mean the risk of localized flooding along Mission Creek, or any of the other tributaries that flow into Okanagan Lake, has lessened.

“The flow in Mission Creek is still high for this time of year, for sure, and the melting of the Mission Creek snowpillow is only at about 20%, so there's still a lot of snow up there that has to come down,” Campbell said.

Earlier this month, the Okanagan snowpack was at 110% of normal. While that might suggest an elevated risk of flooding, the reality is local creeks do not typically over-top their banks unless there is a period of heavy, sustained rainfall.

Kelowna has had about 24 mm of rain so far this month, well below the average for the month of 39 mm. Little rain is forecast for the next 14 days, according to The Weather Network, but June is typically the wettest month in the Okanagan, with 46 mm of rain.

Current flows in Mission Creek are much higher this spring than they were in May and June of 2019. Last year, the velocity peaked at about 25 cubic metres per second on May 16.

Flooding concerns generally develop when the creek flow exceeds 80 cubic metres per second. But flood prediction is an inexact science.

In mid-May 2017, city officials warned of the prospect for massive flooding with a prediction the creekflow would top 140 cubic metres per second. But a forecast heavy rainstorm fizzled out and the flow never topped 60 cubic metres per second.