FILE PHOTO - Kamloops is listed as one of the Interior cities most at risk of flooding this spring. This photo was taken near Riverside Park on May 31, 2017.

(BRENDAN KERGIN / iNFOnews.ca)

A cold April has greatly raised the risk of flooding in B.C. this spring.

“Flood risk has increased considerably due to colder April temperatures across the province and delayed snowmelt,” states the province’s latest snow bulletin issued today, May 10. “Continued cool weather in May is increasing the risk for major flooding if a prolonged heat wave occurs later in the month or June.

“Weather conditions from May through June determine the timing, magnitude, and rate of snowmelt, where heavy rainfall events can exacerbate snowmelt-driven flows. An extreme heat wave – like the heat dome in late June 2021 – could lead to significant provincial flooding if it occurred between mid-May to mid-June.”

The provincial snowpack is 113% above normal but there are marked differences between the Okanagan and Thompson regions.

The Okanagan’s snowpack is the only region in B.C. that is below normal, at 83%

While the South Thompson readings are near normal, at 107%, there are only four recording sites across the entire basin and other snowsheds in the region are considerably higher so it’s reasonable to assume that the South Thompson is nearer those higher levels, the report says.

“Additionally, Shuswap Lake levels were above average earlier this year and were at historic highs over the winter due to the extreme rainfall from the atmospheric rivers in November 2021,” the report says.

The North Thompson basin is at 128% of normal. which is its highest reading since 1999.

“The combination of high snowpack in the Upper Fraser East, Quesnel and North Thompson indicates a heightened concern for flooding for Prince George, Kamloops, and the overall Fraser River,” the report says.

There is some concern that these conditions could trigger flooding in the Lower Fraser similar to what happened in 1948 and 1972.

The Nicola basin is also low. Its readings come from recording stations in the Lower Thompson and Okanagan, so is not considered its own region. Those stations average out to 79% of normal.

READ MORE: Merritt residents are scrambling to save their flood ravaged homes

“However, due to the significant erosion and possible changes in river channel morphology that occurred within many areas (including but not limited to the Coldwater River, Nicola River, Tulameen River, Coquihalla River and lower Fraser River), rivers may be at increased vulnerability to flooding at lower levels than previous freshet seasons,” the report says.

There is also the localized risk of flooding because of wildfires last year.

“Areas that recently experienced severe wildfire are at greater risk for higher peak flows (e.g., Upper and Lower Nicola, Guichon Creek, Deadman River),” the report says. “The Deadman River is currently under a high streamflow advisory from combined snowmelt and heavy rainfall occurring in the first week of May.”

The forecast for the coming months indicates that there’s a 59% chance of La Niña conditions continuing into summer

“Historically, La Niña conditions can lead to cooler April temperatures for British Columbia, resulting in delayed snowmelt and continued snow accumulation in the mountains,” the report says.

Even though the Okanagan has a lower snowpack doesn’t mean it’s immune from flooding.

READ MORE: Drought conditions felt in Thompson Okanagan

“Every region is at risk for flooding, even if the snowpack is below normal,” the report says. “Spring weather is impossible to predict with accuracy in advance, and so communities and residents vulnerable to flooding should prepare accordingly.”

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