City council was briefed Tuesday on the freshet outlook for 2018 as the Fraser River starts to rise slightly around Chilliwack with the warmer weather.
As of April 1, according to the B.C. River Forecast Centre, the snowpack index in the entire Fraser River basin was at 108 per cent of normal based on historical averages.
Frank Van Nynatten, assistant manager of environment services for City of Chilliwack, explained that comparing the 108 per cent to the same time last year, the overall snowpack was at 100 per cent in 2017, and at 96 per cent in 2016.
The first of April is typically when 95 per cent of the seasonal snowpack has accumulated in the Fraser basin, and is considered the “key” time of year to measure.
The 108 per cent level from a month ago is “well below” previous years when the snowpack was higher, but still only “slightly above normal,” he said, providing a “moderate hazard” for this year.
Coun. Sue Attrill said it was “a bit frightening” to see how high the slough water level looks right now, even though she knows the city puts funding in reserve every year to make dike system improvements.
“I’m so relieved we’re not in imminent danger,” Attrill said.
Peak annual steamflows are estimated at this point to reach 9,000 cubic metres per second at the Mission gauge.
But snowpack is only one indicator of seasonal flood risk.
“Weather patterns can play a pivotal role,” the city staffer said.
A few weeks of hotter weather with significant rain will bring the snow down faster.
So the exact peak water levels during the snow melt freshet will depend on the weather, especially in the Central Interior of B.C., and staff will continue to monitor conditions and provide regular updates.
The City is undertaking routine freshet preparations, like mowing and inspecting dikes.