Response planning is underway to address the risk that flooding could possibly cut off access to Sayward.
The small community just off the Island Highway north of Campbell River has known flooding in the past, prompting the Strathcona Regional District to figure out how it should prepare for a repeat.
The Salmon/White River National Disaster Mitigation study looks at flood risk in the Salmon River and White River near Sayward. The resulting study was completed with funding from the National Disaster Mitigation Program.
Flood plain modelling was undertaken in 1980 but did not extend to the Village of Sayward, as it only covered the valley immediately upstream from the village.
Eric Heel from McElhanney Engineering said this work covers the assessment phase. Further funding streams focus on flood mapping, mitigation planning and non-structural or small-small structural mitigation projects.
This process outlines factors to consider in an emergency such as transportation routes, hospitals and population centres.
“We start to identity, if there were to be a flood, who would be impacted,” he said.
Members of the public recalled the last major flood of 1975, as well as lesser events in 1990, 2008, 2011, 2014 and 2018.
Rather than the populated areas themselves, the biggest challenge for the Sayward region seems to be the transportation corridor, especially emergency access. In one case, some people had to be taken out by a helicopter.
“People had generally been safe, but they’d been cut off,” he said.
Heel also touched on old historical records dating back to the 19th century concerning flooding in the region, including one during which the high water mark of the river reached 30 feet above the previous high-water mark.
“It’s hard to really quantify what this flood would’ve looked like, but the numbers are quite staggering,” he said.
The study also included examining meteorological and seasonal factors for flooding. Specifically, this includes factors such as large rainfall events and snowfall melt, along with the potential of climate change to affect flood risk.
“It’s actually a bit of a mixed bag,” he said. “It’s difficult to say how climate change is going to impact flooding in Sayward.”
He expects flood events could be more frequent, though he could not say if they will be more severe, as snowfall pack is expected to decrease but precipitation will likely increase.
He also touched differentiated between “risk” and “hazard,” with the former referring to things that could be affected like populations or transportation corridors , while the latter examines things like water depth and speed. This phase of the program identified the risks while later streams would examine hazards. He said these “risks” mostly relate to previous industrial sites. As far as infrastructure, the main concerns are the evacuation routes out of town.
“We know that both these roads can be cut off during flood events,” he said, adding the sewage system is also a concern, though more from factors such as sea level rise or storm surges rather than rising river levels.
“The ocean presents risks just like the river does,” Heel said.