Smith Creek wildfire fallout: More flames and floods on the horizon
With crews gaining the upper hand on the Smith Creek wildfire, threat of floods lies in wait.
According to David Scott, head of the earth sciences department at UBCO, the risk of "erosion" officials are said to be evaluating, as referenced in Emergency Operations Centre press releases Wednesday, refers to the potential neighbourhoods below the burned out forest will flood during a heavy rainfall.
"What the Americans say is: if you have that heavy rain event on that burn site, then you can have flood and erosion and, if not, if that rain event doesn't happen within the first two or three years, then you've dodged the bullet," said Scott.
Scott's own research is on this erosion phenomenon. If soil is heated to extreme temperatures, it becomes water repellant for a period, he explained, causing flooding below the forest.
Following the 2003 wildfire, water repellant soil sent a torrent of mud and debris from a generally dry stream just past Bellevue Creek out onto Lakeshore Road and into the surrounding neighbourhood. Yet the heavy fire season did not produce the same around the province.
"When something like a quarter million hectares of land in Southern B.C. burned, we got flood events off of something less than 10 per cent of that area," said Scott.
Even if the heavy fires of this year taper off and heavy rains fail to materialize, Scott warns the province is not exactly out of the woods on the fire and flood cycle. In fact, climate change models indicate we're likely to become quite familiar with the double-whammy.
"We need to start preparing for some bad fire seasons to come," he said.
With a warmer climate, the forest is generally going to experience hotter temperatures and events like the pine beetle infestation, largely triggered by a lack of wintertime freeze strong enough to kill the beetle, will leave plenty of fuel for a fire.
Add to this the relative increase in the number of forest fires—an event like this week's would ordinarily happen every 100 years or so at Smith Creek's elevation, yet there have been several such fires in West Kelowna alone in recent years as development brings people further into the forest—and human encroachment will likely permanently alter the local ecosystem, he said.
With more frequent burns, the ponderosa pine and other forest vegetation will be denied the time needed to naturally reseed. Grasslands, hardier as grass is adapted to grazing and can withstand removal of the upper layer of foliage and still reseed the next year, will take over the burned out hills.
The valley bottom, by contrast, has already likely experienced a change, said Scott.
"The general conclusion that everyone makes is that because we've got control of the fire in the valley bottom in the last 100 years, the vegetation is getting more dense," he said, noting the ponderosa pine would likely have been far more sparse before white settlement.