Big snowpack no guarantee of spring flooding
Last spring, the province emerged from a tolerable winter and snowpack measured throughout the Rocky Mountains was at a level that did not have forecasters predicting anything out of the ordinary when it came to seasonal runoff.
So far this winter, the province and Central Alberta in particular have been buffeted by snow, and some measurements in the mountains are well above normal. Given the extensive flooding that hit south and central areas in the province last year, does the huge amount of wintry precipitation in 2014 then presage a precipitous flood more severe than the last a few months down the road?
Not exactly. With the right spring weather conditions, all the snow could disappear as calmly as much of it came; the worst thing that could happen is actually what we will all probably be clamouring for come April and May — a sustained blast of warm weather.
Alberta Environment will not start forecasting spring runoff for Central Alberta until April, but it does track snowpack levels in the Rockies throughout the year.
Many measurements of snows that will melt into the Red Deer River basin are taken at points along the eastern slopes; most so far are registering amounts within the normal range.
However, the accumulation at Limestone Ridge is nearly 90 cm greater in 2014 compared to early January last year.
“The greater the snowpack, the greater the risk. But if the change in temperature is gradual and nighttime temperatures remain below zero, it can be mitigated. You want the snow to melt slowly for a few hours a day rather than immediately over the course of a day,” said Jessica Potter with Alberta Environment.
Last spring, heavy rains combined with mountain runoff to cause major flooding in Calgary and surrounding areas and minor flooding in Red Deer and Central Alberta. Rainfall, snowpack, temperature, and soil moisture are the four main factors which can cause flooding in the province.
At the end of the agricultural season in 2013, soil moisture in the central region was mostly rated as ‘fair’ to ‘good.’ An Alberta Agriculture analysis of the moisture situation at the beginning of December showed that snow accumulations in the region were at minimum at six-year highs with large areas to the southwest and north of Red Deer experiencing 50-plus year highs.
At that time, the two agricultural areas in the province with the deepest snowpacks were around Pigeon Lake and near Magee Lake southeast of Ponoka, where the average winter precipitation amount of 100 mm of water in the snowpack had already been topped.
Alberta Agriculture crop specialist Mark Cutts said the conditions stand to benefit farmers, and especially winter wheat producers, as long as spring temperatures rise gradually. He said soils in the region did not get too frozen before the first snowfall in November, meaning they should be able to accommodate at least some of the melting snow come spring.
In Red Deer County, director of community and protective services Ric Henderson foresees drainage being an issue in the spring.
“Some of our issues rurally are when you have a thaw and a freeze again you get the frozen culverts and that kind of stuff, so that’s going to be something our drainage folks are going to have to worry about,” he said.
In Red Deer, during road-clearing campaigns when snow is plowed to the sides of roadways, efforts are made to keep catch basins clear.
“We’re very aware of it. There’s very little that we’re operationally doing about it right now, quite honestly, but we’re aware of it. So if somebody said ‘Hey, let’s pile a pile of snow there,’ we’re saying ‘Whoa, before we do that let’s consider drainage,” said public works manager Greg Sikora.
He said even if the amount of snow in the city grows leading into the spring, he does not foresee major flooding issues in Red Deer resulting from snow melt.
“Typically our seasonal freeze/thaw cycles allow that water to come off with our infrastructure that’s in place. I would anticipate that this won’t be any different from any other year from a drainage perspective,” said Sikora.
He said the bigger issue, if large amounts of snow remain, could be for individual homeowners with snow buildups around their residences.