Today’s storm could bring up to 250 millimetres of rain to the forests around Maple Ridge, with the possible result of the Alouette Reservoir filling up completely.
BC Hydro provided an update Friday saying that it’s preparing for “another major rain event” and noting that January has seen near record rainfall.
Hydro has already been spilling water from the reservoir into the Stave Lake system and recently opened the crest gate on the Alouette dam that allows water to go down the spillway into the South Alouette River.
“This, along with the significant natural and unregulated inflows downstream of the dam, may cause the Alouette River to further rise and contribute to localized flooding,” Hydro said in a release, Friday.
“Residents along the Alouette River are encouraged to be prepared for potential flooding,” said the release.
“If there’s a lot of snow up in the mountains and it’s very warm, were going to have increased flows in to the reservoir so there’s always the potential for it to free crest,” said Greta Borick-Cunningham, executive-director with the Alouette River Management Society.
If the rain keeps up there could be a free crest spill over the top of the dam and down the spillway but currently, there’s only a 50 per cent chance of that happening, she added. People should stay away from the river, she added.
BC Hydro is regularly updating ARMS and the City of Maple Ridge.
“Hopefully, Hydro got far enough ahead with their spilling. They do it proactively, to do it ahead of these kinds of weather systems coming in,” she added.
But whatever water goes over the top of the dam isn’t controlled, she added.
“People just have to be watching the river heights right now, definitely, if they’re living along the river,” Borick-Cunningham said.
BC Hydro spokesperson Tanya Fish said if water overflows the top of the dam, it doesn’t necessarily mean there will be flooding downstream. Tributaries flowing into the river also raise water levels.
“We are obviously releasing as much water as we can down the river … just to create that additional capacity as we’re seeing more rainfall come in, however there’s a maximum amount we can release,” she said.
So there’s a potential for the water to overtop the dam and come down the spillway, she added. The chances of that happening are currently at 50 per cent.
The City of Maple Ridge issued a flood and weather advisory Thursday, warning people about flooding along the North and South Alouette River system.
“We are recommending that citizens living in areas that are prone to flooding in high rainfall events be on alert for the next 48 hours as this weather system moves through,” the city said.