.

Home page

Text size

E-mail this page

DEH CHO - Helicopters were on standby to evacuate Nahanni Butte when the Liard River began to move last week.

Each year during breakup the community prepares for the possibility of flooding, and this year was no exception.

The Liard River, which rose to the top of its banks during breakup, was a source of concern for residents of Nahanni Butte on May 7. - photo courtesy of Don Hardisty

The water in the Liard River rose up its banks on May 7 as the ice jammed while it made it way along the river.

"The community was at the river bank the whole evening," said Don Hardisty, general manager of the Tthenaago Development Corporation in Nahanni Butte.

Water levels in the river started to rise on May 6 when ice jammed near Swan Point, approximately 10 km from the community.

By 3 p.m. on Thursday afternoon the river was becoming a concern, Hardisty said.

"There was no movement and the water started to rise again," he said

Hardisty was part of group of approximately four people who began monitoring the river.

By 6:30 p.m. river water had started over onto roads in lower lying areas nearest to the river.

At 8 p.m. the water reached a critical level but half an hour later it started to drop.

The level fell more than a foot in the space of an hour. By Friday morning it was down another two feet, Hardisty said, adding flooding wasn't severe enough to threaten any homes and it had already drained off the road.

"Everything's fine this morning," he said.

As the water rose on Thursday, everyone was calm, Hardisty said. The community didn't reach the point of evacuation but there was a plan in place.

Using helicopters, the population would have been moved out starting with elders.

A group of adults would have remained behind to set up camp on a high point and watch the community, said Hardisty.

In contrast to Nahanni Butte's excitement, breakup in Fort Simpson was relatively unremarkable.

"It went without incident," said Duncan Canvin, the village's mayor.

The tipi located on the ice across from the Northwest Territories Power Corporation's plant recorded that breakup occurred there at 4:30 a.m on May 8.

The water level in the Mackenzie River reached 12.5 metres around noon on Friday, which signalled the beginning of the flood watch, Canvin said.

Members of the flood watch committee stayed on alert until 4:30 p.m. that afternoon when water levels had fallen again.

Water did flow across a short span on Mackenzie Drive, the road nearest the river, before receding but that is a normal occurrence, said Canvin.

One aspect of the breakup was notable.

"This is one of the fastest on record," said Roger Pilling, a hydrometrics supervisor with Water Survey Canada.

It usually takes between two to three days for the ice from around the village to make its way past the bend near the Martin River. This year the ice was gone within 12 hours, Pilling said.

By Monday morning the ice pack was already at Root River, which is approximately the halfway point on the Mackenzie River between Fort Simpson and Wrigley.

"The indicators were it wasn't going to stick around here long," said Pilling.

The ice thickness on the Mackenzie River was slightly below average this year. The average ice thickness last year was 1.25 metres and this year in early April it measured 1.1 metres. The ice was smooth and had little snow cover on it which meant the sun could weaken it leading to a smooth breakup, Pilling said.

This year's breakup also demonstrated the change that is occurring in the way the ice breaks.

Traditionally the breakup at Fort Simpson occurs because of a progression from the south along the Liard River, Pilling said.

In the past 10 years it has become more common for the last 80 km of the river to move on its own without waiting for a push from the rest of the ice, he said.

Water levels in this year's breakup were average or slightly above average.

In Fort Liard the Liard River peaked at 10.61 metres.

"That's a little bit above normal but not extremely high," said Pilling.

At its mouth the Liard peaked at 13.5 metres at approximately 7 a.m. on Friday. The level is close to the average for breakup which ranges between 12 to 13 metres, he said.

The Mackenzie River at Fort Simpson peaked at 13.1 metres on Friday morning, which is above the 12- to 12.5-metre average over the past 15 years, said Pilling