Mayo is melting

Mayo residents know when the Stewart River runs high, it's time to flip on their sump pumps to prevent their basements from flooding.

Mayo residents know when the Stewart River runs high, it’s time to flip on their sump pumps to prevent their basements from flooding.

But that’s sometimes not enough, when you live, as they do, on a floodplain at the confluence of the Stewart and Mayo rivers. The village flooded in December.

Most blame, in part, what’s misleadingly called a dike.

Dikes keep water out. But water flows beneath this berm, which was once composed of organic material, such as trees, that have since rotted away, leaving holes that let the Mayo River’s waters through.

The berm is now being studied for repair, but the Yukon government could be doing more to help protect village residents.

At present, no agency is monitoring the movement of Mayo’s subsurface water. If it were monitored, this information could help get a jump on future floods.

In comparison, Whitehorse has long monitored the levels of wells. Similar work in Mayo – which could help anticipate future floods – has been slapdash.

“There is no data to try to quantify what’s going on,” said Kristen Kennedy with the Yukon Geological Survey. She’s an author of a report, released in March, that sizes-up the threats climate change poses to Mayo.

One of the report’s recommendations is that the territory begin a groundwater monitoring program for the village.

The report also recommends further study of permafrost. Much of Mayo sits atop the frozen ground. As the world warms over the next few decades, this could make Mayo’s periodic flooding worst. Or better. Without further study, it’s hard to say.

It’s possible that a sheet of permafrost serves as a floor to underground water, and that as this ice melts, the water table will sink. Or the ice could prevent water from rising. Nobody knows.

“Until you drill, you don’t know for sure,” said Kennedy.

Much of Mayo’s permafrost is already close to melting, and modest projections have temperatures in Mayo rising by 1.7 degrees Celsius by 2030 and 2.1 degrees Celsius by 2050. The medium-high forecast calls for increases of 1.5 degrees Celsius by 2030 and 3.2 degrees Celsius by 2050.

“We’re confident the permafrost will melt,” said Kennedy. “It’s on its way out.”

For evidence, Kennedy needed look no further than the state of the recently built annex used by Yukon College in Mayo. As the ground beneath the building shifts, cracks have appeared on inside and outside walls.

Kennedy spent five weeks wandering Mayo with a backpack and shovel, mapping the area’s geology. To find permafrost, she’d zap the ground with a car battery and watch how the electricity dissipates. Ice does not conduct electricity well.

She also used a small drill, powered with a chainsaw motor, to take core samples.

Much of the resulting report is technical, but it includes an easy-to-read “stoplight map,” so-called because high-risk areas are marked red, medium-risk yellow and low-risk green. It should be useful to planners and developers with the municipality, territorial government and First Nation of Na-cho Nyak Dun.

An area flagged as red won’t necessarily sink. But anyone planning to build on a risk-prone area would be wise to hire a geotechnical engineer to poke around the area first, said Kennedy.

The First Nation built its new headquarters on a hill for good reason. Some older homes in its possession were abandoned after being overcome by black mould, in part because of the tendency for basements to flood.

Part of the Mayo airport’s gravel runway is also slowly sinking. Kennedy suggested demolishing one end and extending the far side. Officials “thought it was hysterical,” she said.

A big gravel patch sits beside the runway, making it far cheaper to repair the runway each year than tear it up and move it.

As Mayo’s permafrost melts, it will likely cause water mains to buckle and break. The subsequent release of water may melt more permafrost, speeding up the process, said Kennedy.

The municipality may want to consider installing bigger culverts around the village, to prepare for the onslaught of water.

Many Mayo residents blame Yukon Energy for the winter flooding. The utility is expanding its nearby hydroelectric facilities.

But construction work was done out of the water at the time of the flooding, said spokesperson Janet Patterson.

Mayo’s biggest flood struck in 1936, when the Stewart River rose 4.8 metres above the usual watermark. The waters washed away houses and destroyed the church while residents fled to high ground across the river.

If there’s a bright spot in the report, it’s this: Mayo may be sinking, but there are few reasons to worry about it being hit by landslides.

And a similar study found Pelly Crossing to be at little risk from climate change. The community is perched up high enough that it’s unlikely to be ever at risk from floods.

The report was prepared by the Northern Climate Exchange, a research arm of Yukon College, with help from the universities of Alberta and Ottawa. The study cost $250,000 and was paid for by Indian and Northern Affairs.

Contact John Thompson at

johnt@yukon-news.com.

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Team Togo member Katie Moen sits in a sled behind a snowmobile for the ride from the airport to Chief Zzeh Gittlit School. (Haley Ritchie/Yukon News)
Coming together: How Old Crow became one of the first communities in the world to be fully vaccinated

Team Togo and Team Balto assembled with a mission to not waste a single dose of vaccine

Main Street in Whitehorse on May 4. If council moves forward with bylaw changes, eating and drinking establishments could set up pop-up patios in on-street parking spaces. (Stephanie Waddell/Yukon News)
Patios may be popping up in Whitehorse this summer

City considers program for downtown restaurants and bars

The Yukon Coroner's Service has confirmed the death of a skateboarder found injured on Hamilton Boulevard on May 2. Gabrielle Plonka/Yukon News
Whitehorse man dies in skateboarding accident

Coroner urges the use of helmets, protective gear, while skateboarding.

The new Yukon Liberal caucus poses for a photo during the swearing-in ceremony held on May 3. (Yukon Government/Submitted)
Liberal cabinet sworn in at legislature before house resumes on May 11

Newly elected MLA Jeremy Harper has been nominated as speaker.

The Yukon Wildlife Preserve’s baby bison, born April 22, mingles with the herd on April 29. (John Tonin/Yukon News)
Yukon Wildlife Preserves welcomes two bison calves

A bison calf was the first 2021 baby born at the Yukon Wildlife Preserve

A map provided by the Yukon government shows the location of unpermitted logging leading to a $2,500 fine. (Courtesy/Yukon government)
Man fined $2,500 for felling trees near Beaver Creek

The incident was investigated by natural resource officers and brought to court.

The site of the Old Crow solar project photographed on Feb. 20. The Vuntut Gwitchin solar project was planned for completion last summer, but delays related to the COVID-19 pandemic pushed it back. (Haley Ritchie/Yukon News)
Old Crow is switching to solar

The first phase of the community’s solar array is already generating power.

Chief Medical Officer of Health Dr. Brendan Hanley. (Crystal Schick/Yukon News file)
One new case of COVID-19 in the Yukon

Case number 82 is the territory’s only active case

Flood and fire risk and potential were discussed April 29. Yukoners were told to be prepared in the event of either a flood or a fire. Submitted Photo/B.C. Wildfire Service
Yukoners told to be prepared for floods and wildland fire season

Floods and fire personelle spoke to the current risks of both weather events in the coming months.

From left to right, Pascale Marceau and Eva Capozzola departed for Kluane National Park on April 12. The duo is the first all-woman expedition to summit Mt. Lucania. (Michael Schmidt/Icefield Discovery)
First all-woman team summits Mt. Lucania

“You have gifted us with a magical journey that we will forever treasure.”

Whitehorse City Hall (Yukon News file)
City news, briefly

Whitehorse goings-on for the week of April 26

The Yukon Department of Education in Whitehorse on Dec. 22, 2020. The department has announced new dates for the 2021/2022 school year. (John Hopkins-Hill/Yukon News file)
Yukon school dates set for 2021/22

The schedule shows classes starting on Aug. 23, 2021 for all Whitehorse schools and in some communities.

Most Read