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Expected deluge could raise Nahanni River over a metre in 24 hours

Nahanni Butte could face a risk of flooding
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Extreme rainfall, like the rain that tore up Franklin Avenue in 2018, is forecast for the southern Mackenzie Mountains. Up to 80 millimetres of moisture is expected to fall from July 10-12, enough to raise water levels over a metre. NNSL file photo

As Nahanni Butte, Sambaa K'e and the Fort Liard region grapple with temperatures in excess of 30 C this week, Environment and Climate Change Canada (ECCC) has another warning in place for the region — a month's worth of rain... in a day.

"There is high confidence there will be a large rainfall event (60 to 80+ millimetres) in the southern Mackenzie Mountains," reads the July 9 announcement from ECCC. "The heaviest rainfall is predicted to start falling in the afternoon of July 10, and will last into the morning of July 12.

"There is less confidence which river will receive the heaviest rainfall — however, forecasts suggest the South Nahanni River basin could see very significant rainfall. A rise in water level of over one metre is possible if the rainfall is concentrated in one basin. When compared to historic data for the general area, this means that over one month’s worth of rain could potentially fall within one day."

Officials are warning anyone in the region who is planning to go out on the land that the sudden rainfall could cause a rapid rise in water levels, potentially flooding areas and cutting people off from one another.

Rapidly increasing water levels can also overpower ships and swimmers and are an extreme drowning risk. If the rainfall is concentrated in the south Nahanni basin as currently forecasts, ECCC warns the community of Nahanni Butte could be facing a risk of flood. The heavy rain could also cause significant damage to drainage and roadway infrastructure.

All residents in the area are advised to have emergency kits ready.

This extreme rainfall warning comes at the same time as a heat warning hits the area. As of 1:53 p.m. July 9, ECCC is advising residents — especially older adults, infants and young children, pregnant people, people with physical and/or mental illnesses, and people with disabilities or mobility issues — to drink plenty of water, limit their time outside to the cooler hours of the day and try to keep to the shade when outside.

"Check several times a day on older family, friends and neighbours," reads the heat warning. "Make sure they are cool and drinking water. Never leave people, particularly children, or pets inside a parked vehicle.

"Watch for the effects of heat illness: swelling, rash, cramps, fainting, heat exhaustion, heat stroke and the worsening of some health conditions. When it’s hot, eat cool, light meals. Avoid using the oven.

"All workers should take regularly scheduled breaks in a cool or shaded space."



About the Author: Eric Bowling

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