‘Larger than normal’ snowpack blamed for April 18 flood

System overwhelmed

Susan Thompson
South Peace News

Water pours out from the manhole between the Centennial Parking Lot and Panago Pizza. Water flowed down the street towards Riverfront Park.

The Town of Peace River says Pat’s Creek was checked the afternoon before it flooded April 18, but despite new measures put in since 2016 to prevent it from flooding, the system was still overwhelmed later in the day.

Pat’s Creek is a known flood risk and was reviewed as part of Peace River’s annual spring break-up measures. The break-up of river ice occurred on April 14 without any issues.

“Town staff had briefed us that they had walked Pat’s Creek when it was safe to do so a few months previously to ensure that any large debris was cleared out,” Mayor Tom Tarpey says.

Tarpey says council was advised the trash racks upstream were clear and ready to screen out any large debris, and the flaps or curtains that hang near the entrance were free and not frozen into any ice dam.

Pat’s Creek was checked on Saturday, April 18 at about 2 p.m. and the creek’s flow appeared normal.

“Certainly, not enough to raise concerns, and the racks were still clear,” Tarpey says.

Flooding began about six and a half hours later at 8:30 p.m.

The Town believes a surge of water and debris coupled with an ice jam caused the backup of water into the town.

“The debris and water overwhelmed the ability of the racks to function and swept into the viaduct carrying Pat’s Creek under the town. Some of this material got caught up in the viaduct and that began acting as sieve. The sieve then just starting capturing more and more debris including ice,” Tarpey says.

“This in turn backed up the flow and blew out the manhole between the Centennial Parking Lot and Panago Pizza. This is when water started careening down the street and flowing towards Riverfront Park.”

Jim McCuaig, Director of Engineering and Infrastructure for the Town of Peace River, adds they are investigating to confirm it was the cause.

“As there was still significant amounts of water coming out of the outfall, this is leading us to believe that this was an issue of capacity. When the ice plugged up part of the culvert that dramatically reduced capacity, which caused the back up and causing the water to divert at the weak points in the system being the access hatch located on 99th Avenue,” he says.

“The higher volume of water was exacerbated by a higher snowpack than normal with Environment reporting snowpacks up to three times normal amounts in some areas. This coupled with warm temperatures increased the melt rate and increased stormwater within Pat’s Creek.”

The Town received flood mitigation funding from the Alberta government to upgrade the Pat’s Creek culvert and drainage system.

In 2015, phase one of the Pat’s Creek culvert rehabilitation took place, a $2.55 million project to repair the floor of the culvert funded largely by the Alberta Community Resilience Program [ACRP]. An additional $2.3 million in funding announced by then Premier Rachel Notley in 2016 was used for phase two of the project.

“That mitigation money was primarily spent on the viaduct/culvert itself,” Tarpey says.

The funding was spent on identifying weak spots and sections in the viaduct and repairing them so that the piping didn’t collapse and plug itself up.

The funding was also used to put in backflow prevention.

“We did also purchase and install a check valve, a duckbill check valve. The purpose of this check valve was to allow us to send pooled water around Riverfront Park out to the river without letting water back in,” Tarpey says.

“The valve was supposed to eliminate the need for us to breach the dike. It did work, but it was unable to keep up to the flood waters.”

Tarpey says the Town was just about to breach the dike when the blockage gave way and the water stopped coming out of the manhole by Panago Pizza.

“We certainly did not want to breach the dike as the ice on the Smoky was suppose to release in the next few days, if not the next day, and with this year’s snowpack the Smoky could raise the Peace River water level two metres,” Tarpey says.

The Town does not yet have an estimate of how much the latest flood damage downtown will cost to repair.

Damage assessments will include a technical review to answer what exactly went wrong and what other flood mitigation options could be installed to eliminate or better control this sort of flooding event in future.

“Obviously, the blockage was the immediate cause, but not the root cause,” Tarpey says.

“But, I do think we should recognize that the damage was much, much less than in 2014, and I think credit needs to be given to the duckbill valve and the better organized berming this time round by our Public Works SWAT team.”

“Due to the location of Peace River within this drainage basin there will always be some risk for flooding within the town whether it be one in 50-year events, or one in 100-year events,” McCuaig says.

“Every year at this time we work with Alberta Environment and BC Hydro to identify upcoming river and stormwater risks for the Peace, Smoky and Heart rivers as well as Pat’s Creek,” he adds.

“Part of this preparation includes check and cycling of all stormwater gates, checking of stormwater outfalls, and conducting a river watch at key locations. Further steps are being looked at to provide additional mitigation measures to reduce this risk to deal with normal flooding events up to and including one in 20 year events.

“For the immediate future, funding for additional mitigation measures needs to be identified and secured to allow the Town to continually improve their stormwater system,” he concludes.

To Town citizens reeling not only from a pandemic but also collapsing oil prices and now flooding, Tarpey says, “Don’t lose faith. Keep fighting. Keep working. Keep driving forward.

“Battling through these adversities will make us a more resilient and successful people. Being Canadian is all about never giving up.”

Water gathers around the gazebo at Riverfront Park in Peace River. Damage in the April 18 flood is unknown at press time.

Share this post