The community of Provo, Utah, showed unity in action following a downpour that carried a massive mudslide into the city from the remnants of the Buckley Draw Fire burn scar.
The fire began on Aug. 17, burning more than 400 acres in the Buckley Draw Canyon above the city. The burn scar that was left in its path turned into a disastrous mudslide after heavy rains occurred 10 days later.
And community residents stepped up.
Provo Mayor Michelle Kaufusi said during a press conference Friday morning that, at one point, so many volunteers showed up to help that many were asked to go home because it was becoming a safety hazard near all the machinery being used to remove debris. It was a good problem to have, she noted.
“It was just almost magical to watch,” Kaufusi said, even though it was a disaster that brought them together.
The mudslide’s greatest impact was on a church building owned by The Church of Jesus Christ of Latter-day Saints. The church house was caked in about 5 feet of mud. Damage was caused to the church building, but fortunately, it did not compromise its structure.
According to experts at the press conference, 1,550 truckloads, more than 23,000 tons of material and 33 equipment vehicles were used in the span of 2½ days to complete the cleanup. It took more than 850 man-hours of work.
In all, approximately 11 to 15 acre-feet of debris came down the canyon into Provo.
How did this happen?
The mudslide was, simply put, the result of Mother Nature being unpredictable.
Shane Ylagan, with the U.S. Forest Service, explained during the press conference that the rainstorm that occurred was considered a “10-year event,” meaning there’s a statistically 10% chance in any given year that that amount of rainfall will happen. But because the storm fell directly on the burn scar, the effects were magnified to the equivalent of a 25-year storm.
Tim Thompson, a senior engineer at GeoStrata Engineering and Geosciences, who collaborated with Ylagan’s team, further explained that even without a fire scar, a mudslide could have occurred with heavy rainfall, “but post-fire conditions trigger a much higher likelihood that debris flows can come out.”
To convey the severity of the recent mudslide, Thompson compared it to a 2003 mudslide that occurred in the same area following a fire. Roughly half an acre-foot of debris came out of the canyon in 2003, though debris fences that were put in place caught most of it; by the third fence, the flow had basically died out, and no destruction was caused to property.
“All of that fencing that was there in 2003 has been removed,” due to ongoing construction in the area, Thompson said. But a series of cement barriers and terraces were put in place and “impeded the flow significantly and pushed the majority of that flow down” and away from residential areas.
“Unfortunately, the volume was so much that they overtopped those barriers eventually. However, the velocity of the flow was diminished to the point where the impact to the church was mostly mud flooding,” he said, noting that if the fences had remained in place, it probably would have caused greater damage because “you would have had an even slope for that energy to continue, but the fact that those terraces were there and the debris was hitting and fanning out and losing velocity, I think was fortunate.”
What preventative efforts are being put in place?
City officials said that beginning Sept. 15, a new 1,200-foot channel extension and a large debris basin will be set for construction and should be completed in about two months. Also, storm drain upgrades and long-term infrastructure projects will be instituted to prepare for future storms.
The channel extension and debris basin design should be able to handle a 25-year storm event.
The No. 1 priority is ensuring the residents who live near the canyon feel safe, Kaufusi said. “There were zero evacuations, we’re really proud of that,” she said. “I worry about another rainstorm too. I’ve never watched the weather so much in my life. But again, we’re ready. We will be there. We will be there to make sure you’re safe, and we’ll do everything we can to take care of you and protect your properties and mitigate these storms.”