The monsoon rains that hit the Museum Fire scar Friday a week ago were pretty average for Flagstaff.
Given the dry summers Flagstaff has had since the Museum Fire burned last year, however, it also was some of the most significant rainfall the location has had since the fire was declared contained in August 2019. Rain gauges measured anywhere from a half an inch to slightly less than an inch hit the fire scar in the Dry Lake Hills above Flagstaff.
Weather watchers may remember the rain that fell during the fire, causing subsequent flooding beneath the Museum Fire scar for residents in Paradise Way. Last week's thunderstorm was different because the rain hit more of the fire scar than the previous one, and fell across the majority of the Spruce Avenue mountainside. The average rain caused an abnormal water flow for the area beneath the scar, creating water flow that crossed streets, flowed through ditches and made its way to Cedar Avenue.
County officials shared a video of the flow and sent out an alert to people living in Mount Elden Estates to shelter in place as the water was coming down.
“I’m pretty comfortable saying this is by far the most intense rainfall event since the fire. Rain also fell across a pretty significant amount of the watershed, which is unique compared to the event last year,” Coconino County engineer Christopher Tressler said.
Tressler was thankful the county didn’t see any failures of the flood protections that were set up for a much more severe storm, including public flood warnings, stabilizing natural landscapes and jersey barriers.
He added that when considering whether to send out a flood warning, authorities must consider both how fast the rain is falling and the duration it's falling. Additionally, county officials believe this flow was more significant because rain had wet the ground the day before.
Lucinda Andreani, director of county public works, said the Coconino County is seeing a similar pattern on this fire scar that they saw as a response to the Schultz Fire, where flows would increase velocity over time due to the continued erosion.
“As we saw in Schultz, as we went through the monsoon season, less amount of rain would have more of an impact,” Andreani said.
That being said, county officials were happy because while the flows contained soot and sediment picked up from the fire scars, it lacked a large amount of debris such as larger rocks present upstream.
Paradise Way saw significant flooding in 2019 during rains that fell before the Museum Fire was contained. The same area was now fortified with jersey barriers to direct the flow away from the homes.
“Without jersey barriers that would have been a different story for a handful of homes in that area,” Tressler said.
Be the first to know
Get local news delivered to your inbox!