USA – Record Rainfall Causes Flash Floods in Flagstaff Burn Areas, Arizona

Officials in Coconino County, Arizona, reported record rainfall fell on burn scar areas on 17 August 2021, causing more severe flooding in areas around the city of Flagstaff.

In a statement of 17 August, Coconino County said rain began around midday, falling over the burn scar of the large 2019 Museum Fire near Flagstaff.

“By the time the large storm system moved out of the area, the entire burn area was saturated, resulting in the largest rainfall event to date,” the statement said. An hourly rate of 3.07 inches (77.98 mm) was recorded in the south of the burn scar area.

“In addition, the rainfall was intense with over 1.14 inches recorded in at the south and west gauges in 15 minutes and 1.06 inches recorded at the east gauge. Not only was significant rainfall experienced on the burn scar itself, but also in the Sunnyside neighborhood. In an hour, 1.22 inches fell at Linda Vista and 1.5 inches was recorded downstream in neighborhoods. The rainfall recorded at the south gauge equates to a 200- to 500-year rainfall event,” Coconino County said.

The rainfall over the entirety of the burn scar, combined with the significant rainfall in the neighborhood, resulted in flooding that closed roads and overtopped mitigation. Significant debris was seen in the storm water given that a large area of the burn scar had not previously experienced heavy rainfall.

Flagstaff Mayor Paul Deasy said on Social Media, “3 inches of rainfall in last hour on the museum fire scar. Shelter in place if in the flood plain. Get your children and pets inside NOW.”

The Coconino County Flood Control District and the City of Flagstaff have mobilized all resources and said clean-up operations will begin as soon as the water recedes.

Areas of Flagstaff experienced similar flooding last month. Flagstaff city spokeswoman Jessica Drum said last month’s floods caused about $5 million in damage to local public infrastructure including roads.

Flood debris in Flagstaff Arizona, July 2021. Photo: Flagstaff City Government

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