Flood Hazard in the Desert
April 25, 2022
Photographer: Thomas McGuire (Author and Town Council Member)
Summary Author: Thomas McGuire (Author and Town Council Member)
On August 18, 2021, a massive flood swept through the remote settlement of Camp Creek, north of Phoenix, Arizona. Damage to this creek-side community was greater than any flood recorded in the past 50 years, or more. Even houses 20 feet (6 m) above the normal stream level were destroyed. But far worse, two tourists in a rental all-terrain vehicle (ATV) died because they were unaware of the danger of these rapid flood events. Regrettably, the death of people who try to drive through flooded stream crossings is an all-too common event in the Phoenix area.
Camp Creek is a minor stream north of Phoenix that’s less than 15 miles (24 km) long. But a combination of moist monsoon winds from the Gulf of California, sparse vegetation within the watershed, ash from recent brushfires acting as cloud-producing condensation nuclei and adiabatic cooling caused by air rising into the highlands, led to a sudden flood event. Although no official measurements exist, the author estimates the brief, but maximum discharge of this small stream was on the order of 10,000 cubic feet per second; comparable to water flowing in the Colorado River through the Grand Canyon.
The top image shows the damage to the riparian environment after streamflow returned to its normal discharge level. The bottom photo is a radar image showing a monsoon wind carrying a narrow band of intense rainfall through the Camp Creek watershed. Note that Cave Creek wash, only 5 miles (8 km) to the west, had relatively modest flooding.