July 2006-Sabino Canyon Floods

An unusual series of storms during the monsoon season in 2006 caused a very rare 5-day rainfall event that produced about 70% of Tucson's annual rainfall. This rain caused 435 slopes to fail over the Santa Catalina Mountains, which caused damaged on Catalina Highway as well as in parts of Sabino Canyon Recreation Area. Many roads in the metro area were flooded and closed for days while torrent flows caused swift-water rescues.

What was the hydrologic response across the region? We'll show you the evolution from July 27th at 00:00 to August 2nd at 23:59 for three streamflow stations:

1. Sabino Canyon Dam, which is located in the Santa Catalina Mountains foothills,
2. Tanque Verde Creek at Sabino Canyon Road, and
3. Rillito River near Dodge Boulevard, which is located downstream near residential areas.

In the US, we measure the volume of water flowing in a river in cubic feet per second (cfs). The easiest way to imagine this is 1 cubic foot being the size of a basketball.

One cubic foot of water is about 7.5 gallons, and 1 gallon weighs approximately 8 pounds. So, 1 cubic foot per second is the equivalent of a basketball weighing 60 pounds passing by every second!

This rainy event led to  435 slope failures  through the Santa Catalina Mountains. The Aspen Fire occurred in 2003, but  scientists confirmed  that this had little effect on the slope failures compared to the Sabino Canyon Flood. The US Forest Service spent  ~$4 million repairing  Sabino Canyon, and Pima County spent  $6.2 million for damages and cleanup  around the metro area.

• Christopher S. Magirl and others, short scientific  article published in Eos 
• Peter G. Griffiths and others, detailed scientific  article published in Water Resources Research 
• Robert H. Webb and others, detailed  USGS open-file report on debris flows and floods over SE Arizona