"The flash flood which occurred July 26, 1981 at Tanque Verde Falls, near Tucson, Arizona resulted from a relatively small, but apparently an intense thundershower occurring in the upper reaches of the basin. The meteorological and hydrological analyses support the premise that while the storm was intense, it was not unusual for the season, but rather was typical of the many storms which occur during the Arizona monsoon season. The nature of the thundershower; i.e., its intensity, slow movement relative to the drainage area, and the configuration of the watershed, combined to produce extremely rapid and concentrated runoff, resulting in a wall of water progressing down the Tanque Verde Wash, through an area where approximately 150 were concentrated. Because of the steepness of the canyon walls and the sudden appearance of the wall of water, people were caught totally unaware. In fact, rescue personnel from the Arizona Department of Public Safety were engaged in a rescue operation at Tanque Verde Falls and were nearly caught in the flash flood themselves. It is significant that these personnel are actively engaged in the county program to warn the public of the dangers of flash flooding in the dry washes of the Tucson Valley"--Summary.

National Weather Service (NWS)

Arizona