The deadliest single flash flood event in Utah in 92 years: 8 people dead, 5 still missing

A violent flash flood swept the Hildale community on the border between the US states of Utah and Arizona on September 14, 2015, claiming at least 8 lives and leaving 5 people missing.

Heavy rainfall have triggered severe flooding, as they pushed waves of water through canyons situated north of Hildale. The National Weather Service (NWS) issued a flash flood warning earlier in the day, leading the local officials to close all canyon openings across the Zion National Park, as a safety measure. 

Severe flooding caused an accident in the area, as a van with 16 passengers has been swept away by the large rushing wall of water and debris, according to Washington County Emergency Services. Several other traffic accidents happened across the affected area due to extreme weather conditions.

The flash flood of September 14 set a new record, being the deadliest single flash flood event in Utah since the 1923 flood near Farmington, the historical even which claimed seven lives.

About 19.56 mm (0.77 inches) of rain was reported to fall in Zion National Park on September 13, according to the NWS. More than 38 mm (1.5 inches) was estimated to fall across Hildale, Utah and Colorado City in Arizona. This amount of rainfall is not usual for the area, as only about 17.3 mm (0.68 inches) is an average September reported precipitation in the nearby Cedar City. 

Video credit: Syndicate News

Despite the flash flood warning it remains unclear whether the residents were aware of the danger, as it is normal for the waters to rise about 0.3 to 0.46 meter (1 to 1.5 feet) at a normal flood stage. "This was several feet deep, at least, and even more treacherous in the narrow channels," Hildale assistant fire chief Kevin Barlow​ said.

During the first flooding wave, a river gauge has risen about 1 meter (3.42 feet) in only 19 minutes on Short Creek at Colorado City while the second water wave caused a significant rise of about 1.6 meters (5.36 feet) in only 17 minutes.

The severe flooding caused several houses in the area to remain without power and water supplies.

Search and rescue attempts are ongoing across the affected areas. "We've got quite an effort going on. It's been pretty amazing to see the community coming together to do what they can," Barlow said.​

Local rains and thunderstorms were forecasted to continue across the area on September 14, according to the NWS.

Featured image: Fatal Hildale flood, September 14, 2015. Image credit: @STGnews