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2015 Utah floods

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2015 Utah floods
NEXRAD image at 20:20 UTC (2:20 p.m. MDT) on September 14, depicting a thunderstorm over Hildale, Utah that produced deadly flash floods
DateSeptember 14, 2015
LocationSouthern Utah, northern Arizona
Deaths18 confirmed

On September 14, 2015, two flash flood incidents occurred in southern Utah. Eighteen people are confirmed dead, with two still missing as of the morning of September 17, 2015. The event ranks as the deadliest flood disaster on record in Utah.[1][2][3]

Background

On September 6, 2015, a tropical depression formed off the western coast of Mexico over the Pacific Ocean.[4] This system, soon named Linda, eventually became a Category 3 hurricane on September 8.[5] After degenerating into a remnant low on September 10,[6] moisture associated with the former tropical cyclone spread across the Southwestern United States. Aided by above-average water vapor levels, a seasonally strong upper-level trough produced scattered thunderstorms across the region on September 14. Two incidents of flash flooding resulted in 18 deaths in Utah, the deadliest flash flood event in the state's history.[1] The previous deadliest event was on August 13, 1923, when seven people died near Farmington.[7]

Flash floods occur annually in Utah, with an average of one to two incidents per year since 1950.[7]

Hildale event

The first incident occurred near the town of Hildale in Washington County when two successive thunderstorms produced more than 2 in (51 mm) of rain;[1] this qualified as a 1-in-100 year event.[8] The National Weather Service issued a strongly worded flash flood warning at 20:22 UTC (2:22 p.m. MDT) for the area,[1] stating "Move to higher ground now. Act quickly to protect your life".[8] The first storm resulted in a 3.42 ft (1.04 m) rise along the Short Creek, as measured by a stream gauge in Colorado City, Arizona, in 19 minutes around 21:18 UTC (3:18 p.m. MDT),[7][8] with residents gathering nearby to observe.[8] Between 22:48 and 23:05 UTC (4:48 and 5:05 p.m. MDT), a second surge of water swept down the creek with the Colorado City gauge reporting a rise of 5.36 ft (1.63 m);[7] the gauge stopped reporting at 23:47 UTC (5:47 p.m. MDT). The second flood swept away two vehicles carrying a collective 16 people while they were observing the rising waters.[8] Twelve people were killed, three children were rescued, and one remains missing as of September 16.[9] Six bodies were recovered in Utah and two in Arizona, 2.5 mi (4.0 km) downstream.[7]

Alongside the fatalities, the floods left several blocks of the town without power.[10]

Around 150 federal personnel and 500 community volunteers conducted search and rescue in the immediate aftermath.[7] Twenty-four members of Utah Task Force One and twenty-six personnel from the Utah National Guard were dispatched to Hildale to assist in search and rescue along Short Creek. Dangerous conditions along the creek slowed the operation.[11]

Zion National Park

The second incident occurred in Keyhole Canyon at Zion National Park after 0.63 in (16 mm) of rain fell in an hour.[12] For the two day period ending September 14, the park saw 1.89 in (48 mm) of rain.[7] The earlier flash flood warning prompted officials at the park to close all slot canyons.[10] Flow along the Virgin River dramatically increased following the rains, with the river's North Fork experiencing a rise from 55 ft3 (1.5 m3) per second to 2,630 ft3 (74.5 m3) per second in just 15 minutes.[13] Seven people were swept away while canyoneering, six of whom died while the seventh remains missing.[12] This was the deadliest weather-related disaster at a national park since 11 people died in a flash flood in Antelope Canyon in 1997.[7]

Elsewhere

In Utah County, the rain resulted in traffic accidents and mudslides, including several at American Fork Canyon that shut down parts of State Route 92 and State Route 144.[14]

References

  1. ^ a b c d Bob Henson (September 15, 2015). "Linda's Moisture Contributes to Heavy Rain, Deadly Flooding in Southwest". Weather Underground. Retrieved September 16, 2015.
  2. ^ Michael Martinez, Cheri Mossburg, and Holly Yan (September 16, 2015). "Floods in Utah kill 16, leave four missing". CNN. Retrieved September 16, 2015.{{cite web}}: CS1 maint: multiple names: authors list (link)
  3. ^ Jenkins, Kevin. "2 now missing after deadly Utah floods kill 18". USA Today. USA Today. Retrieved 16 September 2015.
  4. ^ Eric S. Blake (September 6, 2015). Tropical Depression Fifteen-E Discussion Number 1 (Report). Miami, Florida: National Hurricane Center. Retrieved September 17, 2015.
  5. ^ Michael J. Brennan (September 8, 2015). Hurricane Linda Advisory Number 11 (Report). Miami, Florida: National Hurricane Center. Retrieved September 17, 2015.
  6. ^ Michael J. Brennan (September 10, 2015). Post-Tropical Cyclone Linda Advisory Number 20 (Report). Miami, Florida: National Hurricane Center. Retrieved September 17, 2015.
  7. ^ a b c d e f g h "Authorities Search for 2 Missing in Southern Utah Floods; 18 Killed". The Weather Channel. Associated Press. September 17, 2015. Retrieved September 17, 2015.
  8. ^ a b c d e Angela Fritz (September 16, 2015). "Horrific Utah flood is likely the deadliest U.S. weather event so far in 2015". The Washington Post. Retrieved September 17, 2015. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
  9. ^ "12 found dead, 1 boy missing as crews clean up flood-ravaged Hildale". Hildale, Utah: KTSU. September 16, 2015. Retrieved September 17, 2015.
  10. ^ a b "At least 18 killed as flash floods strike Utah". Fox News. Associated Press. September 16, 2015. Retrieved September 17, 2015.
  11. ^ Zach Whitney (September 17, 2015). "National Guard, Utah Task Force One join search for missing child after deadly flash flood in Hildale". Hildale, Utah: KTSU. Retrieved September 17, 2015.
  12. ^ a b "Crews search for 1 missing in Zion National Park after flash flood, 6 found dead". Zion National Park: KTSU. September 16, 2015. Retrieved September 17, 2015.
  13. ^ "Four Fatalities Confirmed in Zion National Park, Three Still Missing". National Park Service. September 16, 2015. Retrieved September 17, 2015.
  14. ^ "Heavy rain brings mudslides, accidents to Utah County". Daily Herald. September 15, 2015. Retrieved September 17, 2015. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
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