High-Impact Weather and Climate Events

High-impact events cause the majority of societal costs related to weather and climate. They provoke societal responses that can either enhance or detract from long-term adaptation to climate risk. In 2015, WWA began a new research focus on extremes that is designed to place high-impact events in the context of historical climate variability and projected climate change, assess how the risk of these events varies over time and space, and examine how high-impact events interact with place-based vulnerability.

The High-Impact Events Database has 280+ historical high-impact weather and climate events in our three-state region, and a complementary set of regional event maps showing how risk varies seasonally across the region for different types of weather and climate events.

The database is a curated collection of significant weather and climate-related events in the Western Water Assessment region. The types of events included are: avalanches, cold waves, dam failures, droughts, floods, hail, high winds, landslides, tornadoes, wildfires, and winter storms. We search federal, state, county, and local databases, library archives, news accounts, and other sources for current and historic notable weather and climate-related events in Colorado, Utah, and Wyoming. This database is not a scientific collection of extreme events. The majority of events included in this database are incidents that were identified as remarkable by one of the sources listed above.

All CPI-Adjusted Damage costs are 2022 values, calculated from: https://www.usinflationcalculator.com/. CPI-Adjusted Damage costs are unavailable before the year 1913.

WWA High-Impact Events Database Map (1864-2021)

This map is a visual representation of all the high-impact events in our database by county from 1864-2021. The counties with no data represent counties with no events explicitly reported in the database.

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State	County	City	Date	Event Type	Deaths	CPI Adjusted	Unadjusted
Colorado	Denver	Denver	November 26, 1983	Winter Storm		$4,402,050.00	$1,500,000.00	Summary 21.5" of snow. "This storm was known as the "Thanksgiving Blizzard" and was also accompanied by epic cold, with temperatures dipping into the teens and 20s, according to the Farmer's Almanac. What made this storm particularly unique is the fact the snow stuck around for 63 days, and snow removal cost the city $1.5 million." - 9News
Utah	Millard		June 24, 1983	Dam Failure, Flood	1	$17,000,000.00		Summary Delta Millard Abraham Desert Dam. Cause of failure: Spring flood flows; Gunnison Bend Dam purposely breached. $17M (2022 dollars). "DMAD Dam failed in 1983 and a transient was killed trying to cross the flooding river on a suspended wire. The Gunnison Bend Dam was consequently breached proactively to keep it from overtopping." - Utah DEM
Colorado	Statewide		June 01, 1983	Flood	10	$45,170,900.00	$15,392,000.00
Utah	Statewide		June 01, 1983	Flood	7	$880,410,000.00	$300,000,000.00	Summary Record snowpack resulted in severe flooding from extensive runoff. Flooding occurred all along the Wasatch Front, damaging homes and public property. Creeks and rivers across the state saw record flows, including five of the six creeks in Salt Lake Valley. In June, high waters caused the failure of a dam near Delta, the resulting flood destroyed the town of Deseret. Seven people died in the floodwaters.
Utah	Uintah, Carbon, Emery, Wayne, Sevier, Summit, Kane, Garfield, Piute, Millard, Juab, Beaver, Delta, Salt Lake, Utah, Davis		April 13, 1983	Landslide, Flood		$586,940,000.00	$200,000,000.00	Summary Starting on April 13, a landslide caused by heavy precipitation dammed the Spanish Fork River, which then inundated the community of Thistle. The slide also destroyed the Rio Grande railroad tracks and US 6 and US 89. The landslide was the most costly geological event in Utah's history. Presidential Disaster declaration.
Utah	Utah, Davis, Salt Lake, Weber, Cache		April 04, 1983	High Wind		$29,347,000.00	$10,000,000.00	Summary 60-80 mph winds along the Wasatch Front from Utah County northward caused damage to private property and infrastructure. The peak gust of 104 mph was recorded in Hill Field/Layton. Winds damaged or destroyed 54 major transmission towers from the Ben Lomond Substation. Extensive glass damage was reported in Ogden, and 12 flatbed railroad cars were overturned near Farmington.
Colorado	Boulder, Denver, Douglas, Arapahoe	Boulder, Denver	December 23, 1982	Winter Storm		$22,414,400.00	$7,400,000.00
Wyoming	Park, Teton, Hot Springs, Fremont, Big Horn, Sheridan, Johnson, Natrona		September 14, 1982	Winter Storm		$8,329,680.00	$2,750,000.00
Colorado	Boulder	Boulder	January 16, 1982	High Wind		$51,492,600.00	$17,000,000.00
Colorado	Larimer		January 01, 1982	Dam Failure, Flood	4	$93,898,200.00	$31,000,000.00	Summary "Larimer County, Lawn Lake Dam, 1982: The Lawn Lake Disaster of 1982 caused four deaths and over $31 million in property damage when a privately-owned dam failed in Rocky Mountain National Park above the Town of Estes Park in Larimer County. Gradual deterioration of the earthen dam led to a breach that released 220 million gallons of water. A lawsuit awarded $480,000 to the family of one of the four persons killed in the disaster." - CO Hazard Mitigation Plan 2018-2023

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High-Impact Weather and Climate Events

WWA High-Impact Events Database Map (1864-2021)

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