Impacts of Climate Change and Land Use  on the Southwestern United States

Southwestern States Flood and Drought Summaries


This page is excerpted from Paulson, R.W., Chase, E.B., Roberts, R.S., and Moody, D.W., Compilers, National Water Summary 1988-89-- Hydrologic Events and Floods and Droughts: U.S. Geological Survey Water-Supply Paper 2375, 591 p.

Major floods and droughts are those that were areally extensive and have large recurrence intervals‹greater than 25 years for floods and greater than 10 years for droughts. These major events and additional floods of a more local nature are listed chronologically in Table 1. Major floods and droughts in Utah are depicted by streamflow records from six streamflow-gaging stations. The selected gaging stations are on streams that represent natural runoff in Utah's principal river basins. Data from the gaging stations are collected, stored, and reported by water year (a water year is the 12-month period from October 1 through September 30 and is identified by the calendar year in which it ends).

Many other floods and droughts in Utah have been severe locally and have affected considerably smaller areas than the areas of those floods and droughts identified in Table 1. Some of these local floods have caused substantial loss of life and property damage, and local droughts have caused water shortages.

<Table 1. Chronology of major and other memorable floods and droughts in Utah,1884-1988

Flood or DroughtDateArea AffectedRecurrence Interval (in years)Remarks
FloodJuly 4, 1884Colorado River>100Probably snowmelt combined with rainfall
FloodAug. 13, 1923Tributaries to Great Salt Lake between Ogden and Salt Lake City.UnknownLocally intense thunderstorms. Deaths, 7; damage, $3000,000
Drought1930- 36Statewide>25Regional
FloodApr. 28- June 11, 1952Strawberry, upper Price, upper San Rafeal, Ogden, Weber, Provo, and Jordan Rivers; Blacksmith Fork, and Spanish Fork; upper Muddy and Chalk Creeks.25 to >100Melting of snowpack having maximum-of-record water content for Apr. 1. Disaster declared. Deaths, 2; damage, $8.4 million.
Drought1953- 65Statewide10 to >25Regional
FloodJune 16, 1963Duchesne River>100Dam failure
FloodJune 10-11, 1965Ashley Creek and other streams between Manila and Vernal and west of Manila.>100Three days of intense rainfall on thick snowpack above altitude 9,200 feet. Deaths, 7; damage, $814,000.
FloodDec. 6- 7, 1966Virgin and Santa Clara Rivers.25 to >100Four days of light to intense rainfall of as much as 12 inches. Damage, $1.4 million.
FloodAug. 1- 2, 1968Cottonwood Wash and other nearby tributaries to San Jaun River.50 to >100Locally intense thunderstorms following 11 days of rainfall. Damage, $34,000.
FloodSept. 5- 7, 1970San Juan River and tributaries from McElmo Creek to Chinle Creek.25 to >100Record breaking rainfall. Deaths, 2; damage, $700,000.
FloodAug. 27, 1972Vernon Creek>100Locally intense thunderstorms.
Drought1974- 78Statewide10 to >25Regional
FloodApr. 10- June 25, 1983Lower Duchesne and Jordan Rivers and tributaries (including Spanish Fork); upper Price, Bear, Sevier, and San Pitch Rivers; Chalk, East Canyon, Trout, and George Creeks; Great Salt Lake and tributaries between Ogden and Salt Lake City.25 to >100Rapid melting of snowpack having maximum-of-record water content for June 1. Disaster declared by President. Damage, $621 million.
FloodApr. 17- June 20, 1984White, upper Price, and Fremont Rivers; lower Bear and Sevier Rivers and tributaries; Beaver River; Red Butte Creek; Spanish Fork; Jordan River.25 to >100Runoff from greater than average snowpack for Apr. 1 and spring precipitation. Deaths, 1; damage, $41 million.
FloodMay 22, 1984Sevier LakeUnknownRunoff in Sevier River from Nov. 1982 through June 1984 exceeded upstream reservoir capacity; about 1.5 million acre-feet of water conveyed to Sevier Lake. On May 22, 1984 lake reported to be as much as 35 feet deep after being nearly dry since about 1880.
FloodJune 15, 1984Utah LakeUnknownRunoff from greater than normal precipitation since Sept. 1982 increased lake level to 101-year record of 5.46 feet above compromise level on June 15, 1984. Damage, $5.9 million.
FloodJune 3, 1986Great Salt LakeUnknownLarge runoff from greater than normal precipitation since Sept. 1982 increased lake level to 140-year record altitude of 4,211.85 feet on June 3, 1986. Damage, $268 million.


Figure 1. Areal Extent of Floods in Utah. Click on image to view a larger version.

The five major floods of record occurred in 1952,1965, 1966, 1983, and 1984. The areal extent and severity of these floods, as determined from six gaging stations.

The April 28, 1952, flooding on Chalk Creek at Coalville and other flooding during the extensive April 28-June 11, 1952, floods were caused by melting of maximum-of-record snowpack for April 1 (U.S. Soil Conservation Service, 1983). Flooding was severe in central and north-central Utah (fig. 1), and a flood disaster was declared. Two lives were lost in boating accidents on the swollen Ogden River (Wells, 1957, p. 597-613). Flood damage was $8.4 million, of which $1.9 million was in Salt Lake City.

Rainfall on melting snowpack caused the June 11,1965, flood on Ashley Creek near Vernal and the June 10-11, 1965, floods in northeastern Utah. Flooding also was severe on several other streams in the Uinta Mountains near Vernal and Manila. Areas at altitudes above 9,200 feet contributed most to the flooding. During the flood, the snowline receded from about 9,200 to 9.900 feet. Peak discharges were greater than the discharge expected to recur once in 100 years on Ashley Creek on the southern slope of the Uinta Mountains and on streams on the northern slope. On a creek southwest of Manila, floodwaters that were the most severe in 40 years swept away and killed seven campers during the night. Within the storm area, flooding caused estimated damage of $814,000 to roads, bridges, irrigation canals. fences, and crops (Rostvedt and others, 1970, p. E54-E57).

The December 6. 1966 (water year 1967), flood on the Santa Clara River near Pine Valley occurred during the December 6-7, 1966, floods. A rainstorm during December 3-6 was of unprecedented areal coverage and intensity for extreme south-western Utah. Rainfall in the storm area ranged from about 1 to 12 inches. Peak discharges on the Virgin and Santa Clara Rivers and other streams in the storm area had recurrence intervals that exceeded 100 years. Areal extent of the flooding is shown in Figure 1. Total damage to crops, fences, roads, bridges, diversion structures, cropland, and forest lands and improvements was about $ 1.4 million (Butler and Mundorff, 1970, p. A-l9).

The floods of April 10-June 25, 1983, affected 22 counties, or more than three-fourths of the State. On April 10, a landslide caused by precipitation dammed the Spanish Fork, which then inundated the community of Thistle. The landslide, which resulted in damage of about $200 million and a Presidential disaster declaration, was the most costly geologic phenomenon in Utah's history (Utah Division of Comprehensive Emergency Management, 1985, p. 40).

Rapid melting of snowpack that had maximum-of-record water content for June 1 (U.S. Soil Conservation Service. 1983) resulted in the largest and most widespread flooding in the State s history; peak discharges had recurrence intervals that exceeded 100 years on several streams. New discharge records were set on many others, such as Chalk Creek at Coalville. On June 23, the Delta-Melville-Abraham-Deseret Dam on the Sevier River near Delta failed as a result of the flooding on June 23, 1983, and released 16,000 acre-feet of water down the river. Two bridges were washed away, and the town of Deseret was inundated by as much as 5 feet of water (Utah Division of Comprehensive Emergency Management, 1985, p. 41).

Overall damage from the April 10- June 25, 1983, floods totaled $621 million (Stephens, 1984, p. 20-36). No deaths were attributed to the floods.

The May 24, 1984, flood on the Beaver River near Beaver and other flooding during the April 17- June 20,1984, floods caused damage second in magnitude only to damage in 1983. The major cause of the flooding was much greater than average snowpack and greater than normal precipitation that continued throughout the spring. Peak discharges exceeded those in 1983 at some sites on the White, Bear, Jordan, and Beaver Rivers. Owing to severe flooding in 12 counties, a disaster was declared by the President. On May 14, rainfall caused a mudslide near the coal mining town of Clearcreek that killed one person and injured another. The direct impact on people was considerably less in 1984 compared to 1983 because of mitigation measures implemented during the previous year. Total damage for floods and landslides was estimated to be $41 million (Utah Division of Comprehensive Emergency Management, 1985, p. 15).

Floods not only can cause direct loss of life and property, but also can adversely affect the use and quality of surface water, resulting in economic and environmental costs that are not apparent until the floodwaters recede. For example, floods transport large quantities of sediment and debris from eroding channels, then deposit the material on cropland and streets and in homes, reservoirs, and stock ponds. Also, waterfowl nesting can be disrupted when areas adjacent to lakes become flooded.


Figure 2. Areal Extent of Droughts in Utah. Click on image to view a larger version.

The drought analysis for Utah, as determined from 33 gaging stations, indicates that a localized drought has occurred on at least one stream in Utah every year since 1924. Drought duration tends to be longest in basins where runoff is mainly from snowmelt. The frequency of occurrence of major droughts is greater for areas in the Wasatch Range than in the Uinta Mountains, Wasatch Plateau, or the mountains in southwestern Utah.

The drought of 1953-65 had a recurrence interval greater than 25 years in the eastern three-fourths of the State and a recurrence interval of 10-25 years in most of the remaining area. Most of Utah was declared a disaster area (Matthai, 1979, p. 4). Through 1956, the drought in Utah was a part of the regional drought of the 1950's, which extended nationally from the Southwest to the southern Great Plains (Nace and Pluhowski, 1965, fig. 22, p. 48). The effects of the 1953-65 drought in local areas were more severe than the drought of 1930-36, but the overall effects were less critical because of protective procedures that had been undertaken, such as construction of reservoirs, development of ground-water resources, and improved land management.

The drought of 1974-78 had a recurrence interval greater than 25 years mainly in northeastern and south-central Utah (fig. 2) and a recurrence interval of 10-25 years in most of the rest of the State (fig. 2). Several counties in the State were declared disaster areas. Matthai (1979, p.3) reported that the drought had spread nationwide in 1976-77 and had more severely affected the Nation than any other drought during the 20th century.

Current water use in the State relies mainly on surface-water supplies, which can be greatly decreased by multiyear droughts. Surface water provides about 81 percent of the State's offstream water use, and about 35 percent of the population relies on surface water for domestic supply (U.S. Geological Survey, 1990). Because of this dependency on surface-water supplies in Utah, a drought can severely affect the State 's people and industries. For example. Matthai (1979, p. 41-53) reported that, during the drought of 1976-77, record minimum annual discharge in streams caused severe water shortages. Some cities and towns were forced to ration water. In Utah, emergency water needs for irrigation, public, industrial, domestic, and stock uses required drilling wells at 33 locations in 17 counties.

Droughts not only reduce water supplies but can adversely affect water quality as well. During droughts, the inability of streamflow to flush and dilute chemical constituents can cause concentrations to increase to the point that the water is not usable for many purposes. An increase in temperature and a decrease in dissolved oxygen during low streamflow can cause fishkills. Less than average snowpack, low streamflow, and lowered water levels in reservoirs restrict snow- and water-based recreation, a major activity in Utah.

Selected References

Butler, E., and Mundorff,J.C., 1970, Floods of December 1966 in south- western Utah: U.S. Geological Survey Water-Supply Paper 1870- A, 40p.

Matthai,H.F., 1979, Hydrologic and human aspects of the 1976-77 drought: U.S. Geological Survey Professional Paper 1130, 84p.

Nace,R.L., and Pluhowski,E.J., 1965, Drought of the 1950's with special reference to the midcontinent: U.S. Geological Survey Water-Supply Paper 1804, 88p.

Rostvedt,J.O., et. al., 1970, Summary of floods in the United States during 1965: U.S. Geological Survey Water-Supply Paper 1850- E, 110p.

Stephens,M., 1984, Final report, 1983 rain and snowmelt floods, Utah: Sacramento, Calif., U.S. Army Corps of Engineers, 45p.

U.S. Soil Conservation Service, 1983, Water supply outlook for Utah, May 1 and June 1, 1983 monthly reports from January to June: Salt Lake City, Utah, Department of Agriculture, various pagination.

Utah Division of Comprehensive Emergency Management, 1985, Hazard mitigation plan: Salt Lake City, 226p.

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