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<br />National Water Summary 1988-89-Floods and Droughts: COLORADO 209
<br />
<br />established. Records for 44 long-term gaging stations on streams
<br />having minimal upstream regulation were analyzed to dete1TI1ine the
<br />periods and areal extent of floods, and the records for 50 gaging
<br />stations were analyzed for droughts. From these groups of stations,
<br />six gaging stations were selected to depict floods (fig. 3) and droughts
<br />(fig. 4). The gaging stations were selected to include a diversity of
<br />drainage areas and hydrologic settings and to represent runoff con~
<br />ditions from various parts of Colorado; however, the Great Plains
<br />are not well represented because of the few gaging stations in that
<br />part of the State. Drainage-basin size upstream from the six gaging
<br />stations ranges from 164 to 8,050 square miles, and periods of record
<br />range from 55 to 100 years, Streamflow data are coUected, stored,
<br />and reported by water year (a water year is the 12-month period from
<br />October I through September 30 and is identified by the calendar
<br />year in which it ends),
<br />
<br />79, 114-116, and 123-140), but available data are insufficient to
<br />quantify their severities or map their areal extents,
<br />The floods of 1921 are used as a reference when comparing
<br />historical flood magnitudes in Colorado, Flooding was severe in the
<br />North Platte, Yampa, White, Roaring Fork, East, and Uncompahgre
<br />River basins during June '13-17, 1921, as a result of snowmelt and
<br />rainfaIl runoff from low altitudes. Flooding was severe in the
<br />Arkansas River basin from Pueblo downstream, including the
<br />Fountain Creek drainage, during June 4-7, 1921, as a result of
<br />widespread rainfall during June 2-7, 1921. On August 2, 1921, an
<br />isolated, intense thunderstorm in the Arkansas River basin upstream
<br />from Canon City resulted in the peak discharge of record on the
<br />Arkansas River at Canon City (fig. 3, site 2). All these floods in 1921
<br />were considered to be part of a single flood for this analysis because
<br />of the small areal extent of the individual floods.
<br />Severe flooding caused by snowmelt and rainfall occurred in
<br />the upper Arkansas and Roaring Fork River basins from June 29 to
<br />July f, 1957. Floods of less severity affected tributaries of the
<br />Gunnison Riverduring June 4-7, and the North Platte River on June
<br />The areal extent and severity of flooding determined from 15, 1957.
<br />streamflow records from the statewide network and the magnitude The most severe Colorado floods of the 20th century were
<br />of annual peak discharges at the six selected gaging stations are those that affected the South Platte and Arkansas River basins during
<br />shown in figure 3. The magnitudes of discharge having 1 O-year and June 1965. The floods were caused by intense rainfall (as much as
<br />100-year recurrence intervals, which were determined by an analy~ 14 inches in a few hours) during June 14-17, fallowing a relatively
<br />sis of the annual flood series at the sites, are also shown. The five wet spring (Matthai, 1969, p. B-1).
<br />floods depicted in figure 3 were selected on the basis of magnitude Flooding in the South Platte River basin began on June 14,
<br />and areal extent, and are the most memorable since the early 1900's. near Denver. The flood crest did not pass the most~downstream
<br />Several floods occurred in the late 1800's that were widespread and gaging station on the South Platte River in Colorado until June 20,
<br />had large magnitudes (Follansbee and Sawyer, 1948, p, 23-26, 73- 1965, Matthai (1969, p, B-1) reported that eight deaths were attrib-
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<br />Tsble 1. Chronology of major and other memorable floods and droughts in Colorado, 1911-88
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<br />FLOODS
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<br />[Recurrence interval: The average interval of time within which streamflow will be greater than a particular value for floods or less than a particular value for droughts.
<br />SymbolS: >, greater than; <less than. Sources: Recurrence intervals calculated from U.S. Geological Survey data; other information from U.S. Geological Survey,
<br />State and local reports, and newspapers)
<br />
<br />Flood or Area affected
<br />drought Date (fig. 2)
<br />Flood.. . Oct. 4-6, 1911 Rio Grande and San Juan River
<br /> basins.
<br />Floods, . June 2-17 and North Platte, Vampa, White,
<br /> Aug. 2, 1921 Roaring Fork, East,
<br /> Uncompahgre, and Arkansas
<br /> River basins.
<br />Drought. 1930-42 Statewide. . . . . . . . . . .
<br />Floods. . July 7 and Sept. South Platte River basin, Plum,
<br /> 9-10, 1933 Clear, and Bear Creek basins.
<br />Flood. . May 30-June 1, Kiowa, Bijou, Fountain, and
<br /> 1935 Monument Creek basins, and
<br /> South Fork Republican River
<br /> basin.
<br />flood.. . . Sept. 2-4, 1938 Bear and Clear Creek basins. .
<br />Flood. Apr. 23-24, 1942 Purgatoire River basin. . . . . . .
<br />Drought. . 1949-57 Statewide. . . . . . . ......,..
<br />Flood. . . June 4-16, 1952 Colorado, Vampa, White, and
<br /> Dolores River basins.
<br />Floods. . . June 4-JuIY 1, Arkansas. Roaring Fork,
<br /> 1957 Gunnison, and North Platte
<br /> River basins.
<br />Drought. . 1958-70 Statewide. . .' . . . . . . . . . . .
<br />Flood... . June 14-22, 1965 South Platte and Arkansas
<br /> River basins.
<br />Flood. ..' Sept. 5-17, 1970 San Juan and Dolores River
<br /> basins.
<br />Flood.. .. July 31-Aug. 1, 8ig Thompson and Cache la
<br /> 1976 Poudre River basins.
<br />Drought. . 1976-82 Statewide. . . . . . . .........
<br />Flood. ... July 15, 1982 Roaring and Fall Rivers. . . . . . .
<br />Floods.. . June and July Colorado, Dolores, and White
<br /> 1983 River basins (June), and Bear
<br /> Creek basin (July).
<br />Floods.. . May and June Colorado, Gunnison, White,
<br /> 1984 Roaring Fork, Uncompahgre,
<br /> and Vampa River basins.
<br />
<br />Recurrence
<br />interval
<br />(years)
<br />>100
<br />
<br />25 to >100
<br />
<br />20 to >25
<br />50 to 100
<br />
<br />20 to 70
<br />
<br />20 to 60
<br />20 to 40
<br />
<br />10 to >25
<br />20 to 50
<br />
<br />25 to >100
<br />
<br /><10 to >25
<br />5 to >100
<br />
<br />5 to >100
<br />
<br />5 to >100
<br />
<br /><10 to >25
<br />>100
<br />10 to >100
<br />
<br />10 to >100
<br />
<br />Remarks
<br />Widespread, intense rainfall for 3-5 days. Widespread damage in south-
<br />west.
<br />General statewide rainfall and isolated severe thunderstorms and areas of
<br />excessive snowmelt.
<br />
<br />RegionaL
<br />Intense focali;zed rainfall.
<br />
<br />Locally intense thunderstorms. Deaths, 13; damage in Colorado Springs
<br />and Pueblo.
<br />
<br />Locally intense thunderstorms.
<br />Intense rainfall combined with snowmelt runoff. Highway and railroad
<br />bridges destroyed.
<br />Regional.
<br />Snowmelt, probably combined with rainfall runoff.
<br />
<br />Snowmelt combined with rainfall runoff.
<br />
<br />Regional.
<br />Widespread intense rainfall for several days. Declared major disaster area.
<br />Deaths, 24; damage, $570 million.
<br />Intense, sustained rainfall. Declared major disaster area. Damage, $2.9
<br />million.
<br />Intense localized rainfall for about 3 hours. Declared major disaster area.
<br />Deaths, 144; damage. $39 million.
<br />Regional.
<br />Dam failure. Declared major disaster area. Deaths, 3; damage, $31 million.
<br />Snowmelt combined with rainfall runoff.
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<br />Snowmelt combined with rainfall runoff. Declared major disaster area.
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