FLOOD06138 - Laserfiche WebLink

Home Browse Search

tion, bridge, or streambed irregularity. The ice blocks the entire channel section completely down. to the river bottom, and water then has to move through the ic~ plug by infiltration. When infiltra- tion is inadequate, the water-sprface elevation increases until spill occurs and adjacent land lis flooded. However, ice jams are unstable and often break up wh~n the upstream water level increases. Ice jams are usually caused by Chinook winds and temperature inver- sions. During a Chinook, air ~emperature may increase very rapidly (increases of more than 500F in a few hours have been recorded in some areas subject to these winds), and it is not unusual for a two-foot layer of snow to melt iin one day. Temperature inversions cause ice jams by melting uppe~ elevation snow and ice, while freezing conditions remain in ~e lower elevations. The rising water heaves and breaks up riv~r ice which floats into jams. Twice in the last 85 years, in :March 1955 and February 1962, ice jams caused water stages in the White River to reach Main Street between Colorow Street and Birch Avenue. These floods caused damage to homes, businesses, and public utilities. Ice jam floods , have been observed as far back 'as 1891, when Rangely consisted of a saloon, blacksmith shop, sto~e, and hotel. In the late summer of 1910 or ~911, a thunderstorm produced flood stages almost to the 1962 leve~. Another thunderstorm in the 1920s raised the White River to approximately the location of the Rangely Hotel, but the water was 1 foot lower than the 1955 flood. Two of the largest thunderstorms to produce local flooding occurred in August 1946 and July 1953. 'In the 1946 flood, one downtown office building had from six tq eight inches of water covering the floor. On July 31, 1953, 1.42jinches of rain was measured in slightly over one hour at the ~ngely gage, and resultant local flooding washed out a road and!tore away a bridge outside of Rangely. In town, runoff caus~d drainage ditches to overflow, and damage from the floodwaters wa$ aggravated when the high water picked up oily mud from around:a local oil well. Less than two years later, in ~arch 1955, an ice jam in the White River caused the river to leav~ its banks, and at one time the town water supply was cut off ~hen six feet of floodwater covered the water filtration plant. ! Water supply was again interrupted by ice jams above and below the town in February 1962. The flQOd of February 1962 was the largest flood of record. In March 1966 another ice jam diverted the flow of the White River and several'ranches experienced flooding. Most recently, flooding due to an i~e jam occurred in March 1983. Local residents agree that dam~ging floods occur on the average of once every seven to ten years,jwith the majority resulting from ice jams. Shallow flooding, with water characteristically less 6