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<br />- 5,
<br />
<br />"6 -
<br />
<br />FLOOD SITUATION
<br />
<br />Rains occur throughout the su~mer season. Rain prior to
<br />mid-June does not increase the stream flow appreciably.
<br />During this early period before peak snowmelt runoff there is
<br />il.ctuilUy some reduction in the stream flow during periods of
<br />precipitation. After the peak runoff has occurred and snow-
<br />melt begins to d~creasc, Talns tend to increase runoff. The
<br />rains which occur in July and August have the greatest
<br />potential for causing major flooding. Table 2 summarl~es the
<br />peak flows at the Blue River gage above Dillon for flows over
<br />lOOOcfs.
<br />
<br />HYDROLOGIC DATA
<br />
<br />Basic data stations that record information on precip-
<br />itation, snow depth and stream flow are available in the
<br />Breckenridge area. The locations of these stations are shown
<br />on Plate 2. The precipitation gage located at Breckenridge
<br />is a daily station with records from 1947. The precipitation
<br />gage located at Dillon is an hourly recorder with records
<br />dating back to 1907.
<br />
<br />Snow course stations are maintained by the U.S. Depart-
<br />ment of Agriculture, Soil Conservation Service. The stations
<br />measure the SnOw depth and water content at intervals during
<br />the year. There are three such stations in the Breckenridge
<br />area with snow depths and water content information extending
<br />back 39 years.
<br />
<br />Table 2
<br />
<br />FLOOD PEAK STAGES AND DISCHARGES
<br />BLUE RIVERl
<br />
<br />The U.S. Geological Survey maintains several continuously
<br />recording stream gages in the immediate area. The station of
<br />primary interest to the Breckenridge study is locdteu down-
<br />stream of the town and has been in "xistpncp sin"", lQSi. Anoth8r
<br />U.S. Geological Survey gage was located further downstream and
<br />was in existence from 1911 to 1960; however, the construction
<br />of the Dillon Reservoir required that ~ new gage be estab-
<br />lished at its present location in 1957. From the combined
<br />history of the two gages, there arc 64 years of stream flow
<br />records on the Blue River.
<br />
<br /> Date DiSCharge (cfs) Stage (ft.)
<br />June 27, 1912 1,020 3,9
<br />June 2 , 1914 1,180 4 . 3 5
<br />June la, 1921 1,100 4.15
<br />June l4, 1923 1,000 3,'
<br />June 14, 1924 1,180 3,6
<br />June 7, 1926 1,080 3.44
<br />Moy 30, 1928 1,030 3.22
<br />June 17, 1965 1,250 5.382
<br />
<br />FLOOD FLOl~.s
<br />
<br />1. Peal: dischal'ues in e:eei"SS (Jf 1000 ('fs :'"Of" U.S.
<br />Geo"cgiaal Su~vcy Water Supply Popcrs.
<br />2. Gcge ""Ioeated u;ntl'eam i" 1957 (/>td tl"ibutary
<br />drai>t!!JI' area ~td",,~d f"l"'''' /29 sq.,"~. to 119
<br />'11.mi.
<br />
<br />High water resulting from snowmelt is the most prevalent
<br />type ot flood flow occurring in the Blue River basin. Snow-
<br />melt generally begins the first of April and the pedk runoff in
<br />th", ill,-,,' River occurs in mid-June. Snowmelt then de,.,r",,,ses
<br />~nd the flow of the river recedes the latter part of June and
<br />throughout July.
<br />
<br />The peak discharge recorded by the U.S. Geological Survey
<br />on the Blue River near Dillon for the 64 years of record was
<br />1250 cfs and occurred on June 17, 1965. The flow was J. com-
<br />bination of s"owm,,1t and a high intensity thunderstorm or
<br />cloudburst of small arc~l distribution centered in J. trihu-
<br />
<br />tary basin above the town. Plate 1 shows the hydrograph of
<br />
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<br />
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<br />
<br />L,,~,,", R:"C"";<tJI'l!l~"'" f"'iw,"",'or
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