<br />E40
<br />
<br />FLOODS OF 19'65 IN THE UNITED STATES
<br />
<br />S~Y OF FLOODS
<br />
<br />E41
<br />
<br />caused sigr;ificant floods in the east-central and north-central parts of
<br />the State m June. Floods that are considered noteworthy are de-
<br />scribed in the order of their occurrence. The east-central floods of May
<br />and June were also described by Rennick (1966),
<br />
<br />MAY IN EAST-CENTRAL WYOMING
<br />
<br />The storm in May in east-central Wyoming was the result of weather
<br />patt~r~ that com~ined "0,( the right place at the right time" to produce
<br />conditions conducive to heavy precipitation, Moisture-laden air mov-
<br />ing into Wyoming from the southwest was raised over cold fronts from
<br />the north on May 7 and 13. On May 7 this resuLted in a general storm
<br />which started with rain and turned to snow that blanketed the Larami~
<br />Mountains with as much as 32 inches of snow by May 9. Much of the
<br />snow ~t.lower e:evations meLted quickly; however, a general snow cover
<br />contalllmg 4-6 mches of water equivalent remained at elevations ",bove
<br />6,000 fe~t when rain began on May 13. The latter storm, when com-
<br />bmed With the snow cover, resulted in an estimated maximum water
<br />equi~a~ent of 10 inches in some areas when the flood runoff began. The
<br />~reClplt~tl?n I?attern was influenced by orograp)llc factors; the heav-
<br />Iest preCipitatIOn occurred on the north side of the Laramie Mountains,
<br />and subsequently lighter precipitation fell on the south side. Up to 6
<br />inch~ of precipitation was reported from a "bucket survey" of the area,
<br />An lsohyetal map of the storm rainfall for May 13-15 is shown in
<br />figure 18.
<br />
<br />Typical spring-rwlOff p",tterns were developing when the rains
<br />sta,:ted on May 13. The snowfall during the period May 7-9 had
<br />"pr1llled the pump," and the rains during May 13-15 produced spectac-
<br />ular results.
<br />
<br />;Highest runoff occurred on streams flowing from the Laramie Moun-
<br />tams (fig, 18) nort~easterly from stations 2-10,12,17,18, and 20 and
<br />southerly from statIOns 1 and 23 (table 14), resulting in heavy flood
<br />damage on several of the streams, Flooding on Deer Creek inundated
<br />many dwellings in the town of Glenrock and oil-well pumps on the
<br />flood plain, High water on Box Elder, La Prele, Wagonhound, La
<br />Bonte, and Horseshoe Creeks flooded range homes destroyed bridges
<br />eroded or deposited sediment on farm lands, and da:naged or destroyed
<br />headworks of irrigation ditches.
<br />
<br />_ Recurrence intervals for peak discharges on many streams are much
<br />ill excess of 50 years (table 14). The peak discharge on Deer Creek
<br />(sta. 3), 12,800 cis, was 4_5 times the previous maximum recorded dis-
<br />charge, which occul'Tedin 1924. The peak discharge on La Bonte Creek
<br />
<br />
<br />105"00'
<br />
<br />le MILES
<br />
<br />I ~-~"-
<br />
<br />EXPLANATION
<br />5
<br />Flood-de~ination point
<br />Num/Jer cwrespcyn.ds ro
<br />t1w.tin to.6we u"and17
<br />-3-
<br />Isobyet, showing precipitation
<br />in inches, for May 13-15 '
<br />
<br />FIGURE I8.-Location of flood-determination points for May and June and
<br />isohyets for May 13---15, floods of May and June in east-central Wyoming.
<br />
<br />(sta. 10), 8,770 cis, was 3.2 times the previous maximum recorded dis-
<br />charge, which occurred in 1923. The great magnitude of the May floods
<br />is graphically represented by figure 19, which compares the discharges
<br />at two selected stations w1th previous maximum discharges of record,
<br />Three reservoirs on the North Platte River played a major role in
<br />preventing flood damage_ Releases from Alcova Reservoir (upstream
<br />from the area in fig, 18) and from Glendo Reservoir were decreased
<br />sharply on May 14, reducing flood stages along the North Platre River
<br />above Guernsey Reservoir, The peak discharge on North Platre River
<br />above Glendo Reservoir (sta. 12) was 23,800 cis on May 15, whereas the
<br />daily mean discharge below the reservoir was only 1,510 ds. Flood-
<br />waters from La Prele Creek were stored in La Prele Reservoir until
<br />spilling occul'Ted on May 17_ The peak discharge on La Prele Creek
<br />below the reservoir (sta. 8) was only 573 ds on May 20, and above the
<br />reservoir (sta. 7) on May 14 it was 7,300 cfs (3,5 times the theoretical
<br />50-year flood and 6 times the previous maximum in a 4&-year period
<br />ofrecord) ,
<br />
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