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<br />DevBlop~nt on the FlOOd PI~in
<br />The flood plein In the study reech ever~gas about 1,500 feet wlda.
<br />Development began ne~r the mouth of Bear Creek and has progressed up-
<br />stream. The flOOd plein ls about 70 percont developed in the re~ch from
<br />the mouth to W~dsworth 60ulev~rd. From Wedsworth Boulevard to the up-
<br />stream lImit of the study reach there Is little development end agricul-
<br />ture 15 the predominant use. land use In the over~11 study reach Is
<br />about 12 percent commercial, 24 percent resIdential, 9 percent trans-
<br />portlltlon, 4 percent public property, wlththabalance In mIscellaneous
<br />uses. In 1970 about 6,050 people lived In the 6ear Creek flood plain
<br />In the study reech. An estimated 1,600 persons ere employed there.
<br />Wlth expected grellter development In the area It will become Increasln gly
<br />important to regulate bui Idlng In the flood prone areas If Increased
<br />rIsk 01 future floodIng istobeavo1ded.
<br />
<br />FlOOd HIstory in the Study Re~ch
<br />The Bear Creek channel has a capacity of ~bout 2,500 cubic feet
<br />per second (c.t.s.l without c~uslng tlood da""'g", Flood!> In the baSin
<br />usually re!>ult from 1ntense rainstorm!> In the summer months. Tho
<br />Sheridan !>tream gage, wIth stream flow records from 1927 to the present,
<br />Is located at Lowell BouleVllrd. A second stream gage Is IOClltedat
<br />Morrl soo, ~bout 2 miles upst"""m of the study rel'lCh, with partIal records
<br />dating back to lee8. lat>le I snows tne largest floods th"t were recoro...d
<br />at the gages since 1927.
<br />
<br />Table I
<br />FLOOD PEAK DISCHARGES ON nEAR CREEK
<br />
<br /> Sheridan Gilge Morrison GiI?e
<br /> M.."lmum M""im"",
<br /> DIscharge Cischarge
<br />Year Date (c.f.s.l (c.l.s.)
<br />1933 7 July 3,000 8,110
<br />1934 , Aug. 1,300 4,620
<br />'''' 7 Sept. 2,a1O n,21l()
<br />1957 " A~g. 2,560 1,640
<br />1965 25 July 2,900 1,030
<br />1969 7 .., 8,1'j.() 2,34D
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<br />TablelshowSillargevariancelnthepeakdischarqesforeilCh/lood
<br />from gage to gage. In 1933, 1934 and 1938 the storm was apoarently con.
<br />cenfratedinthemountalnsan<:lthefloodattenuate<:lwhlletravellngfrom
<br />thelJorrisOi'1 gage to the Sheridan gaqe. Fortheremainlnafloodssr,own
<br />in table I the runoff was from the area downstream /ram Morrison, pro-
<br />ducing the highest flow at the Sheridan gage. Turkey Creek waS undoubtedly
<br />a large e<mtributor to the increased flows between thetwogilges. Fortu-
<br />nately, past floods were produced by Ilows originatIng either above or
<br />below Morrison but never trom both drainage areas at the same tlma.
<br />F!oodsonBearCreel<,otwhlch little lntormatlon Is available,
<br />occurred in May, 1876, May and June of 1894,and In July of !896. The
<br />peek discharge for the 1896 flood was estlmate<:l to be 8,600c.t.s. at
<br />theMorrlsongage,about2mllesupstreamofthestudyreach. High,
<br />sustained flows through the study reach on 9 May 1957 caused severe
<br />bank erosion and damage toa bridge under construction at Wadsworth
<br />Avenue as woll as to resIdential lots abutlngthe stream. Minor flood-
<br />Ingoccurred in the study reach on 23 and 24 July 1965 and 25 familIes
<br />wereevaCU<lted, 15baserr>entsandatouristcourtwereflooded,and
<br />several bridges were damaged. Heavy rains trom 4 through 8 May 1969,
<br />with a total storm rainfell at 11.27 inches at Morrison, caused the
<br />greatest f 1000d of record I n the study reach. Many peop Ie w..re ev~cuated
<br />trom houses and trailers ne~r Sear Creek from Lowell Boulevard to the
<br />mouth. Many homes sustained basement and first floor damage.
<br />
<br />PotentIal Floods
<br />Two large potential floods are used to study flood halards in the
<br />Bedr Creek study reach. The Intermediate Regl<.>n~ I Flood. CorMlOn Iy
<br />called the IOU year Ilood, has a I percent chance of occurring In any
<br />
<br />\,e~r ~ne I: gcr.cr<:lly :lcce;:toe b\' t~e ;:u~llc a: ~ ,.,Ini",c'''' I,m;t ~cr
<br />
<br />application of local regulations. Based upon a probability analysis
<br />of Bear Creek gag'ng recordS and recordS of other typlc,,1 Fnont Range
<br />streams, peek discharge tor the Infermedlate Regional Flooc at various
<br />points ;~ the study reach w~re c~uted end are pr~sented In t~ble 2.
<br />The Standard Project Flood is presented as a practical upper limit
<br />of tlood;n<l. It is ditficult to assign irequenci~oi occurrence for
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