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<br />smIlller tMm eltt\flr tt\e IOO-ye<lr or 500-yaar floods are much more
<br />comnon. Lerge floods, t\owever, een t\eppen; this WIlS cleerly demon-
<br />streted by thaOenver erell floodsaf 1965,the611lekHIlls, South
<br />DtIkotll eree floods of June 1972, end the July 1976 floods In the
<br />Big Thompson Cenyon neer Lovelend, ColoredO_
<br />
<br />Hezerds of Lllrqe Floods
<br />The extent of dllmege cllused by llny flood depends on the
<br />topogrephy of the ereo flooded, depth and durlltlon of flooding,
<br />velocity of flow, rate of rise, developmenfs on the flood plain,
<br />llmoUn+ of debris In the floodweter, end lee conditions, If lee Is
<br />e prob'~ In thet pertlculer llree. ^ 100-yeer flood or e 500-
<br />year flood on the South Piette River In thflstudy r8llchwould
<br />result In the lnundetlan of end subsequent demeg" to prlmerlly
<br />egrlculturel properties end essocleted developments eS welt as
<br />public utilities !lnd public rOlldWllYS. Deep floodweter flowing at
<br />high velaclty end cllrrylng floetlng debris would creet" conditions
<br />hllzer<:lous to persons "nd vehicles attempting to cross flooded
<br />er_s. In gflnerel, floodwete!" 3 ar ITIOre feet deep end flowing et
<br />II velocity of 3 or more feet per saoond could ellslly sweep en
<br />&Oult person off his feet, thus creetlng definite dllnger of Injury
<br />or drowning. Repldly rising end swIftly flowing tloodwllter mllY
<br />trll~ ~orsons In homes thet lire ultlmlltely destroyed or In vehicles
<br />thetareultlmetelysubmergedarflollted_ Iso'"tlonofllr9<!lsby
<br />floodwaterscouldc,.""t..hiltardslntermsof:nodlClll,flre,t"-''''''
<br />enforcement eMergencies_
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<br />Study Results
<br />The results ot ThIs sTudy lire presented In ttle fanll of flooded
<br />anells, pletes 3 through 22; water surface profiles, plates 23
<br />through 30; elevlltlan-dlscharg9 curves, pllltes 31 throug~ 35; and
<br />flood plein reference datil, te~le 9. ~llter SUrfllC8 elevation data
<br />....s COOIIputfld through the use of the Corps of Engineers CQIIIIluter
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