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<br />1'AllLE 3 - (ConL) <br /> <br />III. FUTIJRE noons <br /> <br />J.Oc.nlON <br /> <br />E;l5t fiown Creek <br />at Elbert <br /> <br />28.6 <br /> <br />1%5 <br /> <br />41,500 <br /> <br />, <br />I <br />I <br />I <br />, <br /> <br />II. De sc: ri p t 10)\ and ~!e thod <br />As required, tr,e flood used for an;;llysi~ in this study is <br />o;'",C) \,..hi.c:h ...ould occur on an avc,,,ge of cr,ce each 100 years, or <br />whi ch might halfe " pTobah i 1 i ty a ~ QCCllrlince of one perce"-t in any <br />given year. This is referred to as the "100 Year Flood". <br /> <br />DRADlAGE AREA <br />Squar" ~li~ <br /> <br />DATE OF FLOOD <br /> <br />P!:.~K DISCIIARGE <br />Second-Feet <br /> <br />\'.'cH Kio"", CTeek <br />~t El hert <br /> <br />35.9 <br /> <br />1%5 <br /> <br />20,000 <br /> <br />I <br />I <br />I <br />I <br />!; <br />I <br />, <br />, <br />I <br /> <br />1'h'o primary r\cthads of il',...estigation were nude>. The first <br />of the~c is the USDA.SCS Synthetic hydrograph r.1ethod as descrIbed <br />by their reference in a later sect inn. The second is a method based <br />on historic records of the regi.onas analyzed by the liS Geological <br />Survey. A complicating factor is thG 60 flood control reservoiTs <br />installed by the SCS \"llich control the runoff of 60 percent of the <br />basin <lrea. <br /> <br />Kiowa Creek 21 <br />~.l il c s be 1 0',; <br />Elbert <br /> <br />100 <br /> <br />1935 <br /> <br />110,000 <br /> <br />Ki\)"", Creek <br />at Ki.ow<J. <br /> <br />III <br /> <br />1965 <br /> <br />19,700 <br /> <br />C. Existing Flood ContnJl ~leasures <br /> <br />I <br />I; <br /> <br />The effects of the~e flood control measures were carefully <br />analy.ed on five typical structures for \\"hich complete data 1...as <br />Dvailabl<,. The results shoh' that these structures provide signif- <br />ic,tnt benefit on floods of a relatively small magnitude. However <br />on the 100 yenr floo<1. their bcne:it is not as great as might be <br />anticipated, .although there is not faIt to be any danger of the <br />failure of thes" struct\lre~ hhi~h \iould create a hazard downstream. <br /> <br />Most of these floods arc considered to be in exce~s of that <br />which might be e,~pectcd to OC<.;UT on an aver;;lge of once each 100 <br />years. <br /> <br />Falloh'ing the 1935 flood, the Corps of Engineecs in~talled <br />embankments to protect the Towns of }:lbcTt and Kio.;r1 from the Creek. <br />The embank:nent at Kioh'" i~ in evidence on pIa tC number 3, ext end in~ <br />:l1ong the South I'Icstprn City limits to th" Creek (lnd adjac"nt to <br />lke Creck to State J-iiy,hHayS6. <br />The ITSDA-Soil Conservation SCtTi~e completed a \"atershcd <br />PTC'lTectio:l Program in 1961 [or the KiQ\"a Creek Watcrshed south of <br />Kiohil reported the second such project in the ,btion. A ~cries uf <br />gr<lde ~tabilization st ructurc5 and <.:hannal i.mprovements "ere instal- <br />led along the Creeks, as well as 60 floodwater retarding structures <br />shown on pl:ltos 1 and 2. :--:ulllerous seeding. furrowinp, and minor <br />In\pl'ove~ent~ were installed as well, bringing to total cost to <br />$780,766, excluding Technical assistance co~ts. The SCS estil"uted <br />that these str\\cturc~ r<JdllCeU the peak discharges from the 1965 <br />flood by 6,000 CFS on West Kiowa Creek, 11,500 CFS on Dast Kio',,'a <br />Creek, and 12,300 Cl'S on Kiowa Creek ~t Kiol;a. They fed the value <br />of dmwge W<l~ reduced due tn these struct\lres by HOO,10S or about <br />37~ of what dama~e could have been ~lJstaiJ\ed withn\lt theln. The l</Titer <br />believes these estimates to be' some,,'hat ()ptimj~t;c. <br /> <br />!; <br /> <br />A substantial amount of Techni,_al infor:nation "'as proce;;sed <br />in this study, and ,>"ill not be pre~"nt.ed in detail herein. The <br />follol':ing is a summary of the 100 year desi,\:n runoff at Kio\~a. <br /> <br />TABLE 4 - PROJECTED 100 YE,\R RU';OH AT K10l'.'.". <br /> <br />Drainage Area <br /> <br />I19. 57 ~qua re 'Iiles <br /> <br />IOU Year Runorf <br /> <br />21 , aoo Cubic ~eet per Second <br /> <br />It may be not ic ed t hat this runo [f is s1 i y,ht 1y ~bove the <br />19,7(lQ CFS recordnd in 1965 but 1'el1 belOh that computed at Flocrt <br />in 1935 (43,500 CFS). Having h-o ~uch storms in the previous 40 <br />years 1,'ould cnst sam" logical doubt on the accuracy of such it pro- <br />jection for a 100 year storm. A regional analy~is"considering the <br />entire area-puts thi~ into perspeccive, and it can be said again <br />that Ki.owa treckhas received f::rT:lore than i.ts fair share of sub- <br />~tantia1 rainfall. <br /> <br />B. FloodPlain Description <br /> <br />Following thf' 1965 fl 0 0<\ , toe highway d<rp;'rtmer:t i~pl'ovcd <br />the F.a~t abutment apprOadl to their bridge h'ith a piling 3nd rock <br />wire pr<lte~t.ive structure ~o ~lS to prevent fl future l(ls~ of the <br />1'0:<:h"ly .1t th(., ,tb\Jtllll"l't. <br /> <br />The lil'!its of the flood plain are ~ho\,n on the thnw sheets <br />of plate 3 in t.he appendix. The creek ;,'as dj,.i,!e(\ by J\Lll\1C'OUS <br />"c ross - sect i (ln~" ut c r i t ieCtI locCl~ ions :ll()n~ its lengt h. The flood- <br />\,':\l.el'~ an' well out of the banks, except at ~hc hi,:"';a,. hri.tlgt', <br />\':hieh is mere than adequata to ca;;cain the rW:loff. The lollo\dng <br />tabl~ will hricfly ~ummarilP the flDodplain of the 100 yr<lr storm. <br /> <br />6 <br />