<br />17
<br />
<br />'"
<br />
<br />FlnodedArea$
<br />The lOO-year frequency flood has been selected by the StateofColo rado
<br />a, the flood event to be "sed for flGGdplain delineation and regulation,
<br />Thus, the Flooded Area pi ates 5ho~' on IV the boundary of tll" 1 OO-y"'" flood-
<br />pl,,;n. Since the case map for tll" FloOded Area pl~te' j S ~ 5-foot contour
<br />O'ilp, the Out II nc, of the Clth"r f I cod event~, 10, 50. and 500-yea r. cannot
<br />be, insomea;"as, readilypl,>ttedwslng the information in Table 3,
<br />The area delineated on the Flooded Area plates as the IOO-year flood-
<br />plainmcets tllerequlrementiofH.B.1041asan..reaof.tilteinterest,
<br />Also, upon official approval of this report by the Colorado Water Con-
<br />,ervatlonBoard, tile area owtlined by the 100-year flood bowndarycan be
<br />de,lgnated a floodplain area and may be regulated accordingly by the local
<br />off ic i a I ~.
<br />AportionofthelOO-year floodplaln between Stations O+OOClnd
<br />60+00, andStation5 123+00 and 145+00 I'subject to flooding due to up-
<br />5tream cond it ion" ,u~h a, i rrigat jon di t~hes "nd topographi~a i character-
<br />15tic~ whiCh divert flood "at~rs VJ ""Id I~nd$. The,e areas are d,,~jgnated
<br />~'i th lIned ,had Ing <lnd repre~enl aced' uf sha Ilow oveciand flood Ing for
<br />the 100-year flood. Because these waters are not hydr~u Ii ca Ily connected
<br />to the channe I, tilt' d~tudl water surface "levat ion I n tile overbank drea~
<br />is genecally hiQhec than th",,, _hnwOl j<1 r~bl~ 3 For t~e ",,,j n c~"nne I.
<br />Que to t~e 5-foot contour i ntcrval there may hI: areas in" luded wi thIn
<br />the 100-year floodplain whiCh are above the 100-yeac water 5urface elevation.
<br />
<br />Flood EleyatiQns
<br />The FloQ~ Frequency-Elev~tion and DISCharge D~ta t~~le, Table 3,
<br />I ins ,he 10, 50, 100, and 500~year flood e levJtion. at selected refer~
<br />ence"oint., The Flooded Area plates giv,-, the pian vle'oJof the flooded
<br />b " ,., . ,'~- '.""r ~Ievat iens for the IOO".,ear
<br />area on a contour ase map an~ " "~,, _~ _
<br />flood Can be interpolated from this, The Flood Profile "Iates Show the
<br />stroac:bed elevation and the high wJter elevations fer all feurfrequcncy
<br />floods. Also, the Cross-Section plates Show a graphical representation
<br />, ' , ,.,'., "'__v ~_M'8.a_,I^n< throunhout
<br />of the 1,lgh water e evat,ons a y~'~ v~ c, ~'v.o ~~~ v, ~
<br />thestudyreJch,
<br />The FlOOd Profiles may be used in areas where controversy arises over
<br />the IOO-year flood boundary on the Flooded Area plate~, Since the Flood
<br />Profi Ie plates giw, the e)evation5 and distance or stationing from <l known
<br />point, the high watec elevations Can be surveyed on the ground to alleviate
<br />anydi"repdncie,,<;>ntneba,effidp.
<br />Tooetermine the depth of flooding or the floodplain limits at an y
<br />]oca,inn In the field, the following procedures should be used,
<br />I. locate the ground point at which tl", depth of flondingnr the
<br />floodpl" in I in'; t is to be cst~hl ished nn the I" '" 400' flo()d~d
<br />nre~ m~p.
<br />2. Deter.",jne the e lev"t ion of the w<lter .urfuce ~t t.he ~el eclcd ground
<br />point fromTable3,andby interpolating between tnewatec surface
<br />elevati<Msgiven for twoddjdcent cross.sectlonsand referring to
<br />the pcofile drawin'ls.
<br />3. Us ing the ~io'est monument for e levat ion controi. determine the 'Ndter
<br />surface elevation at the qround point by standard ,urveying technique,
<br />Th" fi""drlai~ II",it ;s e.ta~lished ~'he~ the "ater ~urf;,ce eleva:ion
<br />i"t~r.~~~t, the yroullJ s~,-faee.
<br />
<br />ground
<br />
<br />An approximate ~epth of flood ing can be estJbl i shed by ,ubtr<!cti n~ the
<br />~levJtl"n e,timJ:ed fro01 the contour map h"m the pc~,'lously dcter-
<br />
<br />lli~"d ,",',]te r ,"dace ",1.-vJt ien.
<br />r" Incate the edge of the rl OQ~pl" i n by simple "d I in~ methods, ,~eaSure
<br />, ,." ".- 'h".'"nbei.;"n-
<br />tne Ji,tane", on tn~ '"dP tlVl' t"" 0'. I,)()r.~ ~"y,;~o '~d,_~., u.
<br />tT "ied both un the ,,,-,p and in th~ fie Id t<.> the c~ge of the floodp lal n, The
<br />
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