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<br />point on the rt,f<<r<<nce line, tb.e flood elev<ltLOll6 can 00 surveyed <Xl th" <br />grotnd to alleviate any discrepancies on the hase map. <br />G. FlOO<kd Areas <br />Flood plain maps, sheets 1 thr<J.lf)l 29, sOOw the boundary of the <br />lOO-~<lr flood plain. Normally the 50U-~ar frequency flood plain is also <br />srown en thes<< maps, however the steep sloping tributaries involved in <br />this study make it impossible in most locations to differentiate oo~en <br />the two frequencies 011 the scale of !lI3.pS published in this report. The <br />flood plain bOUldary was plotted frail the flood profiles by detennining <br />channel stationi~ of flood contours at the same interval as the <br />topographic maps. Flood contours, sh<M1 as wiggly lines, extend <br />perpeooicular to the direction of flow and intersect the ground at the <br />ooge of the flood pl.3.in. <br />The ares includoo within the lao-year flood line ba.mdry is about 613 <br />acres for the 10 tributaries. <br /> <br />!i):drolo?;;: <br />Tributaries to the Coloradol\iwr in the vicinity of DeBeqlre to <br />Glef!l.A:X>dSprings, Colorado are streatn<; that flood frm snowmelt as \010211 as <br />fnn sunmer rain. The intent of this analysis was to separate the <lnmal <br />peak disdJ.arges into rainfall "vents <lfxl sn<himelt events. Separate <br />fre:juency curves should be ccmbined statistically to produce a final <br />discharge frequency curve. There was insufficient strearnfl~ data of <br />rainfall flood events to acc(Illplish this, therefore the SCS TR-20 cunputer <br />program was used to simulate rainfall flood peaks. The llDdel was usw 00 <br />16 waten,heds of varying sizes and a r"gional curve of drainage area vs. <br />peak discharge aoo frequency was developed for rainfall flooding. The <br />TR-2Q analysis included the standard SGS Type II (24 hour) rainfall <br />distribution and curve numbers for an average antecedent soil rroisture <br />ccn:iition (iI.t1:-II). The discharge \is. drainage area data frun this <br />analysis were plotted, and a regression line fitted for several <br />frequencies. <br />A regional alrve was developed for SI1C1Wllelt flood eventS using <br />data frO!!! B strc~ g.:lges in woe area, The Log Pearson III fre:j'-X:!1cy <br />distribution (as defined in \,He llulletin 17-8) was used with a regional <br />skew weigj:lted with each ccrnputed station skew. The data was plotted and <br />discharge-drainage area lines drawn for several frequencies. <br />TIle t\;o regional discharge fra:juency-drainage area curves (rainfall <br /> <br />D. k'ioodway <br />Artifical fill encroachment on flood plains can roouce tho! areal <br />extent of a flood pl.3.in ani provide additional space for other ust:$. AB <br />an alt"rnative to the pr;,s<mt flO<.Xling situation, a possible floodway with <br />flO<.Xl plain encrO<1chment w;]8 analyzed in this study. The resulting <br />effects 011 flood elevations are ahoI.n in an Appendix separate frem this <br />rtlpOrt. <br /> <br />.::m s:n=.clt) were ccrrrbir;cd using a stw,e!;:;.rd prob.:1bilicy Uju.:ltion: <br /> <br />P(comb)-P(snow)+P(rain).(P(snow)xP(rain)). <br />This c<.lllbi~ regional CUPIt' is recomnended for studies along the <br />COlorado Ri.ver TrU>..ltari<os In the vicinity of Debeque to Ul,,~d Spri.ngs, <br />Colorado for strea'llS that have ind"pendent snv..""dt an:! rainfaLl flood <br />histories. <br /> <br />12 <br /> <br />13 <br />