|
<br />July 1,1961. More than three inch"g of rain fall at ,,'ray I<Hhup to 5 inches
<br />hel.ng recorded west of '"'uy. The 10,,'er part of the dty park was under ',Mter.
<br />The ~achinery loe north of the hlghway, where the Wray Implement Company has a
<br />fleet of combines, waa covered, but the machinery WaS settlin~ (sic) out of ~h"
<br />water.
<br />
<br />ClYDROLOGICA..';DHYDRAULICDETERMII;ATlO-XS
<br />
<br />Flood CharacterLstics
<br />
<br />Floodflows in this area of Colorado generally result from high-intensity, short-
<br />duration, cloudburse_type thunderstorms. Most of these thunderstorms occur fro~
<br />late spring to bte su",,,,er. Due to the nature of these highly localized storms,
<br />the runoff is characterized by a quick bu11dup to a peak and then a tapering off.
<br />
<br />Hydrolo~ic Analysts
<br />
<br />A hydrologic analysis was carrie~ out to ~atablish the peak discharge_fre1u~ncy
<br />relationships for floods of 10-, 5D_, 10D_, and SOO-year r~Currenc~ intervals for
<br />the ~orth Fork ReplJbltc;,e River. The ",.slyais lJsed in the report is referred to "1"
<br />lhe Ted.nic..l Add~ndurn '''I tl,e Upptr R"publican River Basin ""!li<.>nal h~q"e""y Study.
<br />This technique is based on statistical analyses of the streamflow recorda of aeveral
<br />drainage basins in the sa~e geographical rcgio~ as the ~orth Fork Republican River
<br />basin. The results of thts study are shown on th" following page.. Forade.tailed
<br />description of ~hg hydrologic analysis, refer to the Technical Addendum.
<br />
<br />Hydraulic Analysis
<br />
<br />Analyses of the hydraulic characteristics of the ~orth Fork Repubtican River
<br />were carried out to provide estimates of the water .urface elevations of fl~ds of
<br />the ~~.lpct~.rl r~curr~nce \nt~rv~l~ slonr, ~h~ r{o.tpr. 11'1P w~te~ ~urf>l~~ ~le.v,.ti"~5
<br />wcre co"puted tl\tough use of th(> COrl'~ of Engineers' HF.C-2 ,;tep_backwater computer
<br />progr"".. Cross s~_ccions for the backwater analysis "'~re me,~sured from 2_foot con_
<br />tou, top"g'''phic mapping. The ,~ppro~im(lte location~ of the cross sectioos used in
<br />th" b4c~water analysis "re sho'"~\ 0" the Flood.>d .'ueu :naps (Plates 3 thru 19 and n
<br />,hru 41) undon tCi", nood Pro[il"s (Plat"" 1,5 tCiru 61). ,he ,"fer"nce points. 100_
<br />year flood ele~ations, and discharge. arc also listed in ,able 2. Channel and over_
<br />batik ,-oui\hn"". [dctor, (Mannin~' s "Nt') ",""l.e <lssig:l."d ')\l the basis of field inspe<:_
<br />tion of the flood ?lain areas. Typical values for channpl roughness factors were
<br />
<br />,
<br />
<br />.055 amd .07 [or overbank coefficients. A detailed description of the hydraulic
<br />analysis is included in the rechnical Addend~..
<br />
<br />Upper Republican River Basin RegLonal Frequency Study Results
<br />
<br /> Discharges Applicable Dischar~e '" Cubic Feet perSerond
<br /> Bet""lenThese Effe~tive Drsin_
<br />I Loca,ion Stre."", Stations age Area (Sq.~1.) 10-Year 50_Year 100_Year sOO_Year
<br />iDownstrearolimit 0+00 434+54 85.6 1500 3700 5100 10010
<br />,
<br />" study
<br />,
<br />~'pstream of Hwy,34 434+54 880+70 %.9 1308 3250 4465 8805
<br />:X_ingabove Laird
<br />:!Jpstre1lltlo! cOn_ 880+70 _ 1070+26 49.6 1115 ''''0 3830 7600
<br />~luence with Holy
<br /> oeCreek
<br />,
<br />rp"t~eam of Hwy.34 1070+26 1115+14 46.9 ,,, 21~3 """ 6350
<br />;Upstream of oo~ 1115+14 1409+2~ 29.3 "0 1700 2350 4600
<br />iluence with Chief
<br /> Creek
<br /> 1:pstreaJllof co"",y 1409+21 1779+89 25.4 'W 1467 2000 4000
<br />,road bridge
<br />.1:pstreat'lof county 1779+89 2153+71 18.6 "0 1104 1510 3000
<br />:road bridge
<br />1.18m11eodo'...._ 2153+71 _ 2216+00 '.0 '06 HB ". 1409
<br /> ~trca~ of upstream
<br />;limH of study
<br />
<br />INTElli'RETATIONlI1WU$E OF REPORT DArA
<br />
<br />Flood Frequency and Discharge
<br />
<br />The 10_, 50_, 100_, and SOD-year flood events were used as the flood frequencies
<br />for this flood plain analysis. Thul<, the data developed in this report ~ill be co"'_
<br />patlhle not oniy for regulation purposes and H.B. ID41 de~tgnation~, but also for
<br />Federal Insurance Administration flOOd insurance rate studiee.
<br />
<br />'. The.se v"tious flood event~ h.ave an aversg~ o~_curr"nce of cnce ir. the "u"'~r cf
<br />,.e"r" in<!1eated. The 10- and SO-vear flood ev"nt.~ ~r" "s~ful f"r future e"gin"-er!.:1.g
<br />studies a.'1.d land ,..e ~1""n1ng purposes related to mi""r road 6}"ste:n~, :ninor chilnnd
<br />irnpra\<e~eat6, ehe location of parka and recreational facilities. a~rieultuTal lands,
<br />and "~purtena"t structures. !'or ~tructur"s and uses of this type On the smaller
<br />
<br />w
<br />
|