Laserfiche WebLink
<br />TABLE 3 <br /> <br />HYDRAULIC S1'UDY REACIlES <br /> <br /> (1) Downstream <br /> Designation Descri"tion Control <br /> , city shop, north of , , , trClcks slope-area <br /> " C , , tracks eo Vine Prive critical depth <br /> vine 1', <br /> " Drive '0 Frey Avenue w.s. from U <br /> N Frey '0 Lurimer .2 W.s. from M <br /> K Reuch , '0 Reach T w.s. from N <br /> T Reach K '0 Larimer " w.s. from K <br /> , South of Vine Dr. Subdivision Slope-area <br /> C Larior.cr #2 '0 Impala "c. slope-areal <br /> critical depth <br /> I <br /> , I ReilCh " '0 Laporte Ave. W.B. from D <br /> Q Laporte '0 Reach R W.s. from C <br />I R Faudre lIiryh SchOOl slope-area <br /> ^ peudre High '0 Overland Tr<J.il "'lope-area <br /> R I Qvorla,,::! Trail '!'railer Park w.s. from " <br />I <br /> , Larimer " through Irish Green slope-areal <br /> critical depth <br /> , IriSh Gre.'n '0 Hollywood Ave. w.s. from ,W"" <br /> <br />(l}:;oc Ro..ch ;.QccJ.tion ",;1>, <br /> <br />(2)waLer s,-,r(act' <br /> <br />Gp TITe! u.sn <br />, HYDRAULIC STUDY REACHES 3 <br /> <br />-;;8- <br /> <br />downstream starting water surface elevation (for subcri tical <br />flow) and cross section data. Peak discharges l1re discClssed <br />in the hydrology section of this report. <br /> <br />I <br />, <br />I <br />I <br />I <br />I <br />I <br /> <br />A field survey, co~plete with photographic documentation, <br />W<ilS compLeted to determine Manning's 'n' values. At the time <br />of this investigation the majority of vegetation was in full <br />foilage. During computation every effort was made to correlate <br />the values with those of similar conditions in photographs <br />originally published by the U.S. Department of Agriculture <br />and reproduced by Chow!61 In some cases. 'n' values were <br />calculated using procedures outlined by Chow. A photo <br />catalo~76f channel reaches and representative '0' values was <br />submitted to the Technical Committee for review on October 30.1980, <br />and is on file with the City of Fort Collins. <br /> <br />, <br />I <br />I <br />, <br />I <br />i <br />. <br />, <br />I <br />I <br /> <br />The standard step method used in HEC-2 is such that dn error <br />in starting water surface elevation is corrected as the program <br />proceeds upstream. Nevertheless an incorrect startin~ point <br />can cause significant changes in the floodplain of the lower <br />r'eache". S~verill mfCthods were used to d~termine the startinq <br />water surface elevati.ons (Tablo ,\. On n'ach",t" wh<'r<" the <br />ulschar~~ oVer-to~pcd d road Or railway the critical depth was <br />computed and used ilt" a starti.ng elevation. Reaches U & Mare <br />examples. OthHr reaches st~rt at natural detention ar(!as <br />(reaches I /;- D). For these rcaches a starting elevation was <br />calculated from the stage-storage relationship modelled in the <br />S.W.M.M. program. ~any reaches had their mOst downstream <br />cross-section ln common with thc upstream cross-5ectio~ of a <br />lower reach. In these Cilses the water surface elevation <br />calculated for the lower reach was used as input to the upper <br />reach. This is by far the most accurute procedure. Fir-ally, <br />flow nplits '>t the Poudre liigh Scr.ool made i.t neceS5ary to <br />establish intermediate wat~r surface elevations. ?hc Slope area <br />method was us<.'d to corr.>,ute a cont-rOl ""at.~r surface. 1'his <br />sp....cial Ci,lSe lS discussed i" 4reater detail in paragraphs t.o <br />follOW. <br /> <br />-29- <br />