FLOOD00668 - Laserfiche WebLink

Home Browse Search

S ]: C l' ION II 1: lIydrology and Ilyd rau lies ^.) Ii2'.drol,~~z Hydrology for the Big Dry Creek was developed in accordance with the procedures outlined in the roinfaU and runoff secc'ions ] n the !l.tJ'_<1 n S to rm -.-Jl_r~J nC! g e,~!,:..i..!cr: i a _}iallll:ll, (He re a He r )"e r e r [c d to os the c:r,i1_C'.rj.'l....~i~nu~U. The fi rs1 step in this study was to obLli n rain[ilIl..frequency elata. The isohyetills map" entitled "R:,inL,ll- l1epth-!luration-l'requency Map, Denver Region," from the Crileria ~1:lllllal (has cd on point rainfall dilt:1) wcrc used to plot a groph of return pcriod In years versus total roi nfal1 depth in inchcs ['or a ]..hour. 6-hour and 24-hour roinfall. !lata from thc ahove graph was in turn used to plot a second graph of duration In minutes and hours versus total rainfall depth in incllcs for ]()-year, 2S-year and l()()- yea r return periods. (See Plate No. IIl'l, Volume 1). No rainfa] reduction was used for the approximately t\\'cnty square milc basin sin c c from ],i g u re IS 0 f the U. S. We a the r [)u rc:w X.c'.clll1__iY~,lL_r):J pcr,..li~J..-....__'I()_ the factor lVould have been an insigni fica'lt thO percent The next step in the development of the l'yc1ro]ogy for the h;'5il1 \Vas to determine the iJmount of rainf:J Il that actual ly lwcoi1Jes runoff, ut il izing the Colorado Urh:JJl Ilydrogr;lph Procedure (ClIlll') as out J i ned 1 nth C' c: l' j tel' i a I<la n u a I . Seven key points \Vere selected along the hasin channel at l\'hich the rate of runoff (in CFS) \vilS to he determined. The (ll'Ca In square miles of the bClsin tributary to each of tbe seven selected points was II -...".