FLOOD02972 - Laserfiche WebLink

Home Browse Search

I , GENERAL CO~DITIONS oed ~lope5 42 feet per mtl~ at the ~pst;eam end of the study rea:h and 18 feet permlleat the downstream end. South 80ulder Creek was studied from Eldorado Springs 9.~ stream miles Jownstream to the <;ontluence with Boulder Creek. South Boulder Creek is smiJller end steeper than 6oul~er Creek. The ,bnne! averages nearly 5 feet deep with a 25 foot bed width and 60 foot too width. Thachannel beo slopoaverages 28S feet per rnlle at Eldorado SpringSiJnd 4Q teet permile neilr the mouth. The South Souldor flood plain varies from 100 teet widc at Eldorado Springs to 2,500 feef wide in tho lower reaches. The wide flOOd plains on both Boulder and Soyth Boulder Creeks otten have One or more parallel drainage courses spaced ac rass tho valley. These s~ales a~e often belo~ the elevation of the st~eam- bankS, and they may extend do~n the valloy for milos beforo jolni ng tho main ChaMol. Local runoff f~om the side hi lis is Intercepted by the s~ales ~hich p~oduces shallOw f lood1ng. Thi s s~"le flood i n<J Gould be mlnlml~ed il inten;epted by trilnsverse dit<;:hes le"ding directly to the c~eek d>annel. This section presents il description of the basin ~Ith emphasis on the study reach. Streil'" and Va I I "y Ch"~i1cte~ i st I cs Boulder Creek Is il steep mountain stream d~aining a portion of the eastern slope of the Rocky mountains In Goui~e~ County. The c~eek extends 22 mi les e"shard from the Conti nential Dlv Ide to ome~ge t~om the mountains and pass through tho City of Bouldo~. Boulde~ C~eek then flows IS mo~e miles ilcross the high plains to ente~ St. V~a in Creek five mi les east of Longmont. Sou Ider C~eek dril i ns an a~oa of 440 square ml los. Slight Iy over one-ha I f of the d~a1nage arOa is I n the mounta Ins. EJ.J~ker Rese~volr, located about 12 miles upstream of Bou Id",~ was conp loted In 1910. I t has a storage capacity of Ii, 500 ac~e-feet and reduces the peak f lows of t lood5 o~iginatlng above that point. South oou I dor Creek, ::I~a i n i "'l I 25 square mi I as, I s a major triDutary to 50u l::Ier Creal'(. Th Is stream ~uns a para i iel course t() El<JU lae~ Cree;' through the mO~<lta I ns \In:;! ome~ges "t ~ I do~aco Spr i ngs. South lJou IdIJr Cr"ok thon tu~ns north and joins Bou Ide~ C~""k about- 2 mIles east at Boulder. Gr05S R,,~ervolr Is located abo"t 7 mi les upst~oum of E idorildc Spd ng5. T~ 15 reservoi ~, with a storage capacity 0/ 43,060 acru-foet, becaMe effectivo in 1955 fo~ reducing peak flOOd fio~s On South Bouldc~ Creok, Th", port Ion of rkJulcJer Cr-eB~ "l-ud i<,:u i" th;:; report extends +rom 28th Street, neil~ the eastorn edgo of !lou Ide~, 12.2 stroam ml Ie:; dow"str"arr.. The cr"e~ rr,"""uers through a flood pia in which averages 2,500 leet wide. Tho creol< bod I s cov"'~ed with 5,]nd. n~ave I. <1nd bou 1 :;!e~s. Trees I I ne the c~1)ek banks in ..,any I oc~t i Qns. See photos on 101 lowing paqes. ihechilMel av"rag",5 f"etd"ep, 45 foot wide at th~ bottQrl "M 9() feet '~Id" ,Jt the top. T~e c'Jannel The follow i ng phot09rilphs I II u5trate the ch"nnel c!)~ractc~- isrics along The t~o creeks. , ,