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<br />sp.cadoverland. FloodflowsontheAnlmasRlvertnkelongertorlse, but <br />are of longer duration. Theduratlonofovorbankflowlsofsubstantlally <br />longe.duration In The Animas Valley. Sna.-melt runoff has a slow rate of <br />rise and lower peak flows, but the large volume Can sustain overbank flow <br />for an oxtended period of tIme, often for many days. SynthesIzed stage <br />hydrographs sho\o/n on Plates 2.5 were used to develop data for the followIng <br />table. <br /> <br />TASLE 7 <br /> <br />AVERAGE VELOCITIES OF FLO~ <br />INTE~~EDIATE REGIONAL FLOOD <br /> <br />Stream <br /> <br />VelocIty <br />(feet per second) <br />Main Channel Overbank Areas <br /> <br />Animas River <br />Vlc!nltyof"AnlmllsRiver <br />atDurl'lngo"Gage <br />VIcInity of FaIrgrounds <br />Animas Valley <br /> <br />" <br /> <br />" <br /> <br />, <br /> <br />TABLE 8 <br />RATES OF RISE AND DURATION OF FLOOOING <br /> <br />, <br />, <br /> <br />, <br /> <br />Lightne. Creek <br /> <br />10 <br />10 <br />7 <br /> <br />6 <br /> <br />Flood <br /> <br />Junction Creek <br /> <br />5 <br /> <br />, <br /> <br />Dry Gulch Creek <br /> <br />It is expected that velocity of flow during 11 Standa.d Project Flood <br />would be slightly hIgher than during an IntermedIate Regional Flood. Ve- <br />lociTy of flow in sheetfla.- areas "III range from 1-3 feet per second. <br /> <br />IntermediaTe Regional <br />Standard Project <br /> <br />Water flo\o/ingata rate of 7 feet per second o.greate,.,,111 cause <br />severe erosion of streamb,mks and Is capable 01 transportIng la.ge rocks. <br />Streambanks and the fIll a.ound bridge abutments ~y be eroded and large <br />amounts of grdvel, sand, and silt may be transported by water flowIng at <br />a rate of 5-7 feet per second. Wate. flowing at about 2 feet per second <br />or less will depos It sand, silt, and othe. de~ri s. <br /> <br />Intermediate Regional <br />Standard Project <br /> <br />Intermediate Ragional <br />Standard Project <br /> <br />RATES OF RISE AND DURATION OF FLOODING <br /> <br />Intense rainfall from general rainstorms centerod over the uppertribu- <br />t<lrydralnageareasorralnfall from cloudburst type storms centered over <br />the smaller b<lslns rapidly collects as .unofl that .eaches the study area <br />soon after tho beginning of storrns. Stream channels in the study area <br />lire generally "ell deflned,buthavellmltedcapacltles. Consequently, <br />flows from flood p.oduclng storms quickly rIse to channel capacIty and <br /> <br />Intermediate Regional <br />Standard Project <br /> <br />Maximum <br />Rateaf <br />Rise <br />ft./hr. <br /> <br />Height <br />of <br />Rlse(a) <br />ft, <br /> <br />n~ <br />0' <br />RiS/b) <br />hrs. <br /> <br />Duration <br />Above <br />FloodStaqe <br />"~, <br /> <br />ANIMAS RIVER <br />(At Mile 63.831(c) <br />1.8 2.8 <br />2.8 5.8 <br />LIGHTNER CREEK <br />(AtMllel.60l <br />2.7 3.0 <br />4.3 4.4 <br />JUNCT!ONCREEK <br />(AtMllel.07l <br />4.0 2.8 <br />5.6 4.0 <br />DRY CULCH Cllf:EK <br />(At Mile 0.35) <br />4.3 1.0 <br /> <br />5,1 <br /> <br />1,' <br /> <br />, <br />, <br /> <br />14 <br />20 <br /> <br />, <br /> <br />, <br />9 <br /> <br />2 <br />, <br /> <br />7 <br />" <br /> <br />, <br />, <br /> <br />I,,) Flood staao to mw:fmurr flood ZeveZ. <br />Ib) Time period corro8par.ding to height af .riBe, rounded to nearest hour. <br />(e) "AnVnaBRiOOl'ato-...ranao"ga:fe. <br /> <br />" <br /> <br />" <br />