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FLOOD11628 (2)
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Last modified
1/26/2010 10:25:17 AM
Creation date
1/5/2009 12:18:10 PM
Metadata
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Template:
Floodplain Documents
County
El Paso
Community
Manitou Springs, Colorado Springs
Basin
Arkansas
Title
Paleohydrologic Flood Investigations for Streams in Manitou Springs and Colorado Springs
Date
12/3/1987
Floodplain - Doc Type
Floodplain Report/Masterplan
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dramatically wit~ increa~ing alevatian. Below 7,500 fe~t larg~ <br />rain~all ilua~a (wi±h pealc disct,ar~es exce?ding 100,~00 ~ubic feet per <br />secon~ and with unit discharges exceeding 2,200 cubic feet p~r second <br />per square mile) have occuried. Above 7,500 fzet, streamflows from <br />•.=n~wmelt ~~r low ir~ten3ity rain have been lesa than 1~Dm cubic feet per <br />::econ~ an~ less than 50 cubic feet per second per square mile. See <br />Figure ~(from Jarrett, 1987) for the unit discharge and ~levation <br />rclatiura for all ot the Arkan~a5 River Basin streamflow dsta which <br />~haws similar ~nd complimentaiy results. <br />An important point i~ that there have been e~:ten5lve streamflow <br />rec~~r~s collected Gy the ~outhern Colorado Powzr Company for small <br />basins in the vicinity of Manitou Springs, howev?r there is no <br />icZdic~tion ~f signi2lcsnt rai.nfall runoft above 7, 500 feEt. It <br />ir~ter~~c rair,fall and frequent were to occur above this ?levation, <br />certainly o:-~e oz the stations Wuuld have rec~rded such an event. This <br />c~ul~ indiC3te that rainiall flooding above 7,500 feet is less common <br />than pr=v~cusly e::FJCCtCl1. <br />DIS~~USSIOT! ArlD CONCLUSIOH <br />Paleor~ydrologic investigatj.ons were done in streams draining into <br />Manitou Springs and Colorado Springs. These investigations indicated <br />rF~e appr~ximate magnitud~ of recent (or frequent), medium, and the <br />largest iluuds ta occ~sr in thes~ ba~ins (Figure 1>. Also, a review ot <br />available streamtlow recor~~s was made, and with the paleofloo~ <br />investigations, indi~~ates that significant rainfall flooding oc~urs <br />v~~-y in2reqantly above 7, 50e~ tc~ 8, OOm teet in the Manitou Springs and <br />Colorado Springs ai-ea; no si_gnificant tlood deposits were found. <br />~arli?r onsite paleohydrologic investigations in the Palme: Lake area <br />~u~~,ort *_he ?, Si~O t~ 8, t~~0 reFt elevation li:mit. <br />Rev~eW oi sll paleoflood information suggests that th?re is a <br />preference for floo~s on basins facing to the southeast (towards the <br />prevailing flow af moisture);, for example Williams Canyon and Camp <br />Creek. Camp Creek appears to have the greatest potential for flooding <br />oi the strcams investigated. Whereas, basins facing towards the <br />northeast !aWay from the pr~vailing moisture source) seem to have <br />lower magni*ude floods; for example, Ruxton Creek and Sutherland <br />Creek. ~u~tan Creek appears to have the lowest potential for <br />floo~ing. The infrequent rair1fa11 flooding that has occurred in the <br />in the Manito~ Springs and Co:Lorado Springs tributaries has resulted <br />rrom runoff from the drainage area below 7,500 to 8,000 feet. Since <br />tlooding occurs in such a sma1:L area (and on extremely stee~ slopes), <br />there Will be minimal time for a flood warning. Additional <br />~nvestigation of the meteoro:Logical cauaes appears to be needed <br />because streams with the graatest flood potential (~uch as Ru:~ton <br />Creek) may have the lowest flood potential. This needs to b~~ tactored <br />into the deaign of the flood-waxning systzm. <br />This analysis suggests that there appears to be a lc~wer flood <br />risk in the study area streams than previously thought and nFeds to be <br />evaluated further. The flood discharges (U.S. Federal Emergency <br />Management Agency, 1983, Tab1e L) indicates that on all tr•ibutaries <br />the lm-year peak discharges are between 1,930 and 2,630 cubiu feet per <br />~3 <br />
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