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<br />Use of paleohydrologic investigations in. developing <br />_~ Flood-Warning System, ~ikes Peak Area, Colorado <br /> <br />Robert D .Jarrett, (USGS, WRD, Box 25046, <br />Mail Stop 412, Denver, CO, 80225-0046; <br />303~236-6447; BITNET RJARRETT@USGSRESV) <br /> <br />RI~ <br />. ......'''cD <br /> <br />M/JD 3 0 '89 <br />OOWIVlUo WA~. <br />~ <br /> <br />The U,S. Army Corps of Engineers is developing a real-time flood warning <br />system for s,reams in the vicinity of Colorado Springs and Manitou Springs, <br />Colorado. These streams drain the rugged foothills and Pikes Peak where <br />elevations range from 1800 to 4.300 m. An ALERT system includes 26. <br />precipitation gages from which rainfall amounts will be automatically entered <br />into a rainfall-runoff model (HEC-2) to provide flow estimates along the <br />streams. H:ydrologic information on flooding is insufficient; thus, <br />reconnaissance paleoflood investigations were conducted to improve the <br />understanding of the flood hydrology in the area. Floods lee.ve distinctive, <br />long-lasting, and easily recognizable erosional and depositional features in <br />channels. Onsite mapping, surveys of the elevatio,",s of the top of flood <br />.- deposits, and relative dating of the deposits were 'made. The approximate <br />magnitude and frequency of recent, . intermediate, and maximum floods were <br />estimated for streams in the study area. The. investigations indicated that: <br />(1) Above 2.300 m, no significant flood deposits were found; (2) below 2,300 <br />m, floods primarily are produced by rainfall; (3) previously estimated floods <br />for specified recurrence intervals are much larger than paleoflood evidence <br />indicate; (4) orography favors floods in southeast-facing basins; (5) <br />infiltration is rapid; and (6) very large but infrequent debris flows have <br />occurred in areas' that are now urbanUed. These paleohydrologic results have <br />been incorporated into the rainfall-runoff model and flood-warning system. <br />The paleohydrologic investigations indicate the need fot. additional <br />information about the flood hydrology of the area. <br /> <br />; <br /> <br />-~ .~.. .- <br /> <br />~-: : <br /> <br />'0,". <br /> <br />-. ,...-~ . <br />:?:'7-~'t..:.~ -' <br />