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<br />\ <br /> <br />hydrologic analysis of the Shell Creek and its tributaries as part of <br />the basin-wide study of potential flood control alternatives. <br /> <br />In October 1990, a hydrology report was prepared for the Union <br />Pacific Railroad by HDR Engineering, Inc. The Union Pacific Railroad <br />requested the information to determine the adequacy and possible <br />replacements of the structures damaged in the June 1990 flood. <br /> <br />HYDROLOGY <br /> <br />" <br /> <br />" <br /> <br />For this study, instantaneous peak discharges were estimated for <br /> <br /> <br />the 30-square-mile Elm Creek' watershed upstream from Platte Center <br /> <br /> <br />using the U.S. Geological SurVey (USGS) regional equations as defined <br /> <br />in the publication "Magnitude and Frequency of Floods in Nebraska, <br /> <br /> <br />USGS Yater Resources Investigations 76-109, 1976." The relative <br /> <br /> <br />magnitude of those flood events was verified using flood frequency <br /> <br /> <br />dat~ from the USGS stream gage at Newman Grove on Shell Creek, crest <br /> <br /> <br />stage data from Skeedee Creek near Genoa,: and South Fork Union Creek <br /> <br /> <br />near Cornlea. The computed values are listed in table 1. <br /> <br />Table 1 <br />Peak Discharge <br /> <br />AVera2e Return Period <br /> <br />USGS 76-109 Re~ion 3 EOUATION <br />(c.f.s. ) <br /> <br />- <br /> <br />la-year <br />50-year <br />100-year <br /> <br />.6,600 <br />U.200 <br />16,800 <br /> <br />4 <br />