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<br />(i.e., streets, curbs, buildings, etc.). Delineation of areas of inundation w~s <br />stopped at intersections with previously established San Miguel River flood <br />lones. <br /> <br />4.2 Floodways <br /> <br />A floodway for Cornet Creek is not recommended because of the absence of a <br />stable, defined channel on the alluvial fan. <br /> <br />7.0 OTHER STUDIES <br /> <br />Four previ ous studi es have been conducted related to the n ood i ng potent i ala long <br />Cornet Creek within the town of Telluride. <br /> <br />The Institute of Artic and Alpine Research of the University of Colorado <br />(Reference 13) prepared a study to determine the causes and characteristics of <br />past floods along Cornet Creek in order to develop design criteria for future <br />flood-protection works. The study reviewed the general nature of Cornet Creek <br />floods in 1914 and 1969. It stated that both floods were caused by short- <br />duration, high-intensity rainfall which occurred after a period of wet weather. <br />A maximum discharge rate of 14,100 cfs was estimated for the 1969 event. The <br />mud flows of this century were judged to not be e:<ception,llly rare events in the <br />history of Cornet Creek. The study recommended that flood-control structures <br />along the creek be designed for a discharge of 14,000 cfs. This discharge value <br />is over twice as large as the value estimated for the 500-year return period mud <br />now peak discharge by the present study. This discrepancy is attributed to the <br />slope/area calculation procedure used to develop the 14,000 cfs estimate. <br /> <br />In the previous Flood Insurance Study for the to~m of Tl~lluridl~, (Reference 14) <br />hydrologic analyses were conducted to establish the peak discharge-frequency <br />relationships for floods with recurrence intervals of 10,50, 100, and 500 years. <br />The Soil Conservation Service curve number method (Reference 15) was used. A <br />lOa-year return period peak discharge of 590 cfs was estimated for Cornet Creek. <br />A discharge of 1,500 cfs was also identified in this study for a mud flow with <br />a 100-year return peri ad. Th i s value was est i mated by assumi ng a 20 percent <br />water content by weight in the mud flow. The estimated peak discharge val ues <br />of lOa-year clear-water flood and mud flow are considerably smaller than the <br />estimates made in the current study. The differences in the estimates are <br />attributed to assumptions related to rainfall and the hydrologic characteristics <br />of the watershed. <br /> <br />Dibble & Associates, Inc. prepared a drainage master plan for the town of <br />Telluride (Reference 16). The investigation focused on street drainage within <br />town limits. Peak discharges werE! determined for 10- and 25-year return period <br />events by use of the Rational Method. ThE' peak discharge estimates presented <br />in this report are comparable to the clear-water peak flow values for the current <br />study. <br /> <br />A second study was conducted by Di bb 1 e & Assoc i ates, Inc. (Reference 17) to <br />eva 1 uate debri sand flood -contra 1 prob 1 el11s along CornE,t Creek. The report <br />included a description of the hydrologic setting and historic flood problems <br />along Cornet Creek, a review of the results of the 1978 FIS for the town, and <br />the results of backwater computations along Cornet Creek for the 10-, 25-, <br />50-, 100-, and 500-year Frs peak flows. A plan for debris and flood control <br />