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 Page 13 Upper and Lower Emerald Valley Dam Failure Report <br /> January 23, 2015 <br /> <br /> <br /> <br /> Figure 15: Schematic of HEC-HMS model <br />The model schematic from HEC-HMS shown above delineates the major model <br />elements taken into consideration during development and refinement. Based on <br />drainage topography, 2 subbasins were created above the Emerald Valley Dams. The 2 <br />dams sit in series, no routing reach was required between them. A routing reach was <br />developed for the Little Fountain Creek Channel from Lower Emerald Valley Dam to <br />Keeton Reservoir Inlet. A subbasin was defined that related specifically to Keeton <br />Dam only and, due to the data development of the SPAS rainfall data and differences <br />in soil infiltration, did NOT include the drainage above the Emerald Valley Dams. The <br />primary control point for calibration of this model is the broad crested concrete weir <br />located at the Keeton Dam spillway control section. At this point, the incremental <br />damage to be evaluated would be at the RR tie access bridge crossing located about <br />1500-ft downstream of the Keeton spillway control section. Flowmaster was utilized <br />to route the outflows from the Keeton spillway through the surveyed RR tie access <br />bridge. A complete compilation of HMS and Flowmaster supporting documentation is <br />provided in Appendix E. <br /> <br />The discussion below for each of these parameters describes some of the details of the <br />calibration process. Associated tables provide the final parameters utilized in the <br />modeling. <br /> <br />7.2.1 Unit Hydrographs <br />Unit hydrographs were developed for each of the drainage basins delineated. <br />The DSB has adopted use of the United States Bureau of Reclamation (USBR) <br />synthetic unit hydrograph procedure outlined in Cudsworth (1989) as part of <br />the process of transforming rainfall to runoff. Input parameters were <br />estimated assuming normal antecedent conditions using guidance from the <br />Hydrologic Basin Response Parameter Estimation Guidelines, (HBRPEG, 2008). <br />Physical parameters for each subbasin were estimated from GIS mapping and <br />known characteristics of the basins. Selection of the Rocky Mountain <br />Thunderstorm dimensionless unit hydrograph was based on the type of storm <br />that occurred in September 2013 and the location of the basins.