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Holly are limited for the years after the construction of John Martin. The record <br /> for Holly consists of nine years from 1944 to 1952. The record at Granada <br /> consists of 27 years exists from the years 1982 to 2008, however no major flood <br /> events from the historic record are represented. Therefore determination of major <br /> flood peak discharges based on statistical analysis was considered less reliable. <br /> Peak discharges for the towns of Holly and Granada were therefore calculated <br /> from Equation EQ-3 from Analysis of the Magnitude and Frequency of Floods in <br /> Colorado (reference 15). This equation determines peak flow for an ungaged site <br /> (Granada or Holly) based on a regionally calibrated regression relationship to a <br /> nearly gaged site at Syracuse, Kansas. The equation is shown below. <br /> x <br /> AU <br /> QTU = QTG A [EQ-3] <br /> G <br /> Where, <br /> QTU =peak flow, for a recurrence interval of T years for the ungaged site, cfs <br /> QTG =peak flow, for a recurrence interval of T years for the gaged site, cfs <br /> AU = drainage basin area for ungaged site downstream of John Martin <br /> Reservoir, square miles <br /> AG = drainage basin area for gaged site downstream of John Martin Reservoir, <br /> square miles <br /> X =mean exponent for hydraulic region (Plains= 0.4, adjusted to 0.6) <br /> The Syracuse, Kansas site was chosen as the gaged site due to the downstream <br /> proximity to Granada and Holly and the availability of stream gage data for <br /> statistical analysis. The method for determining Arkansas River peak flows at <br /> Syracuse was similar to that used for Lamar. The initial HEC-SSP model limited <br /> gage records to the years 1943 to 1982 to match data used in the Hamilton County <br /> FIS at Syracuse. The model was then calibrated to match the FIS results using a <br /> weighted skew factor of-0.24 and a regional skew MSE of 0.302. The additional <br /> gage record from 1983 to 2008 was then added for the final model. Results are <br /> shown in Table 5. As with the Lamar model, the addition to the gage record <br /> caused a significant reduction in peak flows for the various storm frequencies. <br /> Results of the Syracuse analysis were then used to determine peak flows at <br /> Granada and Holly using equation EQ-3. The mean exponent variable in EQ-3 <br /> was calibrated from 0.4 to 0.6 in an effort to more closely match the flows from <br /> the HEC-SSP model at Lamar. Due to the attenuation of flows at John Martin <br /> Reservoir, the area determination for the gaged and ungaged basins excluded the <br /> area upstream of the reservoir. <br /> The peak flows for the new detailed studies along Wild Horse Creek through the <br /> Town of Holly and for Wolf Creek through the Town of Granada were <br /> determined by ICON Engineering, Inc. using the area and precipitation based <br /> regression equation as presented in a 2009 USGS publication (reference 16). This <br /> 8 <br />