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1.7 Willow Creek Tributary Floodplain Revisions and FEMA Submittal <br /> 1.7.1 Hydrologic Data <br /> Peak discharges (revised by Arroyo Engineering and JEF) and the Pre Arroyo Engineering/JEF <br /> FEMA FIS 100-year discharge are provided below in Table 1. Hydraulic modeling of the Willow <br /> Creek Tributary will be based on the peak discharges determined by Arroyo Engineering/JEF. <br /> Table 1: Peak Discharges Associated with Willow Creek Tributary. <br /> Revised per Pre Arroyo <br /> Return Period Arroyo Engineering/JEF Engineering/JEF FEMA <br /> (cfs) FIS <br /> 2-year 425 (cfs) <br /> 10-year 752 - <br /> 25-year 1,025 - <br /> 50-year 1,272 - <br /> 100-year 1,586 697 <br /> 500-year 2,408 - <br /> 1.7.2 Hydraulic Modeling <br /> 1.7.2.1 Effective FEMA Model <br /> JEF will recreate FEMA effective HEC-2 model and incorporate current Clearwater Drive <br /> crossing. Modeling effort will be provided to the City as a Technical Memorandum. <br /> 1.7.2.2 Update HEC-RAS Model and Floodplain Limits <br /> Since the floodplain Mapping Activity submittal to FEMA via the Mapping Information Platform <br /> (MIP) as part of the FEMA Floodplain Mapping of Willow Creek, Bottleneck Wash, and the <br /> Northern Segment of Granite Creek, Mapping Activity Statement No. AZ-Prescott-10-01 study, <br /> January 2012, an additional pipe culvert has been added at the Clearwater Drive crossing of <br /> Willow Creek Tributary. The HEC-RAS hydraulic model prepared for this study will be updated <br /> to include the additional structure. HEC-RAS modeling will be performed for the 10-, 25-, 50-, <br /> 100-and 500-year profiles and the 100-year floodway. In addition the floodplain/floodway will be <br /> redelineated in the vicinity of Clearwater Drive. <br /> 1.7.3 Incorporate Updated Floodplain Results into MIP/TSDN Files <br /> 1.7.3.1 Electronic Files <br /> Electronic files uploaded to the MIP as part of the FEMA Floodplain Mapping of Willow Creek, <br /> Bottleneck Wash, and the Northern Segment of Granite Creek, Mapping Activity Statement No. <br /> AZ-Prescott-10-01, dated January 2012, will be revised to reflect the Willow Creek Tributary <br /> floodplain revisions. These files include: <br /> • S_Wtr_Ln.shp <br /> • S_XS.shp <br /> • L_XS_Elev.shp <br /> • S_BFE.shp <br /> • S_Fld_Haz_Ar.shp <br /> In addition to the DFIRM compliant files noted above, electronic files for the channel profile and <br /> floodway data tables will be updated to incorporate the new data. All revised database files will be <br /> submitted to FEMA via the MIP. <br /> October 8,2012 <br /> Willow Creek and Willow Creek Tributary Restudy Page 4 of 6 <br />