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t <br /> No-Rise/No-Impact Certification <br /> September 11, 2018 <tjC <br /> Page 5 of 6 <br /> The results of the Proposed Conditions Model indicate no impact on the base flood elevations <br /> shown in the duplicate Existing Conditions Model for the proposed CRFT between E-470 <br /> and Ken Mitchell Park/Open Space. <br /> Annotated Effective FIRM <br /> An annotated effective FIRM map showing regulatory floodplain and floodway boundaries, the <br /> additional cross-sections, and the proposed CRFT between E-470 and Ken Mitchell Park/Open <br /> Space is attached as exhibit E. <br /> Annotated Effective Floodway Data Table <br /> An annotated effective Floodway Data Table comparing the results of the Currently Effective <br /> Model, Duplicate Effective Model, Existing Conditions Model, and Proposed Conditions Model <br /> is outlined in table 2. <br /> Source of Additional Cross-Sections and Topographic Data <br /> Topographical data used to prepare the new cross sections utilized for the Existing Conditions <br /> Model, and Proposed Conditions Model was obtained from the city of Brighton GIS Departtpent. <br /> The topographical information was generated from a 2014 digital elevation model (DEM) and has <br /> elevation values every 2.5 feet(pixel size is 2.5'x2.5') from USGS LiDAR with DRCOG <br /> participation attached as exhibit F. <br /> Roughness Parameters <br /> No change in roughness parameters was used in the preparation of the HEC-RAS models outlined <br /> above. <br /> References <br /> Flood Insurance Rate Maps: <br /> • 08001 CO2326H dated March 5, 2007 <br /> • 08001 CO2327H dated March 5, 2007 <br /> • 08001 CO2328H dated March 5, 2007 <br /> • 08001 CO2329H dated March 5, 2007 <br /> Flood Hazard Area Delineation, South Platte River, Adams County, Colorado, prepared by CDM <br /> dated April 2005. <br />