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<br />. <br /> <br />. <br /> <br />. <br /> <br />2 <br /> <br />shown on the topographic work map entitled "Dirty Woman Creek Floodplain Changes," prepared by <br />Turner Collie & Braden Inc., dated June 11,2001, and the data, listed below are received, a revision to <br />the FIRM would be warranted. <br /> <br />For Dirty Woman Creek, the effective FIS base flood profile was based on a HEC-2 hydraulic analysis. <br />, A duplicate effective HEC-2 hydraulic model was used to reproduce the effective FIS base flood profile. <br /> <br />A corrected effective hydraulic model was developed by incorporating an additional cross section just <br />upstream of the existing SH105 bridge into the duplicate effective model to provide a more accurate base <br />flood profile. Our comparison of the corrected effective model to the duplicate effective model revealed <br />that the BFEs for Dirty Woman Creek remained unchanged. <br /> <br />The proposed conditions model was developed by incorporating the updated topographic information <br />and proposed project into the corrected effective model. The effective base flood discharges values were <br />used in the hydraulic analyses. As a result of the updated topographic information and proposed project, <br />the BFEs for Dirty Woman Creek will decrease compared to the corrected effective BFEs. The <br />maximum decrease in BFE, 3,0 feet, will occur just upstream ofI-25. <br /> <br />As a result of the updated topographic information and proposed project, the BFEs for Dirty Woman <br />Creek will decrease compared to the effective BFEs. The maximum decrease in BFE, 3.0 feet, will occur <br />just upstream ofI-25. The width of the SFHA will decrease compared to the effective SFHA width. The <br />maximum decrease in SFHA width, approximately 350 feet, will occur just upstream ofI-25. The width <br />of the regulatory floodway will increase compared to the effective floodway width. The maximum <br />increase in floodway width, approximately 185 feet, will occur approximately 120 feet upstream of <br />1-25. The floodway width increase will be contained within the proposed channel. The base flood will <br />be contained in the existing channel along Dirty Woman Creek from approximately 1,000 feet <br />downstream to just upstream ofI - 25. <br /> <br />Upon completion of the project, your community may submit the data listed below and request that we <br />make a final determination on revising the effective FIRM and FIS report. <br /> <br />. Detailed application and certification forms, which were used in processing this request, must be <br />used for requesting final revisions to the maps, Therefore, when the map revision request for the <br />area covered by this letter is submitted, Form I, entitled "Revision Requester and Community <br />Official Form," must be included, (A copy ofthis form is enclosed,) <br /> <br />. The detailed application and certification forms listed below may be required if as-built <br />conditions differ from the preliminary plans, If required, please submit new forms (copies of <br />which are enclosed) or annotated copies of the previously submitted forms showing the revised <br />information, <br /> <br />Form 4, entitled "Riverine Hydraulic Analysis Form" <br /> <br />Form 5, entitled "Riverine/Coastal Mapping Form" <br /> <br />Form 7, entitled "Bridge/Culvert Form" <br />