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<br />.. <br /> <br />. <br /> <br />Once the criteria are identified, the back-up data are obtained, the computer <br />model input data are available, and an appropriate computer program exists, <br />calibrating to the original floodway results can begin. However, should either the <br />input data or the computer program no longer be available, the long process of <br />constructing a new model and calibrating it to the mapped floodway conditions <br />would be necessitated. It is most important in the reconstruction process to take <br />advantage of all the available back-up, such as topographic mapping, cross <br />section locations, hydrologic data, flood profiles, field notes, Manning's roughness <br />coefficients, and other data noted in reports. It is equally important to <br />thoroughly document the use of these data and outline the decision process used <br />to reconstruct and calibrate the model for the baseline condition. <br /> <br />5. Evaluation the Floodwav Chanlre <br /> <br />. <br /> <br />Once a calibrated original model has been produced, we proceed by upgrading it <br />to existing hydraulic conditions. The conditions and criteria for amending or <br />changing a flood way on NFIP maps are very specific in stating that the model <br />must be upgraded to reflect all fill that has been placed since the original model <br />was developed. Only then can flood way changes be evaluated and the floodway <br />adjusted within the limiting criteria and with community concurrence. <br /> <br />It is also most important that all assumptions be documented and that the logic <br />be organized in a manner that can be followed by the reviewers. By adhering to <br />this process, requests for legitimate floodway changes should be processed <br />expeditiously. <br /> <br />6. Applving Advanced Techniques <br /> <br />Determination that the original hydraulic and floodway models are inaccurate <br />and require correction is generally based upon comparison of actual flood event <br />data to the modeling results. However, developing a new approach to reliably <br />model the hydraulics quite often leads to the application of the most recent <br />technological advances in the science. While these advances have greatly aided <br />our ability to correct modeling inaccuracies, such advances are often extremely <br />costly and may require special administrative procedures to incorporate them. <br /> <br />. <br /> <br />4 <br />