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<br />G. Hydrology. Hydrologic analyses for floodplain studies in Colorado shall be completed using <br />the information contained in Appendix B and other methods approved by the CWCB. In <br />addition, the following rules apply to hydrology studies: . <br />a. All floodplain studies, regardless of the level of detail (e.g. approximate or detailed) <br />shall utilize detailed hydrologic information, The CWCB recognizes existing and future <br />watershed conditions for the purposes of computing flood hydrology. Future watershed <br />conditions shall be evaluated when Foreseeable Development is expected. <br />b. Any new study performed by a sponsor to evaluate precipitation information and/or <br />design storm criteria shall be completed in such a way that it is scientifically defensible <br />and technically reproducible. <br />c. All jurisdictions and communities affected by revised precipitation data, due to their <br />geographic proximity and/or their location within a particular watershed, shall be <br />invited to participate in the update process, and shall be given the opportunity to accept <br />or rej ect the revised information. Opponents to the revised information shall present <br />technically accurate and sound scientific data at a CWCB hearing that clearly refutes <br />the revised information in order for the rejection to be considered valid, The CWCB <br />shall make the final determination regarding disputes. <br />d, Within any given watershed, or hydrologic subregion, consistency in precipitation data <br />and runoff methodology shall be pursued through cooperation of all affected <br />jurisdictions and entities. <br /> <br />H. Detailed Hydraulic Method. Hydraulic analyses for floodplain studies in Colorado shall be <br />completed using protocols as set forth in Appendix C. . <br /> <br />1. Floodplain Delineations. Floodplain delineations shall be completed using protocols that are <br />approved by the CWCB and shall comply with the technical quality assurance standards as <br />follows: <br />a. The flood elevations and the floodplain delineations on the maps must correlate <br />reasonably to the best available topographic information for the stream and adjacent <br />corridor and must meet an acceptable level oftechnical accuracy. <br />b. The plannimetric features on the floodplain maps (streets and highways, stream <br />centerlines, bridges and other critical hydraulic features, corporate limits, section lines <br />and comers, survey benclunarks, etc.) must correlate reasonably to the best available <br />flcrial-photographs oretfter-sllitabl6-inf-ennation for th~e:ml and-the~jacent cOn:W.or----- <br />and must meet an acceptable level of technical accuracy. <br /> <br />J, Special Floodplain Conditions. There are a number of special floodplain conditions, or natural <br />flood hazards, in Colorado that fall outside of the standard riverine environment. Studies for the <br />100-year flood involving special conditions shall be completed using protocols that are <br />approved by the CWCB. The special conditions are: <br /> <br />a. Alluvial fan and debris flow floodplains located within foothill and mountainous <br />regions of Colorado shall be considered on a case-by-case basis. <br />b. Post-wildfire hydrology shall be considered in forested areas immediately following <br />moderate to intense wildfires resulting in approximately 15% or greater bum area of the . <br /> <br />12 <br /> <br />DRAFT <br />