Laserfiche WebLink
<br />based on technically accurate and sound scientific data that clearly refutes the revised <br />information in order to be considered valid. Such objections supported by technical data <br />shall be presented to the CWCB at a scheduled hearing. The CWCB shall make the final <br />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 in conformance with standards as set forth in Appendix C or other methods <br />approved by the CWCB. <br /> <br />1. Floodplain Delineations. Floodplain delineations shall conform to the following technical <br />quality assurance standards or other standards approved by the CWCB. <br />a. The flood elevations and the floodplain delineations on the maps shall correlate <br />reasonably to the best available topographic information for the stream and adjacent <br />corridor and shall meet an acceptable level of technical accuracy. <br />b. The plannimetric features identified on the floodplain maps (streets and highways, <br />stream centerlines, bridges and other critical hydraulic features, corporate limits, section <br />lines and corners, survey benchmarks, etc.) shall correlate reasonably to the best <br />available aerial photographs or other suitable information for the stream and the <br />adjacent corridor and shall 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 />I DO-year flood involving special conditions shall be completed using protocols that are <br />approved by the CWCB. The special floodplain conditions include: <br /> <br />a. Alluvial fan and debris flow floodplains located within foothill and mountainous <br />regions of Colorado as determined on a case-by-case basis. <br />b. Post-wildfire hydrology in forested areas immediately following moderate to intense <br />wildfires resulting in approximately 15% or greater burn area ofthe affected watershed <br />(actual wildfire impacts shall be evaluated on a case-by-case basis). Interim floodplain <br />advisory maps shall be produced for post-wildfire areas subject to increased runoff <br />resulting from hydrophobic soils and lack of vegetation at the request of the local <br />governing authority or by Board initiative. The interim floodplain advisory maps may <br />be produced using CWCB Flood Response Program funding if needed. The post- <br />wildfire floodplain advisory maps shall be evaluated every 3 to 5 years to assess the <br />need for further revision based on watershed recovery, forest regrowth, and other <br />factors. <br />c. Ice jam flooding within stream reaches where this phenomenon is known to occur. Ice <br />jam flooding shall be analyzed utilizing methodologies available through the U.S. Army <br />Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL), <br />located in Hanover, New Hampshire. <br /> <br />12 <br />