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<br />000577 <br /> <br />2. Adverse Flood Impacts and Durability <br />The eweB takes very seriously the flood safety aspects of RIeDs, and will carefully <br />consider flood safety in reviewing the RIeD application.. The ewes recommends that <br />an applicant for an RIel) demonstrate, through appropriate technical analyses, that the <br />proposed boating course is designed and will be (is) constructed in such a manner as to: <br />. Adequately pass all flows up to and including the lOO-year (1% probablity) flood <br />flow without causing adverse impacts to upstream, downstream or adjacent <br />property owners. Verification of "no adverse impact- can be demonstrated <br />through the use of a ewes approved step-backwater hydraulics model such as <br />HEe-RAS. 1 <br />. Adequately withstand stream forces for all flows up to and including the lOO-year <br />flood so that damage and failure of the boating course is avoided.2 <br /> <br />3. Uability <br />The ewes assumes no responsibility for use or misuse of the boating course and is not <br />subject to liability for injuries or damages caused therefrom. eweB approval of or <br />recommendation to endorse an applicant's proposed RIel) water right in no way implies <br />that the ewes accepts responsibility for final design, construction, operation, and <br />safety of the boating course. <br /> <br />I As required by current federal regulations and state floodplain management rules (not new guidance <br />developed for the purposes of this document), the applicant is advised that the proposed boating facility <br />must be analyzed for flood impacts by modeling the "existing conditions- (pre-facility) scenario and the <br />"proposed conditions. (with-facility) scenario. The hydraulic computer modeling must be performed by a <br />registered Professional Engineer (Colorado Registration) having expertise in surface water hydraulic <br />modeling. Impacts that should be analyzed include increases in water surface elevations for the range of <br />flows experienced at the proposed recreational facility, but especially the tOO-year flood event. <br />According to federal regulations, water surface elevations at the proposed RICD facility may not increase <br />at all (zero rise) in the event that the proposed recreational facility is within a stream reach having a <br />designated Floodway (the most hazardous portion within the lOO-year floodplain). For reaches that are <br />not within a designated Floodway, any increases in the tOO-year flood profile for the proposed RIct> <br />facility (up to a maximum of one foot or a lesser amount specified by local floodplain ordinances or codes, <br />whichever is more restrictive) must be documented. Proper notification of adverse impacts (increased <br />water surface elevations) must be provided to affected property owners and a Letter of Map Revision <br />(LOMR) should be obtained as required by FEMA for National Flood Insurance Program purposes. <br /> <br />2It is recommended that the boating course consist of appropriate materials and installation to endure <br />velocities, shear stresses, other erosive conditions, sedimentation, and debris that would be experienced <br />during the range of expected flows and high flow (flood) conditions. For example, a boulder drop <br />structure should be constructed with material having suitable size, hardness, shape and gradation and <br />should be installed in such a manner that it is anchored into the stream bank and streambed to survive <br />long-term operation and flood events. Proper durability of the facility will assist the applicant in avoiding <br />costly repairs and maintenance, and may help to avoid possible abandonment of the RIct> water right in <br />the future. <br /> <br />3 <br />