Laserfiche WebLink
<br />other than the Guidelines methodology (i.e. an at-site stream gage analysis, a regional stream <br />gage analysis, rainfall-runoff modeling, or acceptable regional regression equations) will be <br />required in certain cases and should be performed by a professional engineer and submitted by the <br />developer or development proponent. An approximate hydrologic analysis can be submitted by a <br />developer or development proponent, for the cases listed above (open space, agriculture, bridges <br />and culverts serving single farms or single family homes or cabins, pole barns, and individual <br />single family residential structures), in accordance with the determinations of the Colorado Water <br />Conservation Board regarding the applicability of the Guidelines. <br /> <br />Hvdraulic Analvsis <br /> <br />The hydraulic analysis for the preparation of the existing FHBM likely consisted of interpretation <br />of USGS quadrangle mapping by HOD's engineering consultant, along with telephone <br />discussions with local officials, The telephone discussions addressed any historic flood problems <br />that may have occurred in Akron. The PIA did not perform and did not have the benefit of any <br />detailed hydrologic and hydraulic analyses for the preparation of the FHBM. The hydraulic <br />analysis for any of the new development activities listed above will have to be detailed. Two <br />detailed hydraulic methodologies are acceptable to the Colorado Water Conservation Board: I) <br />step-backwater calculations, such as those performed by computer programs like the Corps of <br />Engineers' HEC-2 or HEC-RAS programs or simplified programs like Quick-2; and 2) normal <br />depth hand calculations. Approximate hydraulic methodologies (assumed depth methods. <br />geomorphic features methods, historic flood methods) may be used for the initial approximate <br />floodplain delineations or as a basis for a comparison to the results of the detailed methodologies. <br />Those approximate hydraulic methodologies may not, however, be used in lieu of detailed <br />approaches for actually guiding development. <br /> <br />Floodplain Mappin~ <br /> <br />The official floodplain information for the Town of Akron is the Flood Hazard Boundary Map <br />(FHBM), dated March 5, 1976. The FHBM was originally prepared by the Federal Insurance <br />Administration (PIA), The FHBM is the only available floodplain mapping for the Town of Akron <br />at this time. Based on CWCB field observations and conversations with the Town of Akron Clerk <br />the CWCB believes that the FHBM provides valid approximate floodplain information for the <br />town. The FHBM is included in the Appendix of this report. <br /> <br />Any proposed development activity in or near the approximate floodplains shown on the FHBM, <br />including construction of buildings, roads, bridges or culverts, or significant grading, should only <br />be designed after detailed floodplain mapping has been prepared for the construction site. That <br />detailed floodplain mapping should be performed as described above, utilizing hydrologic and <br />hydraulic procedures acceptable to the Colorado Water Conservation Board. <br /> <br />6 <br />