Laserfiche WebLink
<br />Locations of selected cross sections used in the hydraulic analyses are <br />shown on the Flood Profiles (Exhibit 1). For stream segments for which a <br />floodway is computed (Section 4.2)f selected cross section locations are <br />also shown on the Flood Boundary and Floodway Map {Exhibit 2) , <br /> <br />Roughness coefficients (Manning's "n") were estimated by field inspection <br />at each cross section and checked for reasonableness against a standard <br />text (Reference 6). Roughness values for the main channel ranged from <br />0.034 to 0.070 on the Animas Riverr from 0.025 to 0.045 on Junction <br />Creekl and from 0.024 to 0.040 on Dry Gulch Creek. Roughness values for <br />the floodplain ranged from 0.060 to 0.080 on the Animas River, and from <br />0.030 to 0,050 on Junction Cceek; a value of 0,050 was used on Dry Gulch <br />Creek. <br /> <br />Water-surface profiles of the selected recurrence intervals <br />developed using the CQE HEC-2 step-backwater co~puter model <br />7) , <br /> <br />were <br />(Reference <br /> <br />Flood profiles were drawn showing computed water-surface elevations to an <br />accuracy of 0.5 foot for floods of the selected recurrence intervals. <br /> <br />The flood profiles p=esented ~n this study are based on the effects of <br />flow ~hrough unobstructed hydraulic structures and are, thus1 considered <br />valid only if these s~ructures do not fail and remain unobstructed, <br />Hydrau~ic analyses were conducted by the CQE (Reference 3) and reviewed <br />by tr.e study contrac:or. <br /> <br />The hydraulic analyses for the reach of the Ani~as River from MP 63.000 <br />to MP 63.251 were conducted by Goff Engineering & Surveying, Ine'r <br />(Reference 1) and reviewed by the study contractor. <br /> <br />All elevations are re=ereneed to the National Geodetic Vertical Datum of <br />1929 (NGVD). Elevation reference marks used in this study are shown on <br />the maps. ERMs shown on the FIRM represent those used during the <br />preparation of this and previous Flood Insurance Studies. The eievations <br />associated with eac~ ERM were obtained and/or developed during FrS <br />production to establish vertical control for determination of flood <br />elevations and floodplain boundaries shown on the FIRM. Users s~ould be <br />aware that these ERM elevations may have changed since the publication of <br />this FIS, To obtain up-to-date elevation information on Natio~al <br />Geodetic Survey (NGS) E~Ms shown on this map, p:ease contact the <br />Information Services Branch of the NGS at (301)713-3242f or visit their <br /> <br />website at www.ngs.noaa.gov. Map users should seek verification of <br />non-NGS ERM monument elevatio~s when using these elevations for <br />construction or floodplain management purposes. <br /> <br />4,0 FLOODPLAIN MANAGEMENT APPLICATIONS <br /> <br />The NFIP encourages State ahd local government to adopt sounc floodpla~n <br />manage~ent programs. To assist in this endeavor, each FIS provides <br />100-yea~ floodplain dataf which may include a combination of tne <br />following: 10-, 50-f 100-, and SOO-year flood elevations; del~neations of <br />the 100-year and SOO-year floodplains; and laO-year floodway, This <br />infor~ation is presented on the FIRM and in many components of the tISf <br />including Flood Profiles, Floodway Data tables and Summary of Stil~water <br />Elevation tables. users should reference the da~a presented in ~he FIS <br />as well as additional information that may be available at the local <br />community map repository before making flood elevation and/or floodplain <br />boundary determinations. <br /> <br />8 <br />