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Table 2 - Manning's "n" Values <br />3.3 <br />Stream <br />Carpenter Wash (City of Cortez) <br />Chicken Creek <br />Denny Lake (City of Cortez) <br />Dolores and West Dolores River <br />Glade Draw (City of Cortez) <br />Industrial Wash (City of Cortez) <br />Lost Canyon Creek <br />Lower Cornett Draw (City of Cortez) <br />Mancos River (Through the Town of Mancos) <br />Mancos River (Upstream and Downstream of <br />the Town of Mancos) <br />South Central (City of Cortez) <br />West South Central (City of Cortez) <br />Walmart Tributary (City of Cortez) <br />Vertical Datum <br />Channel "n" Overbaz <br />0.045-0.090 0.030-( <br />0.030-0.050 0.040-( <br />0.090 0.070-1 <br />0.040-0.045 0.050-I <br />0.100 0.0' <br />0.090 0.0' <br />0.090 0.0' <br />0.035-0.045 0.060-I <br />0.040-0.055 <br />0.090 <br />0.090 <br />0.100 <br />0.0 <br />0.0 <br />«n» <br />070 <br />075 <br />100 <br />120 <br />All FISs and FIRMs are referenced to a specific vertical datum. The vertical <br />datum provides a starting point against which flood, ground, and structure <br />elevations can be referenced and compared. Until recently, the standard vertical <br />datum in use for newly created or revised FISs and FIRMs was the National <br />Geodetic Vertical Datum of 1929 (NGVD29). With the fmalization of t~e North <br />American Vertical Datum of 1988 (NAVD88), many FIS reports and FIRMs are <br />being prepazed using NAVD88 as the referenced vertical datum. <br />All flood elevations shown in this FIS report and on the FIRM are referenced to <br />NAVD88. Structure and ground elevations in the community must, the~efore, be <br />referenced to NAVD88. It is important to note that adjacent commuruties may be <br />referenced to NGVD29. This may result in differences in base flood elevations <br />across the corporate limits between the communities. <br />As noted above, the elevations shown in the FIS report and on the ~IRM for <br />Montezuma County and Incorporated Areas are referenced to NAVD88. Ground, <br />structure, and flood elevations may be compared and/or referenced to ~GVD29 <br />by applying a standard conversion factor. <br />The conversion factor from NGVD29 to NAVD88 is +4.0 feet for the detailed <br />study streams in this county. The elevations shown in the FIS report ax~d on the <br />FIRM were, therefore, converted to NAVD88 using a stream network approach. <br />In this method, a single average conversion was established for each flooding <br />source network and applied accordingly. The conversion factor for each flooding <br />source in the community may be found in the following table, as well as on the <br />FIRM. ~ <br />~ <br />14 <br />