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<br />f2ec: ' J .fw i/'V"\ <br />t.0-~'h. Cc~~ <br /> <br />16794 E. Villanova Circle <br />Aurora, CO 80013 <br />June 18, 1981 <br /> <br />Mr. Steve Isom <br />i-plan, inc, <br />P. O. Box 1002 <br />Eagl e, CO 81631 <br /> <br />Dear Steve: <br /> <br />Re: Eagle River at Peterson Ranch <br />Floodplain Report Review <br /> <br />The following information is in response to Eagle County's and <br />the Colorado Water Conservation Board's (CWCB) request: ' <br /> <br />1, FloOdplain maps on which the one hundred year flood is <br />delineated were submitted with the report on April 12, 1981. <br /> <br />2. One hundred year water surface and thalweg profiles are <br />attached. You should note that the water surface given is <br />generally 0.5 feet higher than that given by HEC-2 to be <br />conservative and account for surface disturbances. <br /> <br />3. A copy of the HEC~2 summary printout and input coding forms are <br />attached: I have spoken with E.I. Jencsok of CWCB and will deliver <br />the water surface profile, HEC-2 runs, and photos of the site <br />di rectly to him. <br /> <br />4. Freeboard was based on the equation developed by the Colorado <br />Hi ghway Department. It is 0 3 <br />FB = O.l(Q)' + 0.5(HV) <br /> <br />Where, FB = Freeboard in feet <br />Q = Flood Discharge in cfs <br />HV = Velocity Head in feet <br /> <br />5. Manning's roughness coefficients (n) of 0.04 and 0.07 for <br />channel and overbanks for this reach of the Eagle are conservative. <br />Values higher than these imply bed material much larger than that <br />existing at the site. Also, due to proximity to critical depth, <br />the dependence of the water surface elevation on n value is reduced, <br /> <br />As stated above, information attached to this letter will be hand delivered <br />to CWCB to expedite the process. If you have any questions, please call. <br /> <br />Sincerely, <br /> <br />;iW.'"tLf/VU[ ~ <br /> <br />Lawrence E. Dezman, P.E. <br /> <br />cc: Parker Croft with Attachments <br />