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<br />11 r .' Me I L ramp t on <br />r,ugust 26, 1976 <br />Page 2 <br /> <br />'~~) <br /> <br />C. USGS Method (Technical Manual No.1, Manual for Estimating <br />Flood Characteristics of Natural Flow Streams in Colorado) <br />This method is not applicable to urban areas unless the <br />effects of urbanization on flood characteristics are in- <br />significant. Also, man made works have a significant effect <br />on discharges. The estimating techniques are least rei iable <br />for basins in mixed population areas. <br /> <br />Since this method cannot be applied consistently to all our <br />study areas in Douglas County and to avoid the use of <br />several different methods, it wi 11 not be used. '. <br /> <br />D. <br /> <br />Synthetic Hydrograph Method (SCS <br />SCS has studied several areas in <br />results have not been published. <br />to our, needs and we wi 11 be able <br />informat:ion in our studies. <br /> <br />National Engineering Handbook) <br />Douglas County, although the <br />The methodology is suited <br />to use some of their. <br /> <br />Based on our evaluation of methods and dIscussions, we hBve decided <br />to apply the SCS Synthetic Hydrograph Method in developing the peak <br />flows for 10, 50, 100 and 500 year floods for non-gaged streams in <br />Douglas County. <br /> <br />Approximate Study <br /> <br />An approximate method would be appl ied in estimating the 100 year <br />flood boundaries for the areas which will not be studied in detai 1. <br /> <br />If you have any questions regarding our selection of hydrologic <br />methodology, please contact us as soon as practical. <br /> <br />Very truly yours, <br /> <br />HOWARD ~JEEDLES TAMMEN & BERGENDOFF <br /> <br />RWA/al <br /> <br /> <br />~-/~7.J. /J. ~_~.J <br />, Robert w. Anzi--;'~O.- <br /> <br />cc: Jerry Olson <br />JaCles E. Goddard <br />Eugene Jencsok <br />Bill DeGroot <br />