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<br />'i <br />! <br /> <br />. <br /> <br />. <br /> <br />! <br />! <br />I' <br />\ <br />i <br /> <br />l <br />, <br />I (1) <br />shall be made <br />stream gaging <br />sub-areas. <br /> <br />A map of all areas draining into the study area <br />showing the location of pertinent rainfall stations, <br />stations, and drainage area of major contributing <br /> <br />, <br />\ <br /> <br />, <br /> <br />I ,(2) Hydrographs of major floods shall be examined <br />t , <br />from gage record d~ta for gages located ~n or near the study area. <br />What, constitutes a major flood shall be determined by study of the <br />gage records, taki~g into account longer streamflow records in <br />adjacent basins if available. <br /> <br />I (3) Develop flood hydrology utilizing the MIT Catchment <br />Moael for the areas delineated in (1) above. It is believed that <br />thb Catchment MOdel provides the ~ost feasible means of generating <br />flrOd hydrographs 2nd related hydrologic parameters for the project <br />ar~a. The model produces, at selected points within the basin, <br />data relative to runoff and infiltration volumes and can be used to <br />I <br />si~ulate the effect of various features such as reservoirs, channel <br />improvements, and diversion structures. <br /> <br />, <br />" <br />I <br /> <br />t <br /> <br />1 <br /> <br />The computed runoff hydrograph shall be compared to <br />observed hydrographs at a gaging station if one exists in the area <br />to test the adopted criteria. Adjustments shall be made until <br />satisfactory reconstitutions are made,' In ungaged areas, alternate <br />methods of substantiating the adopted criteria may be used, Adjust- <br />ment shall be made in the hydrograph to take into account existing <br />and future urban development (within 25 years). <br /> <br />~ <br />; <br /> <br />Actual rainfall records shall be utilized to the <br />extent data are available for a significant period of time. If <br />data are not available, rainfall amounts for known frequency will <br />be taken from Technical Paper 40, U. S. Weather Bureau. Discharge <br />frequency curves shall be prepared at a sufficient number of loca- <br />tions to adequately define the area inundated by floods of each <br />magnitude (o:t;:;frequency). <br />i <br />I <br />l (4) Displays showing final reconstitutions (observed <br />an1 computed hydrographs) shall be submitted for review of the <br />co~tracting authority. <br />, <br /> <br />, <br /> <br />d. Hydraulic Analysis. - <br /> <br />, <br />[~ <br /> <br />(1) Hydraulic computations shall be by the standard <br />step method of backwater computations employing Bernoulli's energy <br />theorem. Manning roughness coefficients and the Manning formula <br />shall be used for computing the friction losses. Values for "n" <br /> <br /> <br />-3- <br />