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<br />1I01244 <br /> <br />7 <br /> <br />UNIT HYDROGRAPH THEORY <br /> <br />The unit hydrograph theory first used by Sherman (1932) and sub- <br />sequently improved and generalized by Snyder (1938), Taylor and Schwarz <br />(19S2), Dooge (19S9), Minshall (1960) and others. The concept of the <br /> <br />synthetic unit hydrograph is an accepted tool in engineering for <br /> <br />developing a design hydrograph for an ungaged catchment given a design <br /> <br />storm and some knowledge about the watershed soils and the watershed <br />physiographic characteristics. <br /> <br />The work of Van Sickle (1962) and Eagleson (1962) have demonstrated <br /> <br />that some of the characteristics of the unit hydrograph change with <br /> <br /> <br />urbanization of the watershed. The flood events assembled in the CSU <br /> <br />Data File are floods recorded on essentially pristine watersheds and <br /> <br />therefore constitute a data base of observed floods from undisturbed <br /> <br />watersheds. <br /> <br />rptimum M~x l~v~~o~ - A computer program was developed to <br />derive unit hydrographs from the observed flood events in the data <br />file, Kavvas (1972). The optimum matrix inversion computer program <br /> <br />was called FINVER. In many instances the derived unit hydrographs <br /> <br />exhibited oscillations in the recession limb. It is known that the <br /> <br />recession after the point of inflection on the recession side of the <br /> <br />peak is water supplied from various storage elements in the watershed. <br />Since the equation of recession is known to be of the form: <br /> <br />Q = Q e -kt <br />o <br /> <br />where <br /> <br />k is a constant. <br />