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<br />001240 <br /> <br />3 <br /> <br />two (or three) parameters. Usually the unit peak discharge, qp' and a <br />measure of the response time, t ,is used. The unit peak discharge and <br />p <br />the response time are interrelated. <br /> <br />There are a number of ways to define the response time. Some of <br /> <br />these response times can be related to measurable features in the water- <br /> <br />shed. The ability to predict changes in the flood response to storm <br /> <br />rainfall is crucially associated with changes in the response time, <br /> <br /> <br />w~t~hed Re6po~e T~e - There are several ways in which the <br /> <br />watershed response time can be defined: <br /> <br />T1ag = Time from the beginning of rainfall excess to the centroid <br />of runoff. (USBR, 1965), <br /> <br />T1ag = Time from center of mass of rainfall excess to centroid of <br />runoff. (Mitchell, 1 948). <br /> <br />Tpeak = Time from center of mass of rainfall excess to the peak <br />discharge. (Eagleson, 1962). <br /> <br />T = Time from low water before the flood to maximum stage. <br />rise <br /> <br />(Gray, 1961) , <br /> <br />T Tlme required for water to travel from the most <br />concentration = . <br />remote point in the watershed to the outlet. (Kirpich, 1940). <br /> <br />T q '1 = Time required for the runoff hydrograph to rise to an <br />e Ul . <br />equilibrium runoff rate. (Kibler and Wool hiser, 1970 or <br /> <br />Izzard, 1946). <br /> <br />A relationship between two of these definitions (T1 and T k) <br />ag pea <br />had been established by Schulz et al. (1971). Wilson (1972) reported <br /> <br />a more comprehensive study on response time utilizing a large number of <br /> <br />the observed floods found in the CSU small watershed data file. Unit <br /> <br />hydrographs were derived from a large number of the natural watersheds <br />