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<br />maximum that can contribute toward the peak flow and runoff volume of the <br />flood without inhibiting the direct runoff from rainfall. The lOst cri- <br />tical snowpack for probable maximum rainflood computations is substan- <br />tially larger than that for the standard project rainflood, because the <br />heavier rainfall and warmer temperatures will have a greater capability <br />to melt snow. <br />As discussed for standard project snowpack in Section 3.04, the <br />critical snowpack in .ountainous regions will ordinarily be located at <br />elevations where most of the rainflood runoff originates. Snowpack is <br />ordinarily greater at higher elevations and less at lower elevations, and <br />hence critical snowpack will not exist at all elevations. <br /> <br />Section 4.06. Probable lIaxi_ snOWlllelt <br /> <br />The discussion in Section 3.05 of factors to be considered in se- <br />lecting melt factors for the standard project flood also apply to the <br />selection of melt factors for the probable lllaxi_ flood. Tl!IIlperatures <br />should be higher for both snOWlelt floods and rain floods, and other melt <br />factors should be correspondingly higher. In the case of snowmelt floods, <br />temperature patterns lllaybe different from standard project sno~lt <br />temperature patterns but the SlIIll! principles for developing such patterns <br />apply. In the case of rainfloods, greater precipitation amounts are <br />usually accompanied by higher temperatures, but again the same principles <br />for developing temperature patterns apply as for the standard project <br />flood. <br /> <br />Section 4.07. Probable ..xiMUI base flow <br /> <br />Base flow for the probable Maximum flood is not such a critical item <br />as for the standard project flood (Section 3.06), because the peak flow, <br />which is not greatly affected by base flow, is the primary characteristic <br /> <br />4-09 <br />