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<br />the melting of the mountain snowpack is augmented by rain. The <br />snoWmelt flood is characterized by sustained periods of high flow <br />and marked daily fluctuations. Peak flows occur typically during <br />April, May, or June. <br /> <br />Flow-frequency relationships presented in the May 1989 J.F. <br />Sato and Associates preliminary report were used with slight <br />modifications for the reach downstream of the confluence with the <br />Gunnison River. The flows and frequencies for the two <br />hYdrologically distinct reaches of the Colorado River which span <br />the inventory study area are presented in table 1. The reaches <br />are the segment from Palisade to the confluence of the Colorado <br />River with the Gunnison River in Grand Junction and the segment <br />downstream of the confluence which also includes all outflow from <br />the Gunnison River. <br /> <br />TABLE 1 <br /> <br />COLORADO RIVER PEAK FLOWS <br /> <br />Retain Period Upstream of Downstream of <br />(Years) Gunnison River Gunnison River <br />10 32,900 51,000 <br />50 44,400 73,000 <br />100 49,300 84,000 <br />500 61,000 108,000 <br /> <br />6. Inventorv Assumptions and Methods. <br /> <br />Following are the criteria used in the study to inspect the <br />levees, field procedures used for the inventory, and stationing <br />and cross referencing used for the inventory. <br /> <br />a. Inspection criteria. - One of the basic levee inspection <br />criteria considered in this inventory has been developed by the <br />FEMA. Region VIII of the FEMA, located at the Denver Federal <br />Center, provided a copy of the "Interim Levee Policy" dated <br />February 10, 1981, for use in this report (Appendix A). The <br />policy specifically addresses: <br /> <br />. Required level of protection (100-year). <br /> <br />. Freeboard requirements (3 feet, with an additional foot <br />within 100 feet on either side of structures within the <br />levee or where flow is constricted; an additional <br />1/2 foot above this minimum is required at the upstream <br />end, tapering to a minimum at the downstream end). <br /> <br />5 <br />