Laserfiche WebLink
<br />vii <br /> <br /> <br />Preface <br /> <br />This report is the result of an intensive eight-month study effort by the <br />Committee on American River Flood Frequencies, a group of experts organized to <br />assist the U.s. Army Corps of Engineers (USACE) by providing an independent <br />scientific assessment of flood frequency relationships for the American River at <br />Sacramento, California. The study was designed and the committee fonned under <br />the auspices of the Water Science and Technology Board (WSTB) of the National <br />Research Council (NRC). It extends the work of the fonner WSTB Committee on <br />Flood Control Alternatives in the American River Basin (whose findings were <br />published in 1995) and aims to achieve better estimation of flood frequency <br />relationships for the American River in light of a major flood in January 1997 and <br />other technical considerations. In its review, the committee considered issues such as <br />the following that were specified by the USACE as technically controversial in the <br />agreement enabling support for the study: <br /> <br />. applicability of (the federally-prescribed) Bulletin 17-B based statistical <br />approach; <br />. appropriateness of skew factor development; <br />. potential censoring of water year 1977 data, considering validity of <br />Bulletin 17- B criteria; <br />. updated river basin probable maximum flood, and its supportive rela- <br />tionship to the selected flow frequency curve; <br />. methodologies to 'bend over' the less frequent portion of the flow fre- <br />quency curve to reflect the American River basin's realistic maximum flow <br />productivity; <br />. applicability of paleoflood methodologies to this flow frequency <br />analysis; and <br />. climatologiclmeteorologiclhydrologic trends and American River basin <br />parameters that may influence the American River flow frequency curve. <br /> <br />This report's fmdings are based on a review of relevant technical literature, <br />extensive flood frequency analyses by the committee, and deliberations among <br />committee members. <br />The committee consisted of 10 volunteer experts in hydrologic and <br />geophysical statistics, hydrologic engineering, geomorphology, hydroclimatology, <br />climatology, and economics (see Appendix A). The committee incorporated input, <br /> <br />- <br />