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<br />. Auxiliary spillway. - Any secondary spillway which is designed to be <br /> <br /> <br />operated very infrequently and possibly in anticipation of some degree <br /> <br />of structural damage or erosion to the spillway during operation. <br /> <br />. Emergency spillway. - A spillway that is designed to provide addi- <br /> <br />tional protection against overtopping of dams and is intended for use <br /> <br /> <br />under extreme conditions such as misoperation or malfunction of the <br /> <br /> <br />service spillway or other emergency conditions. <br /> <br />STILLWATER LEVEL. - The elevation that the water surface would assume if all <br />wave action were absent. <br /> <br />WAVE RUNUP. - Vertical height above the stillwater level to which water from <br /> <br /> <br />a specific wave will run up the face of a structure or embankment. <br /> <br /> <br />WIND SETUP. - The vertical rise in the stillwater level at the face of a <br /> <br />structure or embankment caused by wind stresses on the surface of the water. <br /> <br />E. Estimating Inflow Design Flood Hydrographs <br /> <br />The methods used to develop inflow design flood hydrographs fit within two <br /> <br /> <br />broad categories: (1) statistical analysis of historical streamflow records, <br /> <br /> <br />and (2) synthesis of floods based upon meteorologic and hydrologic studies. <br /> <br /> <br />Discharges from upstream reservoirs should be included as part of the inflow <br /> <br /> <br />hydrographs. When storms serve as a basis for determining inflows, the storm <br /> <br /> <br />centering pattern that is applicable to the site being evaluated should be <br /> <br /> <br />adopted . <br /> <br />Determining flood potential by statistical analysis using existing stream- <br /> <br /> <br />flow records for the site, or others in the vicinity, is usually limited to <br /> <br />5 <br />