Laserfiche WebLink
<br />Domi nant Dis cha rge <br /> <br />The average annual flow volume for a river cannot be used to predict s .. <br />the channel width. The "dominant discharge" of a river has been found <br />to be a controlling factor in channel width. The "dominant discharge" <br />is that discharge which shapes the channel when flowing in regime and <br />has been found to be equivalent to the peak discharge having a recurrence <br />interval of approximately 2 years (USBR, 1973). The long-time 1915 to <br />1975 dominant discharge fOr this reach of the North Platte River was <br />estimated to be 6,930 ft3/s as determined from a flood flow frequency <br />analysis for the Overton gage (USBR, 1977). <br /> <br />Channe.1Width <br /> <br />Wi dthsof the river channel have been reduced since 1938.Compari son <br />of 1938 and 1971 aerial photographs .readily demonstrates this. The <br />size of bridge openings on the Platte River in this reach has had its <br />influence on the width of open channel. Bridges in existence in 1938, <br />as well as bank control measures, i.e., car bodies provided by the <br />local farmers, represented a significant restriction in the width of <br />the open chanQel existing at that time. <br /> <br />Channel widths in the viCinity of Overton as determined from the 1971 <br />aerial photographs are about 1,000 to 1,200 feet. The Blench regime <br />width an~lysis equation was applied to the dominant discharge of <br />6,930 ft Is. It resulted in an estimated regime width of 932 feet <br />which is considered a good check on the 1971 channel widths (USBR, 1977). <br />For all uvi a 1 channels encounteri ng both scouri ng and silti ng, techni ques <br />of regime analysis have been devel~ped to determine conditions of channel <br />5'tabil ity. <br /> <br /> <br />".;<: . <br /> <br /> <br />29 <br /> <br />