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of the survey instrument at each instrument setup and as such, are not tied into a vertical <br />is control. <br />Staff Gage Method 1 <br />Method 1 is the simplest approach and consists of comparing the change in daily average <br />stage values at the closest upstream USGS Platte River flow gage. This difference could <br />then be applied to the water surface elevation at the WC sighting location on the day it <br />was measured to predict the water surface elevation at the WC sighting location on the <br />day the WC roosted. The Overton gage, the main channel gage at Cottonwood Ranch, the <br />Kearney gage and the Grand Island gage were used. Flow travel time was not accounted <br />or in this initial analysis, and real time ilata, which - <br />not used. Also there was no attempt made to account for differences between the flow at <br />the study site and the flow at the gage, although the flow at the site may be less due to <br />multiple channels. <br />Manning's Equation Method 2 <br />The transect survey and water surface elevation was used to compute the flow at the <br />transect during the time of the survey using the Manning's equation. A slope of 0.0012 <br />and a roughness ( Manning's n value) of 0. 00 15 was assumed at each location. The <br />computed flow was compared to the flow at the nearest upstream gage to develop a ratio <br />for the site. For example, where there are multiple channels in a cross section, the <br />surveyed transect may convey only one -half the flow in the river. On the day of the crane <br />sighting, the gaged flow for that day was multiplied by the ratio to estimate the flow at <br />• the surveyed transect. The Manning's equation was then used to compute the flow depth <br />using the estimated flow at the transect (gage flow multiplied by ratio) during crane <br />roosting. <br />• <br />Hydraulic radius in the Manning's equation consists of two variables, the wetted area <br />divided by the wetted perimeter. In a natural channel with an irregular shape (non- <br />trapezoidal) the two variables wetted area and wetted perimeter can be solved for with an <br />iterative approach. For wide shallow rivers where yave/b is less than or equal to 0.02 <br />(where yave average flow depth and b =width of channel), the perimeter of the channel <br />can be assumed to be equal to the width of the channel (Henderson, 1966) for a direct <br />solution of average depth rather than an iterative solution of actual depth. This <br />assumption was made to reduce analysis time for computing the Manning's equation <br />method but actual depth could also be computed with an iterative solution. <br />HECRAS Method 3 <br />The HECRAS 1D hydraulic model constructed by Mohammed Samad for the Platte <br />River Unsteady Flow and Bank Storage Model was used for this computation (Randle <br />and Samad, 2007). The model is constructed using Reclamation cross - sections surveyed <br />in 1989, 1998 and 2002. There are 58 surveyed cross sections in the model beginning at <br />Overton and extending to Chapman. The largest gap in cross section data is near Kearney <br />between RM 219.8 and RM 210.6. In the longitudinal distance between surveyed cross - <br />sections, the user can interpolate cross sections. The HECRAS model used for this <br />Summary of Phase I Whooping Crane Data Analysis November 6, 2007 <br />3 <br />