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riffle developments within relatively short distances, this assumption can introduce up to <br />• a foot of error into the estimate depending on the surveys at each location. <br />Results <br />A summary table of results is presented below. There are 2 decoy sites between Overton <br />and Kearney, 4 decoy sites between Kearney and Grand Island and 4 WC sites between <br />Grand Island and Chapmen. Each line represents a single transect location measured on <br />one date with a water surface prediction for a second date. The Overton and Kearney <br />lines are decoy data so there is a second measured date that was used to develop the last <br />two columns. All three transects at a site were enterea in the rnnt_r%. o iiiuu <br />transects at a site are reported only under the Grand Island sites in the table. <br />The predictions from the three methods are listed in the columns under "Predicted <br />Changes in Water Surface ". The most extreme change in water surface is shaded in gold. <br />Obvious poor results are shaded with pink. The selection of a preferred method is based <br />primarily on: <br />• the predicted values; <br />• the quality and number of assumptions that had to be made for each method; <br />• the number of variables that appeared to affect each method; and <br />• the type of computation associated with each method. <br />The selection of computation method relied very little on the comparison of measured <br />• water surface elevations for reasons described in the next section. <br />Decoy Data Water Surface Comparison <br />A comparison of measured water surfaces is shown in the last two columns, one is based <br />on a Mannings computation of average depth, the other is based on maximum depth. <br />Comparing water surfaces between the two similar decoy sites was not very accurate <br />because there were no reference elevations to relate the two independent surveys. The <br />comparison of measured water surfaces is based on an inaccurate assumption that the <br />thalwegs of the two transects match. This would only be true if the transects are right on <br />top of each other. Otherwise there can be a foot or two of variation due to the pool -riffle <br />pattern of the thalweg. This variation is reflected as up to a 1 ft variation in the water <br />surface comparison data. The last column in the table, change in measured water surface <br />elevation, is therefore not that accurate and does not provide a good check of the gage <br />and HECRAS methods, however it does provide a general indication of increase and <br />decrease in water surface and a general indication of large or small change. Blocks <br />colored pink indicate water surface elevations that change in the wrong direction, due to <br />inaccuracies of the data and assumptions, or do not change when they should. The water <br />surface elevation comparison could possibly be improved by using a different method of <br />relating elevations in the repeat transect surveys, for example, estimating distance and <br />slope between the transect surveys to estimate change in elevation between average <br />depths, or attempting to overlay transects to find reference elevation points. However <br />these approaches have their own inaccuracies and the additional analysis did not appear <br />warranted. Phase I conclusions were made by working through the predictions for <br />Summary of Phase I Whooping Crane Data Analysis <br />5 <br />November 6, 2007 <br />