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28 <br />reference locations on the island to provide accurate locations and mapping. The <br />reference location pins were surveyed in by GPS. <br />Data analysis <br />Channel change comparisons <br />Evaluations of change in channel geometry during water year 2000 were <br />conducted at both Green and Yampa River study sites. At both sites a pre- and post- <br />runoff profile was measured at each transect location (Figures 2 and 3) using a <br />combination of conventional and hydrographic surveying methods described previously. <br />For the Green River site, additional measurement data collected during trips between <br />base flow and peak flow were used to describe channel geometry at intermediate flows. <br />Points used for the intermediate flow profiles were selected from hydrographic survey <br />data collected during repeated channel crossings at transect locations. Only survey points <br />within + 20 cm on either side of the true transect line were included in the intermediate <br />flow data sets. If data for a particular flow and date within 20 cm were not available, <br />survey data from the closest survey date were used to fill in gaps. This approach depicts <br />no change in channel geometry for cases where data were not available. In addition to <br />transect measurements, the topography of the central part of the high flow channel near <br />the upstream boundary of the Green River site was mapped before, during and after peak <br />flow.