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is the rank of the flood. A log Pearson Type III distribution was calculated for these data. To determine whether peak flood magnitudes have changed over time we calculated partial-duration series for three shorter time intervals: 1923--1964, 1965-- 1983, and 1984--1997. Time intervals were chosen to coincide with apparent shifts in peak flood magnitudes, and with the installation of storage and diversion structures. The end of the first period was 1964, when there was a noticeable decrease in peak floods; a major irrigation diversion was constructed at this time, as well. The end of the second period was 1983, the last year the river was not regulated by Taylor Draw Dam, which was completed in 1984. All peaks above 1,000 cfs were used to calculate the partial duration series for the three time periods (Figure A-7). The calculation of recurrence interval using a partial-duration series is the same as above except n = number ofpeal(s instead of number of years. A log Pearson Type III distribution was calculated for data from each ofthe three time periods (Figure A-8). Topographic mapping Topography of the study site was surveyed in April 1997, using a geodetic total station. Specific features which were surveyed included the river channel, thalweg elevation, and extent of flat-lying depositional surfaces that might be either the active flood plain or terraces. Coordinate data from the total station were downloaded to a personal computer for analysis. A technician then used the coordinate data to hand plot a map of the study site at a 1 :400 scale. The hand drawn contour lines were then digitized into a geographic information system using a digitizing table and Arc/Info software (Trademark). Once digitized, control points in each map segment were assigned 10