9658

• UCREFRP Catalog Number: 9658
• Author: Schmidt, J. C. and K. L. Orchard.
• Title: Report A - Geomorphic Analysis In Support of a Channel-Maintenance Flow Recommendation for the White River Near Watson, Utah Draft Report.
• USFW Year: 2002.
• USFW - Doc Type: Logan, UT.
• Copyright Material: NO

discharges. Peak flood values are available at the Watson gage for 1904 and 1905, 1923

to 1979, and 1985 to 1997. Data from the State line gage (station 09306395) were used

for the period when the Watson gage was inactive, between 1979 and 1985. The plotting

position for each annual flood was determined using the formula:

Rl = (n + 1 )/M

(1)

where RI is the recurrence interval of the flood, n is the number of years of record, and M

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 made in 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 made in the 1983, the last year the river was not regulated by Taylor Draw

Dam which was completed in 1984. All peaks above 28 m3/s were used to calculate the

partial duration series for the three time periods. The calculation of recurrence interval

using a partial-duration series is the same as above except n = number of peaks instead of

number of years. A log Pearson Type III distribution was calculated for data from each

of the three time periods.

Topographic mapping

Topography of the study site was surveyed using a geodetic total station in April

1997. Specific features which were surveyed included the river channel, thalweg

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