8252

• UCREFRP Catalog Number: 8252
• Author: Allred, T. M. and J. C. Schmidt.
• Title: Channel Narrowing of the Green River Near Green River, Utah
• USFW Year: 1999.
• USFW - Doc Type: History, Rates, and Processes of Narrowing.
• Copyright Material: NO

15

that could be waded safely. Deeper channel locations were surveyed by
stretching a tag line marked at 3.05-m intervals across the channel and using a
motorboat equipped with a recording depth sounder to mark each interval on a
recorded trace. Four traces were completed for most cross sections. The
depth of flow at each point was calculated as the average of the four traces.
Standard errors also were calculated based on the scatter within the traces.
The survey data were combined with the, depth-sounding trace data for a
complete descriptiolJ of channel response,to a flood event.

RESULTS AND DISCUSSION

Channel Bed Behavior

The Green River scours and fills during flood passage (Fig. 7). Average

bed elevation at the present cableway has not changed appreciably since 1930,

although bed elevation increased several times and then returned to the

previous level. Rising limb scour now only occurs during the largest post-dam

floods. Detailed measurements showed that the channel filled during passage

of the flood.

Channel Cross-Section Change

The channel has narrowed by about 25 m at the old cableway that was

used prior to 1930 (Fig. 8). Most bank accretion occurred on the left bank,

which is the inside of the channel bend. Photographs of the old ferry/eableway ."