9605

• UCREFRP Catalog Number: 9605
• Author: Schmidt, J. C. and e. al.
• Title: Flow Recommendations for the White River, Utah-Colorado Draft Report.
• USFW Year: 2002.
• USFW - Doc Type: Logan, UT.
• Copyright Material: NO

coordinate values in a local grid system. Each line segment (arc) and enclosed polygon

was assigned attributes according to what each represents on the map.

Identifying banlifull discharge and the active flood plain

The active flood plain is defined as the flat depositional surface adjacent to the

channel that is overtopped during times of flooding and is constructed by the present

flow regime. The active flood plain is just overtopped at bankfull discharge. The

recurrence interval of the bankfull discharge varies on different rivers.

We identified bankfull discharge in the study reach by surveying the elevation of

each depositional surface at numerous locations throughout the reach and noting the

vegetation on each surface. After plotting these points, a best-fit line was plotted through

the surveyed elevations and projected through the gage. The discharge of the flood that

inundates each surface was determined from the elevation of the line where it passes

through the rating relationship at the gage. We identified three different flat surfaces

adjacent to the channel within the study reach that might have been the active flood plain.

The active flood plain was distinguished from low elevation terraces by choosing the

lowest widespread depositional surface that is inundated by frequent low magnitude

floods.

Cross Sections

Eleven channel cross sections were established in the study reach near the Watson

gage in May 1995, and three additional cross sections were established in April 1997 .

Cross sections were used to characterize channel geometry; we also identified bed

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