8106

• UCREFRP Catalog Number: 8106
• Author: Anderson, R. M.
• Title: Riverine Fish-Flow Investigations.
• USFW Year: 1998.
• USFW - Doc Type: Fort Collins, Colorado.
• Copyright Material: NO

Bank slopes and water surface elevations were measured using a standard surveying

level. Depth and velocity measurements were taken at 25 to 30 points along the profile.

The first cross section was placed at the most suitable hydraulic control point in the

cluster. Cross sections upstream of the control were positioned in the lower, middle and

upper parts of the run, and through a pool, ifpresent. Also in each cluster at least one

cross-section was positioned across the shallowest part of the riffle upstream of the

hydraulic control. Because of extraordinarily high base flows in 1997, priority was

assigned to sampling riffles, and because of that in some clusters only the riffles were

surveyed. Between one and three cross sections were done in the clusters where only

riffles were sampled.

HYDRA ULIC SIMULATION

The hydraulic equation was used to simulate flows from a range of 1 to 500 cfs.

The conveyance channel module ofRHABSIM (payne 1995) was used to model stage-

discharge relationships for cross sections on riffles. When multiple cross sections were

taken to determine habitat in a cluster, the step-backwater option was used.

This study was designed to determine habitat availability during the base flow

period, when flow typically ranges from 100 to 300 cfs. The plan was to do cross section

work at flows in this range because a single measurement could be accurately

extrapolated down to near zero. However base flows were high in 1997 and cross

sections were made at flows as high as 600 cfs. Concerns about only one stage-discharge

measurement were addressed by increasing the manning n at low flow since roughness

increases as flow decreases. Increasing mannings n at flows of 40% and less of the

measured flow did not change results compared to using the original mannings value.

11