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

calculated bankfull flow. The very high flows of September and October 1997 were an

obstacle for cross section work, and because of the short window when flows were below

600 cfs some of the field work was modified or abandoned.

METHODS

Cross Section Profiles

Cross section methods are frequently used to determine minimal flows for

maintaining habitats required by members of the aquatic community. These methods

operate by determining a stage-discharge relationship, usually across a riffle, and using

that relationship to find a flow that provides adequate depths and velocities for fish

habitat maintenance. This study used a total of 110 cross sectional profiles spread over a

distance of 64 river miles. Sample sites were selected in strata 6 and 8, described above

(Miller et al.I982), and their river mile location is given in Table 1. Sampling sites were

randomly selected by dividing the strata into 0.5 mile segments (called clusters), which

were meant to include two run/riffle sequences. Twelve clusters were randomly selected

from Strata 6 and 13 clusters were randomly selected from Strata 8.

Only one stage-discharge measurement was taken at each cross section. The

concern was for habitat availability during the base flow period, when flow typically

ranges from 100 to 300 cfs. Since a few cross sections were done at flows of about 600

cfs, model runs were compared using the calculated and a higher roughness value to

determine if calculated mannings n values were suitable for extrapolating beyond 40% of
the measured flow.

Cross sectional measurements were made during the base flow period in August

and September in 1996 and in September and October 1997. The bed profile was

surveyed between head pins set at or above the grassline on both sides of the channel.

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