WSP03817

• File Number: 8102
• Description: Arkansas River Basin Basic Hydrology
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 5/7/1999
• Author: Inter Fluve Inc
• Title: Fluvial Geomorphic Assessment of Upper Arkansas River Final Report
• Water Supply Pro - Doc Type: Report/Study

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O~18~9

Minimum shear stresses occur at cross-sections 1, 2, 3, 5, and 6, ranging between 0.4 and
1.2 psffor all discharges. Reach average hydraulic depths range between 2.0 and 3.1 ft
(Figure 7.6, App. B.12). Maximum hydraulic depths, range between 2.6 and 3.8 ft, and
minimum hydraulic depths range between 1.3 and 3.0 ft. Reach average hydraulic depths
are near the maximum value for all discharges up to the 50-year event for all incipient
motion sites.

The average water surface slope at 1M Site 4 (Geomorphic Subreach 4) is approximately
0.6 to 0.7% for the range of discharges from the 1.1- to 100-year return period (Table 7.6,
App. B.l3). The water surface profile shows a break in slope at cross-section 6.
Upstream and downstream water surface slopes are approximately 0.8 and 0.4%,
respectively, from the break point. Average channel velocities for the reach range
between 3.2 and 4.9 fps for the annual peak discharges (Figure 7.4). These average
velocities are generally the highest of all the 1M sites, and are characteristic of shallow
split flows in the island area. Locally, velocities are as high as 6.0 fps, and as low as 2.5
3.8 fps (App. B 14). Reach average shear stresses range between 0.6 to 1.2 psf (Figure
7.5). Maximum shear stresses reach 1.7 psf, and minimum shear stresses range between
0.4 and 0.8 psf for all discharges (App. B.15). Reach average hydraulic depths range
between 1.5 and 3.1 ft (Figure 7.6). Maximum hydraulic depths, reach 3.4 ft, and
minimum hydraulic depths are l.l ft (App. B.16). Reach average hydraulic depths are
the minimum value for all discharges and most 1M sites, except 1M Site 5.

The average water surface slope at 1M Site 5 (Geomorphic Subreach 5) is approximately
0,5% for the range of discharges from the 1.1- to 100-year return period (Table 7.6, App.
B.17), Average channel velocities for the reach range between 2.9 and 4.3 fps for the
annual peak discharges (Figure 7.4), Locally, velocities reach as high as 5.1 fps, and as
low as 2.0 fps (App. B.18). Reach average shear stresses range between 0.6 to 1.0 psf
(Fig. 7.5), and locally range from a maximum 01.3 psfto a minimum of 0.2 psf(App.
B.l9). Reach average hydraulic depths range between 1.5 and 2.7 ft (Table 7.6, Figure
7.6). Maximum hydraulic depths locally reach 3.4 ft. and the minimum value is 1.2 ft
(App. B.20).

The average water surface slope at 1M Site 6 (Geomorphic Subreach 7) is approximately
0.6% for the range of discharges from the 1.1- to 100-year return period (Table 7.6, App.
B.21). The water surface profile shows a break in slope at cross-section 5. Upstream and
downstream water surface slopes are approximately 0.8% and 0.5%, respectively, from
the break point. Average channel velocities for the reach range between 3.0 and 4.3 fps
for the annual peak discharges (Figure 7.4). Local velocities reach as high as 5.4 fps and
as low as 3.2 fps (App. B.22). Reach average shear stresses range between 0.6 and 1.0
psf (Figure 7.5) and locally reach up to 2.0 psf (App. B.23). Reach average hydraulic
depths range between 1.9 and 3.4 ft (Fig. 7,6). Maximum hydraulic depths reach 4.0 ft,
and minimum hydraulic depths are between 1.0 and 2.0 ft (App. B.24).

May 7. 1999

Fluvial Geomorphological Assessment
Upper Arkansas River

Page 64