9670

• UCREFRP Catalog Number: 9670
• Author: Pitlick, J.
• Title: Channel Monitoring To Evaluate Geomorphic Changes On The Main Stem Of The Colorado River.
• USFW Year: n.d.
• USFW - Doc Type: Boulder, CO.
• Copyright Material: NO

discharge is not completely random, and it is clear that the amount of fines carried by the
Colorado River increases systematically with discharge.
A
a
•
9
•
C
a
W
J
N
SILT and CLAY •
•
06 •

4• •••
Z Po

10? 00
• •? f
/-
•;
• ?i
•
y :
••
••• _
iii
103 /•
:
• ••
•
02 •
•
•
••• • rising
• falling
0' 10` 10'
B
SAND
106
•• i

.0
e 10,
•??
z
A

O
1

103, •

• •

9
C got
Nl • gg ,
••

102,
•
• rising
•? • falling

10', •
ud
10' 102 103 1 04
Discharge (m3/6)
Figure 16. Suspended sediment loads of the Colorado River, near Cameo, CO, weighted by the
proportion of (a) silt and clay and (b) sand in suspended sediment samples.
The right panel of Figure 16 shows that there is much less scatter in the relation between
discharge and sand load, as well as a clearer separation between rising-and falling-limb samples.
This observation suggests that sand transport rates are driven perhaps as much by hydraulics as
sediment supply. Least squares regression of the sand data yields the following relations:
Sand load, rising limb: Qs = 0.007Q^2.35 (r2 = 0.49)
Sand load, falling limb: Q, = 0.001 Q^2.44 (r2 = 0.74)
The exponents in the above relations are similar to each other and lie within the range of
values typically observed in alluvial rivers [Leopold and Maddock, 1953; Nordin and Beverage,
1965]. The difference in coefficients and the offset in sample values suggests one of two things:
(i) the sand supply is being depleted over time, thus the same discharge carries a lower sand load
36