WSP05649

• File Number: 8220.101.10.D
• Description: Glen Canyon Dam/Lake Powell
• State: AZ
• Basin: Colorado Mainstem
• Date: 2/1/2000
• Author: Topping et al.
• Title: Colorado River Sediment Transport
• Water Supply Pro - Doc Type: Report/Study

552

TOPPING ET AL: COLORADO RIVER SEDIMENT TRANSPORT. 2

1996 FLOOD DEPOSITS

SUSPENDED SEDIMENT
DURING THE 1996 FLOOD

..-0..- LOWER MARBLE CYN D.n (RIVER MILE 61)
..-0... GRAND CANYON P-61 (RIVER MILE 87)
...lSJ... GRAND CANYON D-n (RIVER MILE 87)
...",... 122-MILE EDDY 0-74 (RIVER MILE 122)
"'-0.-. NATIONAL CANYON P-61 (RIVER MILE 166)

(Endo!
high 1.0
discharge)

__ RIVER MILE 61
__ AIVEA MILE 63
__ AIVEA MILE 72
__ AIVEA MILE 122
--+-- AIVEA MILE 136

1.0 (Top)
z
I
....
i:.... 0.8
....iii
IO
",a.
jjjW 0.6
IO
00
~g 0.4
--,
;iu.
::IE
cr 0.2
0
z
O.o(Base)
a)
1.0 (Top)
z
I
.... 0.8
i:....
....iii
IO
",A. 0.6
-w
~O
00
wO 0.4
NO
--,
;iu.
::IE
a: 0.2
0
z

0.08 0.10

SAND Doo (mm)

q'.
9
?
r

. ..,.0
...,.~...

0.20

-z
lllo
o.a OIJJ
;n~
DC
0.6 g~
mO
"....
~~
0.4 :om
~g
~2:!
0.2 .....z
Gl

(Beginning
of high 00
discharge) .

(End 01
twgl 1.0
d'18CI\argo)

-z
:gO
0.8 Q):IJ
.,,~
,..)>
OC
0.6 g~
~~
'O~
0.4 g]m
fg
~~
0.2 -lZ
Gl

(Beainning
o O(Ba.o\' ofh9> 0.0
. U 10 20 30 40 disd1aJgO)
SILT AND CLAY CONTENT (% OF SAND, SILT, AND CLAY)

b)

Figure 8. (a) Median grain size of sand as a function of normalized height within the deposits of the 1996
flood experiment and measured median grain size of sand in suspension as a function of normalized time
during the 7 days of steady high discharge during the 1996 Dood experiment. See Figure 1 for the locations
of the five bars that were sampled. (b) Silt and clay content as a function of normalized height within the
deposits of the 1996 flood experiment and measured silt and clay content in suspension as a function of
normalized time during the 7 days of steady high discharge during the 1996 flood experiment.

theory and simultaneous field measurements of bed- and sus-
pended-sand grain-size distributions (made during 1956-1970,
the 1996 flood experiment, and the 1997 test flow) suggesuhat
the median size of suspended sand in the Colorado River can
be no more than about 60-65% of the median size of the sand
on the bed.
Examination of the 1983 suspended-sand data of Garrett et
al. [1993] indicates that many samples (especially those col-
lected at the National Canyon gage) exceeded this threshold.
This is understandable given that many of the people involved
in collecting the 1983 data had little or no prior suspended-
sediment sampling experience. Therefore a filter was applied
to exclude all suspended-sand samples with a median grain size
coarser than 75% of the median size of the bed sand present in
the central 2/3 of the channel (i.e., the coarsest part of the
bed). This filter was designed 10 be conservarive in thac it

would allow possible retention of some bed-contaminated data
but would not exclude any good data from the analysis.
Application of this filter excluded 25% of the suspended-
sediment samples collected at the Lower Marble Canyon
gage, 34% suspended-sediment samples collected at the
Grand Canyon gage, 60% of the suspended-sediment samples
collected at the National Canyon gage, and 24% of the sus-
pended-sediment samples collected at the Above Diamond
Creek gage.
The bed-sediment and filtered suspended-sand data col-
lected from mid-September through mid-December are shown
in Figures lOb through JOf. Also shoWTl in Figure JOb are the
predictions of suspended-sand concentration at the Grand
Canyon gage made by the stable sand rating curve approach of
Randle and Pemberron [19871. Integrated sand loads (with un-
certainties) for this period arc shown in Figure 11.