Relative Importance of Eddy 

Channel Sand Storage in Marb

1996-2000

Joe Hazel

Northern Arizona University

David J. Topping

U.S. Geological Survey

John C. Schmidt

Utah State University

Matt Kaplinski

Northern Arizona University

Published 2006 in Journal of Geophysical Research-Ear
DF

P

CM

100 0 100 Meters

Main-channel bed

 primarily composed of gravel, 

boulders and bedrock

 overlying the coarse material 

are discontinuous sandy deposits

Eddies

 debris fans determine the 

locations

 large eddies contain bars that 

may be more than 10 m thick

Channel-margin deposits

 narrow, thin veneers of fine 

sediment on steeply sloping banks

Sediment budgets: a tool to unde

changes in fine-sediment dep

input - output = change in stora
Implication of Whether the B

Eddies is the Primary Reposito

• If eddies are the primary storage site, th

...Marble Canyon will be progressively the face of a long-term and progressive sediment budget (Rubin et al., 1994)
Objectives of this Stud

 Quantify the total volume of 

active storage within the two main storage environments, eddies and the main channel

 Develop sediment budgets for 

two post-dam periods when dam releases were high and when influx and efflux of sediment 

were simultaneously measured

 Determine which environment is 

the primary source of sand 

during high clear water releases from Glen Canyon Dam
Quantify the total volume of active stor

two main storage environme

Sediment Budget Components 

Lees 

Ferry 

Roaring 

Twenties 

Redwall 

Gorge 

Point 

Hansbrough 

Tapeats 

Gorge 

Length (km) 14.0 7.5 10.0 10.8 2.9 Eddies >1000 m2 per km 2.2 4.4 3.3 3.8 5.7 Average eddy area inundated by the 1996 controlled flood (m2) 

6210 3310 3230 6240 5160 

Average new channel margin deposit area in 1996 

520 780 770 3930 1440 

Average new channel margin deposit area in 2000 

--- --- --- 1110 --- 

Channel area excluding eddies at 227 m3/s (m2/km) 

132,840 58,460 70,200 86,330 73,740 

Eddies occupy a small percentage (~17%) oarea51 to 94% of the sand in Marble Canyon is 
Sediment Budgets for the 1996 C

Flood and the September 2000 P

Capacity flow

Sediment input to Marble Canyon

 Determined from a predictive flow and sed

model (Topping, 1997); zero during each h

Sediment output from Marble Canyon

 Suspended sediment samples collected b

the Lower Marble Canyon gage

Sediment Storage, s 

 Sizes of sediment in eddies and the main  The relative distribution of sand on the ch

eddies

 Topographic data
Sand Output from Marble Ca

during the 1996 Controlled F

• Total export

– sand: 670,000 +/- 30,000 Mg

• 41% very fine (0.0625 - 0.125 mm)• 38% fine (0.125-0.25 mm)• 19% medium (0.25-0.50 mm)• 2% coarse and very coarse (>0.5 mm)

– silt/clay: 120,000 +/- 10,000 Mg

• S = I - O • thus, S = ~800,000 Mg in Marble 
Sand Output from Marble Canyon 

September 2000 Powerplant Cap

• Total export

– sand: 220,000 +/- 10,000 Mg

• 62% very fine (0.0625 - 0.125 mm)• 32% fine (0.125-0.25 mm)• 5% medium (0.25-0.50 mm)• 1% coarse and very coarse (>0.5 mm)

– silt/clay: 65,000 +/- 5,000 Mg

• S = I - O • thus, S = ~285,000 Mg in Marble 
Two independent techniqu

used to estimate changes in 

storage ( s)

Source environments based on direct measur

topography

 Relies on substantial extrapolation of area and limit

Source environments based on partitioning b

 No measurements of topographic change Requires measurement of the grain size distribution

environment
Direct measurements of topography at 

study sites
Average thickness changes from the 

Topographic 

Storage 

Components 

1996 Controlled 

Flood 

(m) 

Se

Pow

Capa

High Elevation 

Sand +0.18 

+ .05 +0

Low Elevation 

Sand -0.56 

+ .18 -0.

Channel Margin 

Bar 0.30 to 0.10 0.1

Main-Channel 

Bed -0.49 

+ .13 -0.
Source environments based on p

by grain size

Average median grain sizes of sedim

Eddies

 Subaerial eddy 

sandbars 

~0.13 mm

 Subaqueous eddy 

sandbars ~0.18 mm

 70% of the 

sediment was finer than 0.25 mm

Main channel

 ~0.40 mm 17% of the 

sediment in the main channel was finer than 0.25 mm

0

102030405060708090

100

1997-1999 mean fine sediment inmain channel1997-1999 mean fine sediment in eddies

% Finer Than

Grain S

0.05 0.1 0.2 
Source environments based on p

by grain size

The proportions of eddy and channel derived s

Sediment Size Class (mm)

0

100,000200,000300,000

Fine Sediment (Mg)

EddiesMain-Channel Be

Silt and Clay

(0.037-0.0625)

Very Fine Sand

(0.0625-0.125)

Fine Sand

(0.125-0.25)

Medium Sand

(0.25-0.50)

Coarse S

(0.50-2

Nearly all the silt and clay and the majority of very fine and fine sand wa

whereas the medium to coarse sand was eroded from both eddies and the 
Source environments based on p

by grain size

The proportions of eddy and channel derived s

Nearly all the silt and clay and the majority of very fine and fine sand wa

whereas the medium to coarse sand was eroded from both eddies and the 

Sediment Size Class (mm)

0

50,000

100,000150,000

Fine Sediment (Mg)

Silt and Clay

(0.037-0.0625)

Very Fine Sand

(0.0625-0.125)

Fine Sand

(0.125-0.25)

Medium Sand

(0.25-0.50)

Co

(

EddiesMain-Channe
The estimates of s in eddies pr

estimate of the accuracy of the to

data to the reach scale

 Topographic estimate = 1.0 

± 0.36 million 

 Grain-size estimate = 0.68 

± 0.08 million 

Sept. 2000 Powerplant Capacit

1996 Controlled Flood

 Topographic estimate = 0.34 

± 0.17 mill

 Grain-size estimate = 0.26 

± 0.02 million 
Conclusions

• Two independent sediment budge

techniques indicate that ~90% of sediment exported from Marble Cderived from eddy storage

• Given uncertainties in the method

considerably more than half of the Marble Canyon is stored in eddies dam conditions

• The grain size distribution of the s

in eddies is far more similar to the of the sand supplied by the Paria