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Colorado River in Grand Canyon. Colorado River in Grand Canyon. Fine sediment leads to substantial attenuation along the beam path Fines are mostly clay in the this river. Backscatter (dB). Distance along beam (m). Colorado River in Grand Canyon. Sand sizes influence the backscatter level - PowerPoint PPT Presentation
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Colorado River in Grand Canyon
Colorado River in Grand Canyon
0
10
20
30
40
50
60
70
80
90
0 5 10 15 20 25
slant range, R (m)
FCB
(dB)
Sand concentrations all < 10 mg/L
silt/clay ~ 5,000 mg/L
silt/clay ~ 2,000 mg/L
silt/clay ~ 600 mg/L
silt/clay ~ 100 mg/L
Back
scat
ter (
dB)
Fine sediment leads to substantial attenuation along the beam path
Fines are mostly clay in the this river
Distance along beam (m)
Colorado River in Grand Canyon
40
50
60
70
80
90
100
0 5 10 15 20 25
slant range, R (m)
FCB
(dB)
Silt/clay concentrations all < 100 mg/L
sand ~ 10 mg/L
sand ~ 50 mg/L
sand ~ 600 mg/Lsand ~ 200 mg/L
Back
scat
ter (
dB)
Sand sizes influence the backscatter level
Suspended sand is typically ~100 µm
Distance along beam (m)
y = 0.076x - 4.197R2 = 0.932
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
60 65 70 75 80 85 90 95 100
SCB (dB)
log
10[S
SC
, san
d]
Field calibrations
y = 1345.728xR2 = 0.996
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000
0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
Sediment attenuation (dB/m)
SS
C, s
ilt-a
nd-c
lay
(mg/
L)
Fines SSC correlates with attenuation
Sand SSC correlates with backscatter
Backscatter (dB)
Scattering theory
1E-05
1E-04
1E-03
1E-02
1E-01
1E+00
1E+01
1E+02
1E+03
1E+04
1 10 100 1000
Particle diameter (um)
Bac
ksca
tter
1.E-05
1.E-04
1.E-03
1.E-02
Atte
nuat
ion
Backscatter
Attenuation
sandsilt-and-clay
1000 kHz frequencyNo
t typ
ically
in
susp
ensio
n in
rive
rs
Sacramento River and SF Bay
Calibrate ADV backscatter to LISST concentration
00:00 06:00 12:00 18:00 00:00 06:00 12:000
0.01
0.02
0.03
0.04
0.05
0.06
0.07
Ero
sion
/dep
ositi
on ra
te
00:00 06:00 12:00 18:00 00:00 06:00 12:00
7
7.2
7.4
7.6
7.8
8
Wat
er le
vel (
m)
Water levelErosionDeposition
Compute turbulent sediment fluxes from ADV velocity and calibrated backscatter