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