School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

Lecture 9: River Sediment Transport

CEM001 Hydraulic Structures, Coastal and River Engineering

River Engineering Section

Dr Md Rowshon Kamal

rowshon@legendagroup.edu.my

H/P: 0126627589

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School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

Empirical formulae developed for bedload, suspended load and total sediment transport rate using laboratory and field data. They are based on hydraulic and sediment conditions – Water depth, velocity, slope and average sand diameter etc. There can be significant differences between predicted and measured sediment transport rates, WHY?

Development of Sediment Transport Formulae

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School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

These differences are due to change in:- Water temperature,- Effect of fine sediment,- Bed roughness,- Armouring, and - Inherent difficulties in measuring total sediment discharge.

Use of most appropriate formula based on the availability of conditions, experience and knowledge of the engineer.

Development of Sediment Transport Formulae con’t

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School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

1. Bedload Formula – Meyer-Peter & Müller (1948)

2/3*cS

*b )FF(8q

Critical Shields Parameter = 0.047)1( sgD

o

1sgDD

qsbWhere D is average sand diameter

2/3)047.0(81 ssb FsgDDq

Valid for D > 3.0mm

Sediment Flow Ratem3/s/m

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The Shields diagram empirically shows how the dimensionless critical shear stress required for the initiation of motion is a function of a particular form of the particle Reynolds number, Rep or Reynolds number related to the particle.

School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

Application of Meyer-Peter & Müller Formula (1948)

A river of width 40.0m, depth 4.0m and bed slope 0.00028 carries a discharge of 400m3/s. If the river boundary has a typical grain diameter, D50=10.0mm (s= 2650kg/m3), assuming a rectangular cross-section, estimate the sediment transport rate using Meyer-Peter and Műller formula.

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School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

Answer

Using 2/3)047.0(81 ssb FsgDDq

y

b

Area 20.1600.40.40 mbyA

Perimeter mbyP 0.480.400.422

)1()1()1(00

sD

RS

sgD

gRS

sgDF os

From

0566.0)65.1(01.0

00028.0333.3

sF

2/3047.00566.08165.201.081.901.0 sbq

mPAR 333.3/

msmqsb //100.3 356

School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

2. Total Sediment Transport Load – Ackers & White’s Formula (1973)

Dimensionless Grain Diameter

3/1

2

1)(

sgr

gDD

Mobility Number

n

ms

n

grDD

V

gD

uF

1

*

10log321)(

Flow velocity

Hydraulic mean depth

n

m

m

gr

grs u

V

D

qD

A

FCq

*

1Sediment Flow Ratem3/s/m

Flow discharge

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School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

Total Sediment Transport Load – Ackers & White’s Formula (1973) con’t

60grDIf

025.0

17.0

78.1

0

C

A

m

n

gr

then

601 grDIf then

46.3)(log98.0log79.2log

/23.014.0

/83.667.1

log56.01

2

grgr

grgr

gr

gr

DDC

DA

Dm

Dn

If then1grD Cohesive forces are dominant

1.

2.

3.

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School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

Application of Ackers & White’s Formula (1973)

A river of width 40.0m, depth 4.0m and bed slope 0.00028 carries a discharge of 400m3/s. If the river boundary has a typical grain diameter, D50=10.0mm (s= 2650kg/m3), assuming a rectangular cross-section, estimate the sediment transport rate using Ackers and White’s formula.

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School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

Answery

b

8.231

)1014.1(

165.281.901.0

1)(3/1

26

31

2

s

gr

gDDDimensionless Grain

Diameter

Since 60grD

025.0

17.0

78.1

0

C

A

m

n

gr

then

Mobility Number

n

ms

n

grDD

V

gD

uF

1

*

10log321)(

010*

10log321)(

DD

V

gD

uF

ms

gr

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School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

Answer con’ty

b

mR

mP

mA

333.3

0.48

0.160 2

smgRSu

mbAD

smAQV

m

/0957.0

0.4/

/5.2/

0*

305.0

01.0

410log32

5.2

65.101.081.9

1

grFMobility Number

Parameters

n

m

m

gr

grs u

V

D

Dq

A

FCq

*

1Sediment discharge

msmqs //102.44

01.0)40/400(1

17.0

3050.0025.0 34

78.1

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School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

3. Total Sediment Transport Load – Engelund/Hansen’s (1967) Formula

2/5/ 1.0 f

2/ 2

V

gSyf Friction factor

2/1

3

gDq s

s

t

Ds )(

Shields Parameter

350/

2/5

)1(1.0

Dsgf

q st Sediment transport load

N/s/m

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School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

Application of Engelund/Hansen’s Formula (1967)

A river of width 40.0m, depth 4.0m and bed slope 0.00028 carries a discharge of 400m3/s. If the river boundary has a typical grain diameter, D50=10.0mm (s= 2650kg/m3), assuming a rectangular cross-section, estimate the sediment transport rate using Engelund/Hansen’s formula.

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School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

Answery

b

350

2/5

1'

1.0Dsg

fq st

32

/ 1052.35.2

0.400028.081.92

f

056.0 sF

33

2/5

01.065.181.981.9265010516.3

056.01.0

tq

msNqt //21.2

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School of Civil Engineering/Linton School of Computing, Information Technology & Engineering

Thank You

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