Lecture 9: River Sediment Transport
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Lecture 9: River Sediment Transport CEM001 Hydraulic Structures, Coastal and River Engineering River Engineering Section. Dr Md Rowshon Kamal [email protected] H/P: 0126627589. 1. Development of Sediment Transport Formulae.

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Lecture 9: River Sediment Transport

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Lecture 9 river sediment transport

Lecture 9: River Sediment Transport

CEM001 Hydraulic Structures, Coastal and River EngineeringRiver Engineering Section

Dr Md Rowshon Kamal

[email protected]

H/P: 0126627589

1


Lecture 9 river sediment transport

Development of Sediment Transport Formulae

  • 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?

2


Lecture 9 river sediment transport

Development of Sediment Transport Formulae con’t

  • 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.

3


Lecture 9 river sediment transport

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

Valid for D > 3.0mm

Where D is average sand diameter

Critical Shields Parameter = 0.047

Sediment Flow Rate

m3/s/m

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.

4


Lecture 9 river sediment transport

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.

5


Lecture 9 river sediment transport

b

y

Answer

Using

Area

Perimeter

From

6


Lecture 9 river sediment transport

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

Dimensionless Grain Diameter

Flow velocity

Mobility Number

Hydraulic mean depth

Sediment Flow Rate

m3/s/m

Flow discharge

7


Lecture 9 river sediment transport

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

1.

If

then

2.

then

If

3.

If

then

Cohesive forces are dominant

8


Lecture 9 river sediment transport

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.

9


Lecture 9 river sediment transport

b

y

Answer

Dimensionless Grain Diameter

Since

then

Mobility Number

10


Lecture 9 river sediment transport

b

y

Answer con’t

Parameters

Mobility Number

Sediment discharge

11


Lecture 9 river sediment transport

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

Friction factor

Shields Parameter

N/s/m

Sediment transport load

12


Lecture 9 river sediment transport

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.

13


Lecture 9 river sediment transport

b

y

Answer

14


Thank you

Thank You

15


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