1 / 15

# Lecture 9: River Sediment Transport - PowerPoint PPT Presentation

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.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about ' Lecture 9: River Sediment Transport' - lavinia-vincent

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

CEM001 Hydraulic Structures, Coastal and River EngineeringRiver Engineering Section

Dr Md Rowshon Kamal

H/P: 0126627589

1

• 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

• 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

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

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

y

Using

Area

Perimeter

From

6

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

1.

If

then

2.

then

If

3.

If

then

Cohesive forces are dominant

8

Application of Ackers & White’s Formula (1973) (1973) con’t

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

b (1973) con’t

y

Dimensionless Grain Diameter

Since

then

Mobility Number

10

b (1973) con’t

y

Parameters

Mobility Number

Sediment discharge

11

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

Friction factor

Shields Parameter

N/s/m

12

Application of Engelund/Hansen’s Formula (1967) (1967) Formula

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

b (1967) Formula

y