muet 15ee batch tecaher : fida hussain sidiqui topic : • Sediment Transport • The Earthen Canal Section • Lined Canals & Its Advantages

1. Water Resources &
Irrigation Engineering
Engr. Fida Hussain Siddiqui
Lecturer @ Civil Engineering Department, M.U.E.T Jamshoro
15-EE

2. A Glimpse..!!
• Sediment Transport
• The Earthen Canal Section
• Lined Canals & Its Advantages

3. Sediment Transport
• Sediments may be defined as fragmented solid particles, which
are transported by fluid.
• Water flowing in a canal always tries to scour its surface.
• Boundary materials, which may be silt, gravel or even larger
material are first detached from the bed or bank and swept
downstream by the flowing water.
• This phenomenon is called, sediment transportation.

4. Sediment Transport
• Study of sediment transport is quite necessary in canal design.
• As it helps in achieving the regime of channel.
• Affects the design carrying capacity of channel.

5. Classification of Sediment Load
1. Suspended Load:
It is carried in the fluid away from the bed.
Being smaller in size and light weight.
Moves with increasing velocities.
2. Bed Load:
It moves on or near the bed.
Due to being heavy and larger size.
Moves forward by rolling and sliding.
Total load = Suspended load + Bed load

6. Channel / River Patterns
• Straight Channel
• Water moves parallel to the channel banks
• Sinuosity varies from 1 – 1.05
• Meandering Channel
• Follow the sinuous path
• Braided Channel
• Channels flows in more than one sub-channels, because the
natural topography does not match the hydraulics conditions of
a river.

7. Sinuosity
• The meander ratio or sinuosity index is the ratio of actual
length along a meandering river (Lm) to the straight distance
S between the end points (AB).
• It is an indication of quantification of meandering.
• For a straight river course this ratio is equal to unity. A ratio
varying from 1 to 1.5 defines the river course as sinuous.

8. Geometric features of meander
Meander
Belt

9. Straight Channel

10. Meandering Channel

11. Braided Channel

12. Lined / Unlined Canals
There are two types of canals sections
• Unlined channels, most of our main irrigation canals are
unlined/earthen canals which cause seepage and result in losses
and raising in the water table of the adjoining area.
• Lined channels, lined with RC, PCC, Bricks, Stones etc., to
minimize the seepage losses and increase the efficiency of the
system.

13. Lined Canals & its Advantages
• A canal whose prism has been protected with impervious material
mainly to stop seepage through it, is called a lined canal. The
additional investment in providing lining would be justified
economically, if the cost of the lining can be repaid in monetary
benefits during the life of the lining.

14. Contd.
• Although the initial cost of 'construction of a lined canal is much
greater than that of an unlined canal, the advantages of lining are
extremely significant, that construction of a canal with lining
becomes financially viable.
• The various physical benefits expected from the lining of a canal
are given below:
• Lining helps conservation of water
• Lining helps control of water-logging
• Lining increases the discharge carrying capacity of canal
• Lining prevents failure of canals
• Lining reduces project's total cost
• Lining reduces maintenance cost

15. The Earthen Canal Section
• The essential consideration, for design of the components of canal
section are that the canal prism should have adequate capacity
with stable side slopes, wide berms, sufficient free board over the
full supply level, strong banks and spacious service roads.

16. Section View

17. The Earthen Canal Section’s Components
• Side Slopes
• Free Board
• Berms
• Canal Banks and Service Roads
• Spoil Banks

18. Side Slopes
• Side slopes of the canal prism should remain stable under various
operating conditions, i.e. these should be stable when the canal is
empty; when the canal is running full; or when the canal is
abruptly closed or under the rapid draw down condition.
• Moreover, the canal slopes should also remain safe under 'with! or
without earthquake forces. These forces become important in
case of large capacity canals.

19. Free Board
• Free board is the vertical distance maintained between the full
supply level of the canal and the berms.
• The size of the free board depends upon such factors as canal
size, location, water surface fluctuations caused by regulators
along the canal, wind action etc.

20. Free Board
Following Table show the free boards usually provided for canals of various
capacities in Pakistan.

21. Free Board

22. Berms
• The berms of a canal are the strips of land left between the edge of the
final silted water canal section and the inner toe of the canal banks.
• They are meant to ensure the safety of banks against any side erosion
due to high velocity currents on the side of a canal.
• Under sudden draw down condition during the operation of a canal the
side slopes may tend to slough in.
• A big slip may endanger the banks and may ultimately result in canal
breach.
• The berms of appropriate width, therefore, afford safety against canal
breaches.
• They also permit future widening of the canal section without shifting of
the canal banks.

23. Berm
• The berm width is usually kept between 2D to 3D, where D is the
designed water depth.

25. The Section..

26. Canal Banks and Service Roads
• The banks of the canal should be strong enough to withstand the
pressure of water in the canal.
• The top of banks are usually used for service roads. Service roads
are usually 3 to 8 metres wide and are provided on one side only.
• On important and large capacity canals, service roads are
provided on both sides.

28. Spoil Banks
• The material excavated from the canal prism, if in excess of the
requirement of the banks, should be deposited neatly in what are
called spoil banks.
• The spoil banks should have stable slopes.
• For practical considerations, the side slopes usually range from
1.5 : I to 3 : I and the height of the bank from 5 metres to 10
metres.