IRRIGATION ENGINNERING LAB (RCI6C202)

REPORT ON
“DESIGN OF CROSS DRAINAGE WORKS”

Submitted in the partial fulfilment for the award of degree of Bachelor of

Technology in Civil Engineering (2023-24)

Submitted by

3rd year Section-A

NUTAN BEERO (Regd.2101109064)

GOUTAM JENA (Regd.2101109043)

NIKESH PRADHAN (Regd.2101109062)

KANHU CHARAN SAHU (Regd.2101109049)

LINGARAJ SATAPATHY (Regd.2101109056)

PRAGYAN MAHAPATRA

(Regd.2101109068)

Under Guidance of

Asst. Pro. Uma Maheswar Rao (Guest Faculty)

Civil Engineering Department PMEC

PARALA MAHARAJA ENGINEERING COLLEGE

SITALAPALLI, BERHAMPUR

DEPARTMENT OF CIVIL ENGINEERING

1
PARALA MAHARAJA ENGINEERING COLLEGE BERHAMPUR, ODISHA

2
 CONTENT

1. Introduction................................................................................
1.1 CROSS DRAINAGE WORKS........................................................
1.2 TYPES OF CROSS DRAINAGE WORKS........................................
1.2.1 Type-1: Canal Over Drainage.................................................
1.2.2 Type-2: Drainage Over Canal.................................................
1.2.3 Type-3: Level Crossing...........................................................
1.2.4 Structures to Carry Canal Water Over a Natural
Stream....................................................................................
1.3 Selection of Suitable Site for Cross Drainage Works................
1.4 Advantages and disadvantages
1.5 Factors Which Influence the Choice...................................................
2. DESIGN OF CROSS DRAINAGE STRUCTURE..........................................
2.1 Design of Aqueduct..............................................................................
Conclusion............................................................................................

Reference 35
 CROSS - DRAINAGE WORKS:
• In an irrigation project, when the network of main canals, branch canals,
distributaries, etc. Are provided, then these canals may have to cross the
natural drainages like rivers, streams, nallahs, etc at different points within
the command area of the project.

• The crossing of the canals with such obstacle cannot be avoided. So,
suitable structures must be constructed at the crossing point for the easy
flow of water of the canal and drainage in the respective directions. These
structures are known as cross-drainage works.

Figure1. Canal crossing a natural drainage

Types of Cross-Drainages Works:

Type I (Canal passes over the drainage)

(a) Aqueduct
(b) Syphon aqueduct
Type II (Drainage passes over the irrigation canal)

(a) Super Passage

(b) Syphon Super Passage

Type III (Drainage and canal intersection each other of the same level)

(a) Level Crossing

(b) Inlet and outlet

Canal Passes Over The Drainage:

(a) Aqueduct- In this type, the canal bed level will be above the mainstream’s
High Flood Level. So the canal passes over the drainage without disturbing
the main stream.
(b) Syphon Aqueduct- In this type, the canal bed level is below the
mainstream’s High Flood Level. During the High Flood Level
(HFL), the water level will be maintained by siphonic action.
Drainage passes over the irrigation canal :
(a) Super Passage: The structure is used when the bed level of the
mainstream is above the canal supply level.

(b) Siphon Super Passage: This structure will be used when the canal water is
passed under the drainage (mainstream) through siphonic action.

Drainage and canal intersection each other of the same level:

(a) Level crossing: This type of cross drainage work will be
constructed, when an irrigation canal is taken across and through a
drain at the same level of the drain bed is called Level Crossing.

The level crossing consists of the following components:

 Crest Wall: It is provided across the drainage just at the upstream side of
the crossing point. The top level of the crest wall is kept at the full supply
level of the canal.
  Drainage Regulator: It is provided across the drainage just at the
downstream side of the crossing point. The regulator consists of adjustable
shutters at different tiers.

 Canal Regulator: It is provided across the canal just at the downstream side
of the crossing point. This regulator also consists of adjustable shutters at
different tiers.

(b) Canal Inlet and outlet: In this type of hydraulic structure, the mainstream
water will be allowed to pass through the canal network via the inlet & the
part of the water is drained as the outlet on the other side of the canal which
will allow the mainstream water to flow through the leading pipe.

Structures to carry canal water over a natural stream

Conveying a canal over a natural watercourse may be accomplished in two

ways:

1. Normal canal section is reduced to a rectangular section and carried

across the natural stream in the form of a bridge resting on piers and
foundations. This type structure is called a trough type aqueduct.
 2. Normal canal section is continued across the natural stream but the
stream section is flumed to pass through barrels or rectangular
passages. This type is called a barrel type a aqueduct.

Selection of a suitable type of cross-drainage work:

The following points should be considered while selecting the
most suitable type of cross – drainage work:

1. Relative levels and discharges

2. Performance

3. Provision of road

4. Size of drainage

5. Cost of earthwork

6. Foundation

7. Material of construction

8. Cost of construction and overall cost

9. Permissible loss of head

10.Canal alignment
Selection of site of a cross-drainage work:

The following points should be considered while selecting the site of a cross-
drainage work:

1. At the site, the drainage should cross the canal alignment at right
angles. Such a site provides good flow conditions and also the cost of
the structure is usually a minimum.

2. For economical design and construction of foundations, a firm and

strong sub-stratum should exist below the bed of the drainage at a
reasonable depth.

3. The length and height of the marginal banks and guide banks for
the drainage should be small.
4. The stream at the site should be stable and should have stable banks.

Advantages and disadvantages of cross drainage work

Advantages:

1. Facilitates Water Flow:

Cross drainage works allow water to flow from one side of an
embankment or canal to the other, preventing stagnation and
ensuring continuous flow.
2. Prevents Flooding:
By providing a passage for water to flow under or through
embankments, cross drainage works help prevent flooding,
especially during heavy rainfall or high-water levels.
3. Improves Drainage:
They can improve drainage in agricultural fields, ensuring excess
water is efficiently removed, preventing waterlogging and soil
erosion.
 4. Enhances Irrigation:
Cross drainage works enable the efficient distribution of irrigation
water across fields, ensuring uniform watering and maximizing
crop yields.
5. Aids in Transportation:
Cross drainage structures such as culverts and bridges facilitate
the passage of vehicles, pedestrians, and wildlife over waterways,
enhancing transportation networks.

Disadvantages:
1. Costly Construction:

Cross drainage works can be expensive to design and construct,

especially for large-scale projects or in challenging terrain.
2. Maintenance:

These structures require regular inspection and maintenance to

ensure their continued functionality. Neglecting maintenance can
lead to deterioration and eventual failure.

3. Environmental Impact:
Construction of cross drainage works may disrupt natural
habitats, alter water flow patterns, and impact local ecosystems,
leading to environmental concerns.
4. Sedimentation and Blockages:

Sedimentation and debris accumulation can occur within cross

drainage structures, reducing their effectiveness and necessitating
periodic clearing and desilting.
5. Risk of Failure:

Poor design, construction, or maintenance practices can lead to the

failure of cross drainage works, resulting in property damage, loss
of life, and disruption of services.
Design Considerations for Cross Drainage Works:

Step 1: - DESIGN OF DRAINAGE WATER-WAY:

(i) The wetted perimeter of the river is formed by

Lacey’s Regine Perimeter
P = 4.75√𝑄
(ii) Provide suitable no. of piers and calculate total length
of water way.
Step 2: - DESIGN OF CANAL WATER WAY:

(i) Provide 2:1 splay in contraction.

(ii)
𝐵𝑛−𝐵𝑓
Provide 3:1 splay in Expansion.

]×𝑍
𝐵𝑛−𝐵𝑓 2
Length of contraction = [

]×𝑍
1
Length of Expansion =[
2 2

Step 3: - Design of levels at different section:

Assumed the transitions the side slopes of the
canal 1.5:1

Figure 8: transition Side Slope of Canal

[1]
At section 4-4
Area of trapezium Section = (B + 1.5y) × y
Q
Velocity = V4 =
A
2
Velocity head = V 4
2g

At section 3-3
2
V3
Velocity head = 2g
Assuming that the loss of head in expansion from section
2 2
0.3 V 3−V 4
3 – 3 to section 4 – 4 is taken as, (
2g
)

At section 2-2
From section 2-2to 3-3, the trough section is constant
therefore area and velocity at 2-2 are the same as at 3-3.
But from 2- 2 to 3-3, there is a friction loss between 2-2
and 3-3 which may be computed by manning’s formula as
equal to Head loss in trough
2 2
n ×V × L
H L= 4
3
R

Where n = Rugosity coefficient whose value is

taken as 0.016
L = Length of trough (flumed portion)
 A = Area of trough section
P = Wetted perimeter
R = Hydraulic mean depth (A/P)
V = Velocity in trough (Q/A)
At section 1-1

Loss of head in contraction transition from section 1-1 to

section 2-2

( )
2 2
V 2−V 1
= 0.2 2g

Step 4: - Design of contraction & expansion transition:

Since, depth is kept constant, the transition shall be
designed on the basis of Mitra’s Hyperbolic transition
equation, given by
B n × B f Lf
Bx =
Lf Bn−x ( Bn −B f )

B n × B f Lf
Bx =
Lf Bn−x ( Bn −B f )

Example1. Design a suitable cross-drainage work, given the following

data at the crossing of a canal and drainage.
Canal: Drainage:

Full supply discharge = 32 cumecs High flood discharge = 300 cumecs

Full supply level = R.L. 213.5 High flood level = 210.0 m

Canal bed level = R.L. 212.0 High flood depth = 2.5 m

Canal bed width = 20 m General ground level = 212.5 m
Trapezoidal canal section with 1.5 H: 1 V slopes.
Canal water depth = 1.5 m

Step 1: Design of Drainage Waterway:

Lacey’s regime perimeter (P) = 4.75 √𝑄

= 4.75 √300 = 82.3 m

Let the clear span between piers be 9 m and the pier thickness be 1.5 m

Using 8 bays of 9 m each, clear waterway = 8 × 9 =

72𝑚
Using 7 piers of 1.5 m each, length occupied by piers = 7 × 1.5 = 10.5 𝑚

Total length of waterway = 72 + 10.5 = 82.5 m

Step 2: Design of Canal Waterway:

Bed width of canal = 20.0 m

Let the width be flumed to 10.0 m

Providing a splay of 2: 1 in contraction, the length of contraction transition
20−10
= ×2=10.0 m
2
Providing a splay of 3: 1 in expansion, the length of expansion transition
20−10
= ×3=15m
2

Length of the flumed rectangular portion of the canal between abutments = 82.5 m

In transitions, the side slopes of the canal section will be warped in plan
from the original slope of 1.5: 1 to vertical.

Step 3: Head loss and bed levels at different sections:

At section 4-4

Area of trapezoidal canal section = (B + 1.5 y) y

= (20 + 1.5 × 1.5) 1.5 = 22.5 × 1.5 = 33.75 m2

Velocity (V4) = Q/A

= 32/33.75 = 0.947 m/sec

2
(0.947)
Velocity head = V42 / 2g = =¿ 0.046 m
2× 9.81

R.L of bed at 4-4 = 212.0 m (given)

R.L of water surface at 4-4 = 212.0 + 1.5 = 213.5 m

R.L of TEL at 4-4 = 213.5 + 0.046 = 213.546 m

At section 3-3

Keeping the same depth of 1.5 m throughout the channel, we have bed
Width = 10 m
Area of channel = 10 × 1.5 = 15 m2

Velocity (V4) = Q/A

= 32/15 = 2.13 m/sec
 2
2 (2.13)
Velocity head = V3 / 2g = =¿ 0.232 m
2× 9.81

Assuming that the loss of head in expansion from section 3-3 to 4-4 is taken
2 2
= 0.3×( V 3−V 4 )
2g

= 0.3 [0.232 – 0.046] = 0.056 m

R.L of TEL at section 3-3 = R.L of TEL at 4-4 + loss in expansion

= 213.546 + 0.056 = 213.602 m
R.L of water surface at 3-3 = R.L of TEL at 3-3 – velocity head

= 213.602 – 0.232 = 213.370 m

R.L of bed at 3-3 = 213.370 – 1.5 = 211.87 m

At section 2-2

From section 2-2 to 3-3, the trough section is constant. Therefore, area and
velocity at 2-2 are same as at 3-3, there is a friction loss between 2-2 and 3-
3 which is given by manning’s formula equal to
2 2
n ×V × L
H L= 4
R3

where n is rugosity coefficient whose value in concrete trough may be taken

as 0.016;

L is the length of trough = 82.5 m.

Area of trough section (A)= 10×1.5=15m2

Wetted perimeter (P)= 10 + 2 ×1.5 = 13m

A 15
Hydraulic mean depth (R) = P = 13 =1.16 m
Velocity in trough = Q/A = 32/15 = 2.13 m/sec
2
H L=(0.016) × ¿ ¿

= 0.0787 m; say 0.079m

R.L of T.E.L at section 2-2 = R.L of TEL at 3-3 section + friction loss in trough

= 213.602 + 0.079 = 213.681 m

R.L of water surface at 2-2 = R.L of TEL at 2-2 section – velocity head

= 213.681 – 0.232 = 213.449 m

R.L of bed at 2-2 section = 213.449 – 1.5 = 211.949 m

At section 1-1

( )
2 2
V 2−V 1
Loss of head in contraction transition from 1-1 to 2-2 = 0.2
2g

0.2=¿

= 0.037 m
R.L of T.E.L at section 1-1 = R.L of T.E.L at 2-2 + Loss in contraction

= 213.681 + 0.037 = 213.718 m

R.L of water surface at 1-1 = R.L of T.E.L at 2-2 – velocity head

= 213.718 – 0.046 = 213.672 m

R.L of bed at 1-1 = 213.672 – 1.5 = 212. 172 m

Step 4: Design of Transitions:

(a) Contraction transition: Since the depth is kept constant, the

transition can be designed on the basis of Mitra’s method.

B n × B f Lf
Bx =
Lf Bn−x (Bn −B f )
 Where,

Bf =10m,

Bn =20m,

L f =10m

20 × 10× 10
10× 20−x ( 20−10 )

2000
¿
200−10 x

For various values of x lying between 0 to 10 m, various values of Bx are

worked out by using the above equation as:

x in meters 0 2 4 6 8 10

𝐵𝑥 =
2000
200 − 10 10.0 11.11 12.5 14.29 16.67 20.0
𝑥

The contraction transition can be plotted with these values.

(b) Expansion transition:

Where, Bf =10m, Bn =20m,

Lf =15m
B n × B f Lf
Bx =
Lf Bn−x ( Bn −B f )

20 ×10 × 15
¿
15× 20−x ( 20−10 )

3000
¿
300−10 x

For various values of x lying between 0 to 15 m, various values of 𝐵𝑥 are worked

out by using the above equation as:

𝐵𝑥
x in meters 0 2 4 6 8 10 12 14 15

300 − 10 𝑥
3000 10.0 10.71 11.54 12.5 13.64 15.0 16.67 18.75 20.0
=

Step 5: Design of Trough:

The trough shall be divided into two compartments of 5 m each and

separated by an intermediate wall of 0.3 m thickness. The inspection road
shall be carried on the top of left compartment as shown in figure below.

Figure
A freeboard of 0.6 m above the normal water depth of 1.5 m is sufficient,
and hence the bottom level of bridge slab over the left compartment can
be kept at 1.5 + 0.6 = 2.1 m above the bed level of trough. The entire
trough section can be constructed in monolithic reinforced concrete and can
be designed by usual structural methods.