CROSS-DRAINAGE WORKS

Aaryan Raut 2111001

Group ID : 10
Fasil Firos 2111013
Mushk Sheikh 2111016
Freida Sequeira 2221004
 INTRODUCTION
Cross-drainage works are engineering structures designed
where a canal or irrigation channel intersects a natural
stream or drainage system, such as a river or nalla. These
structures are crucial when both water flows need to
coexist without interference, often at different levels or
directions. Their primary purpose is to maintain the
natural flow of water unobstructed while ensuring that
the infrastructure—whether it is a canal, road, or
railway—remains protected and functional. By enabling
both systems to operate seamlessly, cross-drainage works
prevent disruptions and safeguard the surrounding area
from flooding or erosion.
 Importance of Cross Drainage Work
1.Uninterrupted Flow of Water: They ensure natural streams, rivers, or drainage systems
continue to flow without obstruction, even when intersecting with roads, railways, canals, or
other infrastructure.
2.Prevention of Flooding and Erosion: By directing water safely across or beneath the
infrastructure, they help prevent water from accumulating, which could lead to flooding,
erosion, or structural damage.
3.Protection of Infrastructure: These structures safeguard roads, railways, canals, and
other constructions from water damage, extending their longevity and reducing maintenance
costs.
4.Efficient Irrigation and Water Utilization: In agricultural regions, cross-drainage works
support irrigation systems by enabling canals and drainage channels to coexist seamlessly.
5.Environmental and Urban Development Harmony: They maintain a balance between
human infrastructure and the natural environment, ensuring urban expansion doesn't disrupt
ecosystems.
 Types of Cross Drainage Works

Type I (Irrigation canal passes over the drainage)

(a) Aqueduct
(b) Siphon Aqueduct

Type II (Drainage passes over the irrigation canal)

(a) Super passage
(b) Siphon super passage

Type III (Drainage and canal intersection each other of the same level)
(a) Level crossing
(b) Inlet and outlet
 Type-I Irrigation canal Passes over the Drainage

◦ Aqueduct
◦ The hydraulic structure in which the
irrigation canal is taken over the drainage
(such as river, stream etc..) is known as
aqueduct. This structure is suitable when
bed level of canal is above the highest
flood level of drainage. In this case, the
drainage water passes clearly below the
canal.
 Siphon Aqueduct

In a hydraulic structure where the

canal is taken over the drainage, but
the drainage water cannot pass clearly
below the canal. It flows under
siphonic action. So, it is known as
siphon aqueduct. This structure is
suitable when the bed level of canal is
below the highest flood level.
Type-II Drainage Passes Over the irrigation Canal.
Super Passage
The hydraulic structure in
which the drainage is taken
over the irrigation canal is
known as super passage. The
structure is suitable when the
bed level of drainage is above
the full supply level of the
canal. The water of the canal
passes clearly below the
drainage.
 Siphon Super Passage
The hydraulic structure in
which the drainage is taken
over the irrigation canal, but
the canal water passes below
the drainage under siphonic
action is known as siphon
super passage. This structure
is suitable when the bed level
of drainage is below the full
supply level of the canal.
Type III Drainage and Canal Intersect each other at the same
level

Level Crossings
When the bed level of canal and the stream are
approximately the same and quality of water in canal and
stream is not much different, the cross drainage work
constructed is called level crossing where water of canal and
stream is allowed to mix. With the help of regulators both in
canal and stream, water is disposed through canal and stream
in required quantity.
Level crossing consists of following components
(i) crest wall
(ii) (ii) Stream regulator
(iii) (iii) Canal regulator.
 SUITABILITY FOR CROSS DRAINAGE WORK
•Relative Levels of Canal and Drainage:
If the canal bed is higher than the drainage bed, an aqueduct is suitable.
If the drainage bed is higher than the canal bed, a syphon aqueduct or super passage
may be used.
If both are at the same level, a level crossing is appropriate.

•Discharge Capacity:
The volume of water in both the canal and the drainage stream influences the design. For
high discharges, robust structures like aqueducts or syphon aqueducts are preferred.

•Site Conditions:
Soil type, topography, and geological stability play a role in selecting the structure. For
example, areas with weak soil may require additional reinforcement.
•Economic Feasibility:
The cost of construction and maintenance is a critical factor. Simpler
structures like culverts are chosen for smaller discharges to keep costs
low.

•Hydraulic Considerations:
The velocity and flow characteristics of both the canal and the drainage
stream are analyzed to ensure smooth water passage without turbulence
or erosion.

•Environmental Impact:
The structure should minimize disruption to the natural ecosystem and
avoid waterlogging or habitat destruction
 Design of Bank Connections
◦ Two sets of wings are required in aqueducts and syphon-aqueducts. These are:
◦ Canal wings or Land wings
◦ Drainage Wings or Water Wings
◦ Canal Wings: These wings provide a strong connection between masonary or concrete
sides of a canal trough and earthen canal banks. These wings are generally warped in plan
so as to change the canal section from trapezoidal to rectangular. They should be
extended upto the end of splay. These wings may be designed as retaining walls for
maximum differential earth pressure likely to come on them with no water in the canal.
The foundations of these wings should not be left on filled earth. They should be taken
deep enough to give safe creep length.
 Uplift Pressure on the Underside of the trough or
the Barrel Roof
◦ Uplift Pressure on the Barrel Roof
◦ The amount of the uplift pressure exerted by the drain water on the roof of
the culvert can be evaluated by drawing the hydraulic Gradient line (H.G).
◦ The uplift pressure at any point under the roof of the culvert will be equal to
the vertical ordinate between hydraulic gradient line and the underside of the
canal trough at that point From the uplift diagram it is very evident that the
maximum uplift occurs at the upstream end point near the entry. The slab
thickness should be designed to withstand this maximum uplift.
 Uplift Pressure on the Underside of the trough or
the Barrel Roof
◦ The floor of the aqueduct or siphon is subjected to uplift due to two cases:
◦ (a) Uplift due to Water-Table: This force acts where the bottom floor is depressed
below the drainage bed, especially in syphon aqueducts.
◦ The maximum uplift under the worst condition would occur when there is no water
flowing in the drain and the watertable has risen up to the drainage bed. The maximum
net uplift in such case would be equal to the difference in level between the drainage bed
and the bottom of the floor.
 Uplift Pressure on the Underside of the trough or
the Barrel Roof
◦ (b) Uplift Pressure due to Seepage of water from the canal to the drainage.
◦ The maximum uplift due to this seepage occurs when the canal is running full and there is no
water in the drain. The computation of this uplift due to this seepage occurs when the canal is
running full and there is no water in the drain. The computation of this uplift, exerted by the water
seeping from the canal on the bottom of the floor, is very complex and difficult, due to the fact
that the flow takes place in three dimensional flow net. The flow cannot be approximated to a two
dimensional flow, as there is no typical place across which the flow is practically two
dimensional. Hence, for smaller works, Beligh’s Creep theory may be used for assessing the
seepage pressure, But for larger works, the uplift pressure must be checked by model studies.
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