This set of Irrigation Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Types of Cross Drainage Work”.
1. Which of the following CD works carry drainage over the canal?
a) Aqueduct and Syphon Aqueduct
b) Super passage and Syphon
c) Level-crossing and inlets outlets
d) Canal Syphon and Aqueduct
Explanation: In Aqueduct and Syphon Aqueduct, the canal is carried over the natural drain. In level crossing and inlet and outlets, the canal water and drainage water are allowed to intermingle with each other.
2. The canal water flows freely under gravity in which of the following CD works?
a) Aqueduct and Super passage
b) Super passage and Syphon
c) Canal Syphon and Aqueduct
d) Level-crossing and inlets outlets
Explanation: In canal syphon and syphon aqueduct, canal water flows under symphonic action. The canal and the drainage system approach each other practically at the same level in CD works like Level crossing and inlets and outlets.
3. A Super passage is the reverse of ______________
c) inlets and outlets
d) syphon Aqueduct
Explanation: In Aqueduct, the drainage water runs below the canal either freely or under symphonic action. In Super passage, the drain is taken over the canal such that the canal water runs below the drain. Similarly, a syphon is also a reverse of aqueduct syphon.
4. Which of the following statement is not correct about canal syphon?
a) FSL of the canal is much above than the bed level of the drainage trough
b) To minimize the trouble of silting, a ramp is provided at the exit
c) The canal water flows under symphonic action
d) For siphoning small discharges, barrels are adopted
Explanation: For siphoning higher discharges, horseshoe-shaped, rectangular or circular barrels are adopted. For siphoning small discharges, precast RCC pipes are adopted.
5. Which CD work is generally adopted when the drainage discharge is small and the drain crosses the canal with its bed level equal to or slightly higher than the canal FSL?
a) Syphon Aqueduct
b) Level crossing
c) Inlets and outlets
Explanation: Level crossing is generally adopted when the canal and the drainage are practically at the same level and for high flood drainage discharge but short-lived. Aqueduct or super passage is adopted when high flood drainage discharge is large.
6. The drainage water is sometimes allowed to join the canal water to augment canal supplies through a hydraulic structure is called as ________________
a) canal outlet
b) canal inlet
d) level crossing
Explanation: The structure allows the drainage water to enter the canal and get mixed with the canal water. It helps in augmenting canal supplies. It is adopted when high flood drainage discharge is small.
7. The crossing arrangement preferably made at the junction of a huge canal and a river stream carrying a short-lived high flood discharge at almost equal bed levels is a __________
a) super passage
c) level crossing
d) canal syphon
Explanation: This is a type of cross-drainage works in which the canal water and the drain get intermixed. The arrangement is generally adopted when a huge canal crosses a large torrent carrying a high short-lived flood.
8. In a syphon aqueduct provided with a pucca bottom floor, the uplift will occur on __________
a) the roof slab
b) the bottom floor
c) both the roof slab as well as the bottom floor
d) nowhere since the flow is free in the canal as well as in the drainage channel
Explanation: The uplift pressure on the floor of the aqueduct is caused due to seepage of water from the canal to the drainage and the sub-soil water table in the drainage bed. The drain bed of the aqueduct is generally depressed and provided with the pucca floor.
9. Which of the following is a disadvantage of CD works carrying the canal over the discharge?
a) The damage caused by floods is not rare
b) The canal is not open for inspection and maintenance
c) The CD works are less liable to damage than the earthwork of the canal
d) During heavy floods, the foundations are susceptible to scour or waterway of the drain may get choked
Explanation: In this arrangement, the canal is above the ground hence it is open to inspection. The damage done by light floods is rare. The CD works are less liable to damage than the earthwork of the canal when the canal passes below the drainage.
10. In which of the following arrangement, the perennial drainage discharge is advantageously used?
a) Level crossing
b) Inlets and Outlets
Explanation: In level-crossing, a regulator is provided across the drainage to control the discharge. When there are no floods the torrent regulator is kept closed and during floods, the regulator is opened so as to pass the flood discharge.
11. The number of inlets should be equal to the number of outlets.
Explanation: It is not necessary to have equal values of escaped discharge and admitted discharge. There can be fewer outlets for more number of inlets. The outlet can be combined with some other work where a separate arrangement is provided for escaping at a small extra cost.
12. Which of the following is a disadvantage of CD works carrying drainage over the canal?
a) The arrangement is generally constructed when the drain is very big as compared to the section of the canal
b) The damage caused by floods is not rare
c) The CD works are more liable to damage than the earthwork of the canal
d) The perennial canal is not open to inspection or maintenance
Explanation: The main advantage of this arrangement is that the CD works are less liable to damage than the earthwork of the canal. The major disadvantage is that the inspection road cannot be provided along the canal hence, it is not open to inspection or maintenance.
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