If a canal bed level is 212.0 m and the crossing drainage high flood level is 210.0 m, what type of cross-drainage structure is required________________?
Show answer Hide answer
Answer: C. syphon
Explanation
Cross drainage structures are required when an irrigation canal intersects a natural drainage stream. Here the canal bed level is higher than the drainage high flood level, allowing gravity flow. However, because drainage water must pass under pressure beneath the canal, a syphon is used. Cross drainage works include aqueducts, superpassages, syphons, and syphon aqueducts. A syphon structure forces drainage water to flow under pressure through a closed barrel beneath canals. Hydraulic grade lines determine whether pressurized syphon action is necessary for flood passage.
Civil engineers design cross drainage structures to maintain continuous irrigation and natural flood paths. Selecting the correct structure prevents canal flooding and structural washout during monsoon events. Topographical survey elevations dictate the relative alignment of canals and natural stream crossings. Option A suggests an aqueduct where drainage flows freely under the canal without pressure. Option B proposes a superpassage which carries the drainage channel above the irrigation canal. Option D specifies a syphon aqueduct used when high flood levels submerge the canal underside.
- Subject
- Engineering
- Category
- Civil Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. If D is the scour depth below the original bed level, how wide is the launching apron usually designed________________?
Show answer Hide answer
Answer: B. 1.5 D
Launching aprons are flexible stone blankets placed downstream of hydraulic structures to prevent scour damage. As high velocity flows scour river beds, the stone apron launches into the scour hole naturally. Engineering...
Q2. Cyclonic precipitation originates through the lifting of air masses caused by________________?
Show answer Hide answer
Answer: A. pressure difference
Cyclonic storms develop when contrasting warm and cold air masses create sharp atmospheric pressure gradients. Horizontal pressure differences force warm moist air masses to rise dynamically over denser cold air wedges....
Q3. How do earthen dams compare structurally to concrete gravity dams__________________?
Show answer Hide answer
Answer: D. require less skilled labour
Earthen dams are constructed primarily using locally excavated soils compacted by heavy earthmoving machinery. Unlike precision concrete gravity dams, earthen structures do not demand highly specialized formwork labor. C...
Q4. If a 10% risk of flooding is acceptable over the next 10 years, what design return period should be selected__________________?
Show answer Hide answer
Answer: C. 1/(1-0.9°10)
Flood risk probability formulas relate acceptable risk r, design life n, and return period t. The exact binomial risk equation transforms to solve for the return period t parameter. Algebraic rearrangement yields the exa...
Q5. What is the maximum discharge capacity accommodated by a rectangular crest in a Sarda-type drop structure______________?
Show answer Hide answer
Answer: C. 14 cumecs
Sarda-type drop structures are standard canal drop designs engineered for minor canal bed elevation changes. The rectangular crest configuration in standard Sarda designs accommodates discharges up to fourteen cumecs. Hy...
Q6. How is infiltration capacity defined_________________?
Show answer Hide answer
Answer: D. changes with both time and location
Infiltration capacity varies dynamically across a catchment depending on soil moisture and spatial location. Different locations possess unique soil compositions and vegetation covers that influence local infiltration ra...