Given below are two statements:
Statement (I): In Gridiron drainage system, laterals are provided on both sides of mains.
Statement (II): The Gridiron drainage system is adopted when the land is practically level or where the land slopes away from the sub-mains on one side and when the entire area has to be drained.
In light of the above statements, choose the most appropriate answer from the options given below.
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To remember subsurface drainage layouts:
- Gridiron: Laterals enter the main from one side only (best for flat/unidirectional slopes).
- Herringbone: Laterals enter the main from both sides at an angle (best for central valley depressions).
Both Statement (I) and Statement (II) are correct.
Both Statement (I) and Statement (II) are incorrect.
Statement (I) is correct but Statement (II) is incorrect.
Statement (I) is incorrect but Statement (II) is correct.
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The Correct Option isD
Solution and Explanation
Step 1: Understanding the Concept:
Subsurface drainage systems are designed to remove excess groundwater from the crop root zone using a network of buried pipes (laterals, sub-mains, and mains).
The layout of these pipes is chosen based on the topography, slope, and size of the field to ensure efficient drainage. Step 2: Detailed Explanation:
Let us analyze both statements based on drainage design principles:
- Statement (I): In a Gridiron drainage layout, laterals enter the sub-main or main drain from only one side, running parallel to each other.
This minimizes the total length of sub-main lines and avoids unnecessary double-drainage at the junctions.
A layout where laterals enter the main line from both sides at an angle is called a Herringbone drainage system.
Therefore, Statement (I) is incorrect.
- Statement (II): The Gridiron system is highly efficient and is adopted when the field topography is flat or has a uniform, unidirectional slope.
In this layout, the sub-main is placed along the upper boundary of the field, and the laterals are aligned in the direction of the slope to drain the entire area uniformly.
Therefore, Statement (II) is correct.
Since Statement (I) is incorrect and Statement (II) is correct, option (D) is the correct choice. Step 2: Final Answer:
Statement (I) is incorrect but Statement (II) is correct.
