Question

Given below are two statements :
Statement (I) : Fan shaped catchment give high peak and narrow hydrograph.
Statement (II) : Elongated catchment give broad and low peaked hydrograph.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are true.
• B. Both Statement (I) and Statement (II) are false.
• C. Statement (I) is true but Statement (II) is false.
• D. Statement (I) is false but Statement (II) is true.

Hint:

To visualize this:
- Fan-shaped Circular: All water arrives at the outlet at the same time \(\rightarrow\) High peak, fast response.
- Elongated Long: Water arrives in sequence over time \(\rightarrow\) Low peak, slow response.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The shape of a catchment (watershed) significantly influences the run-off response and the shape of the resulting storm hydrograph.
Catchment shape determines how runoff from different parts of the basin is distributed in time as it travels to the outlet.

Step 2: Detailed Explanation:
Let us analyze both statements:
- Statement (I): "Fan-shaped catchment gives a high peak and narrow hydrograph."
This statement is true. A fan-shaped (or circular) catchment has tributaries of nearly equal lengths that converge toward a central point.
When a uniform storm occurs over the catchment, runoff from various parts of the watershed reaches the outlet at nearly the same time.
This concentration of flow produces a sharp, high peak discharge and a narrow hydrograph with a short base duration.
- Statement (II): "Elongated catchment gives a broad and low peaked hydrograph."
This statement is true. An elongated catchment has a long main channel with tributaries of varying lengths.
Runoff from areas near the outlet exits quickly, while runoff from distant headwaters takes much longer to reach the outlet.
This dispersion of travel times spreads the runoff out over a longer period, resulting in a broader hydrograph with a lower, flatter peak.
Thus, both Statement (I) and Statement (II) are true.

Step 3: Final Answer:
The correct option is (A).