Question

Consider the following statements about H-flumes used for runoff measurement:

(A) H-flumes are well suited for runoff measurement as they have a high capacity and are accurate at different rates of flow.
(B) They are also well suited where sediment sampling of the runoff is done using automatic silt samplers.
(C) The H-flume is useful for flows ranging from 0.009 to 0.85 cumec.
(D) For smaller and greater flows the dimensions of the H-flume are modified and are known as HS flumes for smaller flows and HL flumes for larger flows.
(E) H-flumes need not require calibration and the rating tables are to be used for measuring discharges.

Choose the correct answer from the options given below:

• A. (A), (B), (C) and (D) only.
• B. (B), (C), (D) and (E) only.
• C. (A), (B), (D) and (E) only
• D. (A), (C), (D) and (E) only.

Hint:

Ask yourself where a rating table comes from in the first place, that alone tells you whether a flume truly skips calibration.

Answer 1

The Correct Option is A

Step 1: The H-flume is a widely used self-cleaning runoff measuring structure with a converging, near vertical throat shape, and its main advantages are exactly what statement (A) describes, it handles a wide range of flows with good accuracy and reasonably high capacity. This is correct.

Step 2: The narrow bottom and steep sides of the H-flume let sediment pass through freely instead of settling, which is why it works well with automatic silt or sediment samplers placed at the outlet, matching statement (B). This is correct.

Step 3: Standard H-flume sizes are built to cover a broad discharge range, and the figure quoted, about 0.009 to 0.85 cubic metre per second, falls within the documented capacity range for these flumes, so statement (C) is correct.

Step 4: When the standard H-flume size cannot handle unusually small or unusually large flows, its dimensions are scaled and given separate names, HS flumes for the smaller-flow version and HL flumes for the larger-flow version. This matches statement (D), which is correct.

Step 5: Statement (E) says H-flumes do not need calibration yet rating tables are used for discharge. This is self-contradictory, rating tables themselves are built from careful calibration of head against discharge for each flume size. So the flumes do require calibration, and statement (E) is incorrect.

Step 6: With (A), (B), (C) and (D) correct and (E) wrong, the right combination is (A), (B), (C) and (D) only.