Question

An instantaneous unit hydrograph is assumed to have the duration of rainfall occurrence as:

• A. 1 hour
• B. 0.5 hour
• C. 0.1 hour
• D. Zero hour

Hint:

The Instantaneous Unit Hydrograph (IUH) is a powerful theoretical tool in hydrology. It represents the impulse response of a catchment. All other hydrographs for any rainfall duration can be derived from the IUH through convolution.

Answer 1

The Correct Option is D

Step 1: Define an Instantaneous Unit Hydrograph (IUH). An IUH models a watershed's reaction to 1 cm of effective rainfall applied instantaneously across the entire catchment.
Step 2: Determine the duration of rainfall for an IUH. The term "instantaneously" signifies a rainfall event of zero duration. Thus, the duration of rainfall occurrence is considered negligible. The IUH is a theoretical construct developed by reducing the unit hydrograph's duration to zero.