Question

Given below are five statements about floods:
(A) Floods are exceedingly complex natural events. They are resultant of a number of component parameters and are therefore very difficult to model them analytically.
(B) In the regions having same climatological characteristics, if the available flood data are quite insufficient, the enveloping curve technique can be used to develop a relationship between the minimum flood flow and drainage area.
(C) For design purposes, extreme rainfall situations are used to obtain the design storm.
(D) The rational formula is found to be suitable for a peak flow prediction in small catchments upto 75 km\(^2\) in an area.
(E) The rational formula assumes a homogeneous catchment surface.
Choose the correct answer from the options given below:

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

Hint:

Look for a swapped word (minimum/maximum) and an altered catchment area limit among the five statements.

Answer 1

The Correct Option is A

Step 1: Two of the five statements contain a single altered fact; spot them first.
Step 2: Statement (B) talks about the enveloping curve linking area to the $\text{minimum}$ flood flow. The enveloping curve method is actually built from the highest recorded floods, so it should read $\text{maximum}$ flood flow. This makes (B) false.
Step 3: Statement (D) claims the rational formula works up to $75 \text{ km}^2$. The accepted upper limit in practice is closer to $50 \text{ km}^2$, so (D) is false.
Step 4: The remaining statements (A), (C) and (E) all describe accepted facts: floods are multi parameter and hard to model exactly, design storms come from extreme rainfall, and the rational formula assumes a homogeneous catchment.
\[\boxed{\text{Answer: (A), (C) and (E) only}}\]