Section 4: Soil and Water Conservation Engineering
Hydrology
Subtopic: Hydrograph analysis, unit hydrograph theory and application
Question Statement:
Which of the following fundamental assumptions underlies Sherman's Unit Hydrograph (UH) theory?
Options:
(A) Time invariance and linear response of the watershed
(B) Rainfall excess is non-uniformly distributed over the drainage basin
(C) Base time of direct runoff increases proportionally with excess rainfall depth
(D) Peak discharge is inversely proportional to effective rainfall
Answer Key:
A
Step-by-Step Solution & Explanation
The two classical tenets of Unit Hydrograph theory are:
1. **Linear response (Principle of Superposition & Proportionality)**: Direct runoff ordinates are directly proportional to the rainfall excess depth.
2. **Time invariance**: The catchment direct runoff response to a unit input remains constant irrespective of when the storm occurs.