Section 4: Soil and Water Conservation Engineering
Hydrology
Subtopic: Hydrograph analysis, unit hydrograph theory and application
Question Statement:
Which of the following assumptions form the theoretical basis of Sherman's Unit Hydrograph theory?
Options:
(A) Effective rainfall is uniformly distributed across the entire catchment area
(B) Effective rainfall occurs at a uniform intensity throughout the specified duration
(C) The direct runoff hydrograph reflects the principle of linear superposition
(D) Base period of direct runoff depends heavily on rainfall intensity and total storm depth
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
Unit hydrograph theory assumes:
1. Time invariance (duration of direct runoff is constant for a given rainfall duration, regardless of intensity, making Option D FALSE).
2. Linear response: Direct runoff ordinates are directly proportional to runoff volume (linear scaling and superposition: Option C is TRUE).
3. Uniform spatial and temporal distribution of effective rainfall (Options A and B are TRUE).