Section 4: Soil and Water Conservation Engineering
Hydrology and Runoff
Subtopic: Hydrograph Analysis and Watershed Routing
Question Statement:
A Unit Hydrograph (UH) of duration $D$ is the direct runoff hydrograph produced by:
Options:
(A) Unit depth ($1\text{ cm}$ or $1\text{ mm}$) of direct runoff resulting from an excess rainfall occurring uniformly over the catchment at a constant rate for duration $D$
(B) $1\text{ m}^3/\text{s}$ peak discharge
(C) $1\text{ cm}$ of gross rainfall regardless of infiltration
(D) Rainfall of 1 hour duration
Answer Key:
A
Step-by-Step Solution & Explanation
Unit hydrograph represents direct runoff resulting from exactly $1\text{ cm}$ (or $1\text{ mm}$ in modern SI units) of effective/excess rainfall generated uniformly over the catchment in duration $D$.