Section 4: Soil and Water Conservation Engineering
Hydrology
Subtopic: Drought and its classification
Question Statement:
Hydrology: Hydrological cycle and measurement of its components; meteorological parameters and their measurement; analysis of precipitation data; runoff estimation; hydrograph analysis, unit hydrograph theory and application; stream flow measurement; flood routing, hydrological reservoir and channel routing, Infiltration – indices and equations, drought and its classification.
A soil conservation structure has an expected life of 10 years and is designed for a flood magnitude of return period 50 years. The risk of this hydrologic design in percentage (rounded to 2 decimals) is ______.
Official Answer Key:
18.00 to 18.40
Step-by-Step Solution & Explanation
Hydrologic risk (probability that the design flood is exceeded at least once during the structure's life):
R = 1 − (1 − 1/T)ⁿ, with T = 50 years, n = 10 years.
R = 1 − (1 − 0.02)¹⁰ = 1 − (0.98)¹⁰ = 1 − 0.8171 = 0.1829 = 18.29%. Answer: within 18.00–18.40.
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