Basic rainfall descriptors Pick the correct set of definitions relating to rainfall characteristics.
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AIntensity: the rate at which rain falls (depth per unit time).
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BDuration: the length of time for which rain falls at the specified intensity.
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CFrequency: the number of times a given event (or intensity) occurs in a stated period.
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DAll of the above
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ENone of these
Answer
Correct Answer: All of the above
Explanation
Introduction / Context:Hydrologic design uses three basic rainfall descriptors: intensity, duration, and frequency. Understanding these terms underpins IDF (Intensity–Duration–Frequency) analysis and stormwater design.
Given Data / Assumptions:
- Standard meteorological definitions.
- Frequency often expressed via return period (e.g., 10-year event).
Concept / Approach:Intensity is a rate (e.g., mm/h), duration is the time span over which that intensity is considered, and frequency/return period describes how often events of that magnitude are expected statistically.
Step-by-Step Solution:
State intensity definition clearly (depth/time).State duration as time length of rainfall occurrence.State frequency as occurrence rate or probability over time.Verification / Alternative check:These form the axes and curves of IDF relationships used in drainage sizing and flood estimation.
Why Other Options Are Wrong:Options a–c are individually correct; thus option d (“All of the above”) is the comprehensive correct answer.
Common Pitfalls:Confusing frequency with duration or interpreting return period deterministically rather than probabilistically.
Final Answer:All of the above