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Frequency Factor which varies between 5 to 30 according to rainfall duration is a function of recurrence interval (T) and the coefficient of skew (Cs). It is used in hydrologic frequency analysis to estimate extreme events.
The calculator uses the formula:
Where:
Explanation: The formula calculates the frequency factor by normalizing the difference between the Z series value and the mean of Z variates using the standard deviation.
Details: Accurate frequency factor calculation is crucial for hydrologic modeling and predicting extreme weather events with specific recurrence intervals. It helps in designing infrastructure that can withstand rare but severe hydrological events.
Tips: Enter the Z series value for the desired recurrence interval, the mean of Z variates, and the standard deviation of the Z variate sample. All values must be valid numbers, and standard deviation must be greater than zero.
Q1: What is the typical range of frequency factor values?
A: Frequency factor typically ranges between 5 to 30 depending on rainfall duration and other hydrological factors.
Q2: How is the Z series determined for different recurrence intervals?
A: The Z series is derived from statistical analysis of historical hydrological data using probability distributions like Log-Pearson Type III.
Q3: What does a higher frequency factor indicate?
A: A higher frequency factor indicates a more extreme event with a longer recurrence interval.
Q4: Can this calculator be used for all types of hydrological events?
A: This calculator is specifically designed for frequency analysis using the Z series approach in hydrological modeling.
Q5: How accurate are frequency factor calculations?
A: Accuracy depends on the quality of input data and the appropriateness of the statistical model used for the specific hydrological context.