Plotted the Intensity-Duration-Frequency (IDF) curves by first estimating annual maximum intensity for 1-h, 2-h, 4-h, 8-h, 12-h and 24-h duration storms of return periods 2-, 5-, 10-, 50- and 100-years. A equation is also fitted to that plot.
Rainfall_Data.xls contains hourly rainfall data (in mm) for 99 calendar years.
Intensity-Duration-Frequency (IDF) curves describe the relationship between rainfall intensity, rainfall duration, and return period. IDF curves are commonly used in the design of hydrologic, hydraulic, and water resource systems. IDF curves are obtained through frequency analysis of rainfall observations.
First and foremost, task is to find the annual maximum rainfall intensity for specific durations (or the annual maximum rainfall depth over the specific durations). Durations used for the design applications are: 1-hr, 2-hr,4-hr, 8-hr, 12-hr, and 24-hr.
The development of IDF curves requires that a frequency analysis be performed for each set of annual maxima, one each associated with each rain duration. The basic objective of each frequency analysis is to determine the exceedance probability distribution function of rain intensity for each duration. For the frequency analysis fit a theoretical Extreme Value (EV) distribution (e.g., Gumbel Type I) to the observations and then use the theoretical distribution to estimate the rainfall events associated with given exceedance probabilities.
Results and plotted graphs are in 170492.pdf file.