Intensity-Duration-Frequency curves on short duration storms

The curves intensity-duration-frequency (IDF) are used in hydrology to characterize the intensity of rainfall according to its duration and its return period. These curves are of great importance in the planning of water resources, as well as for the design of hydraulic works. The empirical equation proposed by Sherman in 1931, is still used today. The parameters of this equation are estimated by least squares or optimization methods. However, the values obtained to parameterize this equation do not have a physical sense. Using data from 523 monitored storms every minute, IDF curves are obtained. The results show that the parameter that adjusts the scale factor of the Sherman formula is a function of the typical duration storms. It is concluded that the scale factor must be obtained from physical relationships and not from analytical methods. It is recommended that traditionally calculated IDF curves be reviewed and typical storm durations compared with the scale factor of Sherman's formula.