Generation of Rainfall Intensity-Duration-Frequency Relationship for Rangpur City Corporation in Bangladesh

Abstract

The objective of this study is to generate Rainfall IDF relationship for Rangpur City Corporation of
Bangladesh. The common frequency analysis technique Gumbel distribution was used to develop IDF relationship from
rainfall data of this city corporation. Yearly daily maximum rainfall data for 55 years (1955-2010) from Bangladesh
Meteorological Department (BMD) was used in this study. Indian Meteorological Department (IMD) empirical reduction
formula was used to estimate short duration rainfall intensity from yearly maximum rainfall data. The parameters of the
IDF equation and constants for different return periods (2, 5, 10, 15, 20, 25, 30, 50, 75 and 100 years) were calculated
by using nonlinear regression method. The results obtained presented that in all the cases the correlation coefficient is
very high (R2=1) representing goodness of fit of the equation to estimate IDF curves of Rangpur City Corporation. It was
found that intensity of rainfall decreases with increase in rainfall duration. Further, a rainfall of any given duration will
have a larger intensity if its return period is large.