Effect of discretisation on extreme rainfall analysis: A study of Jaipur city in India

Abstract

A location-based evaluation of the effect of discretisation on extreme rainfall estimates has been reported in the present study using the hourly rainfall records. This analysis aims to develop a correction model to find rainfall correction factor (RCF) for the metro city, Jaipur in the state of Rajasthan, India.  Further, the study addressed the effect of clock hour correction factor (CHCF) on extreme rainfall recorded in the discrete-time interval and compared with the corresponding value suggested by IS 5542-2003. The CHCF was computed using annual maxima series (AMS), and peak-over-threshold (POT) approaches in deriving the rainfall values. The hourly rainfall measurement used to evaluate the differences in extremes evaluated using sliding window (SW) aggregation and fixed window (FW) observation for 24-hour maximum rainfall depth. The extreme value analysis was performed, and the model was checked for its reliability. The peak rainfall depth-duration-frequency curve was plotted for observed 24-hr and 1-hr duration peak rainfall depth. The 1-hour duration peak rainfall was computed for 25-, 50- and 100-year return period using the conversion factor given in Flood estimation report (sub-zone 1b) and compared with the present study results. The peak rainfall for the different return periods for 1-hour and 24-hour duration was worked out which will be useful to the design engineer as per the recent guidelines of the Central Public Health and Environmental Engineering Organization (CPHEEO, 2019).