Comprehensive Extreme Rainfall Analysis: A study on Ahmedabad region, India

Abstract

ABSTRACT Recently, the Central Public Health and Environmental Engineering Organization (CPHEEO), India, emphasized extreme rainfall analysis based on the probabilistic approach. The extreme rainfall analysis was performed using hourly rainfall data for Ahmedabad city, India. The analysis was carried out to obtain (a) clock hour correction factor (CHCF) for annual maximum rainfall series (AMS) and partial duration maximum rainfall series (PDS); (b) empirical factors for converting PDS to AMS for different return period extreme rainfall; and (c) conversion factors for various return period 24-h maximum rainfall. The AMS and PDS were fitted with generalized extreme value and generalized Pareto distribution, respectively, for fixed window (FW) and sliding window (SW). The CHCF for daily maximum rainfall for AMS and PDS were 1.134 and 1.139, respectively, against 1.15 suggested by IS 5542: 2003. The empirical factor for converting PDS to AMS for a 2-year return period of 24-h extreme rainfall (FW) was found to be 0.86. The conversion factor for 24-hextreme rainfall PDS (FW) from a 50-year return period to a 5-year return period was found to be 0.54. The empirical and conversion factors derived in the present study for Ahmedabad city are site-specific.