Analysis of Changes in High-Intensity Rainfall Events in South Australia

Abstract

Understanding the dynamics of high-intensity rainfall is crucial for assessing hydrological risks and informing climate adaptation strategies, particularly in regions vulnerable to climate change and variability, such as South Australia. This study examines the temporal variations in high-intensity rainfall events across four meteorological stations in Greater Adelaide, South Australia, Australia: Adelaide Airport, Kent Town, Hindmarsh, and Parafield. Daily rainfall data obtained from the Scientific Information for Land-Owners (SILO) database were analysed using the Bivariate Truncated Logistic-Geometric (BTLG) model to examine joint relationships between episode duration and peak intensity. Change-point analysis using the nonparametric Pettitt test was conducted to identify the time at which the effect of climate change on the intensity of daily rainfall became evident. The results indicate noticeable changes in the frequency and rainfall episodes, with key shifts around 1985 toward shorter-duration, generally lower-intensity events at several locations with daily data. The joint probability analysis p (peak > 20 mm, duration > 5 days) indicated a reduction in long-duration extreme events. This study highlights emerging trends of concentrated rainfall and their potential effects on urban runoff, flooding, and infrastructure design.