The Climate Change chapter of the Australian Rainfall and Runoff (ARR) guidelines was recently updated in 2024. The guidance has been revised significantly based on the latest science and following the completion of the Intergovernmental Panel on Climate Change’s (IPCC) sixth assessment cycle. Four new future climate scenarios, referred to as Shared Socioeconomic Pathways (SSPs), are proposed to replace the four Representative Concentration Pathways (RCPs) detailed in the current guidance published in 2016.
Traditional design flood estimation has adopted a stationary climate, assuming that unadjusted historical observations are representative of current and future conditions. This is no longer the case, with the updated guidelines requiring the impacts of non-stationarity, a changing climate, to be reflected in the assessment of both current climate and future climate flood risk.
With the updated guidelines comes a need to understand the effects of the changes on our hydrologic and hydraulic assessments, and more broadly how this may impact on TMR projects and policies. This presentation will focus on providing some practical context to the changes, through analysing the outcomes of recent TMR studies across Queensland where the updated guidance has been tested.
Test cases demonstrating the projected effects of a non-stationary climate on catchments of different sizes, with different response times, and which are located within different Natural Resource Management Region clusters across Queensland will be presented. Each of the four new Shared Socioeconomic Pathways (SSPs) will be evaluated, with comparison back to the Representative Concentration Paths (RCPs) used in current practice and in TMR’s Engineering Policy 170. Holistic observations, including limitations and lessons learnt as a result of applying the new guidelines to various projects, will also be presented.
