Impacts of climate change on peak design discharge of unmitigated urban catchments – a comparative analysis

Wiegand, Jeremy (2023) Impacts of climate change on peak design discharge of unmitigated urban catchments – a comparative analysis. [USQ Project]

Text (Project – redacted) WIEGAND_J_CHADALAVADA_Redacted.pdf Download (5MB)

Abstract

For engineers and designers of critical stormwater infrastructure, peak design discharge must be appropriately modelled in order to ensure safety to person and property is upheld respectively. As it is now widely accepted that climate change is attributable to the actions of humans, the prevalence and intensity of rainfall impacts from these actions needs to be quantified in efforts to mitigate the associated risks and implications to existing and the future planning of stormwater infrastructure.

Traditional urban stormwater methodology broadly does not currently account for the unprecedented impacts of climate change. This research will seek to fill this gap providing a comparative analysis of peak design discharge (Q) using the rational method with and without climate change factors for a range of plausible scenarios. Completion of the research aims to understand the difference in peak design discharge Q for respective Annual Exceedance Probability (AEP) events and climate change scenarios to promote resilience in the future proofing of urban drainage systems. In doing so, this project will seek to understand and guide how climate change considerations will influence stormwater infrastructure requirements and the spill over effects onto Council budgets.

A series of model iterations were run for the nominated project site on an unmitigated urban catchment within the Logan City Local Government Area (LGA). Varying AEP rainfall events centred on specific planning design horizons using scaling factors derived from applicable emissions trajectories of Representative Concentration Pathway (RCP) 4.5 and 8.5 were applied. This work is guided by Book 1 of the Australian Rainfall and Runoff 2019 (ARR) and its approach to address the risks of climate change. Q values derived from modelled scenarios allow for drainage infrastructure requirements to be realised with cost comparisons for each outcome presented.

The outcomes from the modelling conducted indicated relatively minor changes in the short term and a large impact over the longer term. Specifically, when considering differences between the RCP 4.5 and RCP 8.5 scenarios, the effect on peak design discharge was observed as a function of increased rainfall intensity. These observed differences are attributable to the increased rainfall intensity as projected by RCPs as influenced by temperature variations as a result of climate change. The impact on infrastructure was realised and appeared negligible under most design scenarios however noting the outlier of the 2090 1% AEP event under RCP 8.5, which indicated a significant increase in costs associated with the additional infrastructure requirements. Nevertheless, on balance, RCP 4.5 was proved to be the optimal choice for Local Councils.

It is hoped that this research and its findings could be extended to apply to LGAs beyond Logan City to assist and guide stormwater infrastructure programs to ensure sufficient budgetary adjustments are accounted for in the forward planning for respective design horizons and inform policy decision making.

Statistics for this ePrint Item

Item Type:	USQ Project
Item Status:	Live Archive
Faculty/School / Institute/Centre:	Current – Faculty of Health, Engineering and Sciences - School of Engineering (1 Jan 2022 -)
Supervisors:	Chadalavada, Sreeni
Qualification:	Bachelor of Engineering (Honours) (Civil)
Date Deposited:	06 Oct 2025 22:17
Last Modified:	06 Oct 2025 22:17
Uncontrolled Keywords:	stormwater infrastructure; climate change
URI:	https://sear.unisq.edu.au/id/eprint/53013

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