Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
30 Jun 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Hydrology and Earth System Sciences (HESS) and is expected to appear here in due course.
Increase in urban flood risk resulting from climate change – The role of storm temporal patterns
Suresh Hettiarachchi, Conrad Wasko, and Ashish Sharma School of Civil and Environmental Engineering, University of New South Wales, Sydney, Australia
Abstract. Warming temperatures are causing extreme rainfall to intensify resulting in increased risk of flooding in developed areas. Quantifying this increased risk is of critical importance for the protection of life and property as well as for infrastructure planning and design. The study presented in this manuscript uses a comprehensive hydrologic and hydraulic model of a fully developed urban/suburban catchment to explore two primary questions related to climate change impacts on flood risk: (1) How does climate change effects on storm temporal patterns and rainfall volumes impact flooding in a developed complex watershed? (2) Is the storm temporal pattern as critical as the total volume of rainfall when evaluating urban flood risk? The updated NOAA Atlas 14 intensity–duration–frequency (IDF) relationships and temporal patterns, widely used in design and planning modelling in the USA, form the basis of the assessment reported here. Current literature shows that a rise in temperature will result in intensification of rainfall. These impacts are not explicitly included in the NOAA temporal patterns, which can have consequences on the design and planning of adaptation measures. We use the expected increase in temperature for the RCP8.5 scenario for 2081–2100, to project temporal patterns and rainfall volumes to reflect future climatic change. The modelling analysis for a 22 km2 developed watershed show that temporal patterns cause substantial variability in flood depths during a storm event. The changes in the projected temporal patterns alone increase the risk of flood magnitude between 1 to 35 % with the cumulative impacts of temperature rise on temporal pattern and the storm volume increasing flood risk by between 10 to 170 % across the locations that were referenced for a 50 year return period storm. The variability in catchment response to temporal patterns show that regional storage facilities are sensitive to rainfall patterns that are loaded at the latter part of the storm duration while the short duration extremely intense storms will cause extensive flooding at all locations. This study shows that changes in temporal patterns will have a significant impact on urban/suburban catchment response and need to be carefully considered and adjusted to account for climate change when used for design and planning future stormwater systems.

Citation: Hettiarachchi, S., Wasko, C., and Sharma, A.: Increase in urban flood risk resulting from climate change – The role of storm temporal patterns, Hydrol. Earth Syst. Sci. Discuss.,, in review, 2017.
Suresh Hettiarachchi et al.
Suresh Hettiarachchi et al.


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Short summary
The study examines the impact of higher temperatures expected in a future climate on how rainfall varies with time during severe storm events. The results show that these impacts increase future flood risk in urban environments and current design guidelines need to be adjusted so that effective adaptation measures can be implemented.
The study examines the impact of higher temperatures expected in a future climate on how...