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Storm Surge Modelling

Storm Surge Modelling

by April 14, 2020

Storm-surge modelling can be a tool for State decision-makers not only during extreme weather events, but also for future planning and operational disaster management, as Gaelle Faivre writes.

A storm surge is a rise of water level during a storm above the normal predicted astronomical tide. A surge can be a threat to life and can be very destructive, affecting properties during a cyclone.

Tropical cyclone behaviour involves a large range of spatial, temporal and intensity uncertainties that makes it difficult to forecast inundation, and as a consequence, the decision to evacuate. The inundation caused by storm tide varies with changes in tropical cyclone parameters, such as the radius of the wind, the speed of the cyclone, the angle of approach to the coast, the intensity that is given by the central pressure, the interaction with the local bathymetry or the time when the cyclone made landfall. The bathymetry is the underwater depth of the ocean. Such changes in the forecast information are required to be considered in the decision-making for evacuation.

The understanding of the current disaster management system and effective hazard forecast, warning and decision support systems are essential to develop a method to support decision-makers and facilitate their actions during an extreme event.

Griffith Centre for Coastal Management has conducted storm-surge modelling to support emergency response management during a tropical

cyclone. The project was funded as a partnership of the Queensland Government through the Department of Science, Innovation, IT and the Arts, Griffith University, Queensland Fire and Emergency Services, the Queensland Cyber Infrastructure Foundation, and DHI Water and Environment Pty Ltd, and was a collaboration with the Bureau of Meteorology.

This project developed QSurge, an integrated stakeholder engagement emergency management decision support system architecture using high- performance computing. QSurge provides a real-time inundation forecast to support decision- makers. It has been developed as a prototype for the North Queensland Coast based on large tropical cyclone scenarios using parametric wind fields of tropical cyclones making landfall along the coast. QSurges informs the timing and location of areas subject to evacuation notices during Tropical Cyclones for coastal areas of Queensland.

Consultation with local area disaster managers highlighted the value of presenting information using maps rather than storm tide levels, and lead to an enhancement of the system to include high resolution information on the areas impacted over time. This enhancement, known as SurgeImpact, provides maps of storm surge inundation at the street level resolution (30m) and identifies the number of residents impacted for a tropical cyclone scenario using a library of pre-calculated simulations. All the maps are provided in a dynamic time dimension from 12 hours prior to the land-falling time, to six hours after the tropical cyclone made landfall; then they consider the tidal variations. Moreover, time series plots per hours of impacts, such as population, main roads, dwelling and area of ecosystems impacted have been added.

The decision-makers have then the possibility of picking the scenario projected by the Bureau of Meteorology and see the impacts from various time of impacts. This tool would have the possibility to support decision-makers in their decision to evacuate a community by identifying the worst case and impacts, and then evaluate the potential risks. The Surge Impact pilot tool can be improved to include climate adaptation options, such as levees and seawalls and the calculation of the value of assets at risk.

Qsurge and Surge Impact are not intended to replace the current hazard forecasting system provided by the Bureau and State government agencies; however, they can be used as a support to help decision-makers in both future-planning and operational disaster management. They could, for example, be extended to areas, which are less impacted by tropical cyclones such as the Gold Coast waterways, particularly in the context of future climate change. The overall framework for decision support could also be applied to other natural hazards such as tsunamis, bush fire or earthquake to provide time-related information about evacuation.





Published in the Jan-Mar 2020 edition.



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