A Storm Surge Inundation Model for Coastal Planning and Impact Studies

Graeme D. Hubbert, Kathleen L. McInnes

Abstract


A high resolution storm surge inundat ion model has been developed to model coastal flooding due to storm surges. The storm surge model, which features a nesting capability and inundation algorithm, is described. The flooding and draining rate is dependent on the modelled current in adjacent 'wet' grid cells which ensures realistic and smoothly varying results. Model simulations are carried out in two distinctly different geographic regions. The first of these is the town of Port Hedlund on th e north west coast of Australia which was severely inundated by a tropical cycloneinduced storm surge in 1939. The model is shown to reproduce the peak flood levels and areas of inundation to a high degree of accuracy. Storm surge heights at the coast produced by a 'fixed-coastline' version of the model are compared with the inundation model results and indicate an overestimation of the storm surge heights by up to 17%. Simulations are conducted with varied horizontal resolution to investigate the robustness of the model. The flooding rates and areas of inundation are relatively unaffected by moderate variations in horizontal resolution. The second region studied is Port Phillip Bay, upon which the city of Melbourne is located. The model is used to simulate the storm surge and inundation produced by two separate cold fronts. The vulnerability of two locations within the Bay is investigated under altered sea level and storm strength conditions to demonstrate the potential impact of climate change. In a final simulation, levee banks on the tributaries draining into the bay are removed. The vastly increased inundation serves to illustrate the importance of maintaining and possibly increasing flood protection measures in this region in the future.

Keywords


Tropical cyclones; cold fronts; coastal flooding; climate change; sea level rise.

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