Tropical Cyclone Debbie (2017): Evaluating Analytically- and Numerically-Driven Wind and Storm Tide Hazards and Impacts

Severe Tropical Cyclone Debbie made landfall near Airlie Beach, Queensland, on 28 March 2017 around 12:40 pm AEST as a Category 4 (Category 3) cyclone on the Australian (Saffir-Simpson) cyclone intensity scale. This dangerous cyclone was a multi-hazard event, causing severe wind and storm surge damage at landfall, as well as, significant inland flooding across a large portion of South East Queensland and northern New South Wales. Debbie was the worst cyclone to impact Queensland since Cyclone Yasi (2011), forcing nearly 25,000 people to evacuate the region.

Landfall events like Debbie are reconstructed by catastrophe modelers and engineers using analytical and numerical models to assess potential impacts on buildings, critical infrastructure and society. The main tradeoffs between the analytical and numerical models are computational speed and complexity. Recently, numerical models like the Weather Research and Forecasting (WRF) model have been used to simulate wind and rainfall hazards, as well as, drive hydrodynamic models to produce storm tide estimates. It is not clear what the added value of using a numerical like WRF is to simulate these hazards and the attendant impacts on the built environment, specifically residential structures.

The primary goal of this case study is to compare the wind and storm tide hazards generated by a coupled analytical-hydrodynamic model and coupled WRF-hydrodynamic model to evaluate the added value of using a complex coupled numerical-hydrodynamic model over a coupled analytic-hydrodynamic model. All hazard simulations will be calibrated using wind and storm tide in situ observations collected during the event. Once the coupled models are calibrated, wind and storm tide-induced impacts on residential buildings in Airlie Beach, Bowen and Proserpine will be simulated using empirically derived wind and storm tide fragility curves based on rapid damage assessment data conducted in the wake of Debbie. Discussion of the strengths and weaknesses of each model configuration will be presented.