The spatial risk of cyclone wave damage across the Great Barrier Reef

Tropical cyclones generate destructive waves that cause large-scale yet patchy structural damage to corals through dislodgement and breakage. Such damage can impede the effectiveness of active management and interventions. Here, we used a process-based spectral wave model combined with over 1500 synthetic cyclone tracks to estimate high-resolution (20–200 m) near-bottom wave velocity on more than 3000 reefs across the Great Barrier Reef (GBR). We then applied a statistical model with likelihood inference to predict damage given cyclone strength and reef spatial arrangement, and calibrated the model using field observations from five cyclones. This enabled us to define effective model-based velocity thresholds of 2.5 m/s for nearshore reefs and 3.1 m/s for offshore reefs to predict coral damage. These thresholds exceed the mechanical strength of branching and tabular corals to withstand wave energy. Reef vulnerabilities to cyclone damage vary across the GBR shelf. Although offshore reefs are more wave-tolerant compared to nearshore reefs, the central outer-shelf reefs have a higher predicted probability of damage given a cyclone (11 %), potentially because these small and sparse reefs are less effective in dissipating wave energy. Across the GBR, we identified the top 10 % most exposed cyclone hotspots as well as the top 10 % least exposed refugia with relatively high probabilities of experiencing high and low cyclonic wave velocities, respectively. Our model provides a predictive tool and risk maps to assess reef vulnerability to cyclones, highlighting natural disturbance refugia to inform management strategies for reef resilience.