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Coastlines around the world are being impacted by storm erosion and Sea Level Rise (SLR). This leads to an increase in damage exposure for coastal assets and structures. We developed a multi-model approach to better understand current and future coastal processes at a Port Fairy beach (Australia), where coastal assets have been impacted by storm erosion and Sea Level Rise (SLR). Our methodology leveraged the output of a long-term shoreline model, as initial conditions for a storm erosion model, on a feedback loop. We first assessed erosion and shoreline retreat trends based on aerial imagery and shoreline datasets. We then ran a one-line shoreline model (GenCade), forced with a long-term SWAN wave hindcast, to estimate alongshore accretion and erosion on either side of proposed seawall structures for the years of 2050, 2070, and 2100. The results of the shoreline model were used to establish shoreline changes and provide an updated bathymetry for use in the XBeach beach erosion model. XBeach was used to analyse the morphodynamic changes for a reconstructed storm centred on the 500-year Annual Recurrence Interval wave. The model provided results of cross-shore changes, as well as potential accretion and erosion areas. Our study offered a useful method for evaluating coastal erosion issues using a multi-model approach that accounted for the trends in shoreline retreat, SLR in future scenarios, storm conditions, and both longshore and cross-shore sediment transport. All of which are crucial factors to consider when mitigating erosion and designing coastal protection structures with potential adaptation of the design over future decades. [ABSTRACT FROM AUTHOR]

Infragravity (IG) waves are surface ocean waves with periods ranging from 25 s to 300 s. They typically have low amplitudes and wavelengths an order of magnitude longer than wind-generated waves. IG waves can penetrate ports and harbours, and their reflection off port's internal walls and structures can generate resonance when the port's basin and IG wave lengths are similar. The amplification of the IG wave energy by resonance can cause surge motion on moored vessels, which can break mooring lines and threaten personnel safety. Most studies considering IG wave effects in harbours use white noise (synthetic) boundary forcings in simulations to identify the wave periods that can cause resonance within a port layout, or in run spectral simulations based on the statistics of the local wave climate. Although synthetic boundaries can effectively provide such resonance periods for ports, it is not possible to predict whether these long-period oscillations or resonance will effectively occur under the natural wave climate. On the other hand, simulations based on the local wave climate use bulk wave parameters, which are not capable to represent the multiple wave systems (i.e., seas and swells) that can be present on the wave spectrum. In this paper, we use concurrent offshore and in-basin wave measurements to study IG waves processes in Eastland Port, Gisborne (NZ). We selected a range of IG wave events recorded by an IG wave radar within the port basin and used the simultaneous spectral offshore wave condition as boundary forcings for SWASH simulations. Results show the different spatial distributions of IG wave heights that can occur within the port basin, and identifies the differences in wave spectra for the cases modelled. The study highlights the importance of using realistic wave conditions for IG wave investigations. [ABSTRACT FROM AUTHOR]