National weather forecasting agencies routinely issue a range of hazard warnings. But to our knowledge, along sandy coastlines where storm waves and storm surge can result in widespread but location-specific beach erosion and beachfront flooding, no national-scale early warning service for these hazards is presently operational. This paper outlines the scientific basis and implementation of a new framework for large area coastal storm hazards forecasting, currently being tested along the southwest (Indian Ocean) and southeast (Pacific Ocean) coasts of Australia. The system provides 7-day rolling predictions of localized beach erosion and/or coastal flooding linked to forecasted extreme weather events. Coastal setting influences the nature and occurrence of these hazards, with sandy beaches along wave-dominated coasts more prone to erosion and at surge-dominated coasts to flooding. An existing nearshore water-level forecasting system and a new inshore wave modeling capability are used to forecast beach erosion and coastal flooding at every 100 m along the shore. At the regional scale O(100-1 000 km of coastline), a threshold-based decision tree model categorises the predicted extent, location, and severity of erosion and flooding. At a more local scale O(100-1 000 m), physics-based modeling using XBeach focuses on vulnerable or high-value locations, providing specific storm hazard indicators tailored to local needs. This twotier approach is feasible for national implementation due to the reduced computational effort, limiting intensive modeling to pre-identified critical locations. Delft-FEWS manages the data and modeling workflow, ensuring scalability and compatibility with existing forecast infrastructure. Initial evaluations of the system are promising, with a detailed 2-year evaluation in progress. Future enhancements could include the use of satellite imagery for real-time beach width and dune topography assimilation and exploring alternative modeling approaches to further improve forecast accuracy.

Coastal storms pose a threat to livelihoods and assets along Australia’s coastlines. By delivering timely information about approaching coastal storms, early warning systems (EWSs) can enhance community preparedness and inform risk-reduction measures, with the goal of reducing potential impacts to property, critical infrastructure, and loss of life. Worldwide, existing coastal hazard EWSs primarily center around the forecasting of coastal flooding risks, which predominantly occur along surge-dominated coastlines. However, many of Australia’s densely populated coastlines are wavedominated, where erosion hazards feature more prominently. This pilot project has developed a multiscale, coastal hazard EWS capability for Australia that uses state-of-the-art scientific methods for predicting both erosion and flooding impacts caused by coastal storms.

To be commercially viable, wave energy converters (WECs) will need to be deployed in arrays or "wave farms" to generate significant amounts of energy and to have the costs of these farms minimised. However, when designing a wave farm, there are a number of trade-offs to be made between competing objectives; for example, between the power production potential and installation costs, with the optimal design for one objective not necessarily favourable for the other. In this study, we developed a multi-objective optimisation methodology to allow rigorous evaluation of the trade-offs amongst multiple objectives. We demonstrate the methodology for four objectives: (1) maximising power production, (2) minimising the foundation loads, (3) minimising the number of foundations and (4) minimising the total export cable length required. However, the method is flexible and can be used for optimising a range of other parameters. A case study examining multi-objective optimisation of a wave farm using the developed probability-based evolutionary strategy was conducted for a proposed development site in Albany, Western Australia. The wave farms were composed of 5, 10 and 20 fully submerged cylindrical point-absorber type WECs similar to Carnegie Clean Energy's CETO-6 device. Simulations show that the optimal layouts preferring maximum power formed a single line perpendicular to the predominant wave direction; the optimal layouts preferring minimum cable length and a minimum number of foundations form multiple lines; whereas the optimal layouts preferring minimum foundation loads formed multiple lines in line with the predominant wave direction. By applying a cost model and non-dominated sorting, the methodology allowed us to quantify the trade-offs between power production and cost.

Typically, the dimensions of OWC chamber have a single resonant frequency which captures efficiently wave energy over a narrow range of frequency of the waves. The high-frequency waves are reflected. Provision of a pair of additional harbour walls in front of the device creates an added resonance enabling it to capture substantial energy from a wider range of frequency of the waves. Although, there exists a substantial loss in energy due to wave deformation as the wave from the offshore approach shallow waters, in which case, the harbour walls prevent any further dissipation till it reaches the device. This chapter reports the influence of harbour walls on the hydrodynamic characteristics of a bottom - mounted OWC. The study was carried out with different configurations of harbour walls, i.e., the projecting length was varied in terms of the ratio of harbour wall length (c) to the breadth of OWC (b), (c/b = 1, 1.5 and 2). The opening angle of harbour wall was varied in the range of [π/2, 7π/8] in an interval of π/8 with respect to the front lip wall of OWC. The results reveal that the efficiency of the OWC with the harbour walls has been significantly improved. The details of such a behaviour are herein discussed.

Wave energy converters (WECs) will have to be arranged into arrays of many devices to extract commercially viable amounts of energy. To understand the potential coastal impacts of WEC arrays, most research to date has relied on wave-averaged models given their computational efficiency. However, it is unknown how accurate wave-averaged model predictions are given a lack of validation data and their inherent simplifications of various hydrodynamic processes (e.g., diffraction). This paper compares the predictions of coastal wave farm impacts from a coupled wave-averaged and flow model (Delft3D-SNLSWAN), to a wave-resolving wave-flow model (SWASH) that intrinsically accounts for more of the relevant physics. Model predictions were compared using an idealized coastal bathymetry over a range of wave conditions and wave farm geometries. Both models predicted the largest impacts (changes to the nearshore hydrodynamics) for large and dense wave farms located close to the shore (1 km) and the smallest impacts for the small and widely spaced farm at a greater offshore distance (3 km). However, the wave-resolving model generally predicted somewhat larger impacts (i.e., changes to the nearshore wave heights, mean velocities and mean water levels). We also found that coupling the wave-averaged model to a flow model resulted in more realistic downstream predictions than the stand-alone wave-averaged model. (c) 2021 Elsevier Ltd. All rights reserved.

A comprehensive experimental investigation on the effect of resonant length and the opening angle of harbour walls integrated with an Oscillating Water Column (OWC) under random sea state has been carried out. The random sea state is entitled to be the reference parameter for analysing the performance of the OWC under controlled conditions. The results on the variations of volume flux of water inside the OWC chamber, pneumatic pressure and relative capture width are depicted as a function of relative water depth for different configurations of the harbour walls in a dimensionless form. The presence of the harbour walls has enhanced the performance characteristics of the OWC. Further, the length and inclination of the harbour walls were varied to achieve a relative capture width, RCW (ratio of output power to the input power) of 75% more than that from the OWC without harbour walls. The details of the models, experimental set-up, testing procedure, results and discussion on the aforementioned study are presented.

The Bayesian Network approach is a probabilistic method with an increasing use in the risk assessment of complex systems.It has proven to be a reliable and powerful tool with the flexibility to include different types of data (from experimental data to expert judgement).The incorporation of system reliability methods allows traditional Bayesian networks to work with random variables with discrete and continuous distributions.On the other hand, probabilistic uncertainty comes from the complexity of reality that scientists try to reproduce by setting a controlled experiment, while imprecision is related to the quality of the specific instrument making the measurements.This imprecision or lack of data can be taken into account by the use of intervals and probability boxes as random variables in the network.The resolution of the system reliability problems to deal with these kinds of uncertainties has been carried out adopting Monte Carlo simulations.However, the latter method is computationally expensive preventing from producing a real-time analysis of the system represented by the network.In this work, the line sampling algorithm is used as an effective method to improve the efficiency of the reduction process from enhanced to traditional Bayesian networks.This allows to preserve all the advantages without increasing excessively the computational cost of the analysis.As an application example, a risk assessment of an oscillating water column is carried out using data obtained in the laboratory.The proposed method is run using the multipurpose software OpenCossan.

In the midst of a variety of wave energy converters (WECs), the oscillating water column (OWC) device that exploits ocean waves for its energy is an important class. It is a partially submerged structure with an opening to the sea below the water line that traps the air above the water column. Owing to the wave motion, the rise and fall of water level in a closed chamber pump the air thus causing its oscillation to drive a turbine coupled to electric generators. The objective of the present study is to analyse the influence of harbour walls on the pressure variation between the inside and front of the lip wall of a bottom mounted OWC. In contemplation of enumerating the influence of the harbour walls, a two-dimensional physical model study was conducted with a model scale of 1:20 in a 72.5 m long, 2 m wide and 2.5 m deep wave flume. The study was carried out with different configurations of harbour walls by changing its projecting length to examine the response of OWC. The dimensions of OWC have been chosen in such a way that the device can absorb more energy for a particular relative water depth (d/L). The model was exposed to the action of regular waves in order to evaluate the hydrodynamic performance characteristics of the device mainly the effect of the harbour walls. The details of test set-up, testing facility, parameters of models, harbour wall configurations, test procedure, analysis of results and discussion are reported in this paper.

Among the numerous wave-energy converters (WECs), the oscillating water column (OWC), which runs on the concept of capturing energy from the rise and fall of the water column in a closed chamber resulting from wave motion, has become quite popular. The compressed water column in the chamber advances an air stream that can drive a turbine coupled to electric generators. The present study aimed to investigate the influence of the projecting sidewalls, or so-called harbor walls, of an OWC on its energy-efficiency characteristics. The design and optimization of the harbor wall's projecting length and its inclination are as important as the hydrodynamics of waves inside the chamber, apart from the characteristics of the air vent and the turbine parameters, which play a critical part in the performance of these devices. The objective of the present study was to optimally convert the incident wave-energy into pneumatic power by analyzing the influence of projecting sidewalls and optimizing the length and inclination (opening angle) of the walls. The projecting length was varied in terms of the ratio of the harbor wall length (c) to the breadth of the OWC (b) (c/b = 1, 1.5, and 2). The inclination of the harbor wall was varied in the range of (/2, 7/8) at an interval of /8 with respect to the front lip wall of the OWC. (C) 2017 American Society of Civil Engineers.