Estimation of Wave Overtopping in Rubble Mound Breakwaters Under Climate Change Scenarios Using SWASH

This paper presents the work developed at the Portuguese National Laboratory for Civil Engineering (LNEC) within the project HYDRALAB+ “Adapting to climate change”, Task 10.5 of JRA3 “Data flux between the laboratory and numerical simulation”. This task aimed at maximizing effective data flux between hydraulic laboratories and among experimental models, numerical models and field case studies, to ensure robust data to inform management of climate change adaptation into the future.

Two-dimensional damage and overtopping tests of a rock armour breakwater under climate change scenarios were performed in a wave flume, at the Ports and Maritime Structures Unit of LNEC, to test different approaches of representing storms in physical models (Mendonça et al., 2017).

The study compares and analyses the performance of the numerical model SWASH to represent wave overtopping over a permeable structure under climate change scenarios.

SWASH, based on the nonlinear shallow water equations, was validated for dunes (Zijlema et al., 2011) and impermeable structures (Suzuki et al., 2017). For permeable structures, some overtopping studies have also been carried out, but several limitations were found in SWASH, suggesting that further investigation is needed to consider more complex structures.

This analysis is important to verify the applicability of the model and the ability of the solver in modelling mean and individual wave overtopping over rubble mound breakwaters.

Moreover, it contributes to a balanced methodology by using the various research tools available, bringing together relevant data from laboratory and numerical simulations to predict the future impacts of climate change on the hydraulic environment.

References

Mendonça, A., Lemos, R., Fortes, J., Reis, M.T., Neves, M.G., Ramos, A. and Capitão, R. (2017). Overtopping events in breakwaters: comparison of 2D physical experiments and empirical formulae. Proc. 37th IAHR World Congress, 13-18 August, Kuala Lumpur, Malaysia.

Suzuki, T., Altomare, C., Veale, W., Verwaest, T., Trouw, K., Troch, P. and Zijlema, M. (2017). Efficient and robust wave overtopping estimation for impermeable coastal structures in shallow foreshores using SWASH. Coastal Engineering, 122: 108-123.

Zijlema, M., Stelling, G. and Smit, P. (2011). SWASH: An operational public domain code for simulating wave fields and rapidly varied flows in coastal waters. Coastal Engineering, 58: 992-1012.