Australasian Coasts & Ports Conference, 2023, Sunshine Coast, Queensland
Modern-day coastal engineering faces two key challenges: firstly, providing adequate protection under anthropogenic increases in sea level, and secondly, reducing environmentally detrimental engineering practices that are further driving changes to the climate. With this, nature-based solutions that minimise detrimental environmental effects whilst providing sufficient protection are increasing in their uptake. At present, the application of these nature-based engineering strategies is restricted to low-energy wave environments with minimal spatial constraints. Hybridisation (combined use of nature-based and traditional hard engineering strategies) enables the use of these nature-based principles in higher-energy and urban environments. This paper explores the use of hybridisation with coastal vegetation, by exploring the ability of vegetation to attenuate wave overtopping flow on the crest of coastal defence structures. Show more…Physical modelling experiments were conducted in the University of Auckland’s wave flume with a small-scale sloped seawall retrofitted with model vegetation on the crest of the seawall. This preliminary testing found that the model vegetation reduced mean overtopping discharges by 60-80% when evaluated against their nonvegetated counterpart. Numerical model testing was conducted by calibrating to and expanding on the physical model analysis. This was achieved by implementing a one-dimensional non-hydrostatic XBeach model. Numerical model testing used a multiple linear regression analysis to test the sensitivity of the wave overtopping response to various vegetation parameters. From this, the reduction in mean overtopping flow due to the incorporation of vegetation was found to be most strongly correlated to vegetation width, stem density and stem diameter, with increases in any of these parameters leading to substantial decreases in mean overtopping flow.
Both the physical and numerical model testing were limited by their use of idealised structure and vegetation parameters. However, despite these limitations, this study provides a framework for future testing that should seek to further solidify the wave overtopping performance of this hybrid strategy. Show less…
