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A simple empirical model is proposed for predicting extreme wave run-up on natural beaches during severe wave events (deep water wave heights H₀ ≳8 m or return periods of about 50 years). The new model departs from traditional approaches that use the slope of the beach face β_f and the Iribarren number ξ₀ as parameters for predicting run-up and instead uses the distance offshore x_h to water depth h to estimate a near-shore profile slope as S = h/x_h, where the depth of closure is the proposed choice for h. Extreme run-up R_x is then expressed in terms of S as R_x/H₀ = CS^2/3. Observations from recent severe storm events in South Africa are used to estimate the dimensionless coefficient C≃7.5. The data are also compared with those of Holman [1986] and the results verify his regression equations and confirm they are valid for significant wave heights extending to 8.5 m for beach-face slopes around 0.1. The run-up predictions of Holman [1986], Nielsen and Hanslow [1991] and Stockdon et al. [2006] are compared to those of the proposed new model. The results suggest that the new model reduces the uncertainties in predicting wave run-up on natural beaches compared with previous models, and thus enables improved estimates of extreme wave run-up and the upper limit of beach change for coastal planning and management.

A method to determine swash zone boundary conditions is developed using remote sensing by video and ARGUS. Guard and Baldock (2007) proposed new numerical solutions for swash hydrodynamics, where the flow field varies according to a free parameter, k. k=0 in the Shen and Meyer swash solution but k=1 appears more realistic for real swash. This study has developed a semi-automated method to obtain values for k from multiple waves in field conditions using ARGUS video data and image analysis techniques. The results indicate that k is greater than 0 and close to 1 for natural swash. No trends were observed between k and run-up length, offshore significant wave height or tidal phase, consistent with the self-similarity of the swash hydrodynamics. In conjunction with modelling, the method offers the possibility of remote sensing of the asymmetry in the swash zone hydrodynamics.

Drawing on expenditure and survey data from the Gold and Sunshine Coasts in Queensland, Australia, this chapter compares expenditures on beaches relative to their recreational benefits. Beaches are found to be exceptional investments. The comparison of the two councils also provides insights into their relative capacity to adapt to the adverse impacts of climate change. The Gold Coast can rely to some extent on historical large investments in infrastructure to defend itself against change. In contrast, the Sunshine Coast has more options which may lower the cost of adaptation e.g., it can rely more heavily on retreating from change in certain locations because of historical investment in dunal buffer zones. However, historical investment patterns impact in different ways on the environmental quality of beaches and the benefits provided to users and non-users. Limitations and areas of future research are also outlined.