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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.

Bangladesh has been identified as one of the countries most vulnerable to climate change and rising sea-level. This is because it is located at the northern end of the funnel-shaped Bay of Bengal, and as a consequence it has experienced a number of severe storm surges in the last three decades. The inhabitants of the coastal region are very poor, and the surges have pushed them to a "tipping-point"; that is, the point of desperation which is exacerbating the socio-economic threats to their existence. The study reported here aimed to explore the perceptions of coastal communities with regard to vulnerability and adaptation (V & A) strategies in four different areas of Bangladesh in order to reduce their vulnerability to future storm surges. After reviewing the impact assessment guidelines of the Intergovernmental Panel on Climate Change (IPCC), United States Country Studies Program (USCSP) and United Nations Environment Programme (UNEP), the researchers applied the Participatory Rapid Appraisal (PRA) method (a behavioural environmental decision-making tool) to survey 160 participants in four case-study areas, with 20 participants in two sessions in each case. The evaluation of V & A was implemented and prioritised in this study by a measuring scale, called the "weighted matrix index". This study not only considered the integrated assessment of V & A but it also classified the levels of vulnerability and adaptation in different categories. Additionally, it provides a comparative picture of the vulnerabilities for similar risks in different types of communities. These key aspects demonstrate and emphasise that adaptation policy needs to be implemented immediately in Bangladesh in order to reduce and manage future vulnerability in the coastal region under the potential climate change regimes.

A methodology to estimate storm-induced morphodynamic risks is presented. The storm-induced coastal response is separately assessed in terms of inundation, beach profile and transport potential. Inundation is calculated by means of the run-up Ru_2% at the peak of the storm. Erosion is characterized by the eroded volume from a beach profile and, overall sediment transport is parameterized in function of the integrated wave power during the storm impact. These three parameters are used to calculate the resulting risk by estimating their probabilities of occurrence using the event and response methods. In the first one, the probability of occurrence is assigned from the extreme wave distribution (events) which is used to calculate the corresponding morphodynamic processes. In the response approach, storm wave data are used to build a data set of storm-induced responses which are later fitted to an extreme distribution. These two methods have been applied to characterize storm wave-induced morphodynamic risks at Costa Brava (NE Spanish Mediterranean coast). Results show that for this case, the use of the event approach significantly under-predicts the morphodynamic response for any probability of occurrence and, in consequence, its use will under-predict storm risks.