Proceedings of the Institution of Civil Engineers Maritime Engineering 162 September 2009 Issue MA3 Pages 127–135 doi: 10.1680/maen.2009.162 .3.127 Paper 700026 Received 02/10/2007 Accepted 10/03/2009 Keywords: coastal engineering/floods & floodworks/safety & hazards E. Tonatiuh Mendoza Researcher, Laboratori d’Enginyeria Marı ´tima, Faculty of Civil Engineering, Universitat Polite `cnica de Catalunya, Barcelona, Spain Jose ´ A. Jime ´nez Professor, Laboratori d’Enginyeria Marı ´tima, Faculty of Civil Engineering, Universitat Polite `cnica de Catalunya, Barcelona, Spain Regional vulnerability analysis of Catalan beaches to storms E. T. Mendoza PhD and J. A. Jime ´nez PhD A framework to estimate coastal vulnerability to storm impacts at a regional scale is presented. It assesses the physical coastal vulnerability to storm impacts by sepa- rately estimating two components: flooding and erosion. It covers the following steps: characterisation of the forcing; evaluation of the induced beach response – inundation and erosion – (hazards quantification); coastal zone characterisation; definition of a coastal vulnerability index to storms – a composite of two partial vulnerability estimations, namely the flood vulnerability and the erosion vulnerability indices; and assessment of the coastal vulnerability. Instead of assessing the vulnerability associated with a given storm, the forcing is defined in terms of representative storms which are obtained by classifying storms in the area using a five-class system similar to that used for hurricanes (weak, moderate, significant, severe and extreme). Later, a vulnerability assessment for the entire coast to each storm category is produced. The method has been derived for and applied to the Catalan coast (north-west Mediterranean) but can be easily adapted to other coasts. It permits managers to identify coastal stretches sensitive to a given storm class for a given induced hazard (flooding, erosion or combi- nation of both) to decide where to take actions. NOTATION B beach/dune crest height D dimensionless fall velocity (Hw f /T) d 50 sediment mean grain diameter E storm energy content EIP erosion intermediate parameter EVI erosion vulnerability index FIP flood intermediate parameter FVI flood vulnerability index H s significant wave height H smax significant wave height at the peak of the storm JA dimensionless beach profile parameter Ru 2% 2% exceedence value of run-up height (above still water level) T p wave peak period T pmax wave peak period at the peak of the storm t time tan b beach slope w f sediment fall velocity z beach elevation above still water level DV eroded volume from the inner part of the beach due to the impact of a storm DX beach retreat due to the impact of a storm j storm surge s Ru standard deviation of run-up estimations of a storm class t storm duration 1. INTRODUCTION The impact of storms in coastal areas induces a series of impulsive morphodynamic responses or hazards, which are especially important in sedimentary environments such as beach and dune erosion, overwash and/or inundation of low-lying areas. When this happens in developed/urbanised areas, they are usually accom- panied by damage to infrastructures and/or effects on coastal uses and resources. This implies a move from coastal hazards to harms and, bearing in mind their potential consequences, one of the usual (and important) needs of coastal managers should be to know the potential of a coastal stretch to be harmed by such processes. Thus, in the recently signed Protocol 1 on integrated coastal zone management (ICZM) in the Mediterranean by the European Union and the Mediterranean countries there is a specific chapter on natural hazards (chapter 22) in which the parties are advised to undertake vulnerability and hazard assessments of coastal zones and take prevention, mitigation and adaptation measures to address the effects of natural disasters. In this context, we adopt the recommendation of the Floodsite project to define (coastal) vulnerability as the potential of a (coastal) system to be harmed. 2 Its assessment should allow coastal managers to anticipate potential damage along the coast to a given agent and this has originated numerous approaches from different standpoints, objectives, processes and scales. 3 In the present study the topic considering a single source of coastal hazards, namely the assessment of coastal vulnerability to the impact of storms, was addressed. Moreover, as a first step only the physical (geomorphic) vulnerability was examined. Even restricting the analysis to a single process – namely storms – to a single component of the coastal system – namely geomorphic – and to a single country – namely the Spanish coast – a number of different approaches can be found. 4–6 The main objective of this paper is to present a methodology to estimate the coastal vulnerability to storm impacts at a regional scale to be applied in the Spanish Mediterranean coast. Due to Maritime Engineering 162 Issue MA3 Regional vulnerability analysis of Catalan beaches to storms Mendoza N Jime ´nez 127