Coastal dunes vulnerability indexes: a new proposal and aplication to Ria Formosa Coast (Portugal)
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In this study, we estimate the shoreline retreat, the vulnerability and the erosion rates of an open beach-dune system under projected sea level rise and the action of wind-waves (separately and in combination). The methodology is based on the combination of two state-of-the-art numerical models (XBeach and Q2D-morfo) applied in a probabilistic framework and it is implemented in an open sandy beach in Menorca Island (Western Mediterranean). We compute the shoreline response to sea level rise during the 21st century and we assess the changing impacts of storm waves on the aerial beach-dune system. Results demonstrate the relevant role that the beach backshore features, such as the berm, play as coastal defence, reducing the shoreline retreat and dune vulnerability rates in the near-term (a few decades ahead) and highlighting the importance of simulating the beach morphodynamic processes in coastal impacts assessments. Our findings point at sea level rise as the major driver of the projected impacts over the beach-dune system, leading to an increase of ~25% of the volume eroded due to storm waves by the end of the century with respect to present-day conditions.
Coastal erosion
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Pretende-se com o presente documento caracterizar hidraulicamente o troço da Ribeira de
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Héquette, A.; Ruz, M.H.; Zemmour, A.; Marin, D.; Cartier, A., and Sipka, V., 2019. Alongshore Variability in Coastal Dune Erosion and Post-Storm Recovery, Northern Coast of France. In: Castelle, B. and Chaumillon, E. (eds.), Coastal Evolution under Climate Change along the Tropical Overseas and Temperate Metropolitan France. Journal of Coastal Research, Special Issue No. 88, pp. 25–45. Coconut Creek (Florida), ISSN 0749-0208.As along many parts of the world's shoreline, the coastal dunes extending along the macrotidal coast of northern France represent important defenses against marine flooding. The impacts of storms on the upper beach and foredunes and their post-storm recovery were analyzed using nearly 10 years of offshore wave measurements, water level records, wind measurements, and in situ and airborne LiDAR topographic surveys of the beach and foredunes. Our results show that coastal dunes located at a relatively short distance apart along a coastal stretch with the same wave exposure can have significantly different responses to storms. Not only the impacts of storm events were greater on some dunes, but post-storm recovery also varied from one foredune to another. A strong alongshore variability in dune erosion and recovery was observed with a positive eastward gradient in dune volume change, probably related to longshore and onshore-directed sediment supply. Our measurements revealed that even where the foredune underwent significant erosion during the first years of the survey period, progressive full dune recovery took place through the development of a sand ramp at the dune toe that favored landward sediment transport from the upper beach to the foredune. This period was followed by an unusual series of closely spaced storms during fall-winter 2013-2014 that had major impacts on the coasts of Western Europe. Several of these storms were responsible for extreme water levels, which resulted in significant retreat of the dune front and massive volume loss in places. Our analyses show that the maximum water levels reached during storms represent a major factor explaining dune erosion compared to wave energy that is of secondary importance along this macrotidal coast. Our results also suggest that dune volume change during storms and subsequent recovery were largely controlled by the initial dune and upper beach morphology. A strong correspondence was found between dune front volume change and initial upper beach width and with dune toe elevation, but a somewhat weaker relationship was observed between dune volume change and initial dune height.
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Sedimentary budget
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Longshore drift
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Coastal erosion
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Breakwater
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This chapter provides an overview of the current knowledge of storm impacts on low-lying coastlines, including beaches and dunes. It first outlines the complexity of identifying a storm event in an objective manner. The impact of storms on dune ridges is then discussed, making a comparison between research recently carried out in both the USA and Europe. The main impacts of storm events are also reviewed, taking into account the development of overwash processes and breaching of the dune system as well as flooding of the hinterland. The chapter also provides a detailed overview of qualitative and quantitative models of dune erosion by considering the most advanced numerical techniques. It finally discusses the methods for hazard and risk evaluation, taking into account the emerging role that early warning systems are playing in this field.
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This book includes papers published in the Special Issue titled "Coastal Dynamic and Evolution", which aimed to collect multidisciplinary studies that involved the evaluation of coastal evolution at different temporal scales, from hours and days to months and years, as well as historical changes. The volume contains investigations carried out by means of aerial photos and satellite images, as well as results from in situ surveys and observations aimed at assessing morphological changes in shoreline and dune systems as a consequence of chronic flooding and erosion processes or the occurrence of specific weather-related events. Studies on the evaluation of past and future sea-level variations and related impacts have also been included. In order to provide the reader with a wide overview of different coastal settings and methodological approaches, case studies from Russia, Italy, California (USA), Morocco, Spain, Indonesia, Ireland and Colombia have been included in this Special Issue. The content may be of interest to those who perform a wide range of investigations related to coastal analysis and management, especially to researchers and academics who can exploit the provided approaches and methodologies.
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