Abstract
Gravel spits of Brittany have experimented a long morphosedimentary evolution over the last millenia. Based on analysis of several back-barrier holocene sediment stratigraphies, distinct phases of construction and barrier breakdown were recognized, indicating the role played by storminess and sediment supply during the late-holocene period. Over the last centuries and decades, a deficit of sediment budget affecting several gravel spits is highlighted. Therefore, actual coastal evolution of most of them is mainly dominated by cannibalization, landward retreat by rollover and complete destruction of the spits in some places. This coastal erosion is related to the lack of significant offshore sediment input or from the erosion of unconsolided cliffs. Locally, anthropogenic forcing have axacerbated the erosion processes by sediment minings and/or the construction of hard defense structures. For the swash-aligned gravel spits, frequency and magnitude of overwash processes is controlling the rate of landward retreat by rollover. This morphodynamic behaviour is illustrated by topo-morphological surveys realised between 2002 and 2012 on Sillon de Talbert spit which has experienced a complete crestal removal during the 10 March 2008 Johanna storm. Although this event have a 50–100 year occurrence, the barrier has exhibited a rapid crestal rebuilding by overtopping processes, illustrating the great resilience of the spit. Thus, coastal erosion management strategies mainly based on hard defense structures are gradually abandoned for new management policies based on soft operations. Nowadays, gravel spits of Brittany are also considered as a geological heritage and management plans are establishing by local authorities.
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Stéphan, P., Suanez, S., Fichaut, B. (2015). Long-, Mid- and Short-Term Evolution of Coastal Gravel Spits of Brittany, France. In: Randazzo, G., Jackson, D., Cooper, J. (eds) Sand and Gravel Spits. Coastal Research Library, vol 12. Springer, Cham. https://doi.org/10.1007/978-3-319-13716-2_15
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DOI: https://doi.org/10.1007/978-3-319-13716-2_15
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