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Uncertainties in Shoreline Projections to 2100 at Truc Vert beach (France): Role of Sea-Level Rise and Equilibrium Model Assumptions
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  • Maurizio D`Anna,
  • Bruno Castelle,
  • Déborah Idier,
  • Jeremy Rohmer,
  • Gonéri Le Cozannet,
  • Rémi Thieblemont,
  • Lucy Bricheno
Maurizio D`Anna
Université de Bordeaux

Corresponding Author:[email protected]

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Bruno Castelle
Université de Bordeaux
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Déborah Idier
BRGM
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Jeremy Rohmer
BRGM
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Gonéri Le Cozannet
BRGM
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Rémi Thieblemont
BRGM
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Lucy Bricheno
National Oceanography Center
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Abstract

Ensemble-based simulations of future shoreline evolution to 2100, including sea-level rise driven erosion, are performed and analysed  Future shoreline projections uncertainties are initially controlled by modelling assumptions and after 2060 by sea-level rise uncertainties  The choice of wave-driven equilibrium modelling approach and incident wave chronology are critical to future shoreline projections 1 Abstract Most sandy coasts worldwide are under chronic erosion, which increasingly put at risk coastal communities. Sandy shorelines are highly dynamic and respond to a myriad of processes interacting at different spatial and temporal scales, making shoreline predictions challenging, especially on long time scales (i.e. decades and centuries). Shoreline modelling inherits uncertainties from the primary driver boundary conditions (e.g. sea-level rise and wave forcing) as well as uncertainties related to model assumptions and/or misspecifications of the physics. This study presents an analysis of the uncertainties associated with future shoreline evolution at the high-energy, cross-shore transport dominated, sandy beach of Truc Vert (France) over the 21 st century. We explicitly resolve wave-driven shoreline change using two different equilibrium modelling approaches to provide new insight into the contributions of sea-level rise, and free model parameters uncertainties on future shoreline change in the frame of climate change. Based on a Global Sensitivity Analysis, shoreline response during the first half of the century is found to be mainly sensitive to the equilibrium model parameters, with the influence of sea-level rise emerging in the second half of the century (~2050 or later), in both Representative Concentration Pathways 4.5 and 8.5 scenarios. The results reveal that the seasonal and interannual variability of the predicted shoreline position is sensitive to the choice of the wave-driven equilibrium based model. Finally, we discuss the importance of the chronology of wave events in future shoreline change, calling for more continuous wave projection time series to further address uncertainties in future wave conditions.