Uncertainties in Shoreline Projections to 2100 at Truc Vert beach
(France): Role of Sea-Level Rise and Equilibrium Model Assumptions
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.