Abstract
The wave regime has a strong influence on the sediment transport in coastal systems. Modifications in wave regime induced by climate changes can influence the sediment dynamics of those coastal systems. To access wave regime changes it is crucial to analyse the future modifications in the wave height, period and direction. This work aims to analyse the influence of a future wave regime in the sediment budget of a coastal lagoon inlet and at the nearshore adjacent coast. To achieve this goal a morphodynamic modelling system was used, forced by present and future waves, corresponding to a typical year of present and future wave climates. A methodology to determine a typical year of each climate was developed based on the determination of correlation coefficients between each climate and corresponding year data. The comparison between present and future wave climates evidences that wave period and height are in general similar for both climates, and confirms the anticlockwise rotation of waves in the future. The morphodynamic simulations revealed analogous results for both wave climates, resulting in similar patterns for the residual sediment fluxes, but slightly more intense in the present. The consequent bathymetric changes show that the deposition trend presently observed offshore the inlet tends to increase for future waves climate. The transport budgets were also analysed for both wave regimes, evidencing that the alongshore transport slightly decreases (~1%) for future waves.
Highlights
The alongshore sediment transport driven by the impinging oblique waves is the result of a complex pattern of sediment fluxes and long-shore currents that eventually leads to a net sediment erosion or accretion at the shorelines
The climate changes evidence modifications in the wind patterns that will result in alterations in extreme wave events and wave directions affecting coastal systems, such as the dynamics of the tidal inlets (Bruneau et al, 2011)
The wind data outputted by climate model ECHAM5/MPI-OM (Roeckner et al, 2003; Marsland et al, 2003) were used to force the wave model WW3 previously implemented for the North East Atlantic Ocean by
Summary
The alongshore sediment transport driven by the impinging oblique waves is the result of a complex pattern of sediment fluxes and long-shore currents that eventually leads to a net sediment erosion or accretion at the shorelines. Modifications in the coastal sediment budget associated, for example, to scarce sediment resources and modifications in the physical agents (e.g. wave climate, mean sea level) can promote over time morphologic changes at the shoreline and at the inlets located nearby. (2006) applied the wave model MAR3G to the Atlantic and found for the Portuguese coast only minor changes in the wave significant height and a clockwise rotation of 5o to 15o in the future wave climate direction, with respect to the present. They studied the impacts of this rotation on the littoral drift. The results show that the clockwise rotation will enhance coastal erosion by 15 to 25%
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