Uncertainties in projections of sandy beach erosion due to sea level rise: an analysis at the European scale

Panagiotis Athanasiou,Michalis I Vousdoukas,Jaap Kwadijk,Alessio Giardino,Roshanka Ranasinghe,Ap Van Dongeren

doi:10.1038/s41598-020-68576-0

Panagiotis Athanasiou, Michalis I Vousdoukas + Show 4 more

Open Access

https://doi.org/10.1038/s41598-020-68576-0

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Abstract

Sea level rise (SLR) will cause shoreline retreat of sandy coasts in the absence of sand supply mechanisms. These coasts have high touristic and ecological value and provide protection of valuable infrastructures and buildings to storm impacts. So far, large-scale assessments of shoreline retreat use specific datasets or assumptions for the geophysical representation of the coastal system, without any quantification of the effect that these choices might have on the assessment. Here we quantify SLR driven potential shoreline retreat and consequent coastal land loss in Europe during the twenty-first century using different combinations of geophysical datasets for (a) the location and spatial extent of sandy beaches and (b) their nearshore slopes. Using data-based spatially-varying nearshore slope data, a European averaged SLR driven median shoreline retreat of 97 m (54 m) is projected under RCP 8.5 (4.5) by year 2100, relative to the baseline year 2010. This retreat would translate to 2,500 km2 (1,400 km2) of coastal land loss (in the absence of ambient shoreline changes). A variance-based global sensitivity analysis indicates that the uncertainty associated with the choice of geophysical datasets can contribute up to 45% (26%) of the variance in coastal land loss projections for Europe by 2050 (2100). This contribution can be as high as that associated with future mitigation scenarios and SLR projections.

Highlights

Sea level rise (SLR) will cause shoreline retreat of sandy coasts in the absence of sand supply mechanisms
The use of the EUROSION versus the satellite derived sandy b eaches9 (SDSB) dataset has a minor effect on the European average shoreline retreat, with absolute differences of less than 3.5% (Fig. 2)
The European average shoreline retreat values computed with the spatially varying nearshore slopes41 (SVNS) data are almost 36% larger compared to that calculated with the 1:100 uniform slope assumption

Summary

Introduction

Sea level rise (SLR) will cause shoreline retreat of sandy coasts in the absence of sand supply mechanisms. The Bruun Rule[34] currently offers the only computationally viable method to assess the retreat of sandy shorelines due to SLR at the global, continental or regional scale, even though so far it has received a lot of criticism on its assumptions and widespread use (see Discussion section) This simple two-dimensional mass conservation principle predicts a landward retreat of the shoreline in response to SLR assuming that the beach will maintain an equilibrium profile. Hinkel et al.[30] assessed the global impacts of SLR using the Bruun Rule in an—at that time—state of the art global framework They described the spatial distribution of sandy coastlines qualitatively for coastal segments of varying length based on an aggregation of various coastal typology datasets. They assumed the same nearshore slope (1:100) across all the sandy beaches globally, neglecting the inherent spatial variability of coastal profile slopes, an assumption that can be quite crucial, since shoreline retreat is linearly dependent on the nearshore slope under the Bruun rule

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