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

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.

Assessment of the Netherlands' flood risk management policy under global change.

Climate change and sea level rise urge low-lying countries to draft adaption policies. In this context, we assessed whether, to what extent and when the Netherlands' current flood risk management policy may require a revision. By applying scenarios on climate change and socio-economic development and performing flood simulations, we established the past and future changes in flood probabilities, exposure and consequences until about 2050. We also questioned whether the present policy may be extended much longer, applying the concept of 'policy tipping points'. Climate change was found to cause a significant increase of flood risk, but less than economic development does. We also established that the current flood risk management policy in the Netherlands can be continued for centuries when the sea level rise rate does not exceed 1.5 m per century. However, we also conclude that the present policy may not be the most attractive strategy, as it has some obvious flaws.