Assessing coastal flooding uncertainties using global sensitivity analysis

Understanding the relative magnitude of uncertainties in total water level estimation is critical for prioritizing research efforts and developing more accurate models and projections of future scenarios. This paper examines the uncertainty factors affecting total water levels at two beaches characterized by entirely different processes and conditions. Using a variance-based global sensitivity analysis, we assess the contributing uncertainty related to sea level rise, astronomical tide, storm surge and runup dynamics, both historically and for different projection scenarios up to 2099. Our analysis highlights the predominant influence of coastal processes and tides in the early 21st century. As the century progresses, the impact of sea-level rise and climate change scenarios intensifies. However, the temporal evolution of uncertainty exhibits site-specific characteristics, with beaches dominated by nearshore processes (waves and storm surge) showing a less important role for climate effects also in the long-term future.