Coastal flooding in Denmark – future outlook

Water loading from all directions due to river discharge, precipitation, groundwater and the sea state (i.e. mean and extreme water levels) need to be carefully considered when dealing with flooding hazards at the coast. Flooding hazard and risk mapping are major topics in low-lying coastal are- as before even considering the adverse effects of climate change and sea level rise (SLR). From an assessment of Danish sea extremes from historical evidence, tide gauge series, and space measurements, we discuss the current and future hazards, exposure, and vulnerability to flooding along the diverse Danish coastline in the transition between the Baltic Sea and the North Sea. The evaluation of the extreme statistics and their applicability in flooding hazard and risk management, and a presentation of the hazard and risk mapping performed through the implementation of the EU Floods Directive using the German XtremRisk approach, form the basis for projecting potential impacts of flooding due to climate change (SLR and increased storminess). Central to this impact assessment are also the evaluation of natural meteorological variability, robustness of the statistics, physical changes, local subsidence, land-use, protection measures a.o. that must be taken into account in order to evaluate current and future flooding hazards and management options. We provide examples from Danish case-studies underlining the necessity of including these factors and we outline an interdisciplinary approach to bring this knowledge together to enable a practice-oriented methodology that combines their effects and future sea extremes in hazard and risk mapping and climate change adaptation schemes in Denmark