No abstract

Information about possible changes of extreme wave heights are essential for the future safe design of coastal and flood protection structures likes dykes, flood protection dunes, revetments etc. In this study, scenarios of regional climate change up to 2100 are used for the evaluation of changes of wave conditions. Analyses on calculated significant wave heights derived from extreme value statistics are showing a different signal of change for the selected locations along the German Baltic Sea Coast. The results are showing that extreme wave heights with a return level of 200 years can increase up to +14%. But also a decrease of down to -14% were found compared to actual conditions, depending on the location and climate change scenario applied. At the location of Warnemünde a slight increasing trend for the change of extreme wave heights could be found for 3 of 4 scenario runs with a maximum increase of +7%.

On the basis of hourly simulated wind data from a regional circulation model (Cosmo-CLM) wave conditions from 1960 to 2100 are calculated for two realisations each of the global emission scenarios A1B and B1 using a numerical wave model for the area of the Western Baltic Sea. Comparisons of the 30 years averages of the wave conditions between the future and the past show that the changes of the average wave conditions can be directly linked to the changes of the average wind conditions. The changes of the average wave conditions and extreme wave events are characterised by high spatial and annual variability. In addition the changes depend on the time period of the comparison, the global emission scenario and the realisation of the climate model run. The bandwidth of the changes is moreover affected by the approach for the calculation of the wave conditions. A significant climate change signal of the average wave conditions is found at westerly wind exposed locations with predominant higher values of the average significant wave heights up to +10%. At easterly wind exposed locations the climate change signal is more weak and higher and lower values are possible (-5% to +5%). Regarding the future changes of the wave directions, in general more wave events from W-NW and fewer events from N-NE can be expected. Analyses of extreme wave heights with a return period of 200 years show both increasing and decreasing values (-0.5m to +0.5m). The climate change signal of the extreme wave events is, as the same for the changes of the average wave conditions, more robust at locations which are exposed to westerly winds.

Low lying coastal areas have always been preferred settlement areas as well as trading and industrial areas. Unfortunately, those areas are strongly endangered by extreme storm surges. In the event of a flood defence failure, protected areas are flooded and damages have to be expected. For the assessment and management of flood risk, the European Union approved the "Directive of the European Parliament and the Council on the assessment and management of flood risk".As one part of a risk and damage analysis the risk of flooding -being the product of failure probability of a certain flood defence and the damages resulting from a failure of this flood defence -has to be determined. One possibility for the assessment of the failure probability is provided by fragility curves. A method for the derivation of fragility curves for flood defence dunes is described. Hence, the applied dune erosion model as well as the method for the derivation of the required input data is explained. Furthermore, first results of the calculation of failure probabilities and fragility curves are presented.