18. A Sensitivity Study of Storm Surges Under the Conditions of Climate Change in the Elbe Estuary

For adequate adaptation strategies in the metropolitan region of Hamburg, a detailed understanding of the future hydrodynamic situation along the German Elbe is required. To achieve this aim, we will investigate the impact of a possible change in climate on storm surge water levels along the Tidal Elbe. The outcomes will help to identify vulnerabilities and aid the development of adaptation measures as part of the project KLIMZUG-Nord. A sensitivity study is carried out for probable future storm surge scenarios: based on historical events, the scenarios are derived by systematic variation of the key parameters influencing storm surge conditions in the estuary. A hydrodynamic numerical model is used to calculate water levels, currents and characteristic numbers in the Elbe whilst a meteorological model provides the local wind field. An increase of mean sea level, wind speed and river discharge influences the storm surge characteristics along the Tidal Elbe. A rise in mean sea level and wind speed leads to an increase in high water levels. Upstream of Hamburg, high water levels are mainly affected by river discharge. However, the sensitivity of water levels to the key parameters varies along the estuary. This behaviour is observed for two investigated storm surge types. The results enable us to identify vulnerabilities along the Tidal Elbe for a range of possible future storm surge conditions. It can be determined whether existing protection strategies will be effective or must simply be replaced by new concepts. In the future the present results can be assigned to climate change projections and estimations of occurrence.