The ten North Frisian Hallig islands are located in Schleswig-Holstein’s part of the UNESCO world heritage Wadden Sea. They are of worldwide uniqueness and strongly influenced by tides, wide systems of tidal inlets and the shallow relief of the sea bottom. One unique feature of these islands is the lack of dikes. For this reason the houses are built on artificial dwelling mounds in order to protect the inhabitants and their goods against frequently occurring inundations during storm surge seasons. Nevertheless, the Hallig islands themselves benefit by these inundations due to sediments, which are accumulated on the island’s surfaces. This sedimentation has enabled a natural adaption to sea level rise in the past. In times of climate change and an accelerated sea level rise it is not confident if this natural vertical marsh accretion can compensate the rise of average water levels as well as an acceleration of sea level rise. These ecologic and cultural characteristics are not the only reason for the great importance of the Hallig islands and the surrounding Wadden Sea. They also reduce wave loads on the sea dikes at the mainland in the east of the islands. Due to the geographic location and the isolation during extreme events special kinds of protection measures have been developed over the last centuries. The construction methods of these measures are mainly based on tradition and the knowledge of the inhabitants. However, no resilient design approaches and safety standards for these special structures like dwelling mounds and elevated revetments exist today and neither a cost efficient construction nor a prioritization of measures is possible. Main part of this thesis is the scientific investigation of the existing coastal protection measures with the objective of the development of design approaches and safety standards. Furthermore, the influence of different parameters on sedimentation on the island’s surfaces is analysed. New impulses for sustainable coastal protection measures and management strategies are given which simultaneously consider future climate conditions and the resulting loads. The inhabitants are directly involved in this process by stating their knowledge, experiences and ideas for future protection measures. To answer these research questions a numerical model is built to calculate the hydrodynamic loads in the area of the Hallig islands. The further investigations follow a typical profile through one of these islands. Beginning at the edge of a Hallig island, the hydraulic performance of the elevated revetments is tested in physical and numerical tests. The results are a weir coefficient and a coefficient for permeability as well as a design approach. This approach respects not only wave overtopping and flow through the structure but also erosion processes on the Hallig island surfaces. The investigations on the main surface areas of the islands show that simple measures can influence the vertical marsh accretion and a sustainable adaption to a rising sea level is possible. A resilient safety standard for artificial dwelling mounds is developed. It considers the location, geometry and hydrodynamic loads of the respective dwelling mound. This safety standard is applied and quantified for selected dwelling mounds. New impulses and ideas for future protection measures are generated during futureworkshops where the inhabitants can develop their own coastal protection concepts under scientific advisory. The following evaluation from the hydraulic engineering perspective guarantee hydrodynamic effective and social accepted measures. The results provide a scientific contribution to future sustainable coastal protection measures in the area of the North Frisian Wadden Sea. Furthermore, partial results also represent an extension of knowledge for other coastal areas.

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2016; Aachen 1 Online-Ressource (220, 30 ungezählte Seiten) (2016). doi:10.18154/RWTH-2017-04570 = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2016

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