Coastal protection strategies increasingly have to take into account the effects of climate change. At present, engineering and natural science models that assess the impact of global climatic transformations on regional coastal zones and their protection structures remain rather detached from societal bodies of knowledge. Various alternative adaptation options such as dike reinforcement, accommodation or retreat may conflict with value-based interests and priorities of different groups of actors.
This paper argues, that innovative coastal protection requires not only interdisciplinary but transdisciplinary research that takes into consideration the whole array of actors involved in regional coastal protection.

The findings presented in this paper result from the five year research project A-KÜST – “Changes in the Coastal Climate: Evaluation of Alternative Strategies in Coastal Protection” – that was launched in 2009 in the context of the Climate Impact Research Programme (KLIFF) of the German federal state of Lower Saxony. The transdisciplinary project is structured into six natural and engineering subprojects and one social science based subproject. In addition, the project comprises an advisory board with all relevant actors participating in coastal protection in the project region of the Ems-Dollard estuary (Southern North Sea). The main objectives of the social science subproject are on the one hand to structure and to organize the communication between science, practice and the society, on the other hand to analyze the perceptions and evaluations of climate change and coastal protection among all actors involved.

The findings presented in this paper are based on an evaluation study which focuses on disclosing and structuring latent value-based interests of different actors and integrating those into a multi-criteria evaluation of alternative adaptation options in coastal protection. Within this framework first a value-tree method was applied to create a qualitative foundation by identifying different value judgements and second the development of evaluation criteria against which different alternative adaptation options are to be evaluated. The main objective of the value-tree method was to create a comparable and sound framework of evaluation patterns of all relevant actors related to regional coastal protection.
During moderated discussions with homogeneous groups of representatives from institutions who are concerned with and affected by coastal protection interests and objectives were value-trees were developed that were consented by each group.

The value-tree analysis reveals a heterogeneous picture of areas of consensus and of striking differences that may have many implications for the collective strategy development process. While nearly all groups perceive defending the region against flooding as the major aim of coastal protection, the interests in how this can be solved diverge. The extracted evaluation criteria broadened the catalogue of criteria against which alternative options for adaptation are evaluated that is mostly characterized by engineering or economic criteria.

The value-tree analysis turned out to be a promising methodological approach that can be embedded in transdisciplinary research contexts, by meeting the requirements of integrating the whole array of societal and scientific actors, their knowledge and interests in a transparent procedure. Reflecting the diverging or resembling interests, objectives and perceptions fosters the communication and common understanding among science and practice and finally fosters the societal anchoring of adaptation strategies within the governance network of regional actors.