Upgrade of coastal defence structures against increased loadings caused by climate change: A first methodological approach

• Concepts of upgrading rubble mound structures exposed to climate changes are presented.
• Application of the upgrading procedure is demonstrated for a conventional revetment.
• A comparative cost optimization analysis of the various upgrading solutions is presented.

The paper presents a design exercise of upgrading a typical rock armoured revetment by modifying the structure profile and adding structure elements. Several concepts of upgrading are examined. A sea level rise corresponding to the mean of the IPCC 2007 predictions is used together with a slight increase in long-term wind/wave conditions as predicted for the North Sea by the Danish Coastal Authority. Both conditions of non-acceptable and acceptable increase in structure crest level are considered. Moreover, a scenario for steepening of the foreshore due to morphological changes caused by increased wave impacts is included. Only desk study tools are used for the upgrade designs. A simple comparative cost optimization analysis of the various upgrading solutions is presented, and conclusions are given for the preferred upgrading concept valid for the case study structure. A short discussion of the uncertainties related to upgrading design is included. The importance of physical model tests of the structures is underlined due to insufficient desk study tools for rubble mound upgrade design.