Relevance of Varying Coastal Defense Systems on Flooding and Damage of Coastal Areas

This paper presents investigations on the effects of varying coastal defence systems on flooding and damage of the protected hinterland in case of failure of the main coastal defences. The mainland coast of the German Federal State Lower Saxony is protected by a coastal defense system consisting of legally defined main dikes and supplemental elements such as forelands or secondary dikes. Within the applied research project HoRisK (Flooding Risk Management for Coastal Areas) consequences of flooding in case of failure of the main dike and the effects of the supplemental elements were investigated by application of a hydro-numerical model and a geographical information system. Results show, that in case of dike breaches a foreland can reduce the affected area significantly, depending on width and height of the foreland. The effects of secondary dikes on consequences of flooding strongly depend on the storage volume between primary and secondary dike as well as on the height of the secondary dike.