Probabilistic assessment of safety against dune retreat along the Northern-Holland coast

Coastal zone management is a multidisciplinary issue that can be assessed from multiple viewpoint s such as safety, recreation, ecology and nature. A possible means for properly maintaining the various functions of the coast is sand nourishments along either the shoreface and/or the beach. To assess the influence of sand nourishments, the time-dependency of appropriate indicators of the various coastal functions can be analyzed. HKV has conducted a study that focuses on the probability of failure for dune erosion, as an indicator for safety. For this purpose, the yearly JarKus measurements from the online OpenEarth-database are used. HKV has computed the probability of failure for dune erosion for the entire Dutch coast, from 1965 until 2010, using the dune erosion model DUROS+ and the probabilistic method FORM (‘First Order Reliability Method’), as implemented in the package PC-Ring. This approach is closely re lated to the approach of the project Flood Risks in the Netherlands (FLORIS/VNK). The current paper presents results of these computations, in relation to previous nourishment activities, for the region of Northern-Holland. These gained results can be used to further analyze the effectiveness of nourishments and can hence benefit future nourishment strategies by providing a decision supporting framework.