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

Abstract

Coastal zone management is a multidisciplinary issue that can be assessed from multiple viewpoints 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 related 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 NorthernHolland. 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.

Fully probabilistic assessment of safety against flooding along the Dutch coast

“…() and Van Balen et al . (), the analysis was limited to the first dune row. The present study clearly shows that for large parts of the Dutch coast, the first dune row is of minor importance in view of flood risks.…”

“…() and Van Balen et al . () did not take failure of dikes into account. The present study makes clear that in most cases, the failure probabilities of the dike stretches dominate the flooding probability of the area behind the flood defences.…”

“…Additionally, Van Balen et al . () relate the trends in the time series with failure probabilities to the nourishments carried out, and demonstrate the (differences in) effectiveness of beach nourishments and shoreface nourishments in maintaining the safety of the sandy coast. Vuik et al .…”

“…In earlier studies of Den Heijer et al (2012) and Van Balen et al (2012), the analysis was limited to the first dune row. The present study clearly shows that for large parts of the…”

Coastal state indicators to assess the morphological development of the Holland coast due to natural and anthropogenic pressure factors

“…4a), which defines a certain residual strength. The modelling package has been used in previous similar studies concerning safety assessment in relation to dune erosion (Van Balen et al, 2012). The model is only suitable to compute the probability of failure of the first and seaward dune row.…”