Using a process-based model for dune safety assessment

Abstract

With the implementation of new legal aspects for dune safety assessment in 2017, the current method, Duros+, is no longer feasible to represent the desired processes. This 1D deterministic, volume-balance model cannot simulate processes like inundation and overwash, which are crucial to fulfil the new requirements for dune safety assessment. Therefore, the implementation of a 2DH XBeach model for dune safety assessment is evaluated. A transformation from 1D to 2DH becomes necessary and several hydrodynamic effects come into play, which are not relevant for a simulation in 1D. Additionally, the definition of a new limit state is a challenging task in order to define failure properly: The legal definition needs to be transformed into a technically feasible one. In this thesis five different limit states have been defined in order to evaluate the influence of a limit state on its consequences. These five limit states are then applied in a case study on the Delfland coast and the consequences of the different definitions are evaluated. Additionally, the safety development of the Delfland coast over the last two decades was analysed. It was found that all nourishment strategies applied at this coastal stretch contributed to an increasing safety. This includes the placement of the Sand Engine and its on-going alongshore spreading.