Projects

Goal of the Project

The goal of the Hybrid Dune work package is to be able to better understand and predict the flood safety of hybrid dunes. Hybrid dunes are flood protections that consist of both sandy dunes and hard elements, for example dike-in-dune constructions, dunes that accrete in front of dams, or buildings present in the dunes. We want to better understand and quantify the interactions between the hard and sandy elements and how this affects the erosion resistance of hybrid dunes. Therefore a full-size hybrid dune will we constructed at the beach, and carefully monitored during storms. With the results, we aim to incorporate hybrid dune systems in a numerical dune erosion models. This should result in knowledge of the applicability of hybrid dunes, and better tools to assess the safety of our flood defenses.

Scientific Motivation

Hybrid dunes are used more and more worldwide. This leads to an increasing need to accurately predict their safety, whether in the design process of new flood defenses or to assess the safety of existing ones. However, this is hampered by a lacking understanding of the interactions between the soft and hard parts of a hybrid dune. For instance, the erosion of the sandy dune is affected by wave reflection and scour at the hard elements. Our field experiment and numerical modelling aims to fill this gap, and quantitatively link hydrodynamics, sediment transport and erosion to the design of a hybrid dune.

Case Study

Hybrid dunes are extensively present in Zeeland, whether in the form of dunes in front of a dam (the Brouwersdam), dunes built in front of a dike as dike reinforcement (Groede) or dunes built behind (landward of) a dike as dike reinforcement and nature development (Breskens). Our research aims to better understand these hybrid dunes, so that Water Authorities can determine if their flood defenses meet the safety standards or require reinforcement.

Expected Outcomes

• A dataset on international cases of hybrid dunes, showcasing their designs, similarities and differences between countries, and knowledge gaps and opportunities for their application.
• A dataset on dune erosion at hybrid dunes, that can be used to validate a numerical dune erosion model for application to hybrid dunes. This data will be collected in a field experiment, and contain the hydraulic conditions and dune erosion over two months, at four different hybrid dune cross sections constructed at the Sand Motor
• Numerical modelling tools for dune erosion at hybrid dunes
• Recommendations for the official safety assessment of hybrid dunes
• Papers reporting
  • An inventory of international hybrid dune cases
  • The setup and results of the field experiment
  • The numerical modelling of dune erosion at hybrid dunes