Dynamics of engineered coastal dune landscapes at the Zandmotor

Coastal dune systems are increasingly threatened by sea level rise, increasing human activities, and changing wind and wave climate, leading to coastal squeeze. One potential adaptation strategy for coastal squeeze is the creation of seaward space for the development of coastal dunes through sand nourishment. The Zandmotor, a large-scale sand nourishment implemented in 2011 near The Hague (The Netherlands), serves as a unique example of creating new space for coastal dunes. While morphological changes at the Zandmotor have been studied extensively, its role in promoting natural dune formation, sediment-vegetation interactions, and long-term dune landscape development remains underexplored. This study quantifies dune growth and vegetation development using an extensive dataset collected at the Zandmotor during more than a decade. Our results demonstrate significant increases in both the extent and elevation of the foredunes after creating new space for coastal dune development. The average growth of dune volume is 18 m3/m/year. The highest growth rates, reaching 49 m3/m/year, were observed in areas with newly formed embryo dunes. Vegetation cover increased over time, contributing to enhanced sediment capture and accumulation. These findings demonstrate that sedimentation–vegetation feedbacks characteristic of natural systems operate effectively in engineered coastal environments, when space for dune development is created through a mega nourishment. They also highlight the importance and potential of ecological processes in supporting long-term coastal resilience in adaptive engineered environments. Applying the findings of this study to other environments and nourishment designs could offer additional insights into a new perspective for mitigating coastal squeeze in dynamic coastal dune landscapes.