Uncertainty in long-term bio-geomorphological dynamics for vegetated foreshores


Persons involved
Ir. P.W.J.M. Willemsen
Prof. dr. S.J.M.H. Hulscher
Prof. dr. T.J. Bouma
Dr. Ir. Bas Borsje

Funding of the project
Van Oord
Boskalis Westminster N.V.
World Wildlife Fund
HZ University of applied science

Other stakeholders
HKV Consultants
It Fryske Gea


Over the last decades, the development of coastal areas shows a growing paradox. The majority of the world population has settled in coastal areas, while coastal flood risks are likely to increase due to global and regional changes, including storm intensity, accelerating sea level rise (SLR) and land subsidence. Conventional coastal engineering solutions are increasingly challenged by these changes and become unsustainable. Ecological engineering can serve as an alternative or add-on to conventional coastal defenses, such as groins, breakwaters, dams and revetments.

The BE SAFE project is focused on developing new methods to assess how, and how much vegetated foreshores can contribute to flood risk reduction. The project will lead to a better understanding of (uncertainties in) the functioning and stability of these ecosystems and the development of governance arrangements. This requires integration of knowledge from ecology, bio-geomorphology, hydraulic engineering and governance.

Within this bio-geomorphologic subproject the main knowledge gap hampering application of intertidal ecosystems within coastal defense schemes is lack in ability to account quantitatively for long-term ecosystem. Several studies indicate that the dynamic foreshore can conceptually be related to SLR and that the bed level decreases after an extreme event. More recently, it is showed that the bed in the vegetated marsh remains stable during extreme weather events, while the tidal flat in front of the marsh is more dynamic and affecting the long-term sustainability of the intertidal ecosystem. The bare flat (in front of the vegetated marsh) and the vegetated marsh are frequent separately studied areas. However to our knowledge, the coupled bio-geomorphological dynamics of the (eco)system as a whole is not considered in the long-term. The aim of this study is β€œto quantify the long-term (50 – 100 year) bio-geomorphological behavior of the coupled system of bare intertidal flats and vegetated foreshores.”