Modeling geomorphological and ecological development of Hedwige and Prosper polders after depolderisation

How, where and when vegetation develops in areas that are depolderised is vital for good management of these new ecosystems. The NIOZ Royal Netherlands Institute for Marine Research has, together with the Flemish Dutch Scheldt Committee and the Rijkswaterstaat, been funding for a four-year development study for indicators for the first settlement of vegetation in depolderised areas such as the Hedwigepolder.

How will the polder develop?

Will the Hedwigepolder for decades remain  a silt flat that is unsuitable for plant life, or will the area soon be suitable for the first settlement of vegetation? Drainage of seawater seems important for the establishment of vegetation. In poor dewatering, the mudflat remains soft and oxygen free, making it very difficult for plants to settle. Also if drainage is better, vegetation does not develop, however distinctive mats of Vaucheria and diatoms emerge. Those algal mats may form remarkable spatial patterns, showing how well dewatering is and what opportunities are for further vegetation.

Spatial patterns of algae

That knowledge forms the basis of this project. We want to investigate how spatial patterns of Vaucheria and diatoms can be used to predict the rate of further vegetation development. The results will guide the monitoring of areas such as those of Hedwigepolder after depolderisation.

In addition, monitoring will enable us to monitor the development of areas to be depolderised and to intervene immediately if developments do not contribute to the restoration of certain habitats lost in the Westerscheldt. This enables us to further develop the important cooperation of the VNSC and the NIOZ.

The project can contribute globally to a new way of managing estuaries, in which the Netherlands has a leading role.