Trial dike made from dried sediment on the Dollard

Published: 9 October 2020

In ideal conditions, the Hunze en Aa's water authority and Ecoshape has built a 40-metre-long test dike in front of the sea dike on the Dollard in recent weeks. The test dike was built of clay taken from the clay ripening plants that processed sediment from the seaport channel of Delfzijl and the Breebaart polder. This material – clay ripened from salty dredged sediment – has never been used for dike upgrades before.

Using locally available material

Researcher Wouter van der Star explains: “The idea behind the trial is to demonstrate scientifically that a safe dike can be made using material available locally.” Erik Jolink of the Hunze en Aa’s water authority adds:”We are demonstrating that we can still build dikes with material that we find or extract locally and that falls (just) short of the formal requirements for clay. We are adapting the design in line with the properties of the local clay so that we can build a safe dike with this material as well.” That is good for nature because the sediment no longer drifts in the Eems-Dollard estuary and because the transport distances are short.

Broad green dike

The construction of this test dike is part of the ‘Broad Green Dike’ demonstration project. The test dike will deliver knowledge that is needed for the proper construction of the’Broad Green Dike’. The idea is that the current sea dike will be wider in the future after it is finished with a thick layer of clay covered with grass. Before we start working on that stage in 2022, we want to identify the best way of processing the different types of clay. In addition, we are looking closely at the structure of this test dike.

Building with Nature

We are building with dried sediment from the Eems-Dollard. The material comes from two locations: the seaport channel of Delfzijl and the Breebaart nature polder. The large-scale use of sediment from the Eems-Dollard reduces the turbidity of the water there,  improving the ecological quality.

Partnership

The partners in the Clay Ripener EcoShape project and the Broad Green Dike are: the Dutch Flood Risk Management Program (HWBP), the Wadden Fund, the Province of Groningen, Groninger Landshap, Groningen Seaports, Rijkswaterstaat and salt-marsh owners.