A dyke made of the clay from our clay ripeners near Delfzijl is currently being tested in the Delta Flume of Deltares. A full-size cross-section of the dyke has been constructed in the flume and is being subjected to the conditions of a super storm.
The tests are part of an extensive study to verify the safety of a dyke reinforced with clay ripened from locally available dredge sediment. Water authority Hunze en Aa’s intends to use this clay to strengthen the seawall in the North of the Netherlands near the German border into a so-called Broad Green Dyke, contributing to key societal ambitions such as flood safety, climate adaptation, circularity and water quality.
The Broad Green Dyke is a dyke with a gentler slope than standard dykes. It is reinforced with clay obtained from salty dredge sediments that have ripened (dried) in only three years. With the results from this trial, the water authority can improve the design of the Broad Green Dyke, assuring its safety. The results will also increase the predictability and applicability of locally extracted dyke material in the Netherlands and abroad. The entire study will be completed in 2022.
Dyke reinforcement in the Netherlands
If the trial is successful, it will be of great benefit to the total dyke reinforcement task for the rest of the Netherlands. Erik Wagener, director of the Flood Protection Program: “We are working in a unique collaboration between the government and the 21 water boards on the largest dyke improvement operation since the Delta Works: the reinforcement of at least 1,300 kilometres of dyke and 500 locks and pumping stations. If we can construct some of the dykes with locally extracted clay from sludge, it will make a huge difference in costs, in environmental impact and in nuisance caused by transport of clay from afar.”
Luca Sittoni, programme manager at EcoShape and Deltares: ‘In many parts of the world, coasts, shores, lakes and rivers have to deal with excess sediment. This negatively affects water quality and biodiversity. In some of these locations dyke reinforcement is also needed. With the knowledge we gain here, we can design solutions to circularly use the excess sediment to improve flood safety and restore water quality at the same time’.
Water authority Hunze en Aa’s is the initiator of the research. The EcoShape partners Deltares, van Oord and Boskalis support and carry out the research. Advice is provided by the Clay Ripener project group led by the Province of Groningen, the workgroup for dyke improvement with locally sourced clay (POV-DGG), and Wetterskip Fryslân. The Flood Protection Program is the main funder and advises on the research.