In the extreme northeast of the Netherlands, a stretch of innovative dike is being built that is unparalleled. The twelve kilometre stretch of seawall between Delfzijl and Eemshaven is the first reinforced dike in our country that is not only in accordance with the latest safety standards, but also earthquake-resistant.
The area faces major challenges: poor ecological conditions in the silted Eems estuary, subsidence and salinization in the hinterlands, and suffering economic carriers. The new dike offers added value for both the economic and ecological problems of the area. And since this project is the first in a long series of dike improvement projects along the Wadden coast, it is an excellent opportunity to test three innovative solutions, and with it, enable subsequent projects to be carried out in smarter, faster and cheaper ways.
That is why the Province of Groningen has asked Bosch Slabs and Alterra Wageningen UR to carry out a spatial exploration and a feasibility study for the concept of a ‘double dyke zone’ between Eemshaven and Delfzijl.
Three innovations have been investigated, dubbed the ‘Rich Dike’, the ‘Double Dike’ and the ‘Tide-resistant Dike’. The basic principle of the Rich Dike is to create a more natural transition between dike and water. The Double Dike means that the dike will not be reinforced, but that a second dike will be constructed behind the current one. The Tide Resistant Dike can resist tidal forces better, preventing breaches in the dike. These innovations have been combined and further developed, to create a single new dike design for the barrier south of Eemshaven.
The new ‘double dike zone Eemsmonding’ consists of a seawall on the waterfront that has been made wave-proof, and a second dike inland. Together, they are at least as robust as a single barrier. The wave resistance is created by strengthening the lining of the dike and the inner slope. The second dyke is made of material excavated from the area between the dykes. A tidal culvert will be built in the seawall, creating an area with ebb and flow between the two dikes, the ‘intermediate area’.
The new “double dike zone Eemsmonding” consists of a seawall on the waterfront that has been made tide resistant, and a second dike inland, which together are at least as robust as a single barrier.
The ‘gap’ between the dikes will stay under tidal influence, and offer numerous opportunities for economic and ecological development. This intermediate area will be made available for the cultivation of saline vegetables, aquaculture (the cultivation of, for example, fish, shellfish, shellfish and aquatic plants) and the capture of silt from the Eems-Dollard. In this way, it helps counter further silting up and muddying of the Eems-Dollard. Silt extraction also ensures the development of additional tidal ecologies.
A ‘pile forest’ of mussels will be planted outside the dikes and a high-water refuge for birds will be built. It is expected that this Rich Dike can lead to a reduction in the wave run-up. In this way, this concept contributes to water safety. In addition, numerous plants and animals can thrive on the Rich Dike. At low tide, water retreats to the tidal pools, while flora and fauna remain visible.
The results of the feasibility study and spatial exploration have contributed to the development of dike reinforcement plans by the Noorderzijlvest Water Board in 2015. At the start of 2018, the Ommelanderdiek consortium started building the second dike and strengthening the sea dike. From 2019 onwards, the province will start shaping the intermediate area.
More (Dutch) information can be found at:
The Double Dike is one of the projects within the Eems-Dollard 2050 Program and contributes to this by restoring nature in the Eems-Dollard area, finding solutions for sea level rise (water safety, salinization) and strengthening the quality of life and economy. BoschSlabbers is also involved in the elaboration of the other projects within this program and has made design sketches and visualisations for this.
Title: Double dike zone Eemsmonding
Location: Zeedijk bij Nieuwstad/Bierum, NL
Size: 50 ha Keringzone, 11,7 km pilot
Client: Province of Groningen
Cooperation: Alterra Wageningen UR, Deltares, waterschap Noorderzijlvest
Contractor: Boskalis Nederland, KWS Infra
Duration: 2014 - 2016
Type: Spatial exploration, feasibility study
Publication: "Een dubbele dijk met driedubbele doelen" H2O-Online, KNW, 18 juni 2015
Image credits: BoschSlabbers, Rijkswaterstaat Beeldbank, waterschap Noorderzijlvest
Project code: HL 14-16