Broad green dikes are cheaper to build and often provide more protection than traditional dikes with stone or asphalt revetments. Generally, they are also a more harmonious match with the surroundings. This alternative should therefore be considered more often during dike upgrades.
This is the conclusion of a study by Deltares and Alterra Wageningen University and Research Centre for the dike upgrade in the Eems-Dollard area. The study looked at the options for a broad green dike along the Dollard, and compared the construction costs and protection level of a broad green dike with those of a traditional dike.
Alternative often used in the past in the Netherlands
A broad green dike has a very shallow slope and a foreland consisting of marshland. The dike is built entirely from clay and covered with grass. Including natural features in the design generates interest from nature conservation organisations and local residents.
This approach to building dikes has been used often in the past in the Netherlands but it is no longer considered as an alternative because there is a preference these days for dikes that take up as little space as possible.
A broad green dike admittedly takes up more space and this makes these dikes inappropriate in locations where space is at a premium. However, the Eems-Dollard area is actually very suitable for this type of dike.
Study in response to rejection of dikes
The ‘Detailed exploration of a green Dollard dike’ study was conducted as part of the national government’s Wadden Area Delta Program in collaboration with Rijkswaterstaat’s corporate innovation program, the rich Wadden Sea program and the Rural Area Department (Dienst Landelijk Gebied).
The study was initiated in response to the rejection of a number of dikes in the northern Netherlands because the hard revetments were no longer able to cope with the waves.
Press Release, May 23, 2014