The Ommelander sea dike and the Lauwersmeer dike are primary water barriers in the Northern Netherlands. These dikes along the Wadden Sea protect the hinterland against flooding. All Dutch dikes have to meet certain requirements regarding aspects such as cladding, height and stability. It is mandatory to inspect the sea dikes for these aspects every six years. If the dike sections are not as they should be, they must be improved before the next inspection round. 

During the third inspection round in 2010, Waterschap Noorderzijlvest rejected 22 kilometres of the Ommelander sea dike. The dike was rejected in various areas on the aspects macrostability, subsidence, piping, grass or asphalt covering. Given the previous inspection, these deficiencies were caused by changes to the calculation standards. Based on the results of the most recent inspection, there is not yet an unsafe situation but it is important to ensure that the dike meets the current and future standards. The dike will therefore be improved prior to the next inspection round. Various improvements are planned during the next few years. 

Noorderzijlvest wants to know more about the dikes before the improvements are made. This is in order on the one hand to keep an extra eye on the dikes and on the other to find out more about the occurrence of failure mechanisms under certain conditions. The dikes will be monitored in real time with a sensor-monitoring system. Aspects such as the temperature, water tension and movement are important signs of piping, subsidence and macrostability problems. The occurrence of these failure mechanisms is detected. An impression is also gained of the location, seriousness and scope of the failure mechanism.

The aims of installing the monitoring system are as follows:

  1. To monitor the safety (early warning) of the rejected dikes until they have been improved;
  2. To provide additional information about the structure of the soil and the dike for the improvement work;
  3. To monitor the dike sections after the improvement work.

Various parties are taking part in the project. As well as Noorderzijlvest and Stichting FloodControl IJkdijk, they include public authorities, knowledge institutes and the companies that supply the sensors and the data collection and processing. The same parties will be jointly defraying the costs of the project. The investments will take the innovative research into water safety in the Netherlands another step further.

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