Storm test on Frisian asphalt can save millions on dikes throughout the Netherlands

Published: 10 July 2017

The Delta Flume at Deltares was the location today for the first storm test on asphalt taken from the Frisian Wadden Sea dike near Lauwersmeer. Trials are being conducted in the enormous flume – which is 300m long, 9.5m deep and 5m wide – to find out when a dike with an old asphalt revetment fails after being battered by strong waves.

Asphalt was transported from Friesland to Delft specially for the test. The results should tell us whether the asphalt in place now will be strong enough in the decades to come, or whether it needs replacing. Some hundreds of kilometres of dike in the Netherlands are covered with asphalt; the storm test could be relevant for many of those dikes and save millions.

Paul van Steeg of Deltares: ‘Asphalt is a strong material for dike revetments but we are not entirely sure how strong asphalt is when it is 30-50 years old. So that is what this test in the Delta Flume will tell us. We will be able to say whether the asphalt will be up to standard for longer than we assume in our current models. That can save a lot of money.’

Jan Hateboer of the Wetterskip Fryslân water authority: ‘This is an important study, and not just for Friesland. In the Netherlands, we have about 300 kilometres of dike with asphalt that can benefit from the results. A quarter of our dikes will be upgraded in the years to come. If the test shows that the asphalt is still strong enough, those upgrade operations can be postponed. That will allow us to work in smarter and more efficient ways and to control our costs because the Netherlands is now planning for the largest dike upgrade operation ever.’

Tests on asphalt dike revetments in the Delta Flume

Asphalt dike revetments tests in the Delta Flume

The study will look at the residual strength of the asphalt on the Lauwersmeer dike. Ten strips of asphalt eight metres long and fifty centimetres wide will be removed from the dike by the Wetterskip Fryslân water authority and positioned on the model of the dike in the Delta Flume. The failure process of the asphalt as it is subjected to the force of the waves will be simulated and monitored. This provides new insights and knowledge for dike improvements in the Netherlands. The test is an opportunity to assess and improve the assessment criteria for asphalt revetments. It is possible that Dutch dike upgrade operations will be cheaper in the future as a result.

The study will cost 2.6 million euros and it is being fully financed by the National Flood Protection Programme, a joint initiative involving Rijkswaterstaat and the Dutch water authorities.