Super waves put old asphalt levee strips to the test at Deltares
The Delta Flume at Dutch-based research institute Deltares was the location for the first storm test on 47-year old asphalt taken from an original Dutch sea levee.
Trials started on 10 July and are being conducted in the enormous flume – which is 300m long, 9.5m deep and 5m wide – to find out when a levee with an old asphalt revetment fails after being battered by strong waves.The 8 m long asphalt strips collected from a 47 year old sea levee (also see the inserted black strips on top photo of the Delta flume).
Strips of the original asphalt were transported from the coast to Deltares specially for the flume test. The battering with the extreme waves must show 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 levee in the Netherlands are covered with asphalt; the storm test could be relevant for many of those levees and save millions.
Hydraulic engineer Paul van Steeg at Deltares: ‘Asphalt is a strong material for levee 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’, says Van Steeg. ‘We will be able to say whether the asphalt will be up to standard for longer than we assume in our current models.’
Ten strips of asphalt of 8 m long and 50 cm wide, have been supplied by regional water authority Wetterskip Fryslân who maintains the particular sea levee.Collection of the asphalt strips from the original sea levee earlier this year.
Upgrading asphalt levees
On the occasion of the start of the flume test, Jan Hateboer of Wetterskip Fryslân highlights the importance of study. ‘In the Netherlands, we have about 300 kilometres of levee with asphalt that can benefit from the results. A quarter of our levees will be upgraded in the years to come.’
‘If the test shows that the asphalt is still strong enough’, Hateboer continues, ‘ 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 levee upgrade operation ever.’
Stricter flood safety standards
The test will cost 2.6 million euro and it is being fully financed by the National Flood Protection Programme, a joint initiative involving national public work authority Rijkswaterstaat and all regional Dutch water authorities.
The Netherlands are facing the largest dike reinforcement task in the country’s history. Due to stricter safety standards adopted by the Dutch government, 1,100 km of dikes have failed to pass the safety tests and will require repairs and maintenance by the year 2028.
To achieve this goal, the current levee reinforcement needs a boost and projects have to be realised quicker and cheaper. Dutch knowledge institutes and the civil engineering sector has been challenged by the National Flood Protection Programme (HWBP) to come up with innovative solutions.
Read also on this website
● Deltares puts vertical composite sea wall to the test in world’s biggest wave flume, 23 December 2016
● World’s biggest man-made wave rolls down Delta Flume during inauguration, 6 October 2015
● New Dutch 20 billion euros flood programme introduces risk-based standards for 2050, 17 September 2014
Delft, the Netherlands
+31 88 335 82 73
National Flood Protection Programme (HWBP)
Utrecht, the Netherlands
+31 88 797 32 70
Regional Water Authority Wetterskip Fryslân
Leeuwarden, the Netherlands
+31 58 292 22 22
Flume test at Deltares with strips of 47-year old asphalt revetment.