Super Waves Tests at Deltares

The Delta Flume at Dutch-based research institute Deltares was the location last week 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.

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.

Current models

Hydraulic engineer Paul van Steeg at Deltares said: “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. 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.

The test will cost 2.6 million euro and it is being fully financed by the National Flood Protection Program, a joint initiative involving national public work authority Rijkswaterstaat and all regional Dutch water authorities.

The Netherlands is 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 realized quicker and cheaper. Dutch knowledge institutes and the civil engineering sector has been challenged by the National Flood Protection Program (HWBP) to come up with innovative solutions.