Designing More Efficient Flood Walls

Coastal cities of low lying countries, such as the Netherlands, Belgium, the UK and Germany often have a gentle beach with a dike and a promenade.

Along the promenade buildings such as hotels and restaurants are present, protected by storm walls. During a heavy storm the waves will run up to the promenade and impact at such structures.

New scenarios for climate change and sea level rise make it worthwhile to invest in research regarding overtopping wave impacts.

Better understanding of complex wave interactions

In the European project called ‘Wave Loads on Walls (WaLoWa)’ Deltares set up large-scale model tests in order to study the wave-induced loads on structures situated on top of a dike under shallow foreshore conditions.

Hence, forces and pressures on the structure will be measured and eventually related to the incoming wave and structural parameters. The results will be compared with small-scale experiments featuring the same geometry and wave conditions, to enable a study of scale effects and the possible influence of aeration of the impacting flow.

The full length of the Delta Flume is used in the tests with a shallow foreshore made of sand. The transformation of the sandy foreshore under the waves is also analysed.

Additionally, the layer thickness and velocity of the wave-induced flow on the promenade will be investigated and the instantaneous overtopping discharges will be calculated. Bichromatic wave tests will enable better understanding of the complex wave interaction processes between incoming and reflected waves on the promenade.

Five universities working together

The project is a cooperation of Flanders Hydraulics (Antwerp) and five universities from across Europe: Ghent University (coordinator), RWTH Aachen, University of Florence, TU Delft and University of Bari.

The project is financially supported by a grant by Hydralab+ in the framework of the EC Horizon 2020 program. The tests are carried out by Deltares in the Delta Flume.

Prof. Andreas Kortenhaus, project leader, Ghent University: “Increased water levels and storms at the coasts could be reasons for more and more severe overtopping on promenades, endangering the safety of both people and assets. Our tests at Deltares will contribute to a better understanding of the underlying processes. This will eventually lead to a higher safety of people at the coasts.

More efficient designing of flood walls

Mark Klein Breteler, project leader Deltares: “The results of this fundamental research give us insights that can be used to design a flood wall on a promenade. Designing such a wall can be more efficient with the new knowledge. That’s important, because such a wall should always be fitted well into the environment, to prevent a barrier between the coastal city and the sea.