Netherlands: Unique test of flood barrier made from glass
On Thursday January 23 directors, employees and relations of Water Board Limburg and the contractor combination Herik / Strukton vof witnessed a unique test in the Delta Flume of Deltares. Will a glass flood defense system during high water be resistant to occurring loads? And are the residents behind this flood system well protected? This innovative application of glass in a flood defense system combines safety with visibility.
The Herik / Strukton consortium is carrying out a two-year project for Waterschap Limburg to strengthen the dyke at Neer in the municipality of Leudal. Within this project, the application of a glass flood defense was conceived. If the tests at Deltares result in a positive result, the Limburg Water Board has the scoop for a glass flood defense that meets all strict safety requirements, ensures visibility on the Maas and can therefore be used as a tested system within dyke reinforcement projects at specific locations.
Protection and preservation of the view
The dike upgrade in Neer consists of strengthening the green dike over a distance of approximately 1,600 metres and strengthening a hard barrier (a retaining wall) of approximately 550 metres. The project interacts intensively with the locality. Raising the hard barrier by 70 cm meant that several houses would no longer have a view of the Meuse river. Local residents want to preserve the view of the Meuse. Safety was the most important factor for the water authority. It therefore initiated discussions with the local residents and looked at the options. In the end, the Limburg Water Authority opted for an innovative concept: part of the flood defences will be made from glass to maintain protection and preserve the view. The Herik/Strukton vof consortium is designing and producing the glass barrier. The plan is to install the barrier in the autumn of 2020 and the completion of the project as a whole is scheduled for late 2020.
Glass panels
The glass panels are made up of several layers of glass and foil: 3 structural panels in the middle, 2 so-called “sacrificial panels” on the outside and between them 1.5 mm films.
In close consultation with the experienced glass supplier Scheuten, the ideal thickness and composition in terms of strength and transparency have been calculated, always keeping in mind the aim of preserving the view of the Meuse river while meeting standards for flood risk management. The quality of the glass and film is high so that the barrier will be able to cope with external factors such as the weather. The glass panels will be installed over a total distance of 80 metres in four locations, the longest of will be 30 metres long.
Barrier tested at Deltares
A test section of the class barrier is tested in various ways at Deltares in Delft. The tests are conducted in the week of 20 January in the test facility the Delta Flume. A full-scale test section of the barrier is studied to see how it copes with wave loads and floating objects. A representative floating object has been selected: it is a 6-metre-long tree trunk weighing 800 kg and with a diameter of 40 cm that will collide with the glass at a certain speed. Various tests are conducted to demonstrate that the glass barrier can withstand the loads that occur at high water levels, providing adequate protection for the local residents who live behind the dikes. On the basis of the test results, the Flood Risk Management Expertise Network (ENW) will be asked to approve the system. On Thursday, January 23, a test was conducted in which the glass flood defense was tested with the load of water waves of 0.5 meters height and the tree trunk at a speed of 2 meters per second.