Such a structure has never before been realised anywhere in the Netherlands. In terms of both technology and scale, the flood defence in Steyl, based on a concept by Vlotterkering BV, is unparalleled. Under normal water levels, the defence remains at rest, concealed within the public square, preserving views of both the river and the village of Steyl. During high water, the deck begins to float and the flood-defending section of the square rises automatically. In this way, a self-closing flood defence measuring 134 metres in length and 3 metres in height protects Steyl – and the area behind it – against flooding.
A strict selection process
The former flood defence in Steyl was neither high nor strong enough. During the high-water event in the summer of 2021, for example, emergency measures were required. Steyl is a nationally protected village conservation area, where both the view of the river and the view from the river are of exceptional value.
The self-closing flood defence obstructs these views only when it is genuinely necessary: during high water. The tender process therefore involved a strict selection procedure, assessing proposals on price, spatial quality, environmental impact and technical reliability. The concept submitted by the Dijkzone Alliance achieved the highest overall score among all bidders.
Flood Protection Programme
The dike reinforcement project in Steyl forms part of the national Flood Protection Programme (Hoogwaterbeschermingsprogramma, HWBP), the largest dike reinforcement operation since the Delta Works. Within this programme, water authorities and Rijkswaterstaat will reinforce more than 2,000 kilometres of dikes across the Netherlands over the next thirty years. Approximately 175 kilometres of this total are located in the province of Limburg.
Waterschap Limburg works every day to strengthen dikes in order to continue protecting residents and businesses in the river valley against future flooding. This requires close cooperation with partners and stakeholders. Together, we determine what is important for the area.
How the self-closing flood defence works
The flood defence consists of 14 individual segments (gates), which are connected to one another by means of special seals to form a continuous flood barrier with a total length of 134 metres. Each gate weighs 11 tonnes and is fitted with three EPS buoyancy elements, each weighing 300 kilograms.
The gates consist of a steel frame to which these buoyancy elements are attached. As a result, they automatically float upwards into a flood-protective position during high water. Rubber profiles provide a watertight seal at the underside and between the gates. Under normal water levels, the gates function as a recreational deck, also known as the “balcony on the Maas”.
Video: ABRAWARE
Riverside balcony
“The technology is actually very simple, yet extremely robust, which gives us confidence that Steyl and Venlo are well protected during high water,” says board member Jos Teeuwen. The design is also distinctive, as the public space has been integrated on the river side of the flood defence.
Teeuwen continues: “This means that residents who live close to the defence experience as little disturbance as possible from recreational users. That is a good thing, because we know they are concerned about increased footfall outside their homes.”
The Dijkzone Alliance is proud to further develop the Vlotterkering®, originally designed in 2006 by G. Jansen and J. Vermond.
Gijs Ploegmakers, Managing Director of Ploegam, adds: “With this project, we are effectively creating a kind of riverside balcony outside the dike for Steyl.”
Production and transport
The gates for this distinctive flood defence were manufactured in the production hall of Hollandia Infra in Krimpen aan den IJssel and subsequently transported to the construction site in Steyl. Installation on the concrete supporting structure commenced there in the summer of 2024.
At the factory, the gates were tilted and then lifted onto lorries for transport to Limburg. The tilting and transport operations were carried out in stages of two gates at a time, spread over several days. This approach ensured sufficient time on site in Limburg to receive the gates, as they were installed directly into the hinge points upon arrival. The first gates were installed on Tuesday, 30 July 2024.