Safeguarding Basel’s Tunnel: AquaFence Mobile Flood Barriers Ensure Resilient Maintenance

Basel, Switzerland faced rising Rhine water levels threatening a two-year maintenance project on a 1.4 km river tunnel beneath the city. AquaFence deployed mobile flood barriers that diverted the river flow and protected the site, enabling safe, uninterrupted repairs throughout the.

Customer Background & Challenge

Basel is one of Switzerland’s major cities, home to critical infrastructure that must be protected from flooding. In the heart of Basel, a 1.4 km tunnel carrying river water beneath the city required extensive maintenance and an enlargement of its entrance – a project slated to last two years.

This tunnel was vulnerable to rising water levels from the Rhine, which posed a constant flood risk. The city’s challenge was clear: how to keep the tunnel dry and workers safe so maintenance could proceed continuously, despite fast-flowing river water threatening to inundate the work zone.

Key challenges included:

• Continuous Flood Risk: The tunnel runs under a river, so elevated water levels or storms could send water rushing in at any time. Basel needed to funnel the river along one side of the tunnel to create a dry, safe area for repairs.

• Prolonged Project Duration: The maintenance and upgrades would span two years, so any flood protection solution had to remain reliable and effective through multiple seasons and high-water events.

• Critical Infrastructure at Stake: Failure to control the water could halt the tunnel works, endangering project timelines and the integrity of a key piece of urban infrastructure.

Solution

To address these challenges, AquaFence delivered a tailored flood protection system designed specifically for Basel’s tunnel. AquaFence’s engineers worked closely with the city to combine standard modular flood barriers with custom-engineered sections, ensuring a perfect fit for the tunnel’s unique geometry and constraints.

The plan divided the 1.4 km tunnel into manageable segments, with approximately 200 meters of AquaFence barriers deployed per stage so that maintenance could proceed in seven sequential phases. As each 200 m section was completed, the mobile barriers were repositioned to the next segment, efficiently leapfrogging down the tunnel.

This adaptive barrier setup effectively diverted the river’s flow to one side, creating a dry corridor where crews could work safely despite the water rushing just beyond the barrier wall. AquaFence’s FloodWall units are self-stabilizing and use the water’s weight for support, meaning they remain sturdy against the current without permanent anchors. The system was also cost-optimized to meet Basel’s budget – a far more economical approach than constructing permanent floodgates for a temporary project.

Importantly, the AquaFence barriers are mobile and easy to deploy, giving the maintenance team a simple tool to erect or move as needed. Each barrier panel folds out on-site, allowing rapid installation with minimal labor or heavy equipment. This simplicity built in high safety margins; the barrier design could handle the force of several cubic meters of water per second, all while keeping workers dry and focused on repairs.

Implementation & Collaboration

Successful implementation required close collaboration between Basel’s engineers and AquaFence’s flood protection specialists. During the planning phase, AquaFence was provided detailed tunnel drawings to fully understand the site conditions and constraints.

The AquaFence team conducted two on-site reviews in Basel alongside the city’s project managers. These joint site visits allowed the engineers to co-develop an optimal barrier layout, refining how the standard and custom sections would be arranged in each stage of the tunnel. Every curve, entry point, and width change in the tunnel was accounted for in the design.

Through this collaboration, the deployment plan was fine-tuned to ensure that as one 200 m section was secured and under repair, the next section’s barriers could be prepared in advance. The staged approach meant the tunnel’s maintenance could proceed without ever leaving a portion unprotected. At each phase, AquaFence’s team assisted the local crew in setting up the barriers, ensuring knowledge transfer on proper deployment and removal. This methodical coordination guaranteed that the tunnel remained operational and safe throughout the two-year project, with flood defenses continuously in place. Even when river levels rose rapidly, the AquaFence system held the water at bay, and work carried on without a hitch.

Results & Outcomes

Over two years of maintenance, AquaFence’s mobile flood barrier solution delivered a resounding success for Basel. The city achieved its project goals with zero downtime due to flooding, even during periods of high Rhine water levels. All seven phases of the tunnel repairs were completed on schedule, as each section stayed reliably dry during the work.

Key outcomes included:

• Robust Safety & Easy Use: The AquaFence system’s high safety margins ensured workers were fully shielded from fast-moving water throughout the project. At the same time, the barrier’s intuitive design made it easy for crews to deploy and dismantle, requiring only a small team and minimal training. This ease of use allowed the maintenance team to remain focused on their tasks, confident in the flood protection.

• Uninterrupted Project Delivery: Thanks to dependable flood barriers, not a single maintenance phase was delayed by water ingress. The tunnel remained accessible and dry at all times, enabling continuous work and the on-time completion of the extensive maintenance and upgrades. Basel’s engineers gained peace of mind knowing that even when the Rhine swelled, the barriers kept the infrastructure secure.

• Cost-Effective & Resilient: The mobile barrier solution proved far more cost-effective than permanent floodworks would have been for this temporary maintenance effort. Additionally, the AquaFence equipment is reusable – the city of Basel now has a proven flood defense asset ready for future deployments as needed. This project has thus enhanced the long-term resilience of Basel’s infrastructure, demonstrating a viable model for protecting critical urban projects against floods.

Conclusion & Call to Action

By deploying AquaFence’s innovative mobile flood barriers, Basel was able to carry out a high-risk tunnel maintenance project safely and without interruption, despite the constant threat of river flooding.

This case exemplifies how proactive flood mitigation can safeguard critical infrastructure and keep essential projects on track, even under challenging conditions. AquaFence provided the city of Basel with both the technology and the partnership needed to overcome a formidable water threat and achieve their maintenance goals on time and on budget.

Is your city or organization facing a similar flood risk challenge? Basel’s success shows that advanced, temporary flood barriers can deliver reliable protection where traditional methods fall short.

We invite public and private sector leaders to learn more about how AquaFence supports critical urban resilience projects worldwide. Contact AquaFence to discuss how our mobile flood barrier solutions can help secure your infrastructure and keep your operations flowing, no matter the waters rise.