Measures for sediment retention at Chratzbach

A large construction site for a small stream

On behalf of the city of Thun, we were commissioned to oversee the second stage of the "Measures for sediment retention of the Chratzbach stream" project. From the SIA tendering phase onwards, we took over project optimisation, the preparation of the implementation planning and construction management throughout the entire implementation phase.

The Chratzbach stream flows through the densely populated district of Lauenen, whose location and geological conditions pose an increased risk of debris flows – the nearby Thun hospital is also potentially at risk. The 2018 hydraulic engineering plan therefore provides for comprehensive protective measures to ensure the safety of the population and infrastructure.

Construction work began in January 2025. A construction pit up to 7 m deep with soil nailed walls was dug for the foundations. To safely dissipate the forces of a potential debris flow, 64 micropiles were driven into the rock and anchored. A total of around 680 m³ of concrete was used for the barrier and 110 m³ for the channel.