Lake Thun Flood Protection – Relief Tunnel

The aim of the project is to guarantee sufficient relief capacity from Lake Thun without endangering the downstream riparians in the event of flooding.  The relief tunnel solution proved to be the most suitable when taking flood protection, economic efficiency, ecological aspects as well as urban development into consideration.  In this way the construction risks and the impact on the cityscape could be kept to a minimum.

The intake and the outlet structures are significant with regard to hydraulic relief performance as well as the impact on design and urban planning.  Project design demanded a synthesis of constructive, operational as well as architectural aspects and boundary conditions.


Civil Engineering Department of Bern Canton, OIK 1, Thun


IUB Engineering AG in Consortium

Construction period


Construction costs

CHF 53.5 million

Scope of services

    • Project development relief tunnel
    • Preliminary project incl. participatory processes for open solutions and tunnel solution
    • Project approval and construction: relief tunnel
    • Tendering process
    • Project execution
    • Construction management and supervision
    • Commissioning