Lyssbach, Flood Protection Lyss, Relief Tunnel

The 2,570 m long relief tunnel passes from Leen at the southern entry to the town  of Lyss up to Fulenmatt where the  Lyssbach flows into the Alte Aare. With a capacity of 68m3/s the tunnel can cope with 1.5 times the water of a hundred year flood.

The following servies were provided by IUB Engineering AG:

  • Excavation pit with nail walls at the inlet and outlet structure within close vicinity of the SBB railway line and the road.
  • Underpass below an operational SBB railway line using a provisional bridge on micro piles. Finally, a concrete frame bridge was inserted.
  • Road underpass and road shifting
  • Concrete inlet and outlet structures at the relief tunnel
  • Grade tunnel using cut and cover method
  • Hydraulic engineering, scouring protection
  • Hydraulic steelwork

Main Data

  • Length of relief tunnel: 2,570 m
  • Inner diameter: 4.2 m
  • Capacity: 68 m³/s
  • Gradient: 0.58 %


Office of Civil Engineering of Bern Canton, OIK III


IUB Engineering AG in Consortium

Construction period

Planning: 2006–2011, Execution: 2009–2012

Construction costs

CHF 47 million

Scope of services

  • Preliminary project
  • Construction project, project approval process
  • Tendering
  • Project implementation, construction management and supervision