EXAR – Extreme Flooding Aare-Rhine

Within the framework of the EXAR study the basis used to date to assess the hazard risk from extreme flooding of the River Aare will be reviewed and hazard assessment will be harmonised. The results will help to better protect infrastructure and cities against flooding. In particular, it will enable a reassessment of the risks of extreme flooding to around 15 weirs and the nuclear power stations Mühleberg, Gösgen as well as Beznau I and II.

Based on specific situations on the River Aare, the study will define the hazards linked with flooding and their possible interaction. In particular, phenomena such as heavy precipitation, dam breaches (also as a result of earthquakes), erosion, channel rearrangement, sediment deposit, debris jams as well as landslides will be examined and their impact on flow behaviour will be analysed. Uncertainties and interactions have to be taken into consideration.

IUB is involved in the work packages "Hydraulics & Morphodynamics" (WP3) as well as "Hydraulic Engineering Constructions" (WP4) in collaboration with Geotest and HZP to ensure successful implementation of the project.


Federal Office for the Environment (BAFU)


IUB Engineering AG in consortium

Construction period

2016 – 2018

Scope of services

Phase A (preliminary study):

  • Data collection, preparation of a methodolo-gy, application example

Phase B (main study):

  • Development of the basis for hydraulic modelling: stage-discharge relationships, impounding of bridges, formation of breaches
  • Behaviour of weirs, bridges, flood protection dams and barrages during excessive flooding and/or other additional problems (earthquakes, driftwood, etc.)
  • Behaviour and hydraulic impact of large landslides onto the river bed of the Aare.
  • Checking failure scenarios
  • Failure probabilities