Exceptional and extreme floods (CRUEX ++)

The CRUEX++ “Exceptional and Extreme Floods” research project follows on from the CRUEX project, which in 2001 proposed a preliminary methodology of the PMP-PMF (Probable Maximum Precipitation-Probable Maximum Flood) type: a methodology for estimating extreme floods capable of integrating the hydrological particularities of the Alpine environment. As the quantitative estimation of extreme floods is still a poorly understood issue, this new project aims to pursue research in this area, with a view to optimizing the safety of the many dams located in the Swiss Alps.

Initiated in 2012 by EPFL’s Laboratoire de Constructions Hydrauliques (LCH), CRUEX++ aims more specifically to complement and refine the previously developed extreme flood estimation methodology with statistical and hydrological simulation methods. CREALP is actively contributing to this EPFL thesis project (led by F. Zeimetz), providing its expertise in hydrological and hydraulic modelling, business tool development and flood management. CRUEX++ is funded by the Swiss Federal Office of Energy(SFOE).

In Switzerland, the safety flood of hydraulic structures must be approximately 1.5 times greater than a flood with a return period of 1,000 years (design flood). Although this margin is significant, it does not rule out the possibility of an extreme flood, which could cause major damage and have catastrophic consequences for the population living downstream of the structure. What’s more, the considerable storage capacity of large Alpine dams makes their safety a major concern.

The real challenge of this project lies in the complexity of the Alpine environment. An environment where orographic effects play a decisive role in determining weather conditions. What’s more, watersheds are also subject to man-made interventions that modify their behavior. The flood control provided by large dams considerably reduces the size and frequency of downstream floods. To fully harness this beneficial effect, the safety of these structures must be guaranteed. In particular, their ability to withstand extreme flooding.