EGU23-1384, updated on 22 Feb 2023
EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Estimating very rare floods at multiple sites in a large river basin with comprehensive hydrometeorological simulations

Daniel Viviroli1, Anna E. Sikorska-Senoner1,2, Guillaume Evin3, Maria Staudinger1, Martina Kauzlaric4,5, Jérémy Chardon6, Anne-Catherine Favre6, Benoit Hingray6, Gilles Nicolet6, Damien Raynaud6, Jan Seibert1,7, Rolf Weingartner4,5, and Calvin Whealton8
Daniel Viviroli et al.
  • 1Hydrology and Climate, Department of Geography, University of Zürich, Zürich, Switzerland (
  • 2now at: MeteoSwiss, Zürich, Switzerland & Center for Climate Systems Modeling ETH Zürich, Zürich, Switzerland
  • 3Université Grenoble Alpes, INRAE, CNRS, IRD, Grenoble INP, IGE, Grenoble, France
  • 4Mobiliar Lab for Natural Risks, University of Bern, Bern, Switzerland
  • 5Oeschger Centre for Climate Change Research, University of Bern, Bern, Switzerland
  • 6Université Grenoble Alpes, CNRS, IRD, Grenoble INP, IGE, Grenoble, France
  • 7Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
  • 8Paul Scherrer Institute, Villigen, Switzerland

Rare to very rare floods (associated to return periods of 1'000–100'000 years) can cause extensive human and economic damage. Still, their estimation is limited by the comparatively short streamflow records available. Some of the limitations of commonly used estimation methods can be avoided by using continuous simulation (CS), which considers many simulated meteorological configurations and a conceptual representation of hydrological processes. CS also avoids assumptions about antecedent conditions and their spatial patterns.

We present an implementation of CS to estimate rare and very rare floods at multiple sites in a large river basin (19 locations in the Aare River basin, Switzerland; area: 17'700 km²), using exceedingly long simulations from a hydrometeorological model chain (Viviroli et al., 2022). The model chain consisted of three components: First, the multi-site stochastic weather generator GWEX provided 30 meteorological scenarios (precipitation and temperature) spanning 10'000 years each. Second, these weather generator simulations were used as input for the bucket-type hydrological model HBV, run at an hourly time step for 80 catchments covering the entire Aare River basin. Third, runoff simulations from the individual catchments were routed for a representation of the entire Aare River system using the routing system model RS Minerve, including a simplified representation of main river channels, major lakes and relevant floodplains. The final simulation outputs spanned about 300'000 years at hourly resolution and cover the Aare River outlet, critical points further upstream as well as the outlets of the hydrological catchments. The comprehensive evaluation over different temporal and spatial scales showed that the main features of the meteorological and hydrological observations were well represented. This implied that meaningful information on floods with low probability can be inferred. Although uncertainties were still considerable, the explicit consideration of important flood generating processes (snow accumulation, snowmelt, soil moisture storage) and routing (bank overflow, lake regulation, lake and floodplain retention) was a substantial advantage compared to common extrapolation of streamflow records.

The suggested approach allows for comprehensively exploring possible but unobserved spatial and temporal patterns of hydrometeorological behaviour. This is particularly valuable in a large river basin where the complex interaction of flows from individual tributaries and lake regulations are typically not well represented in the streamflow records. The framework is also suitable for estimating more common, i.e., more frequently occurring floods.


Viviroli D, Sikorska-Senoner AE, Evin G, Staudinger M, Kauzlaric M, Chardon J, Favre AC, Hingray B, Nicolet G, Raynaud D, Seibert J, Weingartner R, Whealton C, 2022. Comprehensive space-time hydrometeorological simulations for estimating very rare floods at multiple sites in a large river basin. Natural Hazards and Earth System Sciences, 22(9), 2891–2920, doi:10.5194/nhess-22-2891-2022

How to cite: Viviroli, D., Sikorska-Senoner, A. E., Evin, G., Staudinger, M., Kauzlaric, M., Chardon, J., Favre, A.-C., Hingray, B., Nicolet, G., Raynaud, D., Seibert, J., Weingartner, R., and Whealton, C.: Estimating very rare floods at multiple sites in a large river basin with comprehensive hydrometeorological simulations, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1384,, 2023.