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Understanding and forecasting floods

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In Switzerland, flooding causes damages costing on average over three hundred million Swiss francs per year. To prevent increasing damages, we need hazard maps, forecasts, protective structures, and optimally coordinated responses to emergencies. We have been developing the scientific basis for this.

An unusually large number of thunderstorms in quick succession in June and July 2021 led to floods with damage costs of over 435 million Swiss francs – the costliest storm since 2007. Back then, property damage amounted to around 700 million Swiss francs. Overall, the highest costs recorded in the Swiss flood and landslide damage database - around three billion Swiss francs - was also caused by a flood (in August 2005): floods are the natural hazard that causes the highest costs in Switzerland.

Such damages are reduced by avoiding construction in at-risk areas and providing more open space around waterways. If these measures are not sufficient, new protective structures are needed. All this requires hazard maps, for which our research provides the data and basic methodology.

For example, we have been studying steep mountain streams for more than fifty years. Using measuring systems which we developed, we can determine water flows, bedload volumes and snowpack in Alptal (Schwyz). No other mountain torrent in the world has been surveyed as thoroughly as this one.

Floods – today and tomorrow

Additionally, we develop computer models and alarm systems for flood warning. For this, we analyse current events and use our long time series of measurements. Since September 2008, we have been operating a flood early warning system for the city of Zurich and the Sihl valley. It improves safety for the city and Zurich's main railway station.

Snowmelt can play a significant role in causing flooding. At the WSL Institute for Snow and Avalanche Research SLF, we run an operational snow-hydrological service (OSHD). This analyses where and how much snow there is in Switzerland, and how much of it will melt. This enables lowering water levels in reservoirs in good time to prevent flooding.

How will extreme floods alter with climate change? This question is being investigated by a new joint professorship of WSL and ETHZ in Davos.

Flash flood in the Töss river on 22.07.2016 (Video: Christian Hunkeler Swissstorms)

Topics

Swiss flood and landslide damage database

Since 1972 we record storm damages in Switzerland in a database. It is financed by the FOEN and helps evaluating risks.

WSL-database of natural hazard fatalities in Switzerland

The WSL database records deaths due to naturally triggered natural hazards per year since 1946.

Longterm investigation of torrent catchments in the Alptal

In the pre-Alpine Alptal (Canton Schwyz) we have been studying small torrent catchments for over fifty years.

FURTHER INFORMATION

Contact

Research Groups

Publications

Liechti, K.; Badoux, A.; Andres, N., 2020: Unwetterschäden in der Schweiz 2019. Rutschungen, Murgänge, Hochwasser und Sturzereignisse. Wasser, Energie, Luft, 112, 2: 85-92.

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Speich, M.J.R.; Zappa, M.; Scherstjanoi, M.; Lischke, H., 2020: FORests and HYdrology under Climate Change in Switzerland v1.0: a spatially distributed model combining hydrology and forest dynamics. Geoscientific Model Development, 13, 2: 537-564. doi: 10.5194/gmd-13-537-2020

Giordani, A.; Zappa, M.; Rotach, M.W., 2020: Estimating ensemble flood forecasts' uncertainty: a novel "peak-box" approach for detecting multiple peak-flow events. Atmosphere, 11, 1: 2 (17 pp.). doi: 10.3390/atmos11010002

Antonetti, M.; Horat, C.; Sideris, I.V.; Zappa, M., 2019: Ensemble flood forecasting considering dominant runoff processes – part 1: set-up and application to nested basins (Emme, Switzerland). Natural Hazards and Earth System Sciences, 19, 1: 19-40. doi: 10.5194/nhess-19-19-2019

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Projects

Floods and droughts under global change

This project aims to enhance our understanding and modeling capability of regional hydrologic extremes in the Alps in a global change context.

Visitor flow management

An agent-based visitor flow management tool that allows for mitigating the conflict between outdoor recreation and biodiversity conservation will be developed for two riverine environments (lower Wigger valley and upper Glatt valley).

Resiliente Fliessgewässer

Im Projekt "Resiliente Fliessgewässer: Refugien - Vernetzung - Trittsteine " (2022-2026) steht die Untersuchung zur Förderung von resilienten Habitaten und Lebensgemeinschaften durch die Schaffung und Erhaltung von Refugien, Trittsteinen und Vernetzung unter Sicherstellung des Hochwasserschutzes im

Modelling cascading processes with MPM

In this project we use a 3D Material Point Method (MPM) model to simulate the interaction of snow and rock avalanches with water basins and lakes in order to develop knowledge and methods to assess the hazard posed by impulsive waves to tourism infrastructure and populated areas.

Drought and flood statistics in regulated catchments

This project aims to enhance our understanding of the statistical behavior of multivariate hydrologic extremes in the Alps in a global change context where streamflow is increasingly regulated through reservoir operation or water abstraction.

ONEforest

ONEforest develops a multi-criteria planning system for strategic decision makers from forestry, politics and industry and provides information regarding potential social, ecologic and ecologic and economic impacts of alternative forest management options in a medium to long-term perspective.

Using different sensor types to improve the signal interpretation

Indirect bedload transport measurements help to better understand how coarse solid particles are transported in steep streams (torrents) and mountain rivers. We use three different sensor types to improve the signal interpretation: geophone, accelerometer, and microphone.

SedSlope

This project aims at assessing the contribution of sediment erosion from steep slopes adjacent to channel beds to the sediment transport in small catchments.

Wasserkraftwerkportfolio "ewz"

Für die Elektrizitätswerk der Stadt Zürich ("ewz") soll eine Übersicht zum zukünftigen Wasserdargebot in den Kraftwerke ihren Portfolio erstellt werden. Die Ergebnisse sollen für den heutigen und künftigen Wasserverfügbarkeit bereitgestellt werden.

Wasserdargebot Kanton Zürich

In dieser Studie wurden anhand der CH2018 Klimaszenarien und den hydrologischen Projektionen Hydro-CH2018, Abflussszenarien (also das zukünftige Wasserdargebot) für den Kanton Zürich erstellt.

Wasserbilanz der Schweiz

Modellgestützte Bilanzierung des Wasserhaushaltes der Grosseinzugsgebiete der Schweiz

Snow-atmosphere interactions

The main objective of this study is to improve high-resolution seasonal snow cover predictions for large river basins in the Alps. Key to these improvements are the coupling of physically based models for both atmospheric and snow cover processes to better resolve processes that act at the snow - atmosphere interface.

High-resolution soil maps for the Swiss forest

In this project we model high-resolution soil maps with different soil properties such as pH or texture for the entire Swiss forest.

Seeregulierung und Klimawandel

Mit den vorgesehenen Untersuchungen soll die Wirksamkeit der Seeregulierungs-Vorschriften basierend auf den Klimaszenarien CH2018 überprüft werden. Eine mehrstufige Studie klärt den Handlungsbedarf bei den Regulier-Reglementen.

Praxishilfe Murgang- und Hangmurenschutznetze

Netze zum Rückhalt von Murgängen und Hangmuren als "neuere" Massnahmentypen sind seit einigen Jahren auf dem Markt verfügbar. Wichtig ist, dass Vor- und Nachteile und insbesondere die Grenzen in der Anwendung bekannt sind und fallweise das zielführende Massnahmensystem bestimmt wird. Hierzu soll eine Praxishilfe entstehen.

Mehrzweckspeicher als Zukunftsmodell?

Obwohl die Schweiz über reichlich Wasser verfügt, kann es zukünftig lokal zu Engpässen kommen. Mehrzweckspeicher stellen eine Möglichkeit dar, um auf zukünftige Wasserknappheit zu reagieren. Dieses Projekt untersucht die Chancen und Risiken einer gemeinsamen Bewirtschaftung.

CCAMM Task 1.0: Downscaling Meorological forcings.

The WSL program Climate Change Impacts on Alpine Mass Movements (CCAMM) comprises projects covering a range of topics in natural hazards. Most investigations use models and thus require climate forcing data. The aim of this task is to provide meteorological forcings at the slope scale and in high temporal resolution.

SwissSPOT- Swiss forest Soil water POTential network

SwissSPOT is a network to monitor soil water down to 2m soil depth at Swiss Long-term Forest Ecosystem Research (LWF) sites.

Towards automated monitoring of alpine mass movements

This project aims at setting up an interactive network of autonomously communicating instruments to capture processes happening during and directly after alpine mass movements.

The Swiss plate geophone system

This project aims to further develop the Swiss plate geophone system, a passive seismic method to measure bedload transport in water courses, with a new set of controlled experiments and field calibration measurements.

Demonstrator for flexible SHP (SmallFlex): Real-time hydrological forecasts

Dans ce projet, la valeur ajoutée des prévisions hydrologiques à très court terme (< 6 h) et à long terme (1 mois) pour l'exploitation d'une petite centrale hydroélectrique alpine (Gletsch-Oberwald) est étudiée.

Risks for small hydropower plants associated with climate change

estimate the impact of climate change on the inflow in a snowmelt dominated tributary of a small hydropower plant using a stochastic 2-dimensional weather generator, a high-resolution energy balance snow cover and a gridded hydrological model

EXAR

The main goal of the EXAR project is to create a consistent data set in order to assess the hazard for riparian infrastructure caused by extreme flood events on the rivers Aare and Rhine.

WOODFLOW

Wood in rivers fulfills important ecological functions. However, in case of flood events large wood may become a considerable source of danger. The aim of the research program WoodFlow is to better understand large wood dynamics in order to minimize associated risks.

Beurteilung von Schutzwäldern mittels Fernerkundung

Ziel dieses LFI-Projektes ist es, Methoden der Fernerkundung zur Beurteilung der aktuellen Schutzwirkung und Verjüngung von Schutzwäldern zu entwickeln. Im Fokus stehen die Möglichkeiten von terrestrischem (TLS) und flugzeuggestütztem Lasesscanning (ALS).

FORHYCS

A hydrological model is coupled to a forest model to better assess the influence of changing drivers to forests and the hydrological cycle

Rain-on-Snow

Rainfall on existing snowcover frequently occurs in spring. In this project we attempt to identify processes and conditions that determine how snow cover influences runoff formation during a rain-on-snow event.

Codelco's Andina copper mine

In collaboration with two Swiss engineering companies, the SLF has proposed mitigation measures against avalanches, debris flows and rockfalls in order to protect the access road to the Andina copper mine operated by Codelco. The proposal encompasses a combination of temporary and structural protective measures.

Composition of the driftwood

During the floods in August 2005 in Switzerland, many villages encounter problems not only because of a high water flow, but also because of large amounts of driftwood. Therefore the question of the origin and the formation of the driftwood arised.

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