Flood alert map

The flood alert map shows the current flood danger level (1 to 5) for all and for the regions in relation to small and medium-sized rivers. The rivers of national interest are divided into individual stretches of river, each of which has a defined discharge gauging station. The forecast is based on a hydrological model and various weather models. Depending on how the forecasters assess and interpret the models, individual stretches of river and lakes are colour-coded by danger level. If necessary, the FOEN forecasters may request more detailed information on weather developments and the status of snow cover from MeteoSwiss and/or the WSL Institute for Snow and Avalanche Research (SLF). The FOEN also issues alerts and information when a strong increase in discharge is expected locally on small and medium-sized rivers. In such cases – especially during thunderstorms with heavy rainfall – it is not possible to predict precisely which water bodies will be affected. Therefore, the regions likely to be affected are marked on the flood alert map. For small and medium-sized rivers, there are only two possible danger levels in advance of an event: low/no danger (green) and flood danger (yellow, no indication of severity). Red is also used to indicate a very large flood in progress; this is based on current readings and is not issued in advance.