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Data on flood events is managed and statistically evaluated by the FOEN; the findings are made available in the form of graphs and result sheets.
A systematic statistical evaluation of flood data from the discharge measurement network was first carried out by what was then known as the National Hydrological Survey as of 1984 (gauging stations with observation periods of more than 30 years) and 1988 (measurement series over a shorter time span). The results were published in the "Hydrological Bulletins" series. Recalculations and publications for individual stations were usually undertaken following major floods (1987, 1993, 1994 and 1999).
Statistical data on floods is now stored in a special database, updated annually and additionally as required. To ensure comparability with earlier studies, the Hydrology Division applies the "Recommendations on flood risk estimation" issued by the German Association for Water, Wastewater and Waste (DWA, formerly DVWK, 1979). The maximum discharges (checked for plausibility) are used, as published in the Yearbook. Additional considerations (e.g. on flooding) are impossible within the framework of these routine assessments. With regard to the design of a specific hydraulic structure, more comprehensive studies are required. On request, the Hydrology Division also applies newer methods (DVWK, 1999)
The flood statistics database makes it possible to store and manage annual peak discharge data, to select study periods at will, and to carry out statistical analyses in accordance with the "Recommendations on flood risk estimation" (DVWK, 1979). The analysis involves descriptive statistics of flood measurement series, with all the parameters required for fitting of a distribution function and calculation of peak discharges for various return periods (T = 2, 5, 10, 20, 50, 100 and 200 years).
The findings are published in the form of a result sheet and two graphs:
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