Les crues de l'été 1987 dans les bassins versants glaciaires des Alpes Pennines

The floods of 1987 in the glacial basins situated in Pennine Alps in Switzerland

Grande Dixence S.A., rue des Creusets 41, 1951 Sion, Suisse

Abstract

Exceptional rises of 1987 summer have been analysed in detail for some glacial basins situated in Pennine Alps in Switzerland. Precipitations of a recurrence time estimated between 80 and 100 years have affected localy some regions: these rains have increased the already large melting discharges resulting from hot days of July and August. Therefore, for more than 24 hours, some basins have drained off in average a total of 1,400 to 1.500 l/s/km², with some peaks estimated at 4,500-5,000 l/s/km². For the whole land of Valais, all the mountain reservoirs all owed to lower of about 20% the rise on the level with the river Rhône.