Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 8 1 2008 10.5194/nhess-8-1-2008 http://www.nat-hazards-earth-syst-sci.net/8/1/2008/ http://www.nat-hazards-earth-syst-sci.net/8/1/2008/nhess-8-1-2008.html http://www.nat-hazards-earth-syst-sci.net/8/1/2008/nhess-8-1-2008.pdf 1 8 2008-01-09 Snow loads in a changing climate: new risks? U. Strasser u.strasser@iggf.geo.uni-muenchen.de Department of Geography, Ludwig-Maximilians University (LMU), Luisenstr. 37, 80333 Munich, Germany In January/February 2006, heavy snowfalls in Bavaria (Germany) lead to a series of infrastructural damage of catastrophic nature. Since on many collapsed roofs the total snow load was not exceptional, serious engineering deficiencies in roof construction and a sudden rise in the total snow load were considered to be the trigger of the events. An analysis of the then meteorological conditions reveals, that the early winter of 2005/2006 was characterised by an exceptional continuous snow cover, temperatures remained around the freezing point and no significant snowmelt was evident. The frequent freezing/thawing cycles were followed by a general compaction of the snow load. This resulted in a re-distribution and a new concentration of the snow load on specific locations on roofs. With respect to climate change, the question arises as to whether the risks relating to snow loads will increase. The future probability of a continuous snow cover occurrence with frequent freezing/thawing cycles will probably decline due to predicted higher temperatures. However, where temperatures remain low, an increase in winter precipitation will result in increased snow loads. Furthermore, the variability of extremes is predicted to increase. If heavy snowfall events are more frequent, the risk of a trigger event will likely increase. Finally, an attempt will be made here in this paper to outline a concept for an operational warning system for the Bavarian region. This system envisages to predict the development and risk of critical snow loads for a 3-day time period, utilising a combination of climate and snow modelling data and using this together with a snow pillow device (located on roofs) and the results of which. Adrian, G. and Frühwald, D.: Design der Modellkette GME/LM, promet, 27, 3/4, 106–110, 2002. DIN, DIN 1055-5, Einwirkungen auf Tragwerke~-Teil~5: Schnee – und Eislasten, Deutsches Institut für Normung e.V., 2005. DWD, Deutscher Wetterdienst, Klimadaten zu den Stationen Bad Reichenhall, Holzkirchen, Mühldorf/Inn, Fürstenzell, Offenbach, 2006. IPCC, IPCC Fourth Assessment Report. Working group I: The Physical Science Basisof Climate Change http://ipcc-wg1.ucar.edu/wg1/wg1-report.html,last access: 9 January 2008. LfU, Bavarian Environment Agency, http://www.lfu.bayern.de/, last access: 9 January 2008. Maidment, D. R.: Handbook of Hydrology, McGraw-Hill, 1400~pp., 1993. MPI,http://www.mpi-met.mpg.de/wissenschaft/ueberblick/atmosphaere-im-erdsystem/regio nale-klimamodellierung/remo-uba/abbildungen.html, last access: 9 January 2008. Müller-Westermeier, G.: Klimatologische Anmerkungen zu den Schneedecken im Bayerischen Wald im Februar~2006, DWD online, http://www.dwd.de/de/FundE/Klima/KLIS/prod/spezial/regen/KlimatologischeAnmerkungen_Schneedecken_Bayrischer_Wald_Februar_2006_2.pdf, 2006.