Natural Hazards and Earth System Science www.nat-hazards-earth-syst-sci.net 1561-8633 1684-9981 9 1 2009 10.5194/nhess-9-135-2009 http://www.nat-hazards-earth-syst-sci.net/9/135/2009/ http://www.nat-hazards-earth-syst-sci.net/9/135/2009/nhess-9-135-2009.html http://www.nat-hazards-earth-syst-sci.net/9/135/2009/nhess-9-135-2009.pdf 135 144 2009-02-16 Rainfall thresholds and flood warning: an operative case study V. Montesarchio valeria.montesarchio@uniroma1.it F. Lombardo F. Napolitano Department of Hydraulics, Highways and Roads, "Sapienza" University of Rome, 00184 Rome, Italy An operative methodology for rainfall thresholds definition is illustrated, in order to provide at critical river section optimal flood warnings. Threshold overcoming could produce a critical situation in river sites exposed to alluvial risk and trigger the prevention and emergency system alert. 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