Lightning Density Distribution and Hazard in an Alpine Region

Due to the expected climate change driven increase of extreme weather events, damage risks for infrastructure and buildings are rising. Hence spatial decision-support material is necessary to enhance risk management and planning strategies. The presented study contributes to this topic by means of an analysis of cloud-to-ground lightning patterns and their impact on structural facilities using Geographic Information Systems (GIS). Lightning records from 1998 to 2009, ascertained by the European Cooperation for Lightning Detection (EUCLID), were utilized in order to apply three different lightning density approaches to an alpine area comprising the Austrian federal province of Salzburg and southeast Bavaria, Germany. Based on the derived lightning density distribution maps and an elevation model, spatial coherences between lightning activity and various topographic properties such as altitude or surface curvature were evaluated. In order to subsequently estimate the lightning hazard to buildings in the city of Salzburg, the frequencies of hazardous lightning events were estimated in GIS using a European lightning protection standard (EN62305-2 Risk Management) as a foundation. Thereby, the prototypical realization was based on the lightning density, a cadastral dataset, and elevation data. The lighting density results obtained show high lightning activity with more than 3 yearly flashes per square kilometer along the northern edge of the Alps. The hazard analysis in the city of Salzburg showed high hazards for buildings due to electromagnetic induction (up to one dangerous event in each year) and comparatively low hazards due to direct lightning strikes (one dangerous event every 10 to 2200 years).