Potential impact of natural hazards on water supply systems in Alpine regions

One of the most important aspects in water supply management is supply security. In this article a methodology is introduced to first identify vulnerable sites of a water supply system (WSS) and second to estimate the potential effect of alpine natural hazards on this system. The approach serves for the definition of zones with low, medium and high potential risk by combining vulnerability and hazard maps. This approach enables the possibility to accomplish prevention measures on risky sites considering the available budget. A management support tool (VulNetWS - Vulnerability of Water Supply Networks) is developed which quantifies vulnerability based on hydraulic and quality simulations assuming component failure of each single WSS component. Hazards of flooding, landslide, debris flow and avalanches are calculated and categorized in potential low, medium and high hazard zones. For this analysis different GIS data sets (e.g. Austrian hazard zone maps, HORA “Flood Risk Zoning”) are used. The methodology is presented by applying it upon an alpine region encompassing the municipality of Kitzbuhel (Tyrol - Austria) and 4 neighbouring municipalities. The combination of vulnerability and hazard is summarized using a risk matrix that highlights a zone of 0.42 square kilometres within the study area as being potentially risky.