Identification and visualization of areas vulnerable to intense rainfall in Nacka Municipality

This study presents areas in Nacka municipality that are potentially vulnerable to extreme rainfall events. GIS based methods have been used to identify and visualize these areas. Initially, topographic depressions were identified using a new method developed as part of this study. Within these depressions inundation can potentially take place, particularly in case outlets from these areas in the form of surface channels, pipes and sinks are being blocked by for instance vegetation debris, sediments or snow and ice. A risk map was produced showing areas in Nacka within which inundation might occur during extreme rainfall events. These potential inundated risk areas have been identified on the basis of multi-criteria of depressions, hard surfaces, slope steepness and soil conditions. The identified risk areas will be useful in order to find public and private infrastructure or assets that might get damaged during extreme rainfall events, and for hazard preparedness. Furthermore, calculations on how much the lake levels would rise in four of Nacka's lakes during an extreme rainfall event were calculated. Based on the lake level rise, areas around the lake that would become inundated were identified and visualized. These results can be useful for urban planning purposes