Risk of Flash Floods in Urban and Rural Municipalities Triggered by Intense Precipitation in Wielkopolska of Poland

This research analyzed interventions of State Fire Service (SFS) units in the Wielkopolska region of Poland that were triggered by extreme precipitation for the period 2010–2021. Our results demonstrated that the most populated and urbanized towns in the Wielkopolska (Greater Poland, west of Warsaw) region are at the most risk in the event of extreme precipitation occurrence as measured by the total number of interventions made by the SFS. The number of SFS unit interventions in towns, standardized to 10,000 inhabitants, indicates that the highest proportional volume of interventions also occurred in smaller towns. In the rural municipalities the number of SFS unit interventions increases along with higher population density and proportion of infrastructure areas. As analyzed in this study, the 12 years from 2010 to 2021 were characterized by a higher number of days with heavy precipitation, for example, 20, 30, 40, and 50 mm, in comparison to the previous periods 1961–2010 and 1981–2010. Intervention databases collected by emergency services are a valuable source of information for hazard mapping. Based on those and other available data, a statistical model was created and factors influencing the local and regional occurrence of interventions were determined. Increasing suburbanization, the rising proportion of impermeable surfaces, and the impact of climate change are of considerable importance in urban flood risk. It is necessary to help municipalities develop abilities to absorb larger amounts of rainwater.