Flash flood potential index at national scale: Susceptibility assessment within catchments

Abstract Flash floods, which can increase in severity and frequency due to climate and land-use changes, are among the most destructive natural hazards globally, causing significant damage and loss of life. This study employs the Flash Flood Potential Index (FFPI), a parametric model based on terrain and land surface characteristics, to assess flood-prone areas in North Macedonia’s catchments, utilizing Geographic Information Systems and advanced geospatial analytics. The average FFPI values, which typically ranges from low values indicating minimal risk to higher values indicating greater flash flood potential, show values from 1.9 to 9.2 across North Macedonia, with an average of 6.0. Within the main and subcatchments, the FFPI averages vary from 3.9 to 7.2. Based on these results, 24.7% of the subcatchments are identified as very highly susceptible to flash floods (torrential catchments), indicating significant spatial variability in flood risk across the country. The model classifies susceptibility into five categories, from 1 (very low) to 5 (very high). Nationwide, 25.6% of the area is categorized as highly susceptible to flash floods. The FFPI model was validated using flash flood event records and corresponding intense precipitation data. Validation using the receiver operating characteristic-area under the curve method yielded a value of 78.2%, reflecting the model’s high accuracy in identifying flash flood-prone areas. This study contributes to sustainability by providing a scientific basis for resilient land-use planning, flood mitigation strategies, and climate change adaptation. By integrating factors such as slope, lithology, land use, vegetation, and the bare soil index, alongside rainfall, peak discharges, and response times, this research offers critical insights for policymakers and urban planners to enhance flood risk management and promote sustainable development.