Flood Vulnerability Assessment in Ungauged Watersheds: a Simple Approach Using Regional Functions and 1D Hydraulic Modelling

In this study, we identified flood risk areas using maximum streamflow estimates derived from regional functions and 1D hydraulic modelling in an urban ungauged watershed in Lavras, Minas Gerais, Brazil. Our approach focused on employing simple techniques based on secondary data to support flood risk management in regions lacking hydrological monitoring and technical expertise. The study evaluated two maximum streamflow regional functions developed for the Grande River Basin to identify the most suitable for flood mapping. Flood maps for 5, 10, 50 and 100-year return periods were created using the software HEC-RAS and we assessed population vulnerability under current and regulated land use scenarios. By using simple techniques and secondary data, this work provides a practical approach for decision-making in cities with limited resources, highlighting the need for improved urban drainage and flood risk management.