Bridging the Gap in Small Ungauged Basins: Integrating 2D Hydrodynamic Modeling and Social Cartography for Flood Hazard Mapping

Resumo

The occupation of wetlands has intensified the magnitude and frequency of flood damage in Brazilian watersheds. This study validates the accuracy of 2D hydrodynamic simulations against participatory flood hazard mapping in Vila Esperança (Guarapuava, Paraná State), adopting a 10-year return period (RP) as the critical threshold for residential feasibility. The methodology integrated HEC-RAS modeling based on high-resolution LiDAR data (micro-topographic precision) with a Mental Flood Mapping derived from residents' historical reports of the study area's residents. Results demonstrate that the 10-year RP simulation identifies a chronic risk that renders residential maintenance unsustainable, affecting 10.66% of the area (93 housing units and 260 people). In contrast, the Spoken Map, anchored in the extreme 2014 event, characterizes an acute risk, covering 15.67% of the village and affecting 144 housing units and 403 people. The findings reveal that while technical modeling provides geometric flow precision, collective memory offers the "ground truth" necessary for calibrating real hazards in ungauged basins. Consequently, areas within the 10-year flood footprint must be restricted from residential use. Furthermore, risk management must evolve beyond statistical probability to include integrated disaster reduction strategies, such as resettlement and early warning systems, to address the catastrophic scenarios identified by the community.