<p>The extreme flooding that affected Rio Grande do Sul, Brazil, in April–May 2024 was one of the most severe hydrometeorological disasters in South America’s recent history. To better understand the spatial and climatic drivers of this event, this study investigates how landscape exposure, land-use patterns, and future precipitation projections interact to shape flood risk in the Guaíba catchment, providing a basis for identifying priority areas for adaptation. This study’s novelty lies in integrating current spatial exposure with future climate projections to produce an evidence-based prioritization framework for flood-risk management. A multimethod geospatial approach was employed, combining flood-affected area mapping with land use and land cover data, height above the nearest drainage (HAND), and climate projections. Results reveal that municipalities located in low HAND zones with high population density and recent land-use conversion were disproportionately affected. When coupled with projected increases in rainfall intensity across the basin, these patterns suggest that flood risk will expand, requiring targeted adaptation measures. Based on these findings, we recommend basin-scale floodplain zoning to restrict new development in low HAND zones, restoration of riparian vegetation to enhance natural water retention, and integration of HAND-based flood-susceptibility maps into municipal planning. In order to reduce the volume of water and associated runoff that occurs during heavy rainfall events and causes flooding, it is also recommended that land use be adapted (reforestation and sustainable agriculture) in the northern areas of the basin. Strengthening early-warning systems and inter-municipal coordination should also be prioritized to reduce exposure across the Guaíba basin. Future research should combine this spatial framework with socioeconomic vulnerability assessments to guide adaptive and climate-resilient regional planning.</p>