SWOT Reveals How the 2024 Disastrous Flood in South Brazil Was Intensified by Increased Water Slope and Wind Forcing

Climate change is expected to increase the frequency and intensity of flooding, emphasizing the need to better understand these events. Satellite observations provide essential information, and the recent launch of SWOT offers new opportunities to investigate flood dynamics. Here, we use SWOT observations to detect significant hydrologic changes during an unprecedented 2024 flood in southern Brazil. In the Jacuí and Guaíba Rivers, water slopes increased dramatically–up to 11 times (from 0.82 to 9.59 cm/km) and 21 times (0.31–6.58 cm/km) compared to stable conditions. SWOT-derived surface water elevations captured 99% of water level variability compared to in situ observations. Additionally, flooding in Patos Lagoon was intensified by NE–SW wind forcing, causing water levels to rise by up to 40 cm, worsening the flood event. SWOT proves a unique opportunity to understand extreme flooding events, providing new support for flood risk management in the context of climate change.