LAUSR

In May 2024, southern Brazil experienced a severe flood that caused widespread devastation, particularly in the metropolitan area of Porto Alegre. This disaster resulted from a rare combination of atmospheric conditions: a heatwave stalled a cold front, leading to prolonged and intense rainfall. The flood claimed 183 lives, left 27 missing, and displaced many more. Notably, the flood's peak coincided with satellite observations from both SWOT and Sentinel‐2, providing a valuable snapshot of the disaster. To assess the flood's scope, and volume, we integrate these satellite data with FABDEM topography. SWOT's water height measurements, evaluated with in situ data, underscore its flood monitoring potential. The estimated floodwater volume was ∼ ${\sim} $ 1.5 billion m3 ${\mathrm{m}}^{3}$ . While primarily damaging croplands, the flood directly affected ∼ ${\sim} $ 420,000 individuals in the study region, with ∼ ${\sim} $ 16% identified as socially vulnerable. These findings offer insights into floodwater distribution and contribute to future flood dynamics research, mitigation strategies, and disaster preparedness.