Spaceborne multi-sensor tracking reveals hydrologic decoupling during the record-breaking Sahara flood

Satellite remote sensing enables large-scale quantification of extreme hydrologic events in data-scarce regions, yet the integration of multi-sensor observations to resolve hydrologic responses remains limited. The record-breaking 2024 Sahara flood presents a unique opportunity to evaluate satellite-based characterisation of hydrologic extremes in hyper-arid environments. By integrating multi-sensor satellite observations of precipitation, surface inundation, and terrestrial water storage, we provide a comprehensive assessment of this event’s hydrologic scope. Intense rainfall, delivering annual precipitation totals within just a few days, triggered widespread flooding, with the 2024 inundation extent estimated to show an approximate cross-sensor increase of 38 ± 9% relative to the historical GLAD/Landsat benchmark (1999–2023), reaching up to a 40-fold increase in some basins. Concurrently, regional terrestrial water storage exhibited an unprecedented surge, with its intra-annual amplitude doubling the long-term average. However, this hydrologic response was spatially variable. In the eastern basins, surface inundation and terrestrial water storage increased concurrently, indicating strong hydrologic coupling. In contrast, several western basins exhibited pronounced surface flooding but comparatively weak TWS responses, revealing a decoupling between flood magnitude and basin-scale storage response. These findings highlight the capability of multi-sensor satellite observations to resolve spatially heterogeneous hydrologic responses and reveal the non-stationarity in the conversion of flood hazards into terrestrial water storage gains in hyper-arid environments. This study provides a transferable approach for monitoring hydrologic extremes in ungauged regions.