Satellite altimetry reveals heterogeneity in global flood peak timing and its shifts

Flood peak timing (FloPT) is a key indicator of hydrological responses to climate change. Yet global FloPT assessments is limited by sparse and uneven in-situ discharge observations. Here, we demonstrated the capability of satellite altimetry to estimate FloPT worldwide and presented the global map of observed FloPT, with a dramatic improvement in spatial coverage, especially in Global South countries. Altimetry-based FloPT shows distinct behaviors in snowmelt-dominated and precipitation-driven regions. Moreover, FloPT trends during 2008-2025 vary globally and within individual basins. 52.2% of the virtual stations and 27 of the 50 largest river basin outlets exhibit earlier FloPT. Earlier flood peaks are pronounced at high latitudes and elevations, consistent with accelerated snowmelt. Delayed peaks occur in the upper Mississippi, southern Amazon, and central Congo, consistent with shifts in precipitation maxima. Human water management also shapes abrupt FloPT changes, with stronger regulation constraining shifts. These results demonstrate the value of dense satellite altimetry resolving FloPT variability, particularly in remote and data-scarce regions. Flood peak timing shifted earlier at 52.2% of river virtual stations and 27 of the 50 largest basin outlets, especially at high latitudes and elevations, according to a study using satellite altimetry and clustering analysis to investigate global flood peak timing and its trends from 2008 to 2025.