Rivers play a central role in shaping the Earth's surface and ecosystems through physical, chemical, and biological interactions. The intensity, time, and location of these interactions change as rivers continuously migrate across the landscape. In recent decades, human activity and climate change have altered river hydrology and sediment fluxes, leading to changes in river positions. Climate warming, increasing flood extremes, and human-induced land use changes have slowed river migration rates in some river reaches while accelerating them in others. However, a comprehensive, spatially continuous, large-scale perspective on and understanding of these recent changes in the rate of river position shifts is lacking.To address this knowledge gap, we created a continuous global dataset of yearly river positions and migration rates over the past four decades. The continuous annual river positions were detected using Landsat-derived surface-water datasets and processed in Google Earth Engine, a cloud-based parallel-computation platform. The resulting river extents and centerlines reflect their yearly permanent positions, corresponding to the river locations during base flow. This approach improves the representation of position changes derived from geomorphological rather than hydrological processes. To analyze river position changes across different patterns and complexities at large scales, we developed and applied a global reach-based quantification method for river mobility rates.Results show that while some alluvial rivers maintain a stable annual pace of mobility, others exhibit trends in migration rates. For instance, the Amazon Basin, which has experienced significant deforestation and hydrological modifications, has shown increased rates of river position change in recent decades, impacting floodplain forests and communities. In this talk, we will discuss the advantages, limitations, and applications of the detected yearly river positions and mobility rates, offer insights into the forcings driving changes in river positions and their environmental outcomes, and highlight current and future impacts on one of Earth’s most vulnerable hydrologic systems.
