Landscape evolution is controlled by tectonic strain, bedrock lithology, and climatic conditions, and is expressed in the spatial and temporal variations in river channel networks. In response to tectonic and climatic disturbance, river networks shift both laterally and vertically to achieve a steady state. Several metrics are available to assess the nature of river network disequilibrium, upon which the direction of drainage divide migration can be interpreted. However, to link this information to other observational, theoretical, and experimental data requires the knowledge of the rate of migration, which is still lacking. Here we develop a modified method based on Gilbert metrics to calculate the transient direction and rate of drainage divide migration from topography. By choosing a high base level, linear or quasi-linear χ-plots are obtained for rivers on both sides of the drainage divide, and the elevation-χ gradient is proportional to the average normalized steepness index (ksn). In turn, the velocity of divide migration can be quantified theoretically from the cross-divide comparison of χ. We applied this method to eastern Tibet and obtained a uniform, westward migration pattern for 29 points along two drainage divides with rates between 0.02 and 0.66 mm/yr, which is consistent with the great river capture events in the region. The ongoing reorganization of the river network in eastern Tibet is caused by the Cenozoic growth and eastward expansion of the Tibetan Plateau, the strengthening of the precipitation and regional extension throughout East Asia, and the local fault activities.