The River Reorganization Based On The Topographic Metrics And Modeling In The Central Northern Qilian Mountain

River networks will optimize themselves as the responses of changes imposed on them via divide migration and river capture events.Recently,cross-divide topography contrasts extracted via DEM-based analysis are widely used to reveal the direction of divide migration.However,there is still a controversy about which metric is more effective,?anomaly(cross-divide difference in?,a metric from the transform of the bedrock river profile)or cross-divide mean local relief difference(relief anomaly).In this study,we calculated both?and mean local relief for 14 basins in the Northern Qilian,then the divide-migrating directions inferred by both metrics were compared with the published drainage basin erosion rates separately,to reveal which metric can indicate the basin instability better.The results showed that,the ratios that?anomaly and relief anomaly evaluate the divides migrating directions consistent with the differences of erosion rate are 12/21 and 13/21 respectively,the erosion ability difference between the transverse rivers and longitudinal rivers in the Northern Qilian Mountain can be evaluated by both metrics.However,the linear correlations between both metrics and the erosion rate contrasts is poor(R~2 values equal 0.15 and 0.13respectively),and both metrics indicate a unclear correlation with the internal and external forces which control divide migration.So topography contrasts might not indicate drainage stability directly compared to landscape modeling.The divide between Upper Heihe Bain and Liyuan Basin was proved to migrate southwardly by all three drainage stability metrics,with the knowledge of the spatial distribution of rock erodibility,precipitation and uplift in these two Basin,one question was proposed:is that uplift the major factor of divide migration compared to rock erodibility and precipitation?Here two sets of simulation experiments were designed to prove 1)uplift has a higher priority than rock erodibility and precipitation in controlling river network equilibrium time and 2)the divide migrates from rapid-uplifting basin toward the slow-uplifting basin.Based on our simulation results,the divide migration among Upper Heihe Basin and Liyuan Basin might be caused by the difference of uplift difference.