[H-GM03] Geomorphology

[HGM03-01] Uplift-induced drainage divide migration and channel reorganization:Laboratory model experiment

*Akimasa Sakashita¹, Noritaka Endo¹ (1.Kanazawa university )

Keywords:fluvial morphology, drainage divide

A drainage divide, the boundary of a drainage basin, is modified by external forcing, changing its position and elevation along with reorganization of the channel. Non-uniform uplift is a common factor as forcing, and a key for reconstruction and prediction of past and future landforms in tectonically complicated regions such as Japan, but its detailed dynamics are not still well understood. Here, we observed divide migration and channel reorganization caused by non-uniform uplift, through a laboratory model experiment. The experimental tank has two outlets, so two neighboring drainage basins are formed by supplying misty artificial rainfall. We exerted tilting uplift as non-uniform uplift with linearly varying uplift rate.

During uplift activities, the basin under the downstream increasing of uplift did not show a large change of landform, while the basin of upstream increasing of uplift showed the increase in riverbed gradient, but the drainage divide between the two basin was stable. After the uplift ceased, the divide shifted, resulting in the increase in area and the decrease in riverbed gradient of the basin which has been influenced by the upstream increasing uplift. During the landform change, the shape of river varied by modifying its bend (curvature). Because we conducted only one experimental run so far, more data is needed to derive a general law.