[H-GM04] Geomorphology

[HGM04-03] Relation between downward and lateral erosion in bedrock channels: laboratory experiments

*Noritaka Endo¹, Hiroto Igawa² (1.Graduate school of science and technology, Kanazawa University, 2.College of science and technology, Kanazawa University)

Keywords:bedrock river, downward incision, lateral erosion, bedrock erosion

We performed laboratory model experiments to elucidate how channel erosion of bedrock rivers proceeds, focusing on relation between downward cutting and lateral erosion. The initial landforms were single straight channels. With the water discharge and the rate of base level lowering constant, we measured the topographic change at several cross sections, and estimated downward and lateral erosion rates from the difference in depth and width of channels between each measurement time. We found that statistically the trends (rise or fall) of downward and lateral erosions are in negative correlation: most cross sections exhibited such a relationship, and only a few sections showed no correlation, but no section displays positive correlation. Knickpoint migration seems to promote downward erosion and at the same time suppresses lateral erosion. The cases where no correlation was observed seem to be affected by channel sinuosity, suggesting that a structure of water flow (two or three dimensional) influences the mode of channel erosions (whether alternating or mutual waxing and waning between vertical and horizontal erosions).