[H-GM02] Geomorphology

[HGM02-P08] Laboratory model experiment of bedrock channel with downward erosion limited

*Hiroto Igawa¹ (1.Graduate school of science and technology, Kanazawa University)

Keywords:Bedrock river, Downward erosion, Lateral erosion, Laboratory model experiment

Mountain rivers (mostly bedrock rivers) are one of significant factors that characterizes mountainous landscapes, affecting reliefs and valley topographies, etc. In processes of landform development, two types of river incision, downward erosion and lateral erosion, have different roles: downward erosion is a direct reaction to tectonic uplift and determines a longitudinal river-profile, while lateral erosion causes valley widening, enhancing of incised meander, etc. A previous laboratory experiment and conventional interpretation of river terraces mentioned the complementarity relation between downward erosion and lateral erosion about periods of activity, although this concept has not yet been established enough to specify conditions under which it holds. To elucidate the relation between downward erosion and lateral erosion directly, we performed flume experiments (physical model) simulating a bedrock river channel, in which downward erosion was artificially limited at a depth by an unerodible substrate made of a hard board. The results showed that lateral erosion was activated when downward erosion was limited after the board exposure, suggesting a complementarity relation.