Author(s): Jagriti Mishra; Takuya Inoue; Yasuyuki Shimizu; Kazuaki Mutsuura
Linked Author(s): Yasuyuki Shimizu
Keywords: Bedrock meander; Bank erosion; Sediment transport rate
Abstract: Meandering is when river follows a sinuous path instead of flowing straight. Almost no river flows straight. Understanding the process of river meandering is very important for civil projects such as dams, buildings, etc. A complex mutual interaction among factors like flow, sediment transportation, and both bed and bank morphodynamics define the river plane shape in meandering rivers. Meandering is a dominant phenomenon even in Bedrock Rivers. Bedrock meanders are often called as incised meanders because of their dominant trait of being engraved deep into rocky mountains. Bedrock meanders haven’t been studied very widely. Little is known about the effect of bank erosion in incised meander. In this study we tried to study the evolution of bedrock meander due to bank erosion. A U-shaped channel was used to study the effect of bank erosion. The composition of channel consisted majorly of weak mortar. The channel width was 0.12 m, radius of meander was 0.3 m, length of straight channel was 1 m, and height of bank was 0.04 m. We observed effects for different sediment feed rate while keeping the grain sizes, bed slope and flow discharge constant. We observed bank erosion depth using 3D scanner. We also observed sediment transport rate at the downstream end of the channel. The erosion rate of the bank sidewall increased with increase in the sediment transport rate. The formation of point bar lead into thin alluvial thickness near the outer bank. The bedrock near the outer bank was exposed partially and bedrock bed and bank were eroded because of bedload collision. When sediment transport decreased, the bedrock near the outer bank was exposed completely and bedrock bed and bank were nominally eroded.