Spatiotemporal Evolution of Bed Configurations in Mixed Bedrock-Alluvial in Uniformly Curved Channels

Abstract

River courses are rarely straight. Rather, they tend to be meandering. Incision meandering is one of the most common types of meandering discussed in river engineering. The availability of abrasive tools, coverage thickness, appropriate flow velocity, channel geometry, and flow level play a role in the natural phenomenon of bedrock incisions. Any minor change in those parameters, whether internal or external, can significantly impact the bedrock incision. The purpose of this study is to experimentally investigate the bedrock incision under sediment bedload transport along curved channels by varying flow speed with the other parameters kept constant. In this study, a bedrock incision was simulated in an annular flume. Two cases were considered, each with different rotation speeds of the cover lid, using plaster as the bedrock and sediment incision tools. In both cases, sediment motion was the bedload transport. It was found that the sediment deposited along the inner wall differed according to the rotation speed. A uniform transverse slope was found for a rotation speed of 48 RPM and moving bedforms were found for a rotation speed of 40 RPM. The bedrock incision resulted in the formation of the inner channel along the centerline of the flume, which grew more quickly toward the inner wall under the bedforms than under the uniform transverse slope. These findings suggest that the type of bedform has a more significant impact on bedrock incisions than rotation speed.

Keywords

• incision
• meandering
• bedrock
• curved channel
• bed configurations
• annular flume