Effects of conjunction channel on water exchange in riverside embayment

Abstract

A riverside embayment is expected to provide a good habitat for aquatic life. It is often connected with primary river flow through a conjunction channel. It is important to maintain water quality and to prevent siltation in such a dead water zone. In this study, we investigated the effects of the length, location and orientation angle of a conjunction channel on flow structures and water exchange rate. The experiments were conducted in a laboratory flume and velocity vectors were measured by PIV method in horizontal planes. The flow patterns in embayment zones were extremely changed by the angle of the conjunction channel. When the length of conjunction channel is long relatively to the width, an isolated vortex was generated in a conjunction zone. This vortex fluctuates and penetrates intermittently into embayment zone. The water exchange rate was investigated by a dye-injection method. The water exchange rate is generally proportional to the velocity scale in the embayment area but it was affected by vortex structures in a conjunction channel.