Preliminary Study of the Behavior of Floating Material on a Side-pool of a River Channel

Abstract

Field experiment of the behavior of floating material was conducted at a side pool of a side subchannel of the Inukami River which flows into the east coast of Biwa Lake in Shiga Prefecture, Japan. Four types of floating materials with different bulk density were prepared by changing the amount of water injected into ping-pong ball. The materials were put on a starting point on the side pool, and the motion was traced by eyes. The experiment was conducted under no wind condition with the surface velocity of the main current of the side subchannel ranging from 43.7 to 55.7 cm sec^-1.

The frequency of being cast ashore of the materials with the smallest bulk density was significantly larger than those with the largest bulk density. In addition, the materials with the smallest density tended to be cast ashore within shorter time when the surface velocity of the main current was 43.7 cm sec^-1 and 50.6 cm sec^-1. The material with the largest bulk density tended to be cast ashore in shorter time when the main current velocity was larger. The analysis on the trace of floating materials revealed that the trace was strongly affected not only by the general eddy structure but also the complex turbulent structure in the side pool.