Flow structure and air entrainment in riparian riffles in Seomjin River

Abstract

The objective of this study was to present the hydraulic analysis of the flow structure and the air entrainment in the riparian riffles in Seomjin River, and the relationships between the efficiency of the oxygen transfer and the hydraulic parameters. Field estimation on the flow structure in the riffles and the measurements of the oxygen transfer were performed. Meandering streams with relatively coarse bed load tend to develop a riffle-pool sequence with pools in the outsides of the bends and riffles in the crossovers between one meander to the next on the opposite margin of the stream. Air entrainment occurred in the edged gravels more frequently rather than in the round and edgeless ones, and it was formed mainly from behind the trailing edges of the gravels. Oxygen transfer was found to be proportional to the flow velocity, the flow discharge, and the Froude number, but was not proportional to the particle diameter. Average value of oxygen transfer in the riffles of study area was about 0.085, which shows good habitat condition for the aquatic creatures. © World Scientific Publishing Company.