Tomoyuki Suzuki

TURBID WATER BEHAVIOR DURING FLOOD IN THE KAWAJI DAM RESERVOIR

We have conducted field observations for turbid water behavior during flood in the Kawaji dam reservoir in the summer and autumn seasons of 2002. The detailed data sets of water-temperature, turbidity, suspended solid, flow velocity, and grain-size distribution were obtained in the reservoir and its inflow river during flood. The observed data in the curved part of the reservoir indicated that we should take account of three-dimensional flow for more accurate estimation of the turbid water behavior. Furthermore, we also conducted numerical simulation of the behavior in the reservoir using 2D model. The simulated results indicated that the grain-size distribution of inflow water can largely change during flood in the reservoir.

LONGITUDINAL CHARACIERISTICS OF SALT WEDGE INTRUSION AND BOTTOM SEDIMENT IN THE RIVER WITH RIFFLE AND POOL ALIERNAIELY

In this study, field observation was carried out in the Old Kitakami River. As a result, most of the mixture form was of weakness mixing, and it was shown that the saline wedge was almost stopped at the riffle at the 6km site. The result of the bottom sediment survey, proved that the property of the bottom sediment is different in the upstream and downstream of the riffle. Next, numerical simulation was done according to the two-dimensional k-e turbulent model. Simulation result of the saline wedge stopping at the riffle was reproduced in good agreement with the observation result Finally, by changing the flow rates, it was shown in the simulation that features of the saline wedge differed in the upstream and downstream of the riffle. These results suggest that the saline wedge is frequently stopped by the riffle in ordinary water discharge, and then, mound is formed by suspended solid settling on the top of the saline wedge.

ON THE MOVEMENT OF ANAEROBIC WATER IN THE TONE RIVER BELOW THE ESTUARY BARRAGE

Field observations were carried out in order to investigate the generation and the movement of anaerobic water in the Tone River below the Tone estuary barrage. The obtained data shows that anaerobic water frequently appeared in the front part of salt wedge, and part of the anaerobic water sometimes flows down along the interface between the salt and the fresh water. The sediment oxgen demand (SOD) coefficient estimated from the variation of DO concentration contained in the salt wedge agreed fairly well with the SOD coefficient obtained by a laboratory experiment.