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

Abstract

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-ε 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.