抄録
A lot of rivers and channels which were cut for water traffic flow through the center of Osaka City. The Dotombori River flows along and across the city's main streets and the landmark of Osaka. However, it is polluted so that it is the target of urban renewal and some measures are carried out. The water quality of this river is controlled by two water gates because more polluted upstream water and saline seawater in which the concentration of dissolved oxygen is very low flow into the river. In the present paper field observation is conducted to clarify the characteristics of the water quality and asses the operation of the water gates in this tidal urban river. The operation is good for the maintenance of the water quality, but the oxygen-deficient seawater intrudes and spreads onto the river bottom and makes influence on the bottom sediment.
