摘要：Diffusion of filth and backward run of sea in the Naka river, tidal stream of moderate mixing type river, were investigated at the high tide. The results obtained were as follows. 1. Backward run of sea in the river is fixed independently of the sea level. 2. In the tidal river of the moderate mixing type at the high tide is more than that at mean sea level, however the distance of the backward run is almost changeless. 3. The diffusion of filth on side of the bank where a polluted tributary joins the main stream is less than that in the central area of the main stream. Therefore, on side of the band at downstream from junction, the stream may be easy to be polluted successively.
