CHANGE OF RIVER IMPROVEMENT WORKS OF THE LOWER TONE RIVER AND EFFECTIVENESS OF CHANNEL DREDGING

Abstract

River improvement works of the lower Tone River had begun in the Meiji 33rd (1900) and channel form close to the today’s river was made mainly by widening of the river cross-sections. A new river from Sawara to confluence section of Hitachi-tone River (20 to 40km from the river mouth) was made by channel excavation and connected to a region with a wide water surface area which extends from the river mouth. After that period, the present channel form has been constructed by dredging and creating flood channels.

The present paper reports chronological change of the lower Tone River improvement works mainly by channel dredging on the basis of Tone river improvement plan of Showa 24th (1949) and assesses effectiveness and today’issue of implementation works.