The Quaternary Research (Daiyonki-Kenkyu)

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The Tone River and the Arakawa River merged in the central part of the Kanto Plain in the early Edo period (17^th Century) and flowed into Tokyo Bay. The current Tone River has moved its mainstream from the Kazo Lowland to the lower Kinugawa Lowland, and the current Arakawa River flows down through the Arakawa Lowland to the Tokyo Lowland. Based on the historical and prehistoric topographical changes in the Tokyo Lowland, the author considered the pre-modern channels and ages of the Tone and Arakawa rivers, using the microtopography of the plains as clues. In the Kazo and Nakagawa Lowlands, the former Tone River channel can be traced by the development of natural levees and riverine sand dunes. It is required, however, to elucidate where the Tone merged with the Watarase River and the origin of fragmentary former river channels. A large-scale meandering channel trace can be seen from the Arakawa Lowland to the Tokyo Lowland, but there is no record of the trunk river there in the historical era. From the composition of sediments and archaeological data, this can be considered as the trunk river of the Tone River, but it is necessary to clarify the relationship between its age, the river channel transition, and volcanic activity in the basin.

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