Comparison of River Mouth Process in Tohoku District

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Hydraulic and topographical characteristics of river mouth in Tohoku district were surveyed under the cooperation of the universities in six prefectures. The rivers surveyed are as follows :Aomori : Iwaki R. (stability and hydraulics at river mouth), Takase R. (water quality and hydraulics), Mabechi R. (topography change) and Niida R. (hydraulics)Iwate : 42 rivers on Sanriku Coast (Comparison of topography)Akita : Yoneshiro R. (topography change), Omono R. (topography change) and Koyoshi R. (river mouth process)Miyagi : Nanakita R. (river mouth process) and Abukuma R. (river mouth process)Yamagata : Mogami R. (topography change) and Aka R. (topography change)Fukushima : 36 small rivers (comparison of topography)Both the literature and the field survey were carried out for all rivers. Two gatherings were performed in order to discuss the comparison of each river at Jusanko, the Iwaki River mouth, 1989, and at Yunohama, near the Mogami River mouth and the Aka River mouth, 1990.The most important results obtained is that the scale of river controls phenomena observed at river mouths. For example, the topography change observed in large scale river varies over some years. On the other hand, the topography of small river varies according to annual variation of river flow.It was also confirmed that the further field survey may need to reveal the mechanism of river mouth process.