Meandering channels with high thalweg sinuosity were reproduced in a small flume. A mixture of fine-grained plastic sand and kaolin clay was used for bank material. Channel patterns greatly varied depending on the clay content and water saturation of bank sediment. The relationship between the discharge and meandering wavelength in the flume is consistent with those in natural rivers. Meandering river occurred under conditions with high clay content and water saturation, and braided river occurred under conditions with low clay content and saturation. In the area where meandering is maintained, sinuosity increases with decreasing clay content and saturation. However, in between meandering and braided conditions, sinuosity was higher in the meandering condition. The difference in saturation caused the difference in mean curvature of meandering bends: lower curvature predominates in higher saturation. For reproducing a simple meandering river, it is effective to use mixture of light sand and cohesive clay with appropriate water saturation.

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The Inaoigawa irrigation canal was constructed by Tsutou Nitobe and Jyujirou Nitobe in 1855, the grandfather and a father of Inazo Nitobe. It was a huge civil engineering work with the purpose of irrigating the “Scanty land” Sanbongihara Plateau, about 50-90 m above sea level. The ~800 m tunnel water way would have required high-level technology for geographic measurement and tunnel construction for the Edo period. We conducted a field excavation of the tunnel water way in 2012, and surveyed the constructive structures and measured the inclination ratio of the water way. We found many similarities in the methods of tunnel construction between the Inaoigawa irrigation canal and the Persian qanat irrigation systems of central Asia.

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The authors consider the fault movement involved in the fault formation from fault scale relational expression. When the active fault is assumed to be appears in surface of the earth, lead to the following; The active fault activity did not start Quaternary Era at the beginning all together but the starting point of C class active fault is two million years ago (Early Quaternary), B class active fault is 700 thousand years ago (Middle Pleistocene), A class active fault is 200 thousand years ago(Late Pleistocene). The fault at the beginning of quaternary cannot be changed to the active fault without multiple diastrophism. The majority of large scale fault (Length 20 kilometers or more) changes to the active fault. It is thought that major fault repeating faulting from pre-quaternary can become an active fault.

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