地すべり地の地下水については, その起源を知り, 地すべり地への流入個所や経路を知ることができれば, 地すべり活動にどのように影響するかを推定し, ひいては合理的な地下水排除計画に資することができる。本研究ノートでは, 四国の3つの結晶片岩地すべりで実施した, 水質分析の結果を基にして行った地下水の経路 (水みち) の推定過程について論述する。地下水の水質指標の中ではHCO₃^-, SO₄^2-の2つのイオンが地すべり活動にとって重要であることを確認した。HCO₃^-は地すべり移動体全体の風化に関与するが, 一方でSO₄^2-は泥質片岩の風化・粘土化に伴うすべり面の形成に大きく寄与している。水文地質学的な観点から地すべり地内の地下水を見ると地質や断層の存在が地下水の水みちを推定するにあたって大いに影響を与えていることが解った。水質指標の内, 溶存成分のみで水みちを推定することは方法論的には十分条件を満足させるには至っていないが, 一定の方向性が示せた。

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To develop an easy-to-use numerical model explaining flood flow, sediment transport and riverbed variation is important for efficient channel design and management. In this study, we developed a new easy two-dimensional method for the flood flow and riverbed variation analysis using stream line. We applied the new model and the conventional model to 2014 flood in the Nakagawa River whose data of water surface profiles were observed in detail. As a result, the authors’ model is capable of explaining water surface profile, velocity distribution and riverbed variation in the Nakagawa River.

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In ancient Japan there was a unique land system concerning allotment and allocation which was called “Jori system.” So far, many geographers have been studying about the system from historico-geographical point of view.
The purpose of the present paper is in an attempt to clarify the distribution and morphology of the Jori system in ancient Awa province (Prefecture of Tokushima at present) in order to approach general principles of the system in ancient Japan. Especially, the relationship between ancient administrative districts and regionalism was investigated to reveal the political backgrounds of the system.
The main findings are as follows:
(1) The Jori system in ancient Awa province was divided into three areas: the central area of the Yoshino-river alluvial plain (Miyoshi-gun and Mima-gun), the lower area of the plain (Oe-gun, Awa-gun, Itano-gun, Myozai-gun and Myodo-gun) and Minami-gata (Katsu'ura-gun and Naka-gun). In the lower area of the plain, Many Jori land allotment systems are found as seen in Figs. 1, 2, 3 and 4. However, the direction of most Joris is N 10°W even though they are apart situated each other. Therefore, each Jori seems to be constructed under the same planning. The real direction is based on the inclination of the Akui-river delta-fan that the Awa Kokufu (administrative town of ancient Awa province) was situated on.
(2) It may be stated that the Jori system in the lower area of the plain was planned by the Awa-ooshinoatae family ruled this area 6th through 8th centuries as the “Kuninomiyatsuko.” Guns established immediately after the Taikanokaishin (revolution in A.D. 645) were divided into five districts with straight line boundaries each accoridng to the Jori system, and their original boundaries are still present in part even now as seen Fig. 1.
(3) The Niijima manor established in A.D. 749 under the rule of the Todaiji temple owned 42cho, 8tan and 162bu (about 52ha.) area. This manor was sited on the lowland along the Yoshino-river or its former course near the coast as seen in Figs. 5 and 6, however that was destroyed by frequent floods of the river. In addition, a small Jori system is also found near the manor.

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