著者

伊東 敦子

出版者

デジタルアーカイブ学会

雑誌

デジタルアーカイブ学会誌 (ISSN:24329762)

巻号頁・発行日

vol.2, no.4, pp.353-358, 2018-10-01 (Released:2018-11-20)

参考文献数

11

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国立国会図書館東日本大震災アーカイブ(愛称:ひなぎく)は、東日本大震災に関する記録等を包括的に検索できるポータルサイトである。東日本大震災の記録等を国全体として収集・保存・提供するために、様々な機関と連携・協力して国のアーカイブとしての役割を担っている。現在、国内外の47アーカイブと連携しており、検索対象メタデータ数は約376万件となった。震災から7年が経過し、様々な機関との連携を進めると同時に防災学習等にも力を入れている。本稿では、ひなぎくの特色ある記録等の収集を俯瞰するともに、見えてきた課題等を紹介する。

著者

小泉 武栄 伊東 敦子

出版者

日本地形学連合

雑誌

地形 = Transactions, Japanese Geomorphological Union (ISSN:03891755)

巻号頁・発行日

vol.32, no.1, pp.1-14, 2011-01-25

参考文献数

14

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The Tamagawa Josui Canal was excavated in the early Edo period to conduct city water from the Tama River to Edo. In this canal there is a conspicuous asymmetry in slope morphology between both banks. That is, the left bank has steep cliff while the right bank has gradual slope with short cliff on upper part of the bank. To elucidate the cause and the forming process of the asymmetrical slope morphology, we investigated geomorphic surface process on each bank. During January 11th to December 24th in 2003, we set up traps on each bank and weighed monthly the volume of debris fallen down from upper part of the slopes. According to longitudinal measurement of debris volume, failure of soil surface occurs throughout the year on the slope of the both banks, though total amount of debris production on the left bank were twice as high as that on the right bank. Amount of debris in winter season was 9.7 times higher than in summer season. Especially from January to March, debris was intensively produced on the right bank. Debris production was evident to be induced by needle ice. Geomorphic surface processes on the north-facing right bank are as follows. In winter season, frost columns are formed on the surface of Kanto Loam (volcanic ash sediment) under low soil temperature and high soil moisture. A few days later, when needle ice melt, small grains are left on the surface of Kanto Loam. Grains are eventually carried down by the rainfall or winds to lower part of the slope. As a result, cliffs on upper part of the bank retreat and gentle slopes of the lower part expand. On the south-facing left bank, debris production is little throughout the year. On this bank, cliffs are so dried up in winter because of rich sunshine that needle ice don't arise even air temperature fell down under the freezing point. Instead, many cracks arise lengthways and blocks of soil fall down in occasion of heavy rain. In this way, the cliff retreats with its vertical shape. The Tamagawa Josui Canal is supposed to have maintained its original form when it had been brimmed with water, from the construction time till 1965 when water flow stopped by the disuse because of completion of filtration plant. After water flow was stopped and canal became to be dried up, asymmetry of the trench profile has been formed.