Izawa Yasobei

One of the Edo period's leading flood control experts. Born in Mizoguchi Village, Naga County, Kii Province (Wakayama Prefecture). His name was Tamenaga. He was a samurai of the Kishu Domain, and later became a shogunate official after Tokugawa Yoshimune became shogun. In 1722 (Kyoho 7), he was summoned to the shogunate's accounting office, and in 1722 (Kyoho 7), he was appointed as a kanjo ginmiyaku (financial auditor), in 1731 as a kanjo ginmiyaku (financial auditor), and in 1735 he also served as a gundai (district governor) of Mino Province (Gifu Prefecture). In 1737 (Genbun 2), he resigned from his position and became a yoriai (member of the association). He was highly valued by Yoshimune, and during the Kyoho Reforms (1716-1745), he demonstrated his prowess in flood control and agricultural development, developing many innovative ideas in civil engineering, especially for rivers, and becoming the founder of the Kishu school. In particular, the 60-kilometer Minumadai Canal (Saitama Prefecture), which took in water from the midstream of the Tone River and was completed in 1728 (the 13th year of the Kyoho era), was a representative project that made a tremendous contribution to the agricultural development and water transportation of Musashi Province. The Horeki Flood Control Project (1754), which divided the Kiso River into three rivers, was also designed by him.

[Yutaka Takahashi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

江戸時代屈指の治水家。紀伊国（和歌山県）那賀(なが)郡溝口村に生まれる。名は為永(ためなが)。紀州藩士、のち徳川吉宗(よしむね)の将軍就任後幕臣となる。1722年（享保7）、幕府の勘定所に召され、25年勘定吟味役格、31年勘定吟味役、35年美濃(みの)国（岐阜県）郡代兼任。37年（元文2）役を辞し寄合(よりあい)となる。吉宗に重用され、享保(きょうほう)の改革（1716～45）において、治水、農業開発に敏腕を発揮、河川を中心とする土木技術に多くの新機軸を開発し、紀州流の開祖となった。とくに利根(とね)川中流部から取水の見沼代(みぬまだい)用水（埼玉県）60キロメートルは1728年（享保13）に完成、武蔵(むさし)国の農業開発、水運に至大な貢献をした代表的事業である。木曽(きそ)川三川分流の宝暦(ほうれき)治水（1754）も彼の設計である。

［高橋　裕］

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