Last millennium flooding history and geomorphlogical development of crevasse splay along Kinu River

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K16352
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Geography
• Research Institution: National Institute of Advanced Industrial Science and Technology
• Principal Investigator: Sato Yoshiki 国立研究開発法人産業技術総合研究所, 地質調査総合センター, 研究員 (60751071)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: クレバススプレー / 微地形 / 完新世 / 地形発達史 / 平成27年関東・東北豪雨 / 鬼怒川 / 河川氾濫 / 洪水

Outline of Final Research Achievements

We conducted sedimentological investigation on a present flood deposits, microlandform classification, and coring survey in a crevasse splay distributed in central reach of Kinu River for clarifying geomorphological development and flooding history. It was found that the crevasse splay deposits of the 2015 Kanto-Tohoku Torrential Rain Disaster was divided into three units, which were corresponding to changes in flow conditions during the flooding. Total of seven lobes forms crevasse splay in the study area, suggesting that a number of huge flooding events occurred. Results of coring survey suggest that crevasse splay sediment was composed by more than three layers of flooding deposits which had deposited after ca. 800 cal. BP. In addition, detail analysis of grain size composition indicates that flooding events of the upper two layers included breaching of levee.

Free Research Field

地理学

Academic Significance and Societal Importance of the Research Achievements

本研究では，鬼怒川中流域に分布するクレバススプレーが800年前以降の短期間に集中的に形成されたこと，900～4,400 cal BP頃に河川氾濫の少ない時期があったことを示した．これらの知見は，完新世の環境変化に対する河川応答の一事例として，より普遍的なモデル構築にも活用できると考える．また，本研究では，現成の河川氾濫堆積物の特徴を把握し，それを過去に活用することによって，微高地を構成する堆積物から破堤イベントを検出することに成功した．本研究の手法は他地域の堆積物にも応用でき，沖積低地の地形発達史研究に貢献できると考える．