Using meteorological data to elucidate the weathering process of tsunami deposits in coastal forests area along the Sea of Japan

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04086
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17030:Human geosciences-related
• Research Institution: Rakuno Gakuen University (2021-2022); Akita Prefectural University (2020)
• Principal Investigator: Chiba Takashi 酪農学園大学, 農食環境学群, 講師 (60638980)
• Co-Investigator(Kenkyū-buntansha): 井上 誠 秋田県立大学, 生物資源科学部, 准教授 (00599095) ; 西村 裕一 北海道大学, 理学研究院, 准教授 (20208226)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 津波堆積物 / 珪藻群集 / 日本海沿岸域 / 沿岸林 / 風化過程 / 気象観測 / 飛砂

Outline of Final Research Achievements

Forests have been planted along the coastal areas in the north-eastern part of the Sea of Japan to protect against the sands blown by strong winds. To elucidate the characteristics and weathering process of the tsunami deposits left in the soil of this coastal forest, we conducted both geological surveys and studies using observed meteorological data. Additionally, a field experiment was performed to investigate the process through which fine particles are transported by strong wind.
As a result of the survey and analyses, tsunami deposits associated with the 1983 Nihonkai Chubu Earthquake and blown sand deposits associated with the 1991 Typhoon 9119 were identified. Additionally, deposits presumed to be blown sand from Typhoon 9119 were observed from Mitane-cho to Oga-shi. Since these deposits were not found on sand dunes in areas where no coastal forest had been formed, the coastal forest soil was considered to be an environment with high conservation potential for event deposits.

Free Research Field

第四紀地質学

Academic Significance and Societal Importance of the Research Achievements

本研究の成果は，標高の高い砂丘が発達することにより相対的に津波の痕跡が残りにくい日本海側において，初めて津波堆積物の認定を行ったことにまず意義がある．また，砂丘が発達する地域においても沿岸林内に土壌が形成されていれば，津波の痕跡が保存される可能性も高まることが明らかになった．そして，津波堆積物と台風に伴い堆積した飛砂堆積物の特徴及びそれらの違いを明らかにし，それぞれの認定において重要な点を指摘することができた．さらに，調査地域における飛砂の採取や機器観測などを行うことにより，沿岸林内では通常時に飛砂がほとんど運搬されず，何らかのイベントに伴って堆積する可能性が高いことが示唆された．