Reconstruction of the past sediment discharge events based on atmospheric radionuclides and magnetic properties of lacustrine and inner bay sediments

2022 Fiscal Year Final Research Report

• Project/Area Number: 19K04965
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 25030:Disaster prevention engineering-related
• Research Institution: Kanazawa University
• Principal Investigator: Ochiai Shinya 金沢大学, 環日本海域環境研究センター, 助教 (10401936)
• Co-Investigator(Kenkyū-buntansha): 酒井 英男 富山大学, 理学部, 客員教授 (30134993)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 土砂流出イベント / 堆積物 / 大気由来放射性核種 / 磁化特性

Outline of Final Research Achievements

This study aims to reconstruct the past sediment discharge events in river catchments based on atmospheric radionuclides and magnetic properties of lacustrine and inner bay sediments. Vertical changes in excess Pb-210 and magnetic susceptibility of the sediment cores obtained in the West Nanao Bay (Ishikawa Prefecture) and the Lake Dojo-ike in Tateyama area (Toyama Prefecture) were analyzed to identify event layers and estimate their ages. Estimated ages of the event layers in the sediment cores corresponded well to the past heavy rainfall and flood events documented in the catchment area. These results indicate that Pb-210 and magnetic properties of the sediment are useful to reconstruct the past sediment discharge events in the catchment area.

Free Research Field

水文地形学

Academic Significance and Societal Importance of the Research Achievements

近年、豪雨など極端気象現象に伴う土砂災害が相次いでおり、こうした水文環境の変化が流域からの土砂流出に与える影響の予測が不可欠になっている。従来こうした豪雨災害や土砂災害の定量記録は、測器による気象観測が開始された明治時代以降に限られていることから、本研究の成果は特に観測網が整備されていない国土縁辺部における、数十年に一度の規模の流域の土砂流出挙動の詳細把握、土砂流出イベントの発生頻度等の知見の取得につながり、適切な流域管理、防災計画の策定等に寄与できると考えられる。