Japan Geoscience Union Meeting 2016

Presentation information


Symbol H (Human Geosciences) » H-CG Complex & General

[H-CG26] Interdisciplinary approach to earth's changing surface

Sun. May 22, 2016 1:45 PM - 3:15 PM 105 (1F)

Convener:*Naofumi Yamaguchi(Center for Water Environment Studies, Ibaraki University), Hajime Naruse(Department of Geology and Mineralogy, Graduate School of Science, Kyoto University), Koji Seike(Atmosphere and Ocean Research Institute, University of Tokyo), Hideko Takayanagi(Institute of Geology and Paleontology, Graduate School of Science, Tohoku University), Masayuki Ikeda(Shizuoka University), Chair:Naofumi Yamaguchi(Center for Water Environment Studies, Ibaraki University)

2:45 PM - 3:00 PM

[HCG26-05] Formation of a gravelly sand bar in the Yahagi River, central Japan, inferred from a Ground Penetrating Radar (GPR) survey

*Hiroko Okazaki1, Toru Tamura2, Youngjoo Kwak3 (1.Division of Earth Science, Natural History and Institute, Chiba, 2.Institute of Geology and Geoinformation Geological Survey of Japan, AIST, 3.National Research and Development Agency, Public Works Research Institute)

Keywords:the Yahagi River, gravelly sand bar, ground-penetrating radar (GPR) survey

GPR survey is useful for interpreting subsurface structures and revealing formation of fluvial bars. GPR profiles of fluvial bars are characterized by inclined-, horizontal-, trough-shaped reflectors, and set of multiple reflectors bounded by channeled-shaped surface, which represent downstream-migrating foreset of a bar and lateral accretion of a side bar, dunes, bedload sheet, and secondary channel scours and fills, respectively. We conducted a GPR survey of a gravelly sand bar in the Yahagi River, central Japan, which is 725 m long and 160 m wide, to clarify the three-dimensional architecture of the bar deposits. The survey was carried out in January 2015 using 250-MHz antennas. Obtained GPR profiles showed upward accretion of the inner part of the bar, chute channel incision and fill, and lateral accretion of the bar. The formation history of the bar deposits may present changes in bed load transport associated with recent disturbance, including dam constructions and dredging operations.