| 講演要旨(和文) | | 流路変遷による河川微地形の形成過程の復元を目的として，河川敷において比抵抗探査を実施した．調査地は真岡市上谷貝地先の鬼怒川の中流部である．調査地には左岸側に砂礫で覆われた幅400m程度，上下流延長1km程度の拡がりを有する高水敷が発達する．この高水敷上に4本の探査測線を設定し，比抵抗探査を実施した． 探査断面には共通して高比抵抗表層部が認められたが，草本植生に覆われた中位面ではより大きな値を示し，主として粗粒砂からなり，植生に被覆されていない低位面では相対的に低い値を示すこと，旧流路横断部では低比抵抗構造を呈することが特徴的であった． |
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| | 講演要旨(英文) | | A small-scale resistivity surveying was conducted on a river floor at the middle reaches of Kinu River, flowing in Moka City, Tochigi Prefecture. The purpose of the survey was to clarify the fluvial processes in developing small-scale landforms along river beds. Four short survey lines were set on the river floor, covered with sand and gravel, about 400 m wide and 1 km long, divided into upper, middle and the lower floodplain. Resistivity profiles clearly delineated surficial high resistivity layer up to 3 m in thickness. The resistivities of the surficial layer at the middle floodplain, surface of which was covered with grass plants, was greater than those of the lower surface, which was bare and mainly composed of coarse sands. Whereas the water table was estimated about 1 to 4 m below the surveyed surface, resistivity of the lower part showed from 100 to 600 Ohm-m in all profiles. The survey result indicates the river floor consists of thick coarse-grained fluvial sediments and or conductivity of pore water is relatively low due to the infiltration of fresh water. |
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