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The Effects of Incised Meandering Valley and Lithological Differences on the Grain Size and Shape of Channel Bed Materials: A Case Study of the Upper and Middle Reaches of Gongneungcheon River

감입곡류 지형과 암질 차이가 하상 퇴적물 입경 및 형상에 미친 영향: 공릉천 중상류 구간을 사례로

  • Chen, Hui (Department of Geography Education, Seoul National University) ;
  • Kim, Jong Wook (Department of Geography Education, Seoul National University) ;
  • Han, Min (Geological Research Center, Korea Institute of Geoscience and Mineral Resource) ;
  • Byun, Jongmin (Department of Geography Education, Seoul National University)
  • 진훈 (서울대학교 지리교육과) ;
  • 김종욱 (서울대학교 지리교육과) ;
  • 한민 (한국지질자원연구원 지질연구센터) ;
  • 변종민 (서울대학교 지리교육과)
  • Received : 2019.01.03
  • Accepted : 2019.03.04
  • Published : 2019.03.30

Abstract

In this study, we investigated the grain size, lithological type, and shape of coarse bed materials in the upper and middle reaches of Gongneungcheon River. For this purpose, 11 sampling points were selected along the river. For 100 samples of the coarse bed materials at each point, three axes (long, intermediate, and short) of samples were measured, and their lithological types were also identified. By measuring grain size, the sphericity and flatness of samples were calculated. Finally, every particle was classified into four shape categories: sphere, disc, blade and rod. We found that the grain size in incised meandering reach is the largest. This is mainly due to the supply of coarse materials from steep valley sides along the meandering channel. According to the lithological analysis, all samples were identified as granite, gneiss and schist, and quartz. The proportion of granite decreased, whereas the proportion of gneiss and schist increased downstream. These patterns indicate that the bedrock distribution within the study area accounts for the downstream lithological variation of coarse bed materials. With regard to the grain shape, sphericity gradually decreased while flatness gradually increased downstream. In the case of the shape classification, unlike the general downstream pattern of grain shape, the proportion of the sphere type decreased and the proportion of the blade type increased downstream. Such a reversal change in the downstream direction turns out to be determined by the lithology (such as foliation, bedding and the pattern of weathering) of coarse bed materials.

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Acknowledgement

본 논문은 제1저자의 석사학위논문을 요약하고 일부 수정한 것입니다. 논문작성 중 많은 도움을 준 신원정, 백명재에게 감사의 뜻을 전합니다. 이 논문은 2018년 서울대학교 사범대학 "대학원생 주도 연구과제 지원"을 받아 수행되었습니다.