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2024 Vol.25, Issue 12 Preview Page
Numerical Analysis of Flow and Bed Change in Stream Meander of the Downstream of Dam Using a Two-dimensional Model

2차원 수리모형을 이용한 댐 직하류 만곡부에서의 흐름 및 하상변동 해석

Kidoo Park1
,
Yeongjeong Seong2
,
Sewook Oh3
,
Younghun Jung4*
박 기두1
,
성 연정2
,
오 세욱3
,
정 영훈4*
1Research Professor, Climate Crisis Emergency Management Institute, Kyungpook National University
2Research Fellow, Sangju Carbon Neutrality Support Center
3Professor, Department of Advanced Science and Technology Convergence, Kyungpook National University
4Associate Professor, Department of Advanced Science and Technology Convergence, Kyungpook National University
*Corresponding Author
1 December 2024. pp. 53-62
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Abstract

When river flows are blocked by dam, erosion and deposition are limited in the downstream of the dam, it is very important to establish a channel plan for a stable stream that takes into account erosion and deposition caused by sediment transport. In this study, the two-dimensional HEC-RAS sediment transport simulation for the Wicheon, the downstream of Gunwi dam located in the Nakdong watershed, was performed to predict the bed changes. At the meandering exit there is a very high velocity impact zone, which can be very vulnerable to erosion of the stream bed. Using the designed channel cross sections in the river master plan, bed changes to erosion and deposition for the channel cross section of the 80-year and 100-year frequency flood discharges were simulated. In the case of the downstream of the Gunwi dam, due to its hydrodynamic characteristics, high velocities were expected to occur at the impact zone in the meander, expecting in the greatest erosion due to the increase of tractive force. However, in the case of the downstream of Gunwi dam, it was confirmed that very stable channel was formed because the armoring was considerably carried out by the coarse bed materials such as gravel.

Keywords
Erosion
Deposition
Downstream of the dam
Sediment transport
Bed change
Stable channel
Meander
Impact zone
Two-dimensional HEC-RAS sediment transport simulation
Armoring

댐에 의해 하천흐름이 차단되는 경우, 댐 직하류에서는 침식과 퇴적 양상이 일반적인 하천흐름 양상과 다르며, 제한적으로 발생하기 때문에 유사이송으로 인한 침식과 퇴적에 따른 하상변동이 고려된 안정하도로 하도계획을 수립하는 것이 매우 중요하다. 본 연구에서는 낙동강수계에 위치한 군위댐 직하류인 위천에 대한 2차원 HEC-RAS 유사이송 모의를 수행하였다. 본 과업구간 내에는 만곡에 의한 횡방향 유속과 수위차이가 발생하여 만곡이 끝나는 출구점에는 유속이 매우 빠른 수충부가 존재하여 하도의 침식에 대해 매우 취약할 수 있다. 위천 하천기본계획의 하도 계획단면을 이용하여 80년 및 100년 빈도 계획홍수량에 대한 하도 단면의 침식과 퇴적에 대한 하상변동 양상을 모의하였다. 군위댐 직하류의 경우, 동수역학 특성상 만곡부에서 발생하게 되는 수충부지점에서 고유속흐름이 발생되어 소류력 증가로 인한 침식이 가장 크게 발생될 것으로 예상되었다. 그러나 군위댐 하류의 경우, 자갈과 같은 굵은 하상재료에 의해 장갑화가 상당히 진행되었기 때문에 침식의 우려가 매우 작은 안정하도가 형성되었음을 확인할 수 있었다.

키워드
침식
퇴적
댐 직하류
유사이송
하상변동
안정하도
만곡
수충부
2차원 HEC-RAS 유사이송 모의
장갑화
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United States Army Corps of Engineers, HEC-RAS Documentation, U.S. Army Corps of Engineers Hydrologic Engineering Center: Davis, CA, USA, https://www.hec.usace.army.mil/confluence/rasdocs.

Information
  • Publisher :Korean Geo-Environmental Society
  • Publisher(Ko) :한국지반환경공학회
  • Journal Title :Journal of the Korean Geo-Environmental Society
  • Journal Title(Ko) :한국지반환경공학회 논문집
  • Volume : 25
  • No :12
  • Pages :53-62
  • Received Date : 2024-11-13
  • Revised Date : 2024-11-14
  • Accepted Date : 2024-11-20
  • DOI :https://doi.org/10.14481/jkges.2024.25.12.53
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