Journal of Korea Water Resources Association (한국수자원학회논문집)

Korea Water Resources Association (한국수자원학회)
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A study on the feasibility analysis of the current flood season: a case study of the Yongdam Dam

현행 법정홍수기 타당성 검토 및 개선에 관한 연구: 용담댐 사례

  • Lee, Jae Hwang (Department of Civil & Environmental Engineering, Seoul National University) ;
  • Kim, Gi Joo (Department of Civil & Environmental Engineering, Tufts University) ;
  • Kim, Young-Oh (Department of Civil & Environmental Engineering, Seoul National University)
  • 이재황 (서울대학교 공과대학 건설환경공학부) ;
  • 김기주 (Tufts University 건설환경공학부) ;
  • 김영오 (서울대학교 공과대학 건설환경공학부)
  • Received : 2023.10.04
  • Accepted : 2024.05.13
  • Published : 2024.05.31
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Abstract

Korea prepares for potential floods by designating June 21st to September 20th as the flood season. However, many dams in Korea have suffered from extreme floods caused by different climate patterns, as in the case of the longest consecutive rain of 54 days in the 2020's flood season. In this context, various studies have tried to develop novel methodologies to reduce flood damage, but no study has ever dealt with the validity of the current statutory flood season thus far. This study first checked the validity of the current flood season through the observation data in the 21st century and proved that the current flood season does not consider the effects of increasing precipitation trends and the changing regional rainfall characteristics. In order to deal with these limitations, this study suggested seven new alternative flood seasons in the research area. The rigid reservoir operation method (ROM) was used for reservoir simulation, and the long short-term memory (LSTM) model was used to derive predicted inflow. Finally, all alternatives were evaluated based on whether if they exceeded the design discharge of the dam and the design flood of the river. As a result, the floods in the shifted period were reduced by 0.068% and 0.33% in terms of frequency and duration, and the magnitude also decreased by 24.6%, respectively. During this period, the second evaluation method also demonstrated that flood decreased from four to two occurrences. As the result of this study, the authors expect a formal reassessment of the flood season to take place, which will ultimately lead to the preemptive flood response to changing precipitation patterns.

한국은 6월 21일부터 9월 20일까지를 법정홍수기로 지정하여 잠재적 홍수에 대비하여왔다. 하지만 2020년 54일의 역대 최장 장마 사례와 같이 과거와 다른 기후양상으로 인한 극한 홍수로 피해를 겪고 있다. 그동안 홍수 피해 저감을 위한 연구는 매우 많았지만, 법정홍수기가 앞으로도 유효할지에 대한 연구는 시도된 적 이 없었다. 따라서 본 연구는 21세기 관측 자료를 통해 현행 법정홍수기의 타당성을 통계적으로 검토하였으며, 이를 통해 현행 법정홍수기가 강수량 증가 추세와 지역별 강수 특성의 강화를 고려하지 못하고 있음을 확인하였다. 이러한 한계점의 해결을 위해 본 연구에서는 대상 유역에 대한 7개의 새로운 홍수기 후보군을 제안하였고, 이의 타당성을 모의 운영을 통해 분석하였다. 모의 운영 시 댐 운영룰 rigid operation method를, 댐 유입량 예측에는 long short-term memory model을 적용하였다. 제안한 홍수기 각 후보는 댐의 계획방류량과 하천의 계획홍수량을 초과하느냐를 기준으로 평가하였다. 첫 번째 기준으로 평가한 결과, 본 연구에서 제안한 홍수기 적용 시 초과 빈도와 지속시간이 각각 0.068%와 0.33% 감소되었으며, 크기 또한 24.6% 감소하였다. 두 번째 평가 기준으로 평가한 결과 역시, 홍수피해 발생 구간이 기존의 4회에서 2회로 감소하였다. 본 연구 결과를 계기로 법정홍수기 재검토가 공식적으로 이루어져 새로운 양상으로 변화하고 있는 강우 양상에 적극적으로 대비하길 기대한다.

Keywords

Acknowledgement

본 연구는 한국수자원공사(K-water)의 개방형혁신 R&D(20-D-W-005) 사업의 일환으로 수행되었습니다.

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