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Estimating design floods based on bivariate rainfall frequency analysis and rainfall-runoff model

이변량 강우 빈도분석과 강우-유출 모형에 기반한 설계 홍수량 산정 방안

  • Kim, Min Ji (Department of Smart City Engineering, Hanyang University) ;
  • Park, Kyung Woon (Department of Civil and Environmental System Engineering, Hanyang University) ;
  • Kim, Seok-Woo (Department of Civil and Environmental System Engineering, Hanyang University) ;
  • Kim, Tae-Woong (Department of Civil and Environmental Engineering, Hanyang University)
  • 김민지 (한양대학교 대학원 스마트시티공학과) ;
  • 박경운 (한양대학교 대학원 건설환경시스템공학과) ;
  • 김석우 (한양대학교 대학원 건설환경시스템공학과) ;
  • 김태웅 (한양대학교(ERICA) 건설환경공학과)
  • Received : 2022.06.06
  • Accepted : 2022.09.15
  • Published : 2022.10.31

Abstract

Due to the lack of flood data, the water engineering practice calculates the design flood using rainfall frequency analysis and rainfall-runoff model. However, the rainfall frequency analysis for arbitrary duration does not reflect the regional characteristics of the duration and amount of storm event. This study proposed a practical method to calculate the design flood in a watershed considering the characteristics of storm event, based on the bivariate rainfall frequency analysis. After extracting independent storm events for the Pyeongchang River basin and the upper Namhangang River basin, we performed the bivariate rainfall frequency analysis to determine the design storm events of various return periods, and calculated the design floods using the HEC-1 model. We compared the design floods based on the bivariate rainfall frequency analysis (DF_BRFA) with those estimated by the flood frequency analysis (DF_FFA), and those estimated by the HEC-1 with the univariate rainfall frequency analysis (DF_URFA). In the case of the Pyeongchang River basin, except for the 100-year flood, the average error of the DF_BRFA was 11.6%, which was the closest to the DF_FFA. In the case of the Namhangang River basin, the average error of the DF_BRFA was about 10%, which was the most similar to the DF_FFA. As the return period increased, the DF_URFA was calculated to be much larger than the DF_FFA, whereas the BRFA produced smaller average error in the design flood than the URFA. When the proposed method is used to calculate design flood in an ungauged watershed, it is expected that the estimated design flood might be close to the actual DF_FFA. Thus, the design of the hydrological structures and water resource plans can be carried out economically and reasonably.

홍수량 자료의 부족으로 인해 수자원 실무에서는 강우빈도분석과 강우-유출 모형을 이용하여 설계 홍수량을 산정한다. 하지만 임의 지속기간에 대한 강우빈도분석은 호우사상의 지속기간과 크기에 대한 지역적 특성을 반영하지 못한다. 본 연구에서는 호우사상의 특성을 반영하여 유역의 설계 홍수량을 산정하기 위하여 이변량 강우 빈도분석에 기반한 설계 홍수량 산정 방안을 제시하였다. 평창강 유역과 남한강 상류 유역을 대상으로 각 강우 지점별 독립 호우사상을 추출하여 이변량 강우 빈도분석을 수행하였으며, 중앙값을 이용하여 재현기간별 설계 호우사상을 결정하고, 이를 HEC-1 모형에 적용하여 설계 홍수량을 산정하였다. 또한 홍수량 자료를 빈도분석한 결과(DF_FFA)를 기준으로, 단변량 강우 빈도분석 후 강우-유출모형으로 산정한 기존의 홍수량(DF_URFA)과 본 연구에서 제안한 방법으로 산정한 홍수량(DF_BRFA)을 비교분석하였다. 평창강 유역의 경우, 재현기간 100년인 경우를 제외하고 강우량을 기준으로 산정한 연 최대 호우사상에 대한 BRFA 방법으로 산정한 설계 홍수량이 평균오차 11.6%로 FFA로 산정한 설계 홍수량과 가장 근접하게 나타났다. 남한강 유역의 경우, 지점별 강우량을 기준으로 산정한 연 최대 호우사상에 대한 BRFA 방법으로 산정한 설계 홍수량의 평균오차가 약 10%로 FFA로 산정한 설계 홍수량과 가장 비슷하게 산정되었다. 재현기간이 커질수록 URFA에 의한 설계 홍수량이 FFA에 의한 설계 홍수량보다 크게 산정되었으며, URFA의 설계 홍수량보다 BRFA의 설계 홍수량이 FFA에 의한 설계 홍수량과의 차이가 더 작은 것으로 나타났다. 본 연구에서 제안한 설계 홍수량 산정 방안을 활용한다면, 미계측 유역에서도 실제 DF_FFA 값과 근접한 설계 홍수량을 산정할 수 있을 것으로 기대되며 수공구조물 설계와 수자원 계획 등을 경제적이고 합리적으로 진행할 수 있을 것으로 판단된다.

Keywords

References

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