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Original Article

Estimation of Debris-Flow Peak Discharge Using UAV-Derived Topographic Data and Manning’s Equation

UAV 기반 지형자료와 Manning 식을 이용한 토석류 피크유량 산정

Byonghee Jun1*
전 병희1*
1Professor, Graduate School of Disaster Prevention, Kangwon National University
1강원대학교 방재전문대학원 교수
*Corresponding Author
31 March 2026. pp. 11-21
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Abstract

This study quantitatively estimated the velocity and peak discharge of a debris flow that occurred in August 2020 in Seonse-ri, Osan-myeon, Gokseong-gun, Jeollanam-do, South Korea, using UAV-derived orthophotos and a high-resolution digital surface model (DSM). Four representative cross-sections were selected along the debris-flow channel, and cross-sectional area and channel slope were extracted at each location. These parameters were then applied to both the Manning equation and a Takahashi model–based numerical simulation. The results indicate that a maximum flow velocity of approximately 11 m/s and a discharge of about 350 m3/s occurred in the upstream section, whereas in the midstream section the peak discharge increased to approximately 460 m3/s due to an enlargement of the cross-sectional area despite a decrease in velocity. Numerical simulations further revealed locally high velocities exceeding 20 m/s and multi-peaked hydrographs, effectively capturing the nonlinear behavior of debris-flow dynamics. In contrast, discharge estimates obtained using the rational method combined with conventional debris-flow conversion coefficients were limited to approximately 2–3 m3/s, showing a substantial discrepancy from the observed scale of the event. These results demonstrate that the combined use of UAV-based high-resolution field data and numerical modeling provides a more reliable assessment of debris-flow magnitude and dynamic characteristics. The proposed approach offers valuable baseline information for estimating peak discharge, assessing debris-flow hazards, and developing mitigation strategies in small mountainous catchments in Korea.

Keywords
Debris flow
Discharge
UAV
Orthophoto
DSM

본 연구는 2020년 8월 전라남도 곡성군 오산면 선세리에서 발생한 토석류를 대상으로, UAV 기반 정사영상과 수치표고모델(DSM)을 활용하여 토석류 유속 및 피크유량을 정량적으로 산정하였다. 연구 대상 유역 내에서 4개의 대표 단면을 선정하고, 각 단면에 대해 횡단면적과 하상 경사도를 추출하여 Manning 식과 Takahashi 모델 기반 수치해석 기법에 적용하였다. 분석 결과, 상류부에서는 최대 약 11 m/s의 유속과 약 350 m3/s의 유량이 산출되었으며, 중류부에서는 유속 감소에도 불구하고 횡단면적 증가로 인해 최대 약 460 m3/s의 피크유량이 확인되었다. 수치해석 결과에서는 국부적으로 20 m/s 이상의 높은 유속과 다봉형 유량 분포가 나타나, 토석류 유동의 비선형적 특성을 효과적으로 재현하였다. 반면, 합리식과 토석류 변환계수를 적용한 기존 방법에서는 약 2–3 m3/s 수준의 유량이 산정되어, 실제 토석류 규모와 큰 차이를 보였다. 이러한 결과는 UAV 기반 고해상도 현장자료와 수치해석을 병행한 접근법이 토석류의 규모와 동역학적 특성을 보다 정밀하게 평가할 수 있음을 보여준다. 본 연구에서 제시한 방법은 향후 국내 소규모 산지 유역에서 발생하는 토석류의 피크유량 산정, 위험도 평가 및 방재대책 수립을 위한 기초 자료로 활용될 수 있을 것으로 기대된다.

키워드
토석류
유출량
UAV
정사영상
DSM
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Korean References Translated from the English

1

국립재난안전연구원 (2018). 토석류 위험지도 작성 및 대책수립 매뉴얼. 울산: 국립재난안전연구원.

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Information
  • Publisher :Korean Society of Disaster and Security
  • Publisher(Ko) :한국방재안전학회
  • Journal Title :Journal of Korean Society of Disaster and Security
  • Journal Title(Ko) :한국방재안전학회 논문집
  • Volume : 19
  • No :1
  • Pages :11-21
  • Received Date : 2026-02-09
  • Revised Date : 2026-03-12
  • Accepted Date : 2026-03-18
  • DOI :https://doi.org/10.21729/ksds.2026.19.1.11
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