자연하천에서의 표면유속-평균유속 환산계수 산정

초록

For measuring flood discharge by surface flow velocity measurement method, one should know ratio α(conversion coefficient), the depth-averaged to surface velocity. In this paper, α was calculated using 177 surface flow velocity measurement data measured using microwave water surface current meter from 60 stations in 45 rivers of various scale and characteristics. The reference discharge was measured or calculated using ADCP, float and a rating curve. α has a average of 0.84(range: 0.64~1.02), and the 10th and 90th percentile values are 0.76 and 0.94. α increased with deeper water depth and faster velocity. α decreased as the ratio of vegetation area to the flow area increased, and a value of 0.75 was calculated when the ratio of vegetation area was 50% or more. The value of α according to bed roughness was 0.90 for a smooth bed, 0.85 for a normal and rough bed, and 0.80 for a very rough bed. α is a coefficient that reflects filed characteristics, and the trend was clear when comparing the hydraulic characteristics by site. © 2025 Korea Water Resources Association.

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