Author(s): Sinjae Lee; Kisung Lee; Youngryong Ryu; Jihea Lee
Linked Author(s): Jihea Lee, SINJAE LEE
Keywords: Surface velocity depth averaged velocity velocity coefficient α
Abstract: For measuring flood discharge by surface flow velocity measurement method, one should know the depth-averaged to surface velocity ratio α (velocity coefficient). In this paper, α was calculated using 220 surface flow velocity measurement data measured using microwave water surface current meter from 54 stations in 45 rivers of various scale and characteristics in Korea. The depth-average velocity was calculated using data measured simultaneously or at the same water level using ADCP, float and a rating curve. α has a mean of 0.85 (range: 0.59~1.10), the 10th and 90th percentile values are 0.74 and 0.98. α showed a relationship that increased as the depth was deeper and the velocity was faster. In addition, α was classified according to the bed roughness, with a value of 0.90 for smooth bed (sandy) and 0.84 for rough bed (gravel or boulders).
Year: 2025