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2025 Vol.58, Issue 9 Preview Page

Research Article

Calculation of surface-mean velocity conversion coefficient in natural rivers

자연하천에서의 표면유속-평균유속 환산계수 산정

Sinjae Leea*
,
Kisung Leeb
,
Youngryong Ryuc
,
Jihea Leed
,
Seokgeun Parke
이 신재a*
,
이 기성b
,
류 영용c
,
이 지혜d
,
박 석근e
aPrincipal Researcher, Research and Development Department, Korea Institute of Hydrological Survey, Goyang, Korea
bPrincipal Researcher, Gum River Survey Department, Korea Institute of Hydrological Survey, Goyang, Korea
cPh.D, Candidate, Civil Engineering, Inha University, Incheon, Korea
dResearcher, Research and Development Department, Korea Institute of Hydrological Survey, Goyang, Korea
ePh.D, Candidate, Civil Engineering, Inha University, Incheon, Korea
a한국수자원조사기술원 연구개발실 책임연구원
b한국수자원조사기술원 금강조사실 책임연구원
c인하대학교 공과대학 토목공학과 박사과정
d한국수자원조사기술원 연구개발실 연구원
e인하대학교 공과대학 토목공학과 박사과정
*Corresponding Author
30 September 2025. pp. 757-769
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Abstract

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.

Keywords
Surface velocity
Conversion coefficient α
Hydraulic characteristics
Bed roughness
vegetation

표면유속을 측정하여 유량을 산정하는 경우 수심평균유속에 대한 표면유속의 비율인 환산계수 α를 알아야 한다. 본 연구에서는 다양한 규모 및 특성의 54개 하천의 60개 지점에서 전자파표면유속계를 이용하여 측정된 177개 표면유속 측정자료를 이용하여 α를 산정하였다. 기준유량은 ADCP, 부자 등을 이용하여 측정한 자료와 Rating curve를 이용하여 산정하였다. 그 결과 α는 평균 0.84(0.64~1.02)가 산정되었으며, α의 10번째 및 90번째 백분위수 값은 0.76과 0.94였다. α는 수심이 깊고 유속이 빠를수록 증가하였다. α는 흐름 영역 중 식생 영역의 비율이 증가할수록 감소하였으며, 식생 영역 비율이 50% 이상인 경우 0.75의 값이 산정되었다. 하상 거칠기에 따른 α는 부드러운 하상에서는 0.90, 보통 및 거친 하상에서는 0.85, 매우 거친 하상은 0.80의 값을 제시할 수 있었다. α는 현장특성이 반영되는 계수로서 지점별로 수리특성과 비교한 결과 경향이 뚜렷하였다.

키워드
표면유속
환산계수 α
수리특성
하상 거칠기
식생
References
1

Alexandre, H,, Thomas, M., and Léa, D. (2018). “Velocity profile and depth-averaged to surface velocity in natural streams: A review over a large sample of rivers.” E3S Web of Conferences 40, 06015. River Flow 2018, Lyon, France, Vol. 40, No. 6, 06015.

10.1051/e3sconf/20184006015
2

Biggs, H., Smart, G., Doyle, M., Eickelberg, N., Aberle, J., Randall, M., and Detert, M. (2023). “Surface velocity to depth-averaged velocity - a review of methods to estimate alpha and remaining challenges.” Water 2023, Vol. 15, No. 21, 3711.

10.3390/w15213711
3

Cheng, R.T., and Gartner, J.W. (2003). “Complete velocity distribution in river cross-sections measured by acoustic instruments.” Proceedings of the IEEE/DES 7th Working Conference in Current Measurement Technology, San Diego, CA, U.S., pp. 21-26.

10.1109/CCM.2003.1194276
4

Choi, C.W., Ye, S.J., Shin, J.H., and Jeong, T.S. (2024), “Field applicability review of surface-mean velocity conversion coefficient” 2024 Korea Water Resources Association's Conference. KWRA, p. 158.

5

Fujita, I. (2018). “Principles of surface velocity gaugings.” The 4th IAHR-WMO-IAHS Training Course on Stream Gauging. Lyon, France.

6

Fulton, J.W., Mason, C.A., Eggleston, J.R., Nicotra, M.J., Chiu, C.L., Henneberg, M.F., and Laveau, C.D. (2020). “Near-field remote sensing of surface velocity and river discharge using radars and the probability concept at 10 U.S. Geological Survey streamgages.” Remote Sensing, Vol. 12, No. 8, 1296.

10.3390/rs12081296
7

Harpold, A.A., Mostaghimi, S., Vlachos, P.P., Brannan, K., and Dillaha, T. (2006). “Stream discharge measurement using a large-scale particle image velocimetry (LSPIV) prototype.” Transactions of the ASABE Vol. 49, No. 6, pp. 1791-1805.

10.13031/2013.22300
8

Hauet, A., Morlot, T., and Daubagnan, L. (2018). “Velocity profile and depth-averaged to surface velocity in natural streams: A review over a large sample of rivers.” In Proceedings of the River Flow 2018, Lyon, France, 06015.

10.1051/e3sconf/20184006015
9

International Organization for Standardization (ISO) (2021). Hydrometry-Measurement of liquid flow in open channels-Velocity area methods using point velocity measurements. International Standard ISO 748.

10

Johnson, E.D., and Cowen, E.A. (2017). “Remote determination of the velocity index and mean streamwise velocity profiles.” Water Resouerces Research, Vol. 53, pp. 7521-7525.

11

Khan, M.R., Gourley, J.J., Duarte, J.A., Vergara, H., Wasielewski, D., Ayral, P.A., Fulton, J.W. (2021). “Uncertainty in remote sensing of streams using noncontact radars.” Journal of Hydrology, Vol. 603, Part A, 126809.

10.1016/j.jhydrol.2021.126809
12

Kim, D.S., Yang, S.G., and Jung, W.Y. (2014). “Error analysis for electromagnetic surface velocity and discharge measurement in rapid mountain stream flow.” Journal of Environmental Science International, Vol. 23, No. 4, pp. 543-552.

10.5322/JESI.2014.4.543
13

Kim, Y.S., Lee. H.S., Yang, J.R., and Lee, Y.S. (2010). “Assessment of depth-averaged velocity conversion factors in a natural river with measured velocities.” 2010 Korea Water Resources Association's Conference, KWRA, p. 1897.

14

Korea Institute of Hydrological Survey (KIHS) (2022). Guideline microwave water surface current meter Measurement (Ver.1.1).

15

Le Coz, J., Duby, P., Dramais, G., Camenen, B., Laronne, J., Zamler, D., and Zolezzi, G. (2011). “Use of emerging non-intrusive techniques for flood discharge measurements.” In Proceedings of the 5th International Conference on Flood Management, Tokyo, Japan.

16

Lee, S.J., Lee, S.Y., and Park, J.S. (2018). “A review on the mean velocity conversion coefficient of surface” 2018 Korea Water Resources Association's Conference, KWRA, p. 272.

17

Ministry of Environment (ME) (2018~2024). Hydrological annual report in Korea.

18

Moramarco, T., Barbetta S., and Tarpanelli. A. (2017). “From surface flow velocity measurements to discharge assessment by the entropy theory.” Water, Vol. 9, No. 2, 120.

10.3390/w9020120
19

Muste, M., Fujita, I., and Hauet, A. (2008). “Large-scale particle image velocimetry for measurements in riverine environments.” Water Resources Research, Vol. 44, W00D19.

10.1029/2008WR006950
20

Rantz, S.E. (1982). Measurement and computation of streamflow: Volume 1. Measurement of stage and discharge. Geological Survey Water-Supply Paper, U.S. Geological Survey, Denver, CO, U.S., p. 137.

21

Song, J.H. (2022). On applicability of discharge estimation method using surface velocity. Ph. D. dissertation, University of Inha, pp. 7-75.

22

Welber, M., Le Coz, J., Laronne, J.,B., Zolezzi, G., Zamler, D., Dramais, G., Hauet, A., and Salvaro, M. (2016). “Field assessment of noncontact stream gauging using portable surface velocity radars (SVR).” Water Resources Research, Vol. 52, pp. 1108-1126.

10.1002/2015WR017906
Information
  • Publisher :KOREA WATER RESOURECES ASSOCIATION
  • Publisher(Ko) :한국수자원학회
  • Journal Title :Journal of Korea Water Resources Association
  • Journal Title(Ko) :한국수자원학회 논문집
  • Volume : 58
  • No :9
  • Pages :757-769
  • Received Date : 2025-06-20
  • Revised Date : 2025-07-23
  • Accepted Date : 2025-07-28
  • DOI :https://doi.org/10.3741/JKWRA.2025.58.9.757
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