Surface velocity coefficients for application of the float method in rectangular and compound open channels

Marjang, Nat; Merkley, Gary P.

doi:10.1007/s00271-009-0162-3

Cited by 8 publications

(2 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Field observations extend numerical modelling results from [15] (black squares Fig. 3), demonstrating a decrease in as Relative Submergence (RS) decreases.…”

Section: Discussionsupporting

confidence: 67%

Determining Surface Velocity Coefficients in Headwater Streams for Natural Flood Management

Little,

Pan,

Follett

2024

Proceedings of the Cardiff University Engineering Research Conference 2023

View full text Add to dashboard Cite

With concerns about climate change, nature-based solutions for flood risk management have been increasing in popularity across Europe, and targeting headwater streams can be an effective approach by increasing forest floodplains through inundation of surrounding areas. However, accurately measuring stream discharge remains a challenge. One promising method is to measure the surface velocity and apply a surface velocity coefficient. This study investigates the determination of surface velocity coefficient in headwater streams using the float and current meter methods. The relationship between surface velocity coefficient and relative submergence (ratio of water depth to roughness height) is analysed. The results support prior modelling results that the surface velocity coefficient decreases with relative submergence and extend the range of prior work for very small relative submergence, using experimental and field observations. The surface velocity coefficient was observed to decrease from 0.85 to 0.53 as relative submergence decreased from 270000 in a smooth glass laboratory channel to 0.093 in a field setting. Field discharge measurements upstream of a channel-spanning engineered logjam were used to show used to predict local inundation and the uncertainty is reported.

show abstract

“…Field observations extend numerical modelling results from [15] (black squares Fig. 3), demonstrating a decrease in as Relative Submergence (RS) decreases.…”

Section: Discussionsupporting

confidence: 67%

Determining Surface Velocity Coefficients in Headwater Streams for Natural Flood Management

Little,

Pan,

Follett

2024

Proceedings of the Cardiff University Engineering Research Conference 2023

View full text Add to dashboard Cite

show abstract

“…However, further velocity measurements would be necessary to firmly verify that the value of α keeps constant for high discharges (Q > 700 m 3 s −1 ), or highly unsteady events. In the case of overbank flow events, the mean value of α may change significantly and α values may vary throughout the cross-section [18]. This effect is especially marked in the case of non-prismatic compound channel geometry [21].…”

Section: Hydraulic Assumptions For Discharge Computationmentioning

confidence: 99%

Performance of image-based velocimetry (LSPIV) applied to flash-flood discharge measurements in Mediterranean rivers

Coz¹,

Hauet

Pierrefeu³

et al. 2010

Journal of Hydrology

207

133

View full text Add to dashboard Cite

Flash-floods that occur in Mediterranean regions result in significant casualties and economic impacts. Remote imagebased techniques such as Large-Scale Particle Image Velocimetry (LSPIV) offer an opportunity to improve the accuracy of flow rate measurements during such events, by measuring the surface flow velocities. During recent floods of the Ardèche river, LSPIV performance tests were conducted at the Sauze-Saint-Martin gauging station without adding tracers. The rating curve is well documented, with gauged discharge ranging from 4.8 m 3 s −1 to 2700 m 3 s −1 , i.e., mean velocity from 0.02 m s −1 to 2.9 m s −1. Mobile LSPIV measurements were carried out using a telescopic mast with a remotely controlled platform equipped with a video camera. Also, LSPIV measurements were performed using the images recorded by a fixed camera. A specific attention was paid to the hydraulic assumptions made for computing the river discharge from the LSPIV surface velocity measurements. Simple solutions for interpolating and extrapolating missing or poor-quality velocity measurements, especially in the image far-field, were applied. Theoretical considerations on the depth-average velocity to surface velocity ratio (or velocity coefficient) variability supported the analysis of velocity profiles established from available gauging datasets, from which a velocity coefficient value of 0.90 (standard deviation 0.05) was derived. For a discharge of 300 m 3 s −1 , LSPIV velocities throughout the river crosssection were found to be in good agreement (±10%) with concurrent measurements by Doppler profiler (ADCP). For discharges ranging from 300 to 2500 m 3 s −1 , LSPIV discharges usually were in acceptable agreement (< 20%) with the rating curve. Detrimental image conditions or flow unsteadiness during the image sampling period led to larger deviations ranging 30-80%. The compared performances of the fixed and mobile LSPIV systems evidenced that for LSPIV stations, sampling images in isolated series (or bursts) is a better strategy than in pairs evenly distributed in time.

show abstract

Estimation of Velocity Index for Flow Calculation in Open Channels Using Geometric and Hydraulic Characteristics

Patel

Kar

Sarkar

2023

Lecture Notes in Civil Engineering

View full text Add to dashboard Cite

Surface velocity coefficients for application of the float method in rectangular and compound open channels

Cited by 8 publications

References 1 publication

Determining Surface Velocity Coefficients in Headwater Streams for Natural Flood Management

Determining Surface Velocity Coefficients in Headwater Streams for Natural Flood Management

Performance of image-based velocimetry (LSPIV) applied to flash-flood discharge measurements in Mediterranean rivers

Estimation of Velocity Index for Flow Calculation in Open Channels Using Geometric and Hydraulic Characteristics

Contact Info

Product

Resources

About