Continuous monitoring of a dam flush in a shallow river using two crossing ultrasonic transmission lines

Sawaf

2019

Water

Self Cite

This study investigates the tidal discharge division and phase difference at branches connected to a channel junction. The tidal discharge at three branches (eastern, western, and northern branches) was continuously collected using the fluvial acoustic tomography system (FATS). The discharge asymmetry index was used to quantify the flow division between two seaward branches (eastern and western branches). The cross-wavelet method was applied to calculate the phase difference between the tidal discharge and water level. The discharge asymmetry index shows that the inequality of flow division is obviously prominent during the spring tide duration, where the eastern branch has the capability to deliver greater amounts of subtidal discharge, approximately 55–63%, compared with the western branch. However, the equality of flow division between the eastern and western channels can be observed clearly during the neap tide period. The wavelet analysis shows that the phase difference at the western branch is higher than at the eastern branch, because the geometry of the western branch is more convergent than that of the eastern branch. Accordingly, the amplitude of the tidal wave at the western branch is more magnified compared with that at the eastern branch. Moreover, the phase difference at the northern branch is greater than at the two seaward branches, implying that the phase difference is slightly increased after passing through the junction into the northern branch.

Section: The Overview Of the Fluvial Acoustic Tomography Systemmentioning

confidence: 99%

Section: The Overview Of the Fluvial Acoustic Tomography Systemmentioning

confidence: 99%

Characteristics of Tidal Discharge and Phase Difference at a Tidal Channel Junction Investigated Using the Fluvial Acoustic Tomography System

Danial

Sawaf

2019

Water

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“…In the previous study, the flow angle was measured by moving‐boat ADCP measurements (Kawanisi , et al , , Razaz , et al , ). A cross‐path configuration was also used for 19 h (Kawanisi , et al , ). In addition to flow direction uncertainties, mapping the bathymetry of the river along the transmission path with high accuracy was not possible owing to restriction of power‐driven boat operation in the survey site.…”

Section: River Discharge Observationsmentioning

confidence: 99%

“…Therefore, establishing a method and/or technology for quantifying discharge is of paramount importance. The purpose of this study is to demonstrate the feasibility of monitoring streamflow by the use of fluvial acoustic tomography system (FATS) (Kawanisi , et al , , Kawanisi , et al , , Kawanisi , et al , ).…”

Section: Introductionmentioning

confidence: 99%

High‐frequency streamflow acquisition and bed level/flow angle estimates in a mountainous river using shallow‐water acoustic tomography

Bahrainimotlagh

Sawaf

et al. 2016

Hydrological Processes

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Abstract:The acquisition of reliable discharge estimates is crucial in hydrological studies. This study demonstrates a promising acoustic method for measuring streamflow at high sampling rate for a long period using the fluvial acoustic tomography system (FATS). The FATS recently emerged as an innovative technique for continuous measurements of streamflow. In contrast to the traditional point/transect measurements of discharge, the FATS enables the depth-averaged and range-averaged flow velocity along the ray path to be measured in a fraction of a second. The field test was conducted in a shallow gravel-bed river (0.9 m deep under lowflow conditions, 115 m wide) for 1 month. The parameters (stream direction and bottom elevation) required for calculating the streamflow were deduced by a nonlinear regression to the discharge data from the well-established rating curve. The crosssectional average velocities were automatically calculated from the acoustic data, which were collected on both riverbanks every 30 s. The FATS was connected to the internet so that the real-time flow data could be obtained. The FATS captured discharge variations at a cut-off frequency of approximately 70 day À1 . The stream exhibited temporal discharge changes at multiple time scales ranging from a few tens of minutes to days.

“…Different aspects and performance of FAT have been assessed through its application under various scenarios: measurements of Kawanisi et al . [] in a gravel‐bed river by a single ray path indicated that although the signal sound‐to‐noise ratio (SNR) decreases with increasing SSC, the uncertainty in discharge data obtained from the FAT exhibits expected uncertainties when compared to the corresponding rating curve or to moving‐boat ADCP data. By incorporating two crossing ray paths, Razaz et al .…”

Section: Introductionmentioning

confidence: 99%

Application of acoustic tomography to reconstruct the horizontal flow velocity field in a shallow river

Razaz

Water Resources Research

Kaneko

et al. 2015

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A novel acoustic tomographic measurement system capable of resolving sound travel time in extremely shallow rivers is introduced and the results of an extensive field measurements campaign are presented and further discussed. Acoustic pulses were transmitted over a wide frequency band of 20-35 kHz between eight transducers for about a week in a meandering reach of theB asen River, Hiroshima, Japan. The purpose of the field experiment was validating the concept of acoustic tomography in rivers for visualizing current fields. The particular novelty of the experiment resides in its unusual tomographic features: subbasin scale (100 m 3 270 m) and shallowness (0.5-3.0 m) of the physical domain, frequency of the transmitted acoustic signals (central frequency of 30 kHz), and the use of small sampling intervals (105 s). Inverse techniques with no a priori statistical information were used to estimate the depth-average current velocity components from differential travel times. Zeroth-order Tikhonov regularization, in conjunction with L-curve method deployed to stabilize the solution and to determine the weighting factor appearing in the inverse analysis. Concurrent direct environmental measurements were provided in the form of ADCP readings close to the right and left bank. Very good agreement found between along-channel velocities larger than 0.2 m/s obtained from the two techniques. Inverted quantities were, however, underestimated, perhaps due to vicinity of the ADCPs to the banks and strong effect of river geometry on the readings. In general, comparing the visualized currents with direct nodal measurements illustrate the plausibility of the tomographically reconstructed flow structures.