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

Abstract

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.

Sensitivity of Junction Width to Tidal Nonlinearity on Small and Shallow Tidal Junction

“…Using numerical experiments, Buschman et al, (2010) show convergence of tidal waves in junction affects the division of tidal discharge in the branches. Danial et al, (2019) show a similar result to Buschman et al, (2010) and suggest that the neap-spring tidal variation controls discharge asymmetry.…”

“…The tidal effect partly cancels the inequality of discharge division (Buschman et al, 2010;Danial et al, 2019) that influenced the sediment flux division (Wagner & Mohrig, 2019) and channel development (Iwantoro et al, 2020).…”

“…The tidal wave dynamics in estuaries have been studied in a range of topography settings, from single channel estuaries (Cai et al, 2018;Savenije et al, 2008) to branching estuarine systems (Buschman et al, 2010;Danial et al, 2019;Xiao et al, 2021). It was found that the tidal wave dynamics in estuaries are controlled by interaction tides and river runoff and affected by the topography setting.…”

“…The tidal range is up to 2-3.5 in the semi-diurnal tidal regime. The gate controls the discharge, with the normal discharge being around 20-100 m3/s (Danial et al, 2019;Xiao et al, 2020). The average bottom topography is approximately 3 m. Moreover, the Ota River is a branching delta.…”

Influence of Suspended Sediment Concentration and Particle Sizes on the Sound Attenuation of the Fluvial Acoustic Tomography Technique

“…Kawanisi et al (2015) measured energy flux in a strait by employing FATS, where the acoustic transmission line was around 1,204 m [10]. Bahreinimotlagh et al (2016) [11] and Al Sawaf et al (2017) [12] measured the streamflow of a shallow mountainous river using FATS, where the length of transmission line was about -300 m. Danial et al (2019) investigated the characteristics of tidal discharge in the three tidal channel junctions using three pairs of FATS, where their transmission lines were 224, 246 and 290 m [13].…”