A Low-Cost Autonomous Hydrophone System Integrated with Multidisciplinary Observations for Sediment Transport Monitoring in a Large-Scale Field Artificial Channel

Sediment transport is a fundamental process governing river hydraulics and channel morphology. During hyperconcentrated flows and flooding events, conventional optical and in situ sampling techniques are often unable to capture sediment transport behavior continuously. Previous studies have shown that contact-based hydroacoustic measurements can capture acoustic signals generated by particle impacts on the riverbed and enable continuous observations under high stream power conditions (Geay et al., 2017). However, contact-based hydroacoustic sensors are vulnerable to damage during flood events, resulting in high maintenance costs. To address this limitation, this study develops a low-cost, autonomous hydrophone system capable of continuous hydroacoustic recording. The system was tested in a large-scale field artificial channel constructed along the Landao Creek at Huisun Forest Station, Taiwan, where controlled discharges supplied from the upstream Nenggao Main Canal enabled experiments under dry-bed, steady-flow, and flood-peak conditions. To assess the performance of the autonomous hydrophone, a multi-physics sensing framework was established by synchronously deploying the hydrophone, a distributed acoustic sensing (DAS) system, and a microseismic sensor (SmartSolo). Under identical hydraulic and sediment supply conditions, hydroacoustic, ground vibration, and fiber-optic strain-rate signals were simultaneously recorded and analyzed to infer sediment transport behavior and riverbed activity. For data analysis, power spectral density (PSD) was employed as the primary frequency-domain method to analyze band-limited energy variations using a moving-window approach. In addition, waveform clipping events were detected and statistically analyzed to further identify high-energy transient events, which were used as an auxiliary indicator of bedload activity. The results indicate that the autonomous hydrophone reliably captures acoustic signatures associated with sediment transport and exhibits strong consistency with DAS strain-rate and microseismic observations, demonstrating its potential for integrated sediment transport monitoring in controlled artificial channel experiments.

 

Keywords: sediment transport; low-cost autonomous hydrophone; fiber-optic strain rate; microseismic signals