A River on Fiber: Spatially Continuous Fluvial Monitoring with Distributed Acoustic Sensing | CU Experts

Fluvially generated seismo-acoustic waves offer a novel means of investigating river processes, yet interpreting signals from individual seismometers or hydrophones remains challenging. This study demonstrates the potential of distributed acoustic sensing (DAS) for fluvial monitoring. We present strain-rate measurements and power spectra recorded at sub-meter resolution along 160 m of submerged fiber-optic cable in Clear Creek, CO, USA. We find that regions of enhanced turbulence, such as rapids, are associated with broadband signals, whereas reaches with less turbulent flow display spectral power within distinct frequency bands. In three such regions, we observe harmonic frequency banding with pronounced spatio-spectral gliding (i.e., peak frequencies vary systematically along-river). One of these regions is colocated with the source of a recurring impulsive signal characterized by audible "knocking" sounds in the acoustic strain-rate data. We use travel time analysis to determine that this signal is generated by cable-bed impacts due to turbulence-driven cable oscillation. Model results further indicate that along-cable variation in the lags between pulses and their reflections produces the banded spatio-spectral gliding. Our observations highlight the capacity for array methods to interrogate distinct signal sources in DAS data and emphasize the need for improved deployment techniques in dynamic fluvial environments.

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