Seismic analysis of bedload transport in a small mountain creek

Assessing and quantifying bedload dynamics and sediment transport rates in rivers is critical for evaluating the landscape evolution, which in turn controls channel morphology and catchment erosion. In the last decades, seismic observations emerged as one of the most promising tools for monitoring river dynamics. In particular, recorded seismic energy has been shown to correlate with river discharge and with the amount of transported sediments. However, uncertainties persist in quantifying bedload transport using recorded seismic signals. This lack is particularly relevant for small mountain streams, where sediment mobilisation begins, that have been to date poorly studied.

In this study we present the first outcomes of two years of continuous seismic monitoring of the Re della Pietra, a small stream in Tuscan Appennines. Specifically, we analyse data collected by two triaxial seismometers placed in two different channel sections, deployed on the riverbank, ~3 meters from the stream. Root-mean-square amplitude analysis (RMSA) is used for computing the envelopes on recorded data as well as analysis on frequency domain is performed for investigating the spectral content of the signal. Over the two years of observations many flood events were recorded, ranging from small and short (few hours) events to massive and long (days) ones related to exceptional storms. Recorded seismic data shows peculiar waveform and spectral footprints. To investigate how flow dynamics affect seismic radiation, collected seismic data are compared with flow depth data and video images acquired by during the events. Preliminary results highlight important constraints on the mobilizations of the solid particles within small creeks thus suggesting how seismic sensors can be successfully used for monitoring the bedload transport.

This study is being carried out within the interdisciplinary project TRANSFORM (“A new interdisciplinary approach to advance understanding of sediment and large wood TRANSport in FORested Mountain catchments”- https://florenceuniversity.wixsite.com/transform).