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With 7 figures Abstract: Turbulent flow in rivers and the associated movement of sediment creates unique underwater sound- scapes that can be measured passively with hydrophones while Acoustic Doppler Profilers (ADP) are an active form of hydroacoustic sampling that can be used to provide a surrogate measurement of Apparent Bedload Veloc- ity (ABV). In our study, longitudinal profiles of ADP and sound were simultaneously measured, while floating the river in a raft on the Nyack Floodplain of the Middle Fork of the Flathead River, USA during flood events exceeding bankfull conditions. In addition, similar measurements were carried out on the Kootenai River during a prescribed flood release aimed at mobilizing gravel bed sediment to positively impact White Sturgeon spawn- ing. Both data sets revealed spatially explicit zones of coherent ABV and bedload intensity (sound) over the two 12 km river segments. The ability to remotely and in real-time assess bedload transport for large gravel-bed rivers, on the floodplain scale, is a missing piece of information important for basic ecological understanding and applied science, specifically management decisions regarding regulated rivers worldwide. With these data sets we dem- onstrate a new methodology for rapid real-time spatial surveying of bedload transport in large gravel-bed rivers. |
