The transport of coarse material by rivers as bedload is an important element of the terrestrial sediment cascade, but hard to constrain by in-stream devices. A promising alternative are seismic sensors, deployed at safe distance to the hostile conditions in stream, able to continuously record ground motion data due to particle impacts on the river bed. Here we use a network of 15 seismic stations to continuously sense the spectral characteristics of a high gradient Alpine gravel-bed river to invert the signals for water level and sediment transport in the Vallont de Nant catchment, Switzerland. We explore spatially and temporally distinct river activity, especially during the snow melt period, when extreme diurnal runoff is epxected.