Seismic detectors for continuous bed load monitoring in a gravel stream

Abstract

Abstract A field experiment is described for continuous recording of bed load transport rates in a coarse-grained alluvial channel, using instruments typically available to seismologists. The experiment was carried out in 1990 in the Italian Alps, in a small basin equipped since 1982 with instruments conventionally used in hydrological surveys and bed load transport measurements. In July 1990, six seismometers were placed along the alluvial channel for up to about 150 m upstream of the flow gauging station. Continuous microseismic recordings of seven flood flows were analysed, five being associated with coarse sediment delivery. The mechanism of bed load transport was inferred from two or three microseismic impulse peaks occurring before and after the discharge peak shown in the hydrograph. Those microseismic peaks are thought to reflect the pulsed nature of bed load transport while the periods elapsing between them are interpreted as indicating the duration of the transport process and appeared independent of peak discharges.