Continuous measurement of sediment transport in the Erlenbach stream using piezoelectric bedload impact sensors

We report on bedload transport observations using piezoelectric bedload impact sensors (PBIS), an indirect method of estimating the volume of bedload transport of coarse sediment. The PBIS device registers vibrations produced by bedload (particle diameter >similar to 20 mm) and records the signal as a sum of the number of impulses per time. Sediment transport at the Erlenbacb stream has been continuously monitored with a PBIS array starting in 1986. The sensor array spans the width of an entire cross-section and is mounted Hush with the surface of a check dam immediately upstream of a sediment retention basin. We compare PBIS data with long-term sedimentation records obtained from repeated surveys of material stored in the sediment retention basin, with artificial sediment input under controlled conditions in the field, and also with laboratory experiments. The rate of bedload transport is proportional to the number of impacts on the sensor per unit time. The reliability of the calibration relationship increases with the length of the observation period, e.g. for higher numbers of impacts and larger bedload volumes. Sediment volumes for individual flood events estimated with the PBIS method are in agreement with volumes estimated using an independent empirical method based on the effective runoff volume of water, the peak water discharge, and the critical discharge for the onset of sediment transport. Copyright (c) 2007 John Wiley & Sons, Ltd.