Introduction The Swiss plate geophone (SPG) system is a bedload surrogate monitoring technique that has been calibrated in several mountain streams to quantify bedload transport (Rickenmann, 2017). The amplitude of the signal recorded by the SPG contains information about the grainsize distribution of the transported bedload. However, determination of bedload transport with the impact plate system ideally requires calibration with direct bedload sampling in the field. At the Albula stream in Switzerland, bedload samples were collected with a large net attached to a steel-frame and operated from a crane. These measurements were compared with the signal of the impact plate geophone system to convert the signal information into bedload transport rates. In addition, a set of controlled real scale experiments was performed at the outdoor flume facility of the Oskar von Miller institute in Germany. The reconstruction of the field conditions met at the Albula stream enabled to investigate various individual aspects influencing the measurement accuracy of the Swiss plate geophone system. This study is the first step of a project that aims to investigate more in depth various individual aspects influencing the measurement accuracy of the Swiss plate geophone at different field sites, starting with the Albula stream. The objectives of this contribution are: (i) to briefly introduce the Swiss plate geophone system and the amplitude histogram method used to estimate the bedload flux for different grain size classes; (ii) to present the field calibration measurements conducted at the Albula field site; (iii) to describe the controlled flume experiments; and finally (iv) to discuss some results from both sets of calibration measurements and potential errors emerging during their interpretation     «

Introduction The Swiss plate geophone (SPG) system is a bedload surrogate monitoring technique that has been calibrated in several mountain streams to quantify bedload transport (Rickenmann, 2017). The amplitude of the signal recorded by the SPG contains information about the grainsize distribution of the transported bedload. However, determination of bedload transport with the impact plate system ideally requires calibration with direct bedload sampling in the field. At the Albula stream...     »