bedload transport; geophone sensor; acoustic measuring technique; mountain stream; gravel-bed river; torrent
Wyss Carlos R., Rickenmann Dieter, Fritschi Bruno, Turowski Jens M., Weitbrecht Volker, Boes Robert M. (2016), Laboratory flume experiments with the Swiss plate geophone bed load monitoring system: 1. Impulse counts and particle size identification, in Water Resources Research
, 52, 7744-7759.
Wyss Carlos R., Rickenmann Dieter, Fritschi Bruno, Turowski Jens M., Weitbrecht Volker, Travaglini Eric, Bardou Eric, Boes Robert M. (2016), Laboratory flume experiments with the Swiss plate geophone bed load monitoring system: 2. Application to field sites with direct bed load samples, in Water Resources Research
, 52, 7760-7778.
Wyss Carlos R., Rickenmann Dieter, Fritschi Bruno, Turowski Jens M., Weitbrecht Volker, Boes Robert M. (2016), Measuring Bed Load Transport Rates by Grain-Size Fraction Using the Swiss Plate Geophone Signal at the Erlenbach, in Journal of Hydraulic Engineering
, 142(5), 04016003-11.
Turowski Jens M., Wyss Carlos R., Beer Alexander R. (2015), Grain size effects on energy delivery to the streambed and links to bedrock erosion, in Geophysical Research Letters
, 42, 1775-1780.
Wyss C.R. Rickenmann D. Fritschi B. Turowski J.M. Weitbrecht V. Boes R.M. (2014), Bedload grain size estimation from the indirect monitoring of bedload transport with Swiss plate geophones at the Erlenbach stream, in Schleiss A. et al. (ed.), Taylor & Francis Group, London, 1907-1912.
Rickenmann D., Turowski J.M., Fritschi B., Wyss C., Laronne J., Barzilai R., Reid I., Kreisler A., Aigner J., Seitz H., Habersack H. (2014), Bedload transport measurements with impact plate geophones: Comparison of sensor calibration in different gravel-bed streams, in Earth Surface Processes and Landforms
, 39, 928-942.
Turowski J.M., Böckli M., Rickenmann D., Beer A.R. (2013), Field measurements of the energy delivered to the channel bed by moving bed load and links to bedrock erosion, in Journal of Geophysical Research: Earth Surface
, 118, 2438-2450.
Turowski J. M., Badoux A., Bunte K., Rickli C., Federspiel N., Jochner M. (2013), The mass distribution of coarse particulate organic matter exported from an Alpine headwater stream, in Earth Surface Dynamics
, 1(1), 1-11.
Prediction of bedload transport is important for hazard assessment and in engineering applications such as the planning and implementation of flood protection measures. Furthermore, a wide range of scientific disciplines such as geomorphology, sedimentology or river engineering rely on such predictions for modeling work. Despite more than a hundred years of active research, knowledge of bedload transport processes is still limited, and none of the multitude of published models is able to describe observations in all conditions occurring in nature. This is especially true for coarse-bedded gravel rivers and torrents, i.e. high-gradient mountain streams. Bedload transport is typically very variable for given stream-flow conditions. Continuous and reliable measurements of bedload transport are difficult and challenging to obtain, but important to advance our understanding of sediment transport in mountain streams.The main purpose of this proposed research project is to advance the understanding of the indirect bedload transport measuring techniques with geophone sensors. We intend to improve and further develop an existing indirect acoustic method using geophones for measuring bedload transport in gravel bed streams and torrents. Detailed laboratory investigation and comparison with field observations will allow more accurate and detailed interpretation of the data it records and will give further insight into the underlying physical processes. In Task A we will investigate the geophone system in a series of laboratory flume experiments. A particular focus will lie on understanding the origins of signal fluctuations for similar boundary conditions, to characterize in detail the sensor response to changing flow conditions and sediment properties, and on exploring the possibility of extracting information on grain size in addition to the total load. The set-up will include a 50 cm wide flume matching the width of the steel plate under which the geophone sensor is fixed. Particles of varying sizes and shapes will be fed at different rates into the flume. Immediately downstream of the geophone sensor plate, the bedload transport will be monitored using either Particle-Image-Velocimetry (PIV) or Particle-Tracking-Velocimetry (PTV) techniques, to determine both bedload transport rate and particle sizes with high temporal resolution. This will allow a detailed analysis of the geophone signal along with the transport conditions. Results will be compared to field data obtained in the Erlenbach for validation (Task B).In Task B the findings from the flume experiments will be complemented with the analysis of high resolution field measurements with geophone sensors. This will be done in first place for existing and ongoing measurements at the Erlenbach stream in Switzerland. In this stream, a moving basket bedload sampling system has been installed three years ago, allowing accurate measurement of transport rate and grain size characteristics, along with high resolution recording of the geophone signal. For the Erlenbach, more than 20 samples are already available from the preceding project, and more data will be sampled during the planned project. Additional high resolution field measurements are available from the Nahal Eshtemoa stream in Israel, and new measurements will be taken there as well. Further calibration measurements are available from a number of complementary field sites in Switzerland and Austria, which will also be used to test the findings from the controlled flume experiments (Task A).The geophone sensors function at times and under conditions when direct observations of bedload transport are difficult or impossible, for example during high stage floods. We expect that the present research project will allow more accurate determination of bedload transport rates from the acoustic data. In addition we will attempt to extract further information about the transported material, such as the median grain size and the grain size distribution.