| Abstract: | Non-invasive techniques to continuously measure the rates or intensities of bedload transport in gravel bed rivers would be quite useful for both research and practice. Since 1986 measurements have been made with piezoelectric bedload impact sensors (PBIS) in several mountain torrents. In 1994 and 1995, a calibration campaign was carried out at a water intake in the Pitzbach mountain stream in Austria, where weighing cells and a water pressure sensor in the settling basin allow sediment transport loads to be determined in 15 minute intervals. Daily averages of PBIS impulses correlate reasonably well with the measured sediment load. Using a linear calibration relation, the relative error between predicted and measured sediment loads is within a factor of about 1.5 to 2. The scatter between PBIS impulses and bedload volumes is much larger if the measurements are averaged over one hour intervals or when the original 15 minute values are considered. A comparison with measurements from the Swiss Erlenbach torrent and from laboratory experiments using sediment particles from the Erlenbach torrent indicates that the proportionality coefficient between PBIS impulses and sediment load appears to depend on site specific conditions, including factors such as flow intensity and sediment properties. |
