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Bedload

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Jens M Turowski – 1st expert on this subject based on the ideXlab platform

  • Bedload transport measurements with impact plate geophones comparison of sensor calibration in different gravel bed streams
    Earth Surface Processes and Landforms, 2014
    Co-Authors: Dieter Rickenmann, Andrea Kreisler, Johann Aigner, Jonathan B Laronne, Jens M Turowski, Bruno Fritschi, Carlos R Wyss, Ronel Barzilai, Ian Reid, Hugo Seitz

    Abstract:

    Indirect Bedload transport measurements have been made with the Swiss plate geophone system in five gravel-bed mountain streams. These geophone sensors record the motion of Bedload particles transported over a steel plate mounted flush with the channel bed. To calibrate the geophone system, direct Bedload transport measurements were undertaken simultaneously. At the Erlenbach in Switzerland, a moving-basket sampler was used. At the Fischbach and Ruetz streams in Austria, a Helley–Smith type Bedload sampler provided the calibration measurements. A Bunte-type Bedload trap was used at the Rofenache stream in Austria. At the Nahal Eshtemoa in Israel, Reid-type slot Bedload samplers were used. To characterize the response of the geophone signal to Bedload particles impacting on the plate, geophone summary values were calculated from the raw signal and stored at one second intervals. The number of impulses, i.e. the number of peaks above a pre-defined threshold value of the geophone output signal, correlated well with field measured gravel transport loads and was found to be a robust parameter. The relations of impulses to gravel transport loads were generally near-linear, but the steepness of the calibration relations differed from site to site. By comparing the calibration measurements from the different field sites and utilizing insights gained during preliminary flume experiments, it has been possible to identify the main factors that are responsible for site specific differences in the calibration coefficient. The analysis of these calibration measurements indicates that the geophone signal also contains some information about the grain size distribution of Bedload. Copyright © 2013 John Wiley & Sons, Ltd.

  • damage costs due to Bedload transport processes in switzerland
    Natural Hazards and Earth System Sciences, 2013
    Co-Authors: Alexandre Badoux, Norina Andres, Jens M Turowski

    Abstract:

    Abstract. In Alpine regions, floods are often associated with erosion, transport and deposition of coarse sediment along the streams. These processes are related to Bedload transport and pose a hazard in addition to the elevated water discharge. However, it is unclear to what extent they contribute to total damage caused by natural hazards. Using the Swiss flood and landslide damage database – which collects financial damage data of naturally triggered floods, debris flows and landslides – we estimated the contribution of fluvial Bedload transport processes to total damage costs in Switzerland. For each database entry an upper and lower limit of financial losses caused by or related to Bedload transport processes was estimated, and the quality of the estimate was judged. When compared to total damage, the fraction of Bedload transport damage in the 40 yr study period lies between 0.32 and 0.37. However, this value is highly variable for individual years (from 0.02 to 0.72). Bedload transport processes have induced cumulative financial losses between CHF 4.3 and 5.1 billion. Spatial analysis revealed a considerable heterogeneous distribution with largest damage for mountainous regions. The analysis of the seasonal distribution shows that more than 75% of the Bedload damage costs occurs in summer (June–August), and ~ 23% in autumn (September– November). With roughly 56%, by far most of the damage has been registered in August. Bedload transport processes are presently still inadequately understood, and the predictive quality of common Bedload equations is often poor. Our analysis demonstrates the importance of Bedload transport as a natural hazard and financial source of risk, and thus the need for future structured research on transport processes in steep streams.

  • Damage costs due to Bedload transport processes in Switzerland
    Natural Hazards and Earth System Sciences Discussions, 2013
    Co-Authors: Alexandre Badoux, Norina Andres, Jens M Turowski

    Abstract:

    Abstract. In Alpine regions, floods are often associated with Bedload erosion, transport and deposition along the streams. These processes pose hazard in addition to the elevated water discharge. However, it is unclear to what extent they contribute to total damage caused by natural hazards. Using the Swiss flood and landslide data base, which collects financial damage data of naturally triggered floods, debris flows and landslides, we estimated the contribution of fluvial Bedload transport processes to total damage costs in Switzerland. For each data base entry an upper and lower limit of financial losses caused by or related to Bedload transport processes was estimated, and the quality of the estimate was judged. When compared to total damage, the fraction of Bedload transport damage in the 40 yr study period lies between 0.32 and 0.37. However, this value is highly variable for individual years (from 0.02 to 0.72). Bedload transport processes have induced cumulative financial losses between 4.3 and 5.1 billion Swiss Francs. Spatial analysis revealed a considerable heterogeneous distribution with largest damage for mountainous regions. The analysis of the seasonal distribution shows that more than 75% of the Bedload damage costs occurs in summer (June–August), and ∼23% in autumn (September–November). With roughly 56%, by far most of the damage has been registered in August. Bedload transport processes are presently still inadequately understood, and the predictive quality of common Bedload equations is often poor. Our analysis demonstrates the importance of fluvial Bedload transport as a natural hazard and financial source of risk, and thus the need for future structured research on transport processes in steep streams.

Helmut Habersack – 2nd expert on this subject based on the ideXlab platform

  • Bedload TRAP MEASUREMENTS AS PART OF AN INTEGRATIVE MEASUREMENT SYSTEM
    , 2020
    Co-Authors: Andrea Kreisler, Markus Moser, Hugo Seitz, Florian Rudolf-miklau, Helmut Habersack

    Abstract:

    Data of Bedload transport form the fundamentals of planning in the fields of river engineering, flood protection, torrent control and waterway management. Furthermore, Bedload information is needed for issues concerning ecology and hydropower. In addition, Bedload transport measurements are essential to select, apply and calibrate Bedload transport formulas and numerical models. Bedload traps enable continuous and automatic Bedload transport measurements. Thereby, the method is applicable for all water stages, especially during floods, when other sampling methods are not operable anymore. Besides, it facilitates the determination of the complete grain size spectrum. At the mountain torrent Urslau a fixed Bedload trap forms an indispensable part of the 2010 installed integrative Bedload measurement system, including a geophone device and mobile basket samplers. This paper is focused on the applied Bedload trap and aims to discuss the possibilities of this measurement method in combination with direct and surrogate measurement methods.

  • insights into Bedload transport processes of a large regulated gravel bed river
    Earth Surface Processes and Landforms, 2018
    Co-Authors: Marcel Liedermann, Andrea Kreisler, Michael Tritthart, Philipp Gmeiner, Helmut Habersack

    Abstract:

    A comprehensive monitoring program focusing on Bedload transport behaviour was conducted at a large gravel-bed river. Innovative monitoring strategies were developed during five years of preconstruction observations accompanying a restoration project. A Bedload basket sampler was used to perform 55 cross-sectional measurements, which cover the entire water discharge spectrum from a 200-year flood event in 2013 to a rare low flow event. The monitoring activities provide essential knowledge regarding Bedload transport processes in large rivers. We have identified the initiation of motion under low flow conditions and a decrease in the rate of Bedload discharge with increasing water discharge around bankfull conditions. Bedload flux strongly increases again during high flood events when the entire inundation area is flooded. No Bedload hysteresis was observed. The effective discharge for Bedload transport was determined to be near mean flow conditions, which is therefore at a lower flow discharge than expected. A numerical sediment transport model was able to reproduce the measured sediment transport patterns. The unique dataset enables the characterisation of Bedload transport patterns in a large and regulated gravel-bed river, evaluation of modern river engineering measures on the Danube, and, as a pilot project has recently been under construction, is able to address ongoing river bed incision, unsatisfying ecological conditions for the adjacent national park and insufficient water depths for inland navigation.

  • analysis and classification of Bedload transport events with variable process characteristics
    Geomorphology, 2017
    Co-Authors: Andrea Kreisler, Markus Moser, Johann Aigner, Rolf Rindler, Michael Tritthart, Helmut Habersack

    Abstract:

    Abstract Knowledge about the magnitude of Bedload fluxes at given hydraulic conditions in natural streams is essential for improved process understanding, for the application, calibration and validation of Bedload transport formulas, and for numerical sediment transport models. Nonetheless, extensive field measurements of Bedload transport are challenging and therefore data from such efforts are rare. Bedload transport has been measured comprehensively at the downstream section of the Urslau torrent in Salzburg, Austria, since 2011. We used an integrative monitoring system that combines direct (mobile basket sampler, slot sampler) and indirect measuring devices (geophone plates). Continuous information about the intensity and distribution of Bedload transport within the channel cross-section is available in high spatial and temporal resolution. Seven geophone plates at a stream width of 8 m are part of a measurement system that delivers data in 1-min intervals. These geophone data are calibrated using results of direct Bedload measurements, providing an opportunity to calculate Bedload rates and Bedload yields in selected time periods. Continuous data on the Bedload transport process over three years enabled assessing several Bedload transport events. The investigation of Bedload transport rate/discharge relationships reveals order-of-magnitude changes. For individual events, we observed shifts in the data, reflecting different Bedload rates at comparable hydraulic conditions. This study reveals that variable sediment supply conditions affect the prevailing Bedload transport rates at the Urslau stream. Calculating the Bedload transport efficiency enables comparing Bedload transport events that exhibit similar process characteristics. Finally, we provide a conceptual model of Bedload transport process types as a function of Bedload transport efficiency and dimensionless stream power.

Dieter Rickenmann – 3rd expert on this subject based on the ideXlab platform

  • Bedload transport measurements with impact plate geophones comparison of sensor calibration in different gravel bed streams
    Earth Surface Processes and Landforms, 2014
    Co-Authors: Dieter Rickenmann, Andrea Kreisler, Johann Aigner, Jonathan B Laronne, Jens M Turowski, Bruno Fritschi, Carlos R Wyss, Ronel Barzilai, Ian Reid, Hugo Seitz

    Abstract:

    Indirect Bedload transport measurements have been made with the Swiss plate geophone system in five gravel-bed mountain streams. These geophone sensors record the motion of Bedload particles transported over a steel plate mounted flush with the channel bed. To calibrate the geophone system, direct Bedload transport measurements were undertaken simultaneously. At the Erlenbach in Switzerland, a moving-basket sampler was used. At the Fischbach and Ruetz streams in Austria, a Helley–Smith type Bedload sampler provided the calibration measurements. A Bunte-type Bedload trap was used at the Rofenache stream in Austria. At the Nahal Eshtemoa in Israel, Reid-type slot Bedload samplers were used. To characterize the response of the geophone signal to Bedload particles impacting on the plate, geophone summary values were calculated from the raw signal and stored at one second intervals. The number of impulses, i.e. the number of peaks above a pre-defined threshold value of the geophone output signal, correlated well with field measured gravel transport loads and was found to be a robust parameter. The relations of impulses to gravel transport loads were generally near-linear, but the steepness of the calibration relations differed from site to site. By comparing the calibration measurements from the different field sites and utilizing insights gained during preliminary flume experiments, it has been possible to identify the main factors that are responsible for site specific differences in the calibration coefficient. The analysis of these calibration measurements indicates that the geophone signal also contains some information about the grain size distribution of Bedload. Copyright © 2013 John Wiley & Sons, Ltd.

  • Bedload transport measurements at the erlenbach stream with geophones and automated basket samplers
    Earth Surface Processes and Landforms, 2012
    Co-Authors: Dieter Rickenmann, Jens M Turowski, Bruno Fritschi, Angela Klaiber, Andreas Ludwig

    Abstract:

    In the Erlenbach stream, a pre-alpine steep channel in Switzerland, sediment transport has been monitored for more than 25 years. Near the confluence with the main valley river, stream flow is monitored and sediment is collected in a retention basin with a capacity of about 2000 m3. The basin is surveyed at regular intervals and after large flood events. In addition, sediment transport has been continuously monitored with piezoelectric Bedload impact and geophone sensors since 1986. In 2008–2009, the measuring system in the Erlenbach stream was enhanced by installing an automatic system to obtain Bedload samples. Movable metal baskets are mounted on a rail at the downstream wall of the large check dam above the retention basin, and they can be moved automatically into the flow to take Bedload transport samples. The wire mesh of the baskets has a spacing of 10 mm to sample all sediment particles coarser than this size (which is about the limiting grain size detected by the geophones). The upgraded measuring system permits to obtain Bedload samples over short sampling periods and to measure the grain size distribution of the transported material and its variation over time and with discharge. The analysis of calibration relationships for the geophone measuring system confirms findings from very similar measurements which were performed until 1999 with piezoelectric Bedload impact sensors; there is a linear relationship between impulse counts and Bedload mass passing over the sensors. Findings from flume experiments are used to discuss the most important factors which affect the calibration of the geophone signal. The Bedload transport rates as measured by the moving baskets are among the highest measured in natural streams, with values of the order of several kilograms per meter per second. Copyright © 2012 John Wiley & Sons, Ltd.

  • Start and end of Bedload transport in gravel‐bed streams
    Geophysical Research Letters, 2011
    Co-Authors: Jens M Turowski, Alexandre Badoux, Dieter Rickenmann

    Abstract:

    [1] The threshold of incipient Bedload motion, expressed either as a critical force or as a critical water discharge, is a key parameter in Bedload transport prediction. Measuring the threshold of motion is difficult, and reliable data from natural streams are rare. By recording the vibrations triggered by Bedload particles when moving over a steel plate mounted in the channel bed, we determined the time at start and end of Bedload transport in four streams, where discharge is continuously monitored. The threshold discharge scatters over approximately one order of magnitude for each stream, reinforcing previous observations that critical discharge is characterized by a distribution of values. We interpret a strong correlation between the discharge at the start of transport and the discharge at the end of transport of the previous event to reflect temporal changes in bed structure and consequent effects on the driving and resisting forces acting on the bed.