The Experts below are selected from a list of 9447 Experts worldwide ranked by ideXlab platform
Jens M Turowski - One of the best experts 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, 2014Co-Authors: Dieter Rickenmann, Andrea Kreisler, Johann Aigner, Jonathan B Laronne, Jens M Turowski, Bruno Fritschi, Carlos R Wyss, Ronel Barzilai, Ian Reid, Hugo SeitzAbstract: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, 2013Co-Authors: Alexandre Badoux, Norina Andres, Jens M TurowskiAbstract: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, 2013Co-Authors: Alexandre Badoux, Norina Andres, Jens M TurowskiAbstract: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.
-
a demonstration of the importance of Bedload transport for fluvial bedrock erosion and knickpoint propagation
Earth Surface Processes and Landforms, 2013Co-Authors: Kristen L Cook, Jens M Turowski, Niels HoviusAbstract:We provide field evidence for the role of Bedload in driving fluvial incision and knickpoint propagation. Using aerial photographs, field surveys, and hydrological data, we constrain the incision history of a bedrock gorge 1200 m long and up to 20 m deep cut by Da'an River in western Taiwan. This reach of the river experienced 10 m of uplift during the 1999 Chi-Chi earthquake. For five years following the earthquake, Bedload was prevented from entering the uplift zone, the knickpoint was static and little incision took place. Bedload transport across the uplift zone resumed in 2004, initiating extremely rapid incision, with 620 m of knickpoint propagation and up to 20 m of downcutting by 2008. This change highlights the relative inefficiency of suspended sediment and the dominant role of Bedload as a tool for fluvial erosion and knickpoint propagation. Once Bedload tools became available, knickpoint propagation was influenced by geological structure, lithology, and drainage organization. In particular, a change in dip of the sandstone beds at the site caused a decrease of knickpoint propagation velocity. Copyright © 2012 John Wiley & Sons, Ltd.
-
Bedload transport measurements at the erlenbach stream with geophones and automated basket samplers
Earth Surface Processes and Landforms, 2012Co-Authors: Dieter Rickenmann, Jens M Turowski, Bruno Fritschi, Angela Klaiber, Andreas LudwigAbstract: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.
Helmut Habersack - One of the best experts on this subject based on the ideXlab platform.
-
Bedload TRAP MEASUREMENTS AS PART OF AN INTEGRATIVE MEASUREMENT SYSTEM
2020Co-Authors: Andrea Kreisler, Markus Moser, Hugo Seitz, Florian Rudolf-miklau, Helmut HabersackAbstract: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, 2018Co-Authors: Marcel Liedermann, Andrea Kreisler, Michael Tritthart, Philipp Gmeiner, Helmut HabersackAbstract: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, 2017Co-Authors: Andrea Kreisler, Markus Moser, Johann Aigner, Rolf Rindler, Michael Tritthart, Helmut HabersackAbstract: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.
-
integrated automatic and continuous Bedload monitoring in gravel bed rivers
Geomorphology, 2017Co-Authors: Helmut Habersack, Andrea Kreisler, Johann Aigner, Rolf Rindler, Hugo Seitz, Marcel Liedermann, Jonathan B LaronneAbstract:Bedload monitoring techniques have been developed and applied for many years in rivers ranging from steep mountain torrents to the large gravel-bed Danube River in Austria. Most monitoring stations use a combination of direct (mobile bag samplers, slot samplers) and indirect (geophones, hydrophones) measurement methods. Each individual technique is adequate, yet features particular boundary conditions and limitations related to hydraulic and sampling efficiency, functionality during floods, sampling duration or grain size. We show the capabilities and limitations of the different monitoring devices with respect to technical, operational and economic criteria, evaluating their suitability for determining Bedload transport parameters. Bedload monitoring results of a measuring site at the Drau River in Carinthia/Austria are used to illustrate the specific range of the device application. We present an integrated automatic and continuous Bedload monitoring system. It complements the specific limitations of single monitoring methods by additional measurement devices, enabling comprehensive monitoring of the Bedload transport process. We then derive the Bedload Discharge Integrated Calculation Approach and the Bedload Rating Curve Approach and discuss their application for determining Bedload discharge Qb and total Bedload mass Vb. Whereas the integrated approach combines data from direct monitoring methods with indirect techniques, the rating curve approach uses only data from direct Bedload monitoring devices. We demonstrate that applying an integrated automatic and continuous Bedload monitoring system and combining the Bedload Discharge Integrated Calculation Approach and Bedload Rating Curve Approach yields accurate Bedload discharge results.
-
Bedload pulses in a hydropower affected alpine gravel bed river
Geomorphology, 2017Co-Authors: Johann Aigner, Andrea Kreisler, Rolf Rindler, Christoph Hauer, Helmut HabersackAbstract:Abstract This study investigated the sediment resupply and transport dynamics at the Upper Drau River upstream of Lienz (Eastern Tyrol, Austria). Due to a hydropower plant, a 24 km long river reach of this alpine gravel bed river is under residual flow conditions, although sediment is still resupplied into the reach through many active torrents and tributaries. As a result, sediment deposition in the residual flow reach intensified, hence increasing maintenance efforts to stabilize this river section and ensure flood protection. In combination with a new sediment management program, a continuous Bedload monitoring system was installed 2 km downstream of the residual reach in 2001 to support the development of adapted sediment management strategies. The surrogate Bedload monitoring system consists of 16 impact plate geophones, installed over a 17 m wide cross section. The unprecedented 15-year dataset of high-resolution Bedload intensity revealed a complex process of gravel storage and intermittent resupply from the residual reach, allowing the authors a detailed analysis of frequently occurring Bedload pulses. These transport features are triggered by increased discharges during floods in the residual reach and created pronounced anticlockwise Bedload hysteresis or, with a temporal shift to the event peak, caused distinct shifts in the Bedload activity downstream. Bedload pulses produce very high Bedload fluxes while in transit, tend to increase Bedload flux in the post-event phase, and can alter and reduce the upstream sediment storage leading to a lowering of Bedload availability for future pulses. The observed time lags between main discharge events and the arrival of the macro-pulses are correlated with mean water discharge during pulse propagation, thus enabling a prediction of the pulse arrival at the monitoring station solely based on the hydrograph. In combination with the hydrological setup of the reach, the observed Bedload pulse time lags allowed an estimation of pulse velocities in the range 0.002 − 0.05 m s − 1 .
Dieter Rickenmann - One of the best experts 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, 2014Co-Authors: Dieter Rickenmann, Andrea Kreisler, Johann Aigner, Jonathan B Laronne, Jens M Turowski, Bruno Fritschi, Carlos R Wyss, Ronel Barzilai, Ian Reid, Hugo SeitzAbstract: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, 2012Co-Authors: Dieter Rickenmann, Jens M Turowski, Bruno Fritschi, Angela Klaiber, Andreas LudwigAbstract: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, 2011Co-Authors: Jens M Turowski, Alexandre Badoux, Dieter RickenmannAbstract:[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.
-
start and end of Bedload transport in gravel bed streams
Geophysical Research Letters, 2011Co-Authors: Jens M Turowski, Alexandre Badoux, Dieter RickenmannAbstract:[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.
-
the partitioning of the total sediment load of a river into suspended load and Bedload a review of empirical data
Sedimentology, 2010Co-Authors: Jens M Turowski, Dieter Rickenmann, Simon DadsonAbstract:The partitioning of the total sediment load of a river into suspended load and Bedload is an important problem in fluvial geomorphology, sedimentation engineering and sedimentology. Bedload transport rates are notoriously hard to measure and at many sites only suspended load data are available. Often the Bedload fraction is estimated with rule-of-thumb methods such as Maddock’s Table, which are inadequately field-tested. Here the partitioning of sediment load for the Pitzbach is discussed, an Austrian mountain stream for which high temporal resolution data on both Bedload and suspended load are available. The available data show large scatter on all scales. The fraction of the total load transported in suspension may vary between zero and one at the Pitzbach, while its average decreases with rising discharge (i.e. Bedload transport is more important during floods). Existing data on short- and long-term partitioning is reviewed and an empirical equation to estimate Bedload transport rates from measured suspended load transport rates is suggested. The partitioning averaged over a flood can vary strongly from event to event. Similar variations may occur in the year-to-year averages. Using published simultaneous short-term field measurements of Bedload and suspended load transport rates, Maddock’s table is reviewed and updated. Long-term average partitioning could be a function of the catchment geology, the fraction of the catchment covered by glaciers and the extent of forest, but the available data are insufficient to draw final conclusions. At a given drainage area, scatter is large, but the data show a minimal fraction of sediment transported in suspended load, which increases with increasing drainage area and with decreasing rock strength for gravel bed rivers, whereby in large catchments the Bedload fraction is insignificant at ~1%. For sand bed rivers, the Bedload fraction may be substantial (30-50%) even for large catchments. However, available data are scarce and of varying quality. Long-term partitioning varies widely among catchments and the available data are currently not sufficient to effectively discriminate control parameters.
Andrea Kreisler - One of the best experts on this subject based on the ideXlab platform.
-
Bedload TRAP MEASUREMENTS AS PART OF AN INTEGRATIVE MEASUREMENT SYSTEM
2020Co-Authors: Andrea Kreisler, Markus Moser, Hugo Seitz, Florian Rudolf-miklau, Helmut HabersackAbstract: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, 2018Co-Authors: Marcel Liedermann, Andrea Kreisler, Michael Tritthart, Philipp Gmeiner, Helmut HabersackAbstract: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, 2017Co-Authors: Andrea Kreisler, Markus Moser, Johann Aigner, Rolf Rindler, Michael Tritthart, Helmut HabersackAbstract: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.
-
integrated automatic and continuous Bedload monitoring in gravel bed rivers
Geomorphology, 2017Co-Authors: Helmut Habersack, Andrea Kreisler, Johann Aigner, Rolf Rindler, Hugo Seitz, Marcel Liedermann, Jonathan B LaronneAbstract:Bedload monitoring techniques have been developed and applied for many years in rivers ranging from steep mountain torrents to the large gravel-bed Danube River in Austria. Most monitoring stations use a combination of direct (mobile bag samplers, slot samplers) and indirect (geophones, hydrophones) measurement methods. Each individual technique is adequate, yet features particular boundary conditions and limitations related to hydraulic and sampling efficiency, functionality during floods, sampling duration or grain size. We show the capabilities and limitations of the different monitoring devices with respect to technical, operational and economic criteria, evaluating their suitability for determining Bedload transport parameters. Bedload monitoring results of a measuring site at the Drau River in Carinthia/Austria are used to illustrate the specific range of the device application. We present an integrated automatic and continuous Bedload monitoring system. It complements the specific limitations of single monitoring methods by additional measurement devices, enabling comprehensive monitoring of the Bedload transport process. We then derive the Bedload Discharge Integrated Calculation Approach and the Bedload Rating Curve Approach and discuss their application for determining Bedload discharge Qb and total Bedload mass Vb. Whereas the integrated approach combines data from direct monitoring methods with indirect techniques, the rating curve approach uses only data from direct Bedload monitoring devices. We demonstrate that applying an integrated automatic and continuous Bedload monitoring system and combining the Bedload Discharge Integrated Calculation Approach and Bedload Rating Curve Approach yields accurate Bedload discharge results.
-
Bedload pulses in a hydropower affected alpine gravel bed river
Geomorphology, 2017Co-Authors: Johann Aigner, Andrea Kreisler, Rolf Rindler, Christoph Hauer, Helmut HabersackAbstract:Abstract This study investigated the sediment resupply and transport dynamics at the Upper Drau River upstream of Lienz (Eastern Tyrol, Austria). Due to a hydropower plant, a 24 km long river reach of this alpine gravel bed river is under residual flow conditions, although sediment is still resupplied into the reach through many active torrents and tributaries. As a result, sediment deposition in the residual flow reach intensified, hence increasing maintenance efforts to stabilize this river section and ensure flood protection. In combination with a new sediment management program, a continuous Bedload monitoring system was installed 2 km downstream of the residual reach in 2001 to support the development of adapted sediment management strategies. The surrogate Bedload monitoring system consists of 16 impact plate geophones, installed over a 17 m wide cross section. The unprecedented 15-year dataset of high-resolution Bedload intensity revealed a complex process of gravel storage and intermittent resupply from the residual reach, allowing the authors a detailed analysis of frequently occurring Bedload pulses. These transport features are triggered by increased discharges during floods in the residual reach and created pronounced anticlockwise Bedload hysteresis or, with a temporal shift to the event peak, caused distinct shifts in the Bedload activity downstream. Bedload pulses produce very high Bedload fluxes while in transit, tend to increase Bedload flux in the post-event phase, and can alter and reduce the upstream sediment storage leading to a lowering of Bedload availability for future pulses. The observed time lags between main discharge events and the arrival of the macro-pulses are correlated with mean water discharge during pulse propagation, thus enabling a prediction of the pulse arrival at the monitoring station solely based on the hydrograph. In combination with the hydrological setup of the reach, the observed Bedload pulse time lags allowed an estimation of pulse velocities in the range 0.002 − 0.05 m s − 1 .
Normand E Bergeron - One of the best experts on this subject based on the ideXlab platform.
-
The effect of Bedload transport on mean and turbulent flow properties
Geomorphology, 2000Co-Authors: Patrice E. Carbonneau, Normand E BergeronAbstract:This paper reports the results of a flume experiment that was designed to investigate the effect of Bedload transport on mean and turbulent properties of the flow. The experiment consisted of varying the Bedload transport rate for a given hydraulic condition, and of measuring the flow velocity profiles using an Acoustic Doppler Velocimeter (ADV) for each transport rate in order to allow for comparison. Bedload transport was produced by injecting gravel-size particles (D50= 7.4 mm) with a conveyer belt mounted at the upstream end of the flume. The results indicate that the effect of Bedload on flow characteristics is complex. It is shown that Bedload transport causes opposite effects on flow velocity depending on the roughness of the bed and the relative magnitude of flow and sediment transport variables. A better understanding of these conflicting results is obtained from the application of an energy budget approach to the analysis of velocity data. This approach demonstrates that Bedload affects flow velocity by modifying the rate of dissipation of turbulent kinetic energy. However, the mechanisms responsible for the modification of turbulent dissipation are still unknown. (C) 2000 Elsevier Science B.V. All rights reserved.
