bedload-transport measurements with geophones bedload-transport measurements with geophones dieter...
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![Page 1: Bedload-transport measurements with geophones Bedload-transport measurements with geophones Dieter Rickenmann WSL - Swiss Federal Research Institute Mountain](https://reader036.vdocuments.mx/reader036/viewer/2022062408/56649ef65503460f94c0968d/html5/thumbnails/1.jpg)
Bedload-transportBedload-transport
measurementsmeasurements
with geophoneswith geophones
Dieter Rickenmann
WSL - Swiss Federal Research Institute
Mountain Hydrology and Torrents
Birmensdorf, Switzerland
Séminaire GESTRANS Ancien Monastère de Sainte-Croix (26), 3 November 2010
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1) Introduction
2) Measuring method and test sites2) Measuring method and test sites
3) Calibration of bedload sensors
4) Results of additional investigations
5) Conclusions and outlook
ContentContent
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Erlenbach stream (Alptal, CH)
A = 0.7 km²
S = 0.17
Runoff and sediment measuring station
array of PBIS or geophone sensors
on check dam
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Erlenbach stream (Alptal, CH): A = 0.7 km², mean channel slope S = 0.17
measuring sites with PBIS or geophone sensor arrays
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Erlenbach, PBIS measuring site at sediment retention basinErlenbach, PBIS measuring site at sediment retention basin
array of PBIS or geophone sensors
on check dam
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PBIS: piezoelectric bedload impact sensor PBIS: piezoelectric bedload impact sensor
Example of original PBIS signal, for a 3.8 kg particle passing over a sensor
rolling, center sliding, right side
Threshold voltage for impulse counting = 0.2 V
time [s] time [s]
volta
ge [
V]
volta
ge [
V]
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piezoelectric / geophone bedload impact sensor piezoelectric / geophone bedload impact sensor
fixing of PBIS or geophone sensors on a steel plate
since the year 2000 we use geophone sensors (instead of
the piezoelectric sensors)
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Q = 10 m3/sQ = 0.7 m3/sQ = 15 l/s
Sediment transport measurements: Sediment transport measurements: Erlenbach (Alptal)Erlenbach (Alptal)
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ErlenbachErlenbach
coarse sediment along channel bed
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14 July 199514 July 1995
Erlenbach, Alptal (Switzerland):Erlenbach, Alptal (Switzerland): flood eventsflood events
25 July 198425 July 1984
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Erlenbach, Erlenbach, flood event of 25 July 1984:flood event of 25 July 1984: 2000 m 2000 m33 sediment deposition sediment deposition
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Pitzbach (A): second test site for PBIS measurements Pitzbach (A): second test site for PBIS measurements
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Pitzbach (A), test site for PBIS measurements Pitzbach (A), test site for PBIS measurements
Pitzbach
water intake
Austria
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Grain size distributions of sediment at test sites Grain size distributions of sediment at test sites
0
10
20
30
40
50
60
70
80
90
100
0.1 1 10 100 1000
% finer by weight
grain size [mm]
0102030405060708090
100
0.1 1 10 100 1000
Pitzbach: settling basin
Pitzbach: bed materialupstream of intake
Erlenbach: retention basin(mean 1984-1987)
Erlenbach: surface bedmaterial (1993)
% finer by weight
grain size [mm]
range of estimated threshold size for detection with PBIS sensor
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1) Introduction
2) Measuring method and test sites
3) Calibration of bedload sensors3) Calibration of bedload sensors
4) Results of additional investigations
5) Conclusions and outlook
ContentContent
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10
100
1'000
10'000
100'000
1'000'000
10'000'000
100'000'000
20.06 05.07 21.07 06.08 21.08 07.09
sensor pulses
1
10
100
1'000
10'000
daily bedload [m3]1984
Pitzbach (A): comparison of sediment transport measurements Pitzbach (A): comparison of sediment transport measurements
and bedload sensors (hydrophones) and bedload sensors (hydrophones)
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B: y = 4.326x1.228
R2 = 0.759
A: y = 5.321x0.995
R2 = 0.556
C: y = 2.258x1.264
R2 = 0.912
0.01
0.1
1
10
100
1000
10000
0.01 0.1 1 10 100 1000
data set A (15 min)
data set B (1hour)
data set C (1 day)
G [m3]
SP (sensor impulses)
PBIS sensor, no. of impulses
PBIS calibration: Pitzbach (A) measurements PBIS calibration: Pitzbach (A) measurements
sediment volume [m3]
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0.01
0.1
1
10
100
1000
0 2 4 6 8 10
data set A (15 min)
data set B (1 hour)
data set C (1 day)
Logarithmisch (dataset C (1 day))Logarithmisch (dataset B (1 hour))Logarithmisch (dataset A (15 min))
SP/G
Qmax/Qc
PBIS calibration: Pitzbach (A) measurements PBIS calibration: Pitzbach (A) measurements
= sensor impulses / sediment volume
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Erlenbach, Erlenbach, sediment sediment
retentionretention
basin,basin,
view upstream view upstream
Moving basket system for bedload transport measurements Moving basket system for bedload transport measurements
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New installations at Erlenbach bedload measuring siteNew installations at Erlenbach bedload measuring site
rotating crane
metal basket with wire mesh
supporting rail
geophone sensors
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Sediment from flood of 4 July 2009
Moving basket system for bedload transport measurements Moving basket system for bedload transport measurements
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Erlenbach: Geophone calibration with moving basket samplesErlenbach: Geophone calibration with moving basket samples
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Drau river (Dellach, A): Geophone calibration with slot samplerDrau river (Dellach, A): Geophone calibration with slot sampler
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Geophone calibration from several field sites in CH and AGeophone calibration from several field sites in CH and A
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1) Introduction
2) Measuring method and test sites
3) Calibration of bedload sensors
4) Results of additional investigations 4) Results of additional investigations
5) Conclusions and outlook
ContentContent
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Erlenbach (CH), second bedload measuring siteErlenbach (CH), second bedload measuring site
Test of PBIS measurements with two
successive rows of sensor arrays
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Erlenbach (CH), second bedload measuring siteErlenbach (CH), second bedload measuring site
two successive rows with PBIS sensor arrays
bridge
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Erlenbach (CH), second bedload measuring siteErlenbach (CH), second bedload measuring site
Test of PBIS measurements with two successive rows of sensor arrays
y = 0.7868x1.0128
R2 = 0.8639
0.01
0.1
1
10
100
1000
0.01 0.1 1 10 100 1000
sensor impulses downstream row, SPd
sensor impulses upstream row, SPu
er row
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Laboratory study: PBIS measurements with particles from ErlenbachLaboratory study: PBIS measurements with particles from Erlenbach
b-axis: 3.5 - 4.5 cmb-axis: 9 - 11 cm
b-axis: 18 - 20 cmb-axis: 14 - 16 cm
Sample weight of uniform grains [kg]
No
. of s
en
sor
impu
lse
s
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Laboratory study: PBIS measurements with particles from ErlenbachLaboratory study: PBIS measurements with particles from Erlenbach
Normalized cummulative frequency curves.
Top: uniform material (4 cm) with different sample weights.
Bottom: 4 different grain sizes with 2 sample weights for each size class
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1) Introduction
2) Measuring method and test sites
3) Calibration of bedload sensors
4) Results of additional investigations
5) Conclusions and outlook 5) Conclusions and outlook
ContentContent
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- robust technique requiring only very few maintenance
- continuous measurement of bedload transport intensities
- detection of beginning and ceasing of bedload motion
- relatively low costs for measuring equipment and necessary
constructions at measuring site
- for longer observation periods and larger bedload volumes a reasonable
accuracy is obtained for the calibration relationships (considering
natural variability of bedload transport in mountain streams)
Advantages of PBIS measuring systemAdvantages of PBIS measuring system
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- calibration of the system is necessary
- no information on particle sizes in transport can be obtained
- there is a limit for the lower critical particle size which can be detected
- influence of hydraulic conditions and sediment properties on calibration
are almost unknown at present
- changing flow intensities are likely to change the size distribution of
transported bedload particles (resulting in non-linear calibration
relations, if such effects are not averaged out)
Disadvantages of PBIS measuring systemDisadvantages of PBIS measuring system
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Objective: Comparison of two complementary indirect
bedload transport measuring approaches:
- Geophone measurements as applied by WSL
- Hydrophone measurements as applied by Université Joseph Fourier, LTHE,
Grenoble
Possible sites for comparative measurements:
- Erlenbach stream (operated by WSL)
- Draix experimental catchment (Cemagref)
- Experimental flume (Cemagref, LTHE)
Possible travel support:
- Germaine de Staël program (submitted proposal)
Outlook: WSL – GESTRANS cooperation projectOutlook: WSL – GESTRANS cooperation project
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Bedload-transport measurements with geophonesBedload-transport measurements with geophones
Dieter Rickenmann
WSL - Swiss Federal Research Institute
Mountain Hydrology and Torrents
Birmensdorf, Switzerland
Séminaire GESTRANS Ancien Monastère de Sainte-Croix (26), 3 November 2010
Thank you for the attentionThank you for the attention
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piezoelectric / geophone bedload impact sensor piezoelectric / geophone bedload impact sensor
fixing of PBIS or geophone sensors
on a steel plate