Bedload-transport measurements with geophones Bedload-transport measurements with geophones Dieter...
-
Upload
joanna-gallagher -
Category
Documents
-
view
241 -
download
2
Transcript of Bedload-transport measurements with geophones Bedload-transport measurements with geophones Dieter...
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
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
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
Erlenbach stream (Alptal, CH): A = 0.7 km², mean channel slope S = 0.17
measuring sites with PBIS or geophone sensor arrays
Erlenbach, PBIS measuring site at sediment retention basinErlenbach, PBIS measuring site at sediment retention basin
array of PBIS or geophone sensors
on check dam
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]
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)
Q = 10 m3/sQ = 0.7 m3/sQ = 15 l/s
Sediment transport measurements: Sediment transport measurements: Erlenbach (Alptal)Erlenbach (Alptal)
ErlenbachErlenbach
coarse sediment along channel bed
14 July 199514 July 1995
Erlenbach, Alptal (Switzerland):Erlenbach, Alptal (Switzerland): flood eventsflood events
25 July 198425 July 1984
Erlenbach, Erlenbach, flood event of 25 July 1984:flood event of 25 July 1984: 2000 m 2000 m33 sediment deposition sediment deposition
Pitzbach (A): second test site for PBIS measurements Pitzbach (A): second test site for PBIS measurements
Pitzbach (A), test site for PBIS measurements Pitzbach (A), test site for PBIS measurements
Pitzbach
water intake
Austria
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
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
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)
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]
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
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
New installations at Erlenbach bedload measuring siteNew installations at Erlenbach bedload measuring site
rotating crane
metal basket with wire mesh
supporting rail
geophone sensors
Sediment from flood of 4 July 2009
Moving basket system for bedload transport measurements Moving basket system for bedload transport measurements
Erlenbach: Geophone calibration with moving basket samplesErlenbach: Geophone calibration with moving basket samples
Drau river (Dellach, A): Geophone calibration with slot samplerDrau river (Dellach, A): Geophone calibration with slot sampler
Geophone calibration from several field sites in CH and AGeophone calibration from several field sites in CH and A
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
Erlenbach (CH), second bedload measuring siteErlenbach (CH), second bedload measuring site
Test of PBIS measurements with two
successive rows of sensor arrays
Erlenbach (CH), second bedload measuring siteErlenbach (CH), second bedload measuring site
two successive rows with PBIS sensor arrays
bridge
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
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
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
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
- 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
- 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
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
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
piezoelectric / geophone bedload impact sensor piezoelectric / geophone bedload impact sensor
fixing of PBIS or geophone sensors
on a steel plate