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Presented by LE THU HIEN
Environmental Engineering
November 11, 2009
Nanyang Technological University
School of Civil and Environmental Engineering
FINAL YEAR PR!ECT
Prediction of
Total Bed-Material Load
in Alluvial Streams
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INTRODUCTION
BACK GROUND
Sediment transport is known as one o many problems to
rivers and natural streams
Monitoring the eect o sediment discharge on alluvial
stream is a challenge to many scientists and engineers
Modeling and orecasting the sediment rate in rivers is animportant stage
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INTRODUCTION
OBJECTIVE !ormulate an e"uation to predict the rate o
sediment discharge in alluvial streams
Minimi#e the inaccuracy and amend any
unreliable assumptions o other previous studies
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PASTSTUD
SEDIMENT DISCHARGE RATE
Indirect definition
$he sum o two separated elements% bed load andsuspended load
"irect definition
Consider $otal &ed Material 'oad ($&M') as the
most signiicant part *ash load is neglected in natural rivers
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PASTSTUD
Sediment discharge vs#
Flo$ discharge Discontinuous
Double valued
Sediment discharge vs#
%ean &elocity Continuous
Single valued
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PASTSTUD
'ennedy ( 'arim)s *rediction model
Pro+lems
Unrelia+le *arameters
Ins,fficient data so,rce
Ina**ro*riate ass,m*tions
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M!T"ODOLO#
Dimensional Analysis
Regression Analysis
Evaluation and Discussion
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DATASOURC!S
Collected by *illiam R+ &rownlie rom ield
investigation
,ncluding -. lows and /01. records
Sediment discharge rate was given in orm o
Cppm 23s4(3s 5 3) and can be obtained by
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DIM!NSIONALANALSIS
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DIM!NSIONALANALSIS
Selection of parameter
Physical consideration
Mean velocity should be used instead o *ater discharge
*ater 6 sediments inter6relationship should be taken into
consideration
Stream power includes the incipient motion7 which is not
a reliable actor should be discarded
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DIM!NSIONALANALSIS
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DIM!NSIONALANALSIS
Selection of parameter
Regression conditions
8igh correlation between dependent variable and
independent variables
'ow correlation between independent variables
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DIM!NSIONALANALSIS
Correlation +et$een varia+les
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DIM!NSIONALANALSIS
Selection of parameter
Chosen parameters
Dependent% P-9 ,ndependent% (P-7 P.7 P: )
(P-7 P; 7 P: )
(P07 P.7 P: )
(P07 P; 7 P: )
Correlation was ound in each data set at
speciic location
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DIM!NSIONALANALSIS
Selection of parameter
Correlation was computed in each data set at
speciic location
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R!#R!SSIONANALSIS
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R!#R!SSIONANALSIS
$hree approaches
Regression on all data
Regression on data at speciic location
Regression on all data with the neglection o
abnormal and unreliable value
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R!#R!SSIONANALSIS
Approac! "#
Regression on all data
%odel -% ln(P-9) 2 >95 >/ln(P.) 5 >-ln(P/) 5 >?ln(P0)
%odel .% ln(P-9) 2 >95 >/ln(P.) 5 >-ln(P/) 5 >?ln(P0) 5 >.ln(P.) @ ln(P/)
%odel 1% ln(P-9) 2 >95 >/ln(P.) 5 >-ln(P/) 5 >?ln(P0) 5 >;ln(P/) @ ln(P0)
%odel /% ln(P-9) 2 >95 >/ln(P.) 5 >-ln(P/) 5 >?ln(P0) 5 >1ln(P0) @ ln(P.)
%odel 2% ln(P-9) 2 >95 >/ln(P.) 5 >-ln(P/) 5 >?ln(P0) 5 >0ln(P.) @ ln(P/) @ ln(P0)
%odel 3% ln(P-9) 2 >95 >/ln(P.) 5 >-ln(P/) 5 >?ln(P0)
5 >.ln(P.) @ ln(P/) 5 >;ln(P/) @ ln(P0) 5 >1ln(P0) @ ln(P.)
5 >0ln(P.) @ ln(P/) @ ln(P0) Le Thu Hien
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R!#R!SSIONANALSIS
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R!#R!SSIONANALSIS
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R!#R!SSIONANALSIS
Approac! $#
Regression on data at s*ecific location
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R!#R!SSIONANALSIS
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R!#R!SSIONANALSIS
Approac! %#
Regression on all data e4ce*t for a+normal and
,nrelia+le records
Data set . and -? are discarded
Some o abnormal points picked rom the previous
graph are also ignored
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R!#R!SSIONANALSIS
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!$ALUATION % COMPARISON
RESU&TS Coeicients are almost consistent in magnitude and signs
8igh reliability and itness% very high R6s"uare value
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!$ALUATION % COMPARISON
DISCUSSION All models could be used to predict sediment discharge
Approach - is less accurate compared to other two
Approach ? can discard abnormal records and limit thesmaller range
A**roach - A**roach . Le Thu HienA**roach 1
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!$ALUATION % COMPARISON
RECOMMENDATIONS
Model ? is most suitable and reliable to use in normal
cases
8igh accurate range applied to the model% P-9 rom
(6?+; ;+9)
Errors o measurement made by human and e"uipments
should be avoided as much as possible to increase thereliability o prediction
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!$ALUATION % COMPARISON
comparion
'ennedy ( 'arim )s *rediction
Same physical consideration% Mean velocity7 Shear
velocity B sediment si#e
Critical shear velocity eceed the mean velocity7 make the
regression terms not applicable to use
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CONCLUSION
A model of sediment load has +een com*,ted $o help civil and hydraulic engineers to predict the sediment
discharge in natural systems
$o be a tool in urther design and controlling o streams problems
Advantages More accurate than most o the previous studies7 even not yet
/99 but still it is acceptable Applicable in very wide range o low7 ecept or laboratory range
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THANK
'OU L Th Hi
Nanyang Technological University
School of Civil and Environmental Engineering
Supervisor% Assoc Pro Cheng =ian Sheng
Moderator% Assoc Pro 'im Siow ong