THESIS FINAL EXAM SEDIMENTATION STUDY OF REJOSO … · WSE=HWL+Ru . Proposed jetty design...
Transcript of THESIS FINAL EXAM SEDIMENTATION STUDY OF REJOSO … · WSE=HWL+Ru . Proposed jetty design...
THESIS FINAL EXAM
SEDIMENTATION STUDY OF REJOSO JETTY USING
NUMERICAL MODEL
By :
Ardiansyah Fauzi (115876)
(Joint Degree Master Student AIT-ITS)
Examination Committee : Prof. Mukand S. Babel (Chairperson)
Dr. Sutat Weesakul (Co-chairperson)
Dr. Sangam Shrestha
Dr. Akiyuki Kawasaki
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4
Introduction
Flood location around
Rejoso River
• Flood depth varies from 30-50 cm
• Flood duration is ± 4 hours
• Occurred frequently1-2 times in a year
Flood in Jarangan and
Kedungbako village
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+ 2.603
35,60
3,14
3,24
+ 2.493
39,50
Cross Section II-II
Not To Scale
Cross Section I-I
Not To Scale
Introduction
I I
II II
Deposition in the estuary, which reduce river discharge
capacity
Flood occurs regularly in the upstream area.
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Statement of Problem
Introduction
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WSE=HWL+Ru+Freeboard WSE=HWL+Ru
Proposed jetty design
(Wiratman, 2010)
Breaking wave location
Breaking wave
location with
H=0.9 m; T=4 m Study location
Overall objective
To determine the effect of jetty construction in the
hydrodynamics and sediment transport
Specific objectives
To determine the coastal climate (current and sedimentation)
due to jetty construction
To verify and propose geometric and length of jetty
Objectives of the Research
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Introduction
Dataset
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Methodology
No. Type of Data Periods Frequency Stations Source Coordinates
1 Wind data 2004-2010 Hourly 1 Station
-W1
- BMKG 7° 37.711' S 112°
56.547'E
2 Topography
and
Bathymetry
2010 DWR
3 Tidal data 2010 (Mike
Predicition)
October
2010 (Obs)
Hourly 2 Stations
- T1
- T2
- MIKE
Software
- Obs
7° 33.451' S 112°
58.481'E (T1)
7° 37.479'S 112°
57.340'E (T2)
4 Sediment data
- Grain Size
- Suspende
d load
Oct 5th 2010 1 day
measurement
2 Stations
-S1
-S2
DWR 7° 37.475' S 112°
57.368'E (S1)
7° 37.437' S 112°
57.484'E (S2)
5 Current Oct 5th 2010
(10 hours)
Hourly 2 Stations
-C1
-C2
DWR 7° 33.451' S 112°
58.481'E (C1)
7° 37.462'S 112°
57.473'E (C2)
6 Rain data 2001-2010 Daily 7 Stations DWR
7 Discharge
recording in
river
2010 Daily 1 Station
- Q1
DWR 7° 38.468‘ S, 112°
57.245'E
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(Source : BMKG)
(Source : Observation)
Methodology Wind Rose(W1 Location)
Tidal (T1 Location)
(Source : MIKE Prediction)
Tidal (T2 Location)
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Methodology
(Source : Department of Water Resources)
(Source : DWR)
Catchment Area Characteristic
Observed River Discharge (Q1 Location)
Average Wind Speed (W1 Location)
(Source : BMKG)
Monthly averaged
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Results and Discussion
Model Setup
Water Surface Elevation (WSE)
- For calibration : WSE on October
2010
- For Scenario : WSE on January
2010
Flow Rate (FR)
- For calibration : FR on Oct ober 2010
- For scenario : FR on January 2010
Model Domain
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Results and Discussion
Consist of :
- 9322 triangular elements
- 4 quadrilateral elements
- 19320 nodes
The digital elevation is
interpolated linearly
with elements.
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Model Calibration
Current velocity observation
Current velocity and water surface observation
T2, C1 C2
Results and Discussion
Observation point for calibration
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Results and Discussion Model Performance
Tidal (T2)
Current Velocity Current Velocity (C1)
Current Velocity (C2)
Eddy
Viscosity (Pa-
sec)
Manning RMSE (m) R
Tidal (T2) 4000 0.03 0.0023 0.996
Velocity 1 (C1) 4000 0.03 6.48804E-05 0.9477
Velocity 1 (C2) 4000 0.03 0.0006 0.8143
Parameter Statistical performance
Calibration
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Sensitivity Analysis
Simple channel with single
material.
- Length is 800 meters
- Width is 100 meters.
Boundary condition in inlet is
100 m3/s and water surface
elevation in oulet is 6 meters.
100m3/s 6 m
Results and Discussion
Simple Channel
This sensitivity analysis is done to obtain
which parameters give great effect in the
model.
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Constrained flume with single
material.
- Length is 800 meters
- Width is 100 meters.
- Constricted to 20 m wide
through the middle
Boundary condition in inlet is
100 m3/s and water surface
elevation in oulet is 6 meters.
100m3/s 6 m
Results and Discussion
Constrained Channel
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Sensitivity Analysis at the Model Domain
Cross section for sensitivity analysis in ocean
A
B
Results and Discussion
Observation arc for sensitivity analysis at the ocean
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Results and Discussion
D
C
Long section for
sensitivity analysis
Observation arc for sensitivity analysis at the river
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Jetty Selection Criteria Designed length of jetty is 1170 m. The length
jetty is planned up to the depth before
breaking wave. It aims to bring the sediment
supply to the area with calm current (before
breaking waves), so there is no deposition in
the area of breaking waves that can cause
siltation of estuary (Wiratman, 2010).
Criteria for Rejoso jetty :
1. Accommodated the sediment deposition.
2. Less maintenanced.
3. Accommodated natural processes in the
estuary.
Jetty function :
1. To prevent sedimentation in the estuary
2. To move sedimentation process from the
the estuary to the sea
3. To prevent longshore sediment transport
block the river mouth
(Source : The Overseas Coastal Area
Development Institute of Japan, 2002)
Results and Discussion
Layout of jetty
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Model Simulation
There are 4 scenario model simulation as follows:
1. No jetty
This condition is purposed to simulate the existing condition
2. Jetty length 100%
This condition is to simulate the condition with original proposed design from local government
3. Jetty length 50%
By reducing the length of jetty by 50%, it is expected to show the condition where proposed jetty
design is based on breaking wave, but the actual condition in Rejoso estuary is dominated by river
discharge. It is expected that the length of jetty no need too long until before breaking wave
location.
4. Jetty length 50% with constrained
Length of jetty 50% from proposed design with constrained 15 meter in the jetty tail end is used
in model by considering the function of jetty is only to maintain the the sedimentation process in
the estuary, there is no function for navigation canal. By this assumption, it is expected the
velocity inside the jetty will be higher and it can flush the sediment inside the jetty better.
Results and Discussion
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Results and Discussion
Global current condition at
time step 138 hours (spring
tide condition)
Near estuary current
condition at time step 138
hours (spring tide
condition)
Scenario 1
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Results and Discussion
Global current condition at
time step 144 hours (neap
tide condition)
Near estuary current
condition at time step
144 hours (neap tide
condition)
Scenario 1
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Suspended load at time step
138 hours (spring tide
condition)
Suspended load at time step
144 hours (neap tide
condition)
Results and Discussion
Scenario 1 (no jetty)
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Results and Discussion
Scenario 2 (Jetty 100%)
Global current condition at
time step 138 hours (spring
tide condition)
Near estuary current
condition at time step
138 hours (spring tide
condition)
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Results and Discussion
Scenario 2 (Jetty 100%)
Global current condition at
time step 144 hours (neap
tide condition)
Near estuary current
condition at time step
144 hours (neap tide
condition)
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Suspended load at time step
138 hours (spring tide
condition)
Suspended load at time step
144 hours (neap tide
condition)
Results and Discussion
Scenario 2 (Jetty 100%)
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Results and Discussion
Scenario 3 (Jetty 50%)
Global current condition at
time step 138 hours (spring
tide condition)
Near estuary current
condition at time step
138 hours (spring tide
condition)
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Results and Discussion
Scenario 3 (Jetty 50%)
Global current condition at
time step 144 hours (neap
tide condition)
Near estuary current
condition at time step
144 hours (neap tide
condition)
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Suspended load at time step
138 hours (spring tide
condition)
Suspended load at time step
144 hours (neap tide
condition)
Results and Discussion
Scenario 3 (Jetty 50%)
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Results and Discussion
Scenario 4 (Jetty 50% constrained)
Global current condition at
time step 138 hours (spring
tide condition)
Near estuary current
condition at time step
138 hours (spring tide
condition)
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Results and Discussion
Scenario 4 (Jetty 50% constrained)
Global current condition at
time step 144 hours (neap
tide condition)
Near estuary current
condition at time step
144 hours (neap tide
condition)
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E
F
Scenario 1
Scenario 3
Scenario 2
Results and Discussion Observation at the river before and after
jetty construction
K
L
G
H
I
J Scenario 4
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WATER SURFACE CHANGE USING RETURN PERIOD DISCHARGE IN 720 HOURS TIME
STEPS
at time step 138 hours
(spring tide condition)
at time step 144 hours
(neap tide condition)
CONCLUSION The effect of jetty construction will block the the current flow from
east to west and cause turbulence in the west side of jetty and reduce the current velocity up to 56% in the west side of jetty. The sedimentation process in the estuary can not be simulated well, because it is difficult to apply radiation stress in the model domain.
The result in scenario 2-4 provides weakness and advantages. If using jetty length 100%, it will be good in moving sediment deposition from estuary to the offshore, but the length of jetty is no need that long because Rejoso estuary is river dominated, and also the longshore sediment transport is difficult to move bypass the jetty. If using jetty length 50 % with unconstrained, the velocity and the water surface elevation changes in the river is not much different with jetty length 100%, it is showed that with jetty length 50% from proposed design is enough to maintain condition in the river. If using jetty length 50% with constrained, the velocity in the river is higher than the other simulation, but the changes of water surface elevation in the river is need to be noticed. By that condition, the jetty length 50 without constrained can be better than proposed design and jetty with constrained, because considering the velocity and water surface elevation changes in the river is not quite different with existing condition.
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Conclusion
It needs time series sediment concentration data to represent the
process sedimentation more representatively with actual
condition.
Wave-current simulation is needed to make more representative
model for longshore sediment transport
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Recommendation
RECOMENDATION
PUBLICATIONS
1. Studi Dampak Pembangunan Jetty Kali Rejoso Pada Daerah
Pantai Dengan Menggunakan Model Numerik. Seminar
Nasional Aplikasi Teknologi Prasarana Wilayah 2014
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Regional
Domain
Local Domain
Results and Discussion
Regional domain using grid dimension Dx=Dy = 80 meters
Local domain using grid dimension Dx = Dy = 2 meter.
Wave Model Setup
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Spectral energy with H=0.93 m, T=6.14 s
Results and Discussion
Specified Spectrum
1-D Transformed
Spectrum
1-D Transformed
Spectrum
Zero Spectrum
Boundary Conditions