CRUZ & SANTOS - Engineering Study of Coastal Erosion in an ...

Engineering Study of Coastal Engineering Study of Coastal Erosion in an Embayment Erosion in an Embayment Shore and its MitigationShore and its MitigationEric C. CruzEric C. CruzInstitute of Civil EngineeringInstitute of Civil EngineeringUniversity of the Philippines DilimanUniversity of the Philippines Diliman

Jose Carlo Eric L. SantosJose Carlo Eric L. SantosAMH Philippines, Inc.AMH Philippines, Inc.UP Diliman Campus, Quezon City, PhilippinesUP Diliman Campus, Quezon City, Philippines

3rd JSPS3rd JSPS--DOST International Symposium on Environmental EngineeringDOST International Symposium on Environmental Engineering“Symposium on Harmonizing Infrastructure Development with the En“Symposium on Harmonizing Infrastructure Development with the Environment”vironment”March 9March 9--10, 200910, 2009SEAMEO INNOTECH, University of the Philippines Campus, Diliman, SEAMEO INNOTECH, University of the Philippines Campus, Diliman, Quezon CityQuezon City

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INTRODUCTIONINTRODUCTION

Mindoro OrientalMindoro Oriental

Existing protectionExisting protectionCoastal erosionCoastal erosion

Coastal erosionCoastal erosion

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INTRODUCTIONINTRODUCTION

at headlandat headland

at embaymentat embayment

DarongDarong, Davao del , Davao del SurSur

Existing protectionExisting protection

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INTRODUCTIONINTRODUCTION

PanglaoPanglao Island, Island, BoholBohol

White beach sandWhite beach sand

Coastal erosionCoastal erosion

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Outline:Outline:

1.1. IntroductionIntroduction2.2. Objectives of StudyObjectives of Study3.3. Coastal OceanographyCoastal Oceanography4.4. Wave Field AnalysisWave Field Analysis5.5. Sediment Stability AnalysisSediment Stability Analysis6.6. Engineering InterventionsEngineering Interventions7.7. ConclusionsConclusions

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OBJECTIVES OF STUDYOBJECTIVES OF STUDY

1.1.To present a methodology to To present a methodology to numerically analyze the erosion of a numerically analyze the erosion of a coastal embaymentcoastal embayment

2.2.To apply the methodology to an To apply the methodology to an actual embayment shoreactual embayment shore

3.3.To propose measures to mitigate the To propose measures to mitigate the site’s coastal erosionsite’s coastal erosion

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Project LocationProject Location

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Project Location: Project Location: BoracayBoracay IslandIsland

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Project DescriptionProject Description

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WindroseWindrose diagrams:diagrams:CuyoCuyo Station (Station (PalawanPalawan))

COASTAL OCEANOGRAPHYCOASTAL OCEANOGRAPHY

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Astronomical Tides:Astronomical Tides:((CuyoCuyo Tide Station, for ref.)Tide Station, for ref.)

-0.50

-0.25

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

19.00 20.00 21.00 22.00 23.00 24.00 25.00 26.00Heig

ht (m

abo

ve M

LLW

)

Time (Day)

Height vs Day (Jan.-Feb.)

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Water Levels:Water Levels:

-1.25-1.13Lowest Low Water LevelLLWL-0.87-0.74Low Water LevelLWL-0.67-0.55Mean Lower Low WaterMLLW-0.57-0.4Mean Low WaterMLW

00Mean Tide LevelMTL0.560.47Mean High WaterMHW0.70.58Mean Higher High WaterMHHW1.030.79High Water LevelHWL

CuyoSan Jose

ELEVATION (m)TIDE LEVEL

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Offshore Wave HindcastOffshore Wave Hindcast

2nd highest4.541.3971.80.4OctOct9-123.570.7971.80.1OctOct5-8

Not Potentially critical direction

2.230.2771.80.4JunJun--Jul, OctJul, Oct1-4WNWHighest wave5.752.28100.20.2OctOct13-16

4.871.55100.20.2OctOct9-123.790.86100.20.7JulJul--OctOct5-8 Not critical2.330.28100.23rd prevailing3.1AprApr--OctOct1-4W

3rd highest4.921.8051.20.3JuneJune13-16(Simulated)4.221.2451.24th prevailing1.6JunJun--OctOct9-12Not critical3.340.7251.2Next prevailing3.4JunJun--OctOct5-8

Not critical2.130.2551.2Prevailing Wind9.1MayMay--Nov.Nov.1-4SW

(Simulated)3.460.9222.20.4JunJun--Aug.Aug.9-122.800.5522.20.4JunJun--AugAug5-8 Not critical1.860.2122.21.2MayMay--SeptSept1-4SSW

Period (s)

Height (m)

Annual Frequency

(%)

Months exceeding

1% occurrence frequency

Wind Speed (m/s)

Direction

Note on Wave

Offshore Significant Wave

Fetch (km)

Note onWind

Wind Conditions

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Tropical Cyclones:Tropical Cyclones:

SW20TS NinaMay-31-1972

WSW27TS MamengJul-20-1980

W28TS NitangSep-02-1984

DirectionHighest Wind (mps)Cyclone NameDate

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Historical Storm:Historical Storm:

PHILIPPINES

Philippine Sea

South China Sea

Boracay Island

Track of Tropical Storm Nitang, 02-Sep-1984

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Historical Storm:Historical Storm:

Track of TS Mameng, 20-Jul-1980

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Project Area Data:Project Area Data:Digital Terrain Model (local bathymetry):Digital Terrain Model (local bathymetry):

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Offshore and Nearshore DepthsOffshore and Nearshore DepthsNorthNorth

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[ ])()(

6)(

21

2

ηγγ

η

∇⋅∇∇−⎟⎠⎞

⎜⎝⎛

∂∂⋅∇∇+−

⎟⎠⎞

⎜⎝⎛

∂∂⋅∇+∇+∇⋅+

∂∂

hght

hh

thg

tU

UUUU

)2(0=++++ UFFF εwsb

[ ] )1(0)( =+⋅∇+∂∂ ηη h

tU

Wave Model Equations:Wave Model Equations:

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Wave Model:Wave Model:

( ) )5(UF ∇⋅−∇= σs

)4(2 UF ∇−= Db f

( ) )6(2/3ηασ += hgm

)7()(2||

UU

Fη+

=h

fww

Wave breaking dissipation:Wave breaking dissipation:

Structure damping:Structure damping:

Bottom friction:Bottom friction:

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NorthNorth

WAVE FIELD ANALYSISWAVE FIELD ANALYSIS(Prevailing Waves)(Prevailing Waves)

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WAVE FIELD ANALYSISWAVE FIELD ANALYSIS(Prevailing Waves)(Prevailing Waves)

NorthNorth

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WAVE FIELD ANALYSISWAVE FIELD ANALYSISNorthNorth

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WAVE FIELD ANALYSISWAVE FIELD ANALYSIS(Prevailing Waves)(Prevailing Waves)

NorthNorth

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WAVE FIELD ANALYSIS:WAVE FIELD ANALYSIS:StormStorm--induced Waves:induced Waves:

TS Mameng (20-Jul-1980)

NorthNorth

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WAVE FIELD ANALYSIS:WAVE FIELD ANALYSIS:StormStorm--induced Waves:induced Waves: North

North

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SEDIMENT STABILITY ANALYSISSEDIMENT STABILITY ANALYSIS

)()1(

2

grcr

br dgs

udψ−

=

Residual Grain Size:Residual Grain Size:Minimum sediment grain size at the Minimum sediment grain size at the threshold of motion due to wavesthreshold of motion due to waves

ract

ract

dddd<

≥ :Unstable

:Stable

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SEDIMENT STABILITY ANALYSISSEDIMENT STABILITY ANALYSIS(Prevailing Waves)(Prevailing Waves)

North

North

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SEDIMENT STABILITY ANALYSIS:SEDIMENT STABILITY ANALYSIS:(Storm(Storm--induced)induced)

TS Mameng (20-Jul-1980)

North

North

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ENGINEERING INTERVENTIONSENGINEERING INTERVENTIONS

A.A. PEBBLE BEACHPEBBLE BEACH(Reference photo: Shimizu Coast, Shizuoka, Japan)(Reference photo: Shimizu Coast, Shizuoka, Japan)

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Engineering Interventions:Engineering Interventions:B. BREAKWATER (SurfaceB. BREAKWATER (Surface--Piercing)Piercing)

(Project site(Project site--specific)specific)

Private Cove Beach

Walkway

Rock formation

Breakwater

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Private Cove Beach

Walkway

Rock formationBreakwater

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Effectiveness of BreakwaterEffectiveness of Breakwater

NorNorthth

NorthNorth

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CONCLUSIONSCONCLUSIONS1.1. A methodology of quantitative A methodology of quantitative

analysis of coastal erosion is analysis of coastal erosion is presented. This accounts for the presented. This accounts for the wave forcing, local bathymetry, wave forcing, local bathymetry, shoreline configuration, water shoreline configuration, water levels, tropical storms, and levels, tropical storms, and sediment properties.sediment properties.

2.2. An application to a Philippine An application to a Philippine coastal embayment is discussed. coastal embayment is discussed. SiteSite--specific mitigating measures specific mitigating measures are shown.are shown.

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ACKNOWLEDGMENTACKNOWLEDGMENT::

AMH Philippines, Inc.AMH Philippines, Inc.EngrEngr. Jose Carlo Eric L. Santos. Jose Carlo Eric L. SantosEngrEngr. Jason P. . Jason P. PalacioPalacioEngrEngr. Joel A. Aguirre. Joel A. AguirreApprAppr. . EngrEngr. Jeff Carlo T. . Jeff Carlo T. OlivaOliva

VinnellVinnell--BelvoirBelvoir Corp.Corp.EngrEngr. Michael V. Gonzales. Michael V. Gonzales

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End of PresentationEnd of Presentation

THANK YOU.THANK YOU.