Luận văn thạc sỹ Kỹ thuật và Quản lý vùng ven biển: Study on inundation due to storm surge for Phu Quoc island

Observed and computed water levels for model verification Figure 13, Observed and computed water levels in verification step Figure 14.Typhoon zoning along the Vietnam coasts Figure 15.B

MINISTRY OF EDUCATION AND MINISTRY OF ARGICULTURE

TRAINING AND RURAL DEVELOPMENT

THUY LOI UNIVERSITY

VU VAN LAN

STUDY ON INUNDATION DUE TO

STORM SURGE FOR PHU QUOC ISLANDS

THESIS OF MASTER DEGREE

MINISTRY OF EDUCATION AND MINISTRY OFARGICULTUREÍ

‘TRAINING AND RURAL DEVELOPMENT

‘THUY LOI UNIVERSITY

hereby certify the work which is being presented inthis thesis entitled, “Study on stormsurge due to inundated for Phu Quoc island” in partial fulfillment of the requirement forthe award of the Master of Coastal Engineering Management, isan authentic record of

my own work cartied out under supervision of Ass Prof PRD Vu Minh Cat The matter

‘embodied inthis thesis has not been submitted by me for the award of any other degree

or diploma

Date: May 30, 2016

Vu Van Lan

1 would like to thank faculty of Marine and Coastal Engineering of Thuy Loi Universityand Faculty Marine Science & Island, Ha Noi University for Natural Resources andEnvironment for enabling me thesis before the deadline.

Finally, I would like to express my special appreciation to my friends and colleagues fortheir support, encourage and advices The deepest thanks are expressed to my familymember for their unconditional loves

TABLE OF CONTENSLIST OF FIGURES

LIST OF TABLES

INTRODUCTION

1 The necessity of the study

2 Objectives

3 Objects and scope of the study

4, Study approaches and methodology

5 Structure of the thesis

CHAPTER 1: OVERVIEWS ON STORM SURGE STUDY AND STUDY AREA

11, Literature reviews

1.1.1, International researches on storm surges

1.1.2 Storm surge researches in Viet Nam

1.2 Brief description on study area

1.2.1.Natural eonditior

1.2.2 Climatic and oceanographic characteristics

1.2.3, Hydrological and oceanographic characteristics,

1.2.4, Social and economic features

CHAPTER 2: APPLICATION OF DELFT3D TO STUDY STORM SURGE

2.1, Data used for he simulation

2.1.1 Statistical typhoon data

161620212124252ï

29

2929363636364350s0sĩ

2.34, Other parameters 52.4, Model calibration 33CHAPTER 3: SIMULATION OF STORM SURGE IN PHU QUOC ISLANDS 593.1 Typhoon zoning along the coastlines of Viet Nam 593.2, Generation of typhoon scenarios for Phu Quoc areas ¬3.3, Extraction of water level around Phu Quoc islands 6.3.3, Simulated results 63.3.1 Scenario 1: Simulation of typhoon namely Linda (later is called Lindatyphoon) that approached to the study area in November, 1997 63.3.2 Scenario 2: Scenario 1 in case of the typhoon Linda coming at the sametime of flood tide at the study area, 663.3.3, Scenario 3: Simulation of typhoons according scenarios approved by

Ministry of Natural Resources and Environment (MoNRE), but wind velocitychanges with the time V= f0 69

CHAPTER IV: BUILDING INUNDATED MAPS CAUSED BY STORM SURGE

FOR PHU QUOC ISLANDS 724.1 Introduction on application of GIS n4.2 Application of ArcGIS software to build up inundated map, 144.2.1 Topographic data 754.2.2 Hydrologie data n4.3, Building up inundation maps 784.3.1 The inundation map of scenario Ì T84.3.1 The inundation map of scenario 2 824.3.2 Inundation of Phu Quoe island according scenario 03 85CONCLUSION AND RECOMMENDATION 89Conclusion 89Recommendation 90

References 92

LIST OF FIGURESFigure 1 Flowchart to illustrate the study approach 12

1D model with experimental data of Bowen (1986)

Figure 3 Location of Phu Quoe islands on satellite image

Figure 4 Statistical storm paths approaching to Viet Nam coasts

Figure 5 Grid calculated in the study area

Figure 6:Topography in Phu Quoc area

Figure 7.The model grid and boundaries

Figure 8 Phu Quoc oceanographic station

Figure 9 Observed and computed water level at Phu Quoc (C=55)

Figure 10, Observed and computed water level at Phu Quoc (C=60)

Figure 11 Observed and computed water level at Phu Quoc (C=65)

Figure 12 Observed and computed water levels for model verification

Figure 13, Observed and computed water levels in verification step

Figure 14.Typhoon zoning along the Vietnam coasts

Figure 15.Basie characteristics and storm risk in Viet Nam Coasts

Figure 16, Extracted points of simulated water level

Figure 17.The track of Linda typhoon in the study area

Figure 18, Water level field around Phu Quoc islands in seenario |

Figure 19, Storm surge at 8 points around islands in scenario 1

Figure 20-Tidal series at Phu Quoc during Linda typhoon

Figure 21 Storm surge at 8 points around islands in scenario 2

Figure 22 Storm surge at 8 points around islands in scenario 3

Figure 23.Topographie data layer of Phu Quoc island

Figure 24 Vegetation cover layer on the Phu Quoc island

Figure 25,Cadastral data layer of Phu Quoc island

Figure 26 Hydrological data layer around Phu Quoc island

Figure 27.Simulated water level and topography in coast of Duong Dong and HamNinh

Figure 28 Inundated mapping Phu Quoc with seenario 1

55

36

78

80

Figure 29 Inundation maps of the Cua Duong, Duong Dong, Duong To communes 81Figure 30 Inundation mapping at the Ham Ninh commune seFigure 31, Inundated map in scenario 2 saFigure 32 Inundated mapping of Duong To, Cua Duong and Duong Đông communes,

_

Figure 33 Inundated mapping of Duong To, Cua Duong and Duong Đông communes

¬Figure 34.Spatial disribution of flooded areas in the Phu Quoc island in scenario 3 86Figure 35, Inundated mapping of Duong Dong and Cua Duong commune 87Figure 36 Inundated mapping of Ham Ninh commune 87Figure 37 Inundated mapping of Dương To commune 88

LIST OF TABLES

Table 1 Coordinate of Phu Quoc area shown in map scale of 50/0)

Table 2 Monthly and yearly average temperature in Phu Quoe and Rach Gia

Table 3 Monthly and yearly average and minimum humidity (%) at Phu Quoc

‘Table 4.Monthly and yearly average and minimum humidity (%6) at Phu Quoe

Table 5 Monthly wind velocity and main direction at Phu Quốc

‘Table 6.The statistical result of wave height and its period at Phu Quoc

‘Table 7.Water level at Phu Quoc (103958 E ~ 1013 N) station (1990-2008)

Table 8 Stat ics on typhoon hitting to Phu Quoc and surrounding areas

Table 9 Characteristics of typical typhoons approaching to the southern coasts

Table 10.Tidal constituents at 3 boundaries

‘Table 11.Coefficient RMSE

‘Table 12.The locations where water level is extracted

Table 13.Linda typhoon’s parameters

‘Table 14.Highest storm surge and appearance time at the extracted points

‘Table 15.Adjustment of Linda typhoon time to fit to spring tide

Table 16.Highest water level and appearance time at 8 points in scenario 2

Table 17 Typhoon parameters used to simulate in scenario 3

‘Table 18, Highest water level and appearance time at 8 points in seenario 3

Table 19 The maximum storm surge at the point around Phu Quoc islands

‘Table 20,Clasification of inundated depth

‘Table 21 Flooded area for Phu Quoc island in scenario 1

‘Table 22 Flooded area for Phu Quoc island in scenario 2

‘Table 23 Flooded area of Phu Quoe island in scenario 3

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81

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In recent years due to the impact of global climate change, natural disasters becomemore complex, especially storms, accompanied by rising sea levels caused flooding ofcoastal estuaries The sea level rise due to storm caused flooding of coastal areas andbreak dike, especially storm occur during high tides So the study, calculated andforecasting extreme storm surge in coastal area and flooding risk due to storm arepositive tasks to find appropriate solutions for prevention and reduction of damages incoastal areas The components cause extreme water level during storm including tides,storm surge, and wave surge, in which the storm surge is an important one.

‘Storm surge is a dangerous natural phenomenon which causes lost lives, destruction ofsocio-economic infrastructures and valuable resources when typhoon attacking tocoastal areas Worldwide, storm surge has caused major damages such as the typhoon

in 1970 and 1990 with water surge more than 7 m, generated large wave, inundated todelta of Bangladesh and over 400,000 people were killed On the Caribbean, highestwater surge of typhoon Flora is 8 meter, it had cause flood and over 5000 people werekilled, Coastal of the United States had been affected by historic storm surge of up to7.4 m The countries on the Northern coasts of Europe had been affected serious of stormsurge in 1916, 1953, 1962, 1976, in which the storm occurred in 1953 in Netherlandcaused large inundation and over 1400 people killed

‘Storm surges may be defined as high sea water level above mean sea level which iscaused by strong winds and low atmospheric pressures of a storm, Winds which blowtowards land exert a shearing stress on the surface, causes an increase in the sea waterlevel near the coastlines Low atmospheric pressure also produces high elevation due tothe so-called inverted barometer effect The highest surges have generated by strongtropical cyclones The surge belongs to the same class of phenomena as tide waves andtsunamis, Its horizontal scale depends on the parameters of the storm In general thestorm surge oceurs in duration of several hours, but it ean sometimes last fora few daysItis obvious that prediction of surges is a very urgent issue to be addressed, especially

atempts to develop methods for forecasting storm surges in Vietnam, At present, allkinds of activities are inereased in number and almost marine constructions need sealevel data for designing, Sometimes they need the values of sea level rise which happen

at rare frequencies, while the observed stations located along coasts and islands arescarce That’s why in this study numerical models are used to simulate storm surge basedcon the data of bathymetry, figure of coastlines, climate characteristics of typhoons and

‘oceanic data at sea and coastal stations

2 Objectives

‘The general objective of the present work, therefore, is to develop a method based onhydrodynamic models to determine maximum surface water elevation generated bytyphoons The computed results of model produce an atlas of pre-computed surges and4a collection of several possible typhoon conditions from many potential surges It isstraightforward to determine the highest possible surge at all vulnerable coastal locationsfrom a particular family of tracks and simulated storm surges as input data forpreparation of potential map of inundation in Phu Quoc island

3 Objects and scope of the study

+ Objects of the study: The extreme water level during storm at the shorelines andpotential inundation caused by storm surge

+ Scope of the study: Phu Quoc islands and surrounding areas

4 Study approaches and methodology

‘The simulation of storm surge and land inundation by using Delft3d is shown in figure

1, of which the following steps are conducted

‘Step 2: Set up computational model

It includes computation network, meshes, defined boundaries such as tide series, seabedtopography and typhoon information including central typhoon pressure, typhoon

rs thal are fitdata, the calibration and verification are conducted to find model paramet

between simulated and real observed data both for hydrodynamic as well as typhoonmodels

‘Step 3: Create scenarios for simulation of storm surg n the study area

‘The scenarios proposed for study of storm surge are based on the real typhoon whichhad been occurred in the past and potential typhoon that can occur under the climate

‘change conditions These are presented in detail in chapter 3

‘Step 4: Simulation of storm surge around the study area according to scenarios proposed

in step 3

Results of this step are resultant water level fields (including tide plus storm surge) atthe study areas The real storm surge can be taken by subtracting total water level andastronomical tide at the same time The computation of resultant water level, potentialland inundation around the island at many points is taken for each scenario

Step 5: Inundated mapping for each scenario

By overlapping simulated water level map on to topographical map with the support ofGIS software, the potential inundated map can be produced for each scenario,

‘Step 6: Conclusions and recommendations

In this content, author will summary the results conducted in the research and also

propose the future works that should be continued to serve socio-economic development

in Phu Quoc islands

5 Structure of the thesis

Besides the introduction, conclusion, recommendation and annexes, the study isconsisted 4 chapters as following:

Chapter 1: Overviews on storm surge study and study area

Chapter 2: Application of Delfi 3D to study storm surge

‘Chapter 3: Simulation of storm surge in Phu Quoc islands,

Chapter 4: Building inundated maps caused by storm surge

CHAPTER 1: OVERVIEWS ON STORM SURGE STUDY AND STUDY AREA

Storm surges may be defined as high sea water level caused by strong winds and lowatmospheric pressures at the center of a storm Winds which blow towards land exert ashear stress on the surface, causing an inerease in the sea surface elevation near thecoastline Low atmospheric pressure also produces high elevation due to the so-calledinverted barometer effect The highest surges are generated by strong tropical yelonesand itis considered the same category of phenomena as tide waves and tsunamis Itshorizontal scale depends on the parameters ofthe storm In general, the storm surge can

‘occurs in the duration of several hours, but it can sometimes last for a few days It is

‘obvious that prediction of surges is a very urgent issue to be addressed, especially incoastal regions which are affected by tropical cyclones,

‘There have also been many attempts to develop methods for forecasting storm surges inVietnam, At present, on the coastal areas, all kinds of activites are inereased in numberand almost marine structures need sea level data for designing Sometimes they need thevalues of sea level rise which happen at rare frequencies, while the sea level stationslocated along coasts and islands are scarce, That's why we need to find another way todefine the maximum values of sea level rise that can happen in the chosen areas The

Way mentioned here is numerical model that is used to simulate sea level ce with thedata of bathymetry, coastal topography and climate characteristics of typhoons, tide and

Wave conditions occurred at the chosen places

‘Worldwide, storm surge has caused serious damages in the coastal areas For examplethe typhoons attacked the Bangladesh in 1970 and 1990 created a storm surge of morethan 7 m, generating high waves, and inundated large area of Bangladesh delta and morethan 400,000 people were killed in these events On the Caribbean Sea, the highest watersurge of typhoon Flora was 8 m causing serious flood and over 5,000 dead peoplesCoastlines of the United States had been affected by big storm with storm surge up to7-4 meters The countries on the Northern coasts of Europe had also been affected byserious storm surge in 1916, 1953, 1962, 1976 in which the typhoon in 1953 hitting the

coastlines of Netherlands caused sea dike breaches, resulting large inundation and over

1400 dead people

Storm surge is very dangerous natural phenomenon which causes to destroy valuableproperties, lost lives and all socio-economic infrastructures when typhoons attack tocoastal areas, Friction of wind on water surface and decreasing pressure at typhoon

‘center are main reasons to create high storm surge The bathymetry and parameters oftyphoon including center typhoon pressure, maximum wind radius, wind velocity, stormtrack, river flow, and tidal regime are factors which affected to storm surge That's whythe problem is very urgent and important to study

‘There have also been many attempts to develop methods for forecasting storm surges inVietnam, At present on the coastal areas, all kinds of activities are increased in numberand almost marine construct s need data for designing in which sea water level is veryimportant because it happens at rare frequencies, meanwhile the observed stationslocated along coasts and islands are scarce Thats reasons why we need to find otherways to define maximum values of sea level rise occurred in a certain are The way

‘mentioned here is an application of numerical models for simulation For doing this data

of bathymetry, coastal topography, hydrodynamic parameter such as tide, waves, sea

‘currents and typhoon characteristics in the interested areas are needed

According to Le Van Thao et al (2000), storms occur in Viet Nam unevenly The mostaffected areas are the northern and the central coasts The southern coastis less affectedboth in number and intensity, but damages was more serious because less awareness onthe typhoons of local people Typhoon Linda in November 1997 was an example and

‘considered as a very uncommonly strong storm in the past 100 years to the southerncoasts area, There was about 778 people killed, 1142 and 2541 injured and missing,

2789 boats sank etc The total economic loss was estimated about 480 million USD (Le

Van Thao et al, 2000)

Phu Quoc and Tho Chu islands belonging to Kien Giang province are located in the

‘westem sea of Thailand gulf They are considered as strategic locations in economic development as well as defense and security in the south of Viet Nam due to

socio-there terrain and resources For sustainably economic development and environmentalprotection, the study all on natural disasters, specially typhoon and storm surges is apriority tasks For which we can assess the flood inundation and damages duc to typhoonand storm surges to serve marine spatial planning as well as to make strategy formitigation of natural disasters for Phu Quoc islands.

1.1 Literature reviews

1.1.1 International researches on storm surges

Because of the direness of the storm surge disaster, the studies of theory and scene fromwhich construct methods, technological modeling to calculate and forecast storm surge,which have been conducted for so long According to Brestschneider (1959), differentfactors can cause change of the water level in coastal areas during a hurricane are: theparameter of storm (atmospheric pressure, wind speed ), the rotary motion of the earth,

‘wave, and rain, Later, Pore (1965) has added factors: tide, shape ofshoreline and waterdepth

Currently there are several methods of calculation and forecast storm surge such as

‘method uses semi-empirical formula, diagram method, artificial neural systems methodand numerical model methods

In the method using semi-empirical formula (Ippen and Hallerman, 1966), surgemagnitude is calculated based on ground level wind speed, wind fetch length, the anglebetween the wind direction and the axis perpendicular to the shoreline and the waterdepth This method is very simple but precision is not high because it does not describeall the factors which impact on storm surges

Diagram method (Yang et al, 1970, Horikawa, 1985) is often used to forecast stormsurges for some ports, where have many monitoring data on hurricanes and storm surges

‘The content of the method is to construct the monogram based on the relationship

‘between monitoring data of water level with parameters of hurricane storm (the largest

‘wind speed, wind direction, reduce of pres ssure in the center) Therefore, the method isvery limited when data series is not long enough (usually around 100 years if requireresult is high precision) and often only true for the nearest observation station

Numerical models method was created to overcome the deficiencies of empiricalmeasurement data The advantage of this method is reduction of cost compared with

‘experimental measurement methods In addition, this method also allows calculation,forecast the evolution of the phenomenon based on a lot of assumed scenarios, whichdoes is not yet exist in reality present but likely to happen in the future.

In studies by numerical models, storm surge phenomenon is modeled based on theshallow water equations (2 or 3 dimensions) Depending on the purpose, in forecastabout storm surges, 2-dimensional model does not take much time to calculate but it canachieve full accuracy When the need for simulation and calculations in more detail, egdistribution according to the flow rate of the water layer, 3-D model is needed, Withmore detail simulation and calculations, such distribution flow rate under water layers

is revealed in 3-dimensional model At the beginning, the numerical models were built

to simulate storm surge, which are limited by several reasons: (1) Usually onlysimulation, calculation of individual phenomena such as tide, wave, storm surges: (2)

‘The grid is very course, which docs not cover about the detailed topography of coastalarea; (3) In addition, many effects that affect to storm surges in the equations system isignored, Therefore, accuracy of the results of the model varies among areas orsimulation is very good for a storm but limited with other storms, For example,Jelesnianski's model (1965), which has ignoted friction component and nonlinear

‘component, so calculated results were reasonable in spatial distribution of water rise andthe time storm surges is the highest, however tends to overestimate the water height insome 1 SPLASH model (Special Program to List Amplitude of Surge from Huricanes)

\vas built in 1972 by Jelesnianski and then SLOSH model (Sea, Lake, and Overlandsurges from Hurricanes) was developed to simulate the storm surge in coastal areas, seaand lake, which NOAA (National Oceanic and Atmospheric Administration) used tosimulate coastal flooding caused by storm surge in the United States (Jelesnianski et al,

1984, 1992) but there are many restrictions such as the use a grid with fixed structure,

‘which cannot simulate the coastal areas with complex topography and shoreline

‘The Concept of storm surge in the previous calculations usually understood as the waterlevel rises due to the impact of the wind stress and reduction of pressure in center of the

storm, Howe + in fact wave stress generated surge wave, which occupies a verysignificant part of the storm in the shallow waters Therefore, recently wave setup hasbeen inter ‘fed and considered as an important part in the warning news, fore

countri like the US, Japan, UK Due to the complexity of the wave setup phenomenon,calculation has just followed by the analytic formula Longuet- Higgins and Stewart

(1963)

‘This study has shown that the magnitude of wave set up depends on the horizontalgradient variation of wave radiation stresses, Longuet-Higgins and Stewart’s theory hasexplained the mechanism of phenomenon of rising water and ebb water around breakwater area in shallow water zones, Longtuet-Higgins and Stewart's theory proved quitesuitable, when verified with experimental data of Bowen etal (1968) about phenomenon

of rising water and ebb water in points around break water area, Bowen et a'sexperiments (1968) on the phenomenon of wave surges and ebb water, which are caused

by waves have been used to verify numerical models, which simulate the phenomenon

‘of wave propagation in coastal zones as shown in figure 2

— Dinh sóng Bung séng —— Marc nước biển trung bình

Chen et al (2008) in 2005 Hurricane Katrina in the US, which concluded that stormsurge by affection of coastal wave contribute 80% in extreme water levels while otherinfluen such as tide, surface wave and rising water by wind contributed only 204.

In 2010, You! Kim Soo et al have developed model to predict storm surges, whichintegrated tide both waves (Surge Wave and Tide - Suwat) This model was designedwith integrated mesh to calculate storm surges in the Tosa Gulf - Japan and the resultsare consistent with the measured data, while previ sly many models not interestedWave setup give lower results Youl Kim Soo's research also shows that to study wavesetup need to perform on the calculated grid which has detailed resolution After YoulKim Soo model has been used to forecast storm surges in many ports in Japan

In recent years, due to the development of systems of monitoring and transmit waterlevel data in real time, data assimilation techniques of water level in tidal forecast model,from that storm surges has been built and development (Lewis and Derber, 1985;

‘Thacker and Long, 1988),

To accurately predicting storm surge depends on accurately predicting the field ofpressure and wind in storms However, if the water level monitoring data is regularlyupdated in the forecast calculations, the error will be decrease significant WhenLionello P (1996) used data assimilation techniques in water level forecasting modelsshowed that the storm surge forecasting results in report in Atlantic Beach has reducederrors up to 50% for forecast from I to 3 day

Assess the risks of hurr Iso follow the traditional approach ofanes and storm surges

a wsters is based on statistical methods In developedsing risk method of natural dicountries like the US, Canada, Australia, the European Community (England, Poland,Croatia, Italy, Netherlands, Spain), Asia (Japan, South Korea, the East Asian countries(SY Wang et al, 2007), there have many research programs to develop response methodscarly, To calculate the possibilities of disaster ts Monte-carlo (PPMC) method is usedalot in disaster applications: storms, storm surges, waves and waves in storms, floods,landslides, earthquakes Specifically with surges in Australia, scientists have simulatedstorm for 3,000,000 years from data of historical hurricanes in 30 years, the US used

storm simulated data from 2,000 y from data of historical hurricanes in 100 years,which is used as input of the storm surge model, from that construct frequency line ofstorm surge with period from 2-100 years and distributed risk map of large wave,1.1.2 Storm surge researches in Viet Nam

Vietnam is a coastal country with high potential risk of storm surges That's why thestudy storm surges is paid much attention long time ago with many methods from

‘experiences to mathematical models,

According to stati ial researches, the frst study of Vu Nhu Hoan (1988) was presented,

in which storm surges are estimated according to statistical methods and charsRecently, Hoang Trung Thanh (2010) used observed data of water levels in the

‘oceanographic and estuary stations t0 assess water surge generated by wind and thus

‘gave overview about time and rise and set down trends at the monitoring stations.Although there the advantage of being simple and easy to use but limited the application

‘of statistical methods Because of very sparsely observed stations, the accuracy of thismethod is not so high ‘Therefore this method is only suitable in some monitoringstations where data series are long enough and with thi son it is rarely used inVietnam,

In research methods using numerical models, there are three main directions being used,

‘These are included self-built models, research and development of open source modelsfrom abroad; and using commerce models from abroad These information can be seen

in the researches of Vu Nhu Hoan, Do Ngoc Quynh, Le Trong Dao, Bui Xuan Thong,Dinh Van Manh, yen Thi Viet Lien, Nguyen Vu Thang and Nguyen Xuan Hien

When arching storm surges in coastal areas of Tokin Gulf, Le Trong Dao (1998)have used finite element method to calculate tide and storm surges and had conclusionthat due to large tidal difference up to 4.0 m, so storm surge was more impacted by tidalregimes Also by using this method, Nguyen Vu Thang (1999) got result about

prediction storm surges at Hai Phong coast using finite element methods,

Also by using finite element method, in the governmental projects namely KT.03.03,

equations to calculate the tide and storm surges for all Vietnam coastal areas.Accordingly, the current situation and the risk of storm surges was calculated andpartitioned by latitude The served for dissults of the study hav: ister prevention andbuild coastal constructions Also according to the finite difference method, Bui Xuan

‘Thong (2000) has developed cage mesh to increase the details the points need calculated

as well as reducing the time to calculate when the calculate storms surges In 2001, themodel predicted storm surge had calculate to tidal and design on the cage mesh by theInstitute of Mechanics have been applied on calculated the storm surge with detailedresolution to 1.0 km serving the coastal constructions such as dikes, jeties, after that,this model has been applied in many subjects different projects related to storm surge

in Vietnam Author Phung Dang Hieu (2013) have built mod Is that predict storm surgesthat taking into account the influence of the tide on the system nonlinear shallow water

‘equations and according different method of SMAC combined with schemetic CIP the

ae tertiary accuracy for nonlinear components, The model was applied to simulatesurges and flooding coastal areas of Thua Thien Hue very reliable results when

‘compared with observation data

ent years, due to the development of computational systems and informationtechnologies have had many foreign models are built and developed towardscommercialization as well as shape open source to community develop The popular

|| model is being applied in Vietnam as models MIKE Danish HydraulicInstitute (DHI), SMS model of the US Navy, the Delft-3D model of the HydraulicInstitute Delft In the thesis had used Delft 3D- Flow simulation about storm surge inPhu Quoc Island,

1.2 Brief description on study area

112 km and 45 km accordingly Administratively, Phu Quoc district consists of Phu(Quoc island and 2 other smaller islands namely An Thoi and Tho Chu with total area of

593.05 km* in which Tho Chu archipelago is farthest from the main land (about 115km)

(beh Sa eae seed 2 HMNG

Figure 3 Location of Phu Quoc islands on satellite imageThe shape of Phu Quoc island is nearly triangular, base side in the north, narrow

‘gradually to the south (Figure 1.3) The research site would be covered Phu Quoc waterarea of 220 km2, from the coastline of island to the water depth up to 20 m, The studyarea is defined by the points from AI to A26 with coordinates (National CoordinateSystem VN 2000) showed in table 1

Table 1 Coordinate of Phu Quoc area shown in map sale of 1/ 50.000

Northern astern Northern Eastern

Point Point latitude longiude latitude longitude

AI | 103°595455" |9562354" [and [103°594759° | 10°28" 696"

A2 Ì103°894378" |9°59 60 ais [104° 02'092" | 10°26 965AZ| 103°5831.95" 110032162" [Ate | 104" oF 887" | 10" 2456.19"

‘The typical topography of Phu Quoc island is low hill The coastline is zigzag, divided

by various channels and rocky mountain, The sea bed bathymetry of Phu Quoc is clearlydistinguished into 2 levels of depths:

+ From 0 — 8 m: generally even and flat, At the southern site, bathymetry is morecomplicated with unstable slope, submerged dunes and deep channels due to the impacts

Of submarine canyons The estuarine topography is consisted of submerged dunes, barbetween channels and varies with seasons due to river-sea dynamic interaction,

++ From 8 -20 m: the bathymetry is deeper from the shorelines to the offshore It is theboundary of modern sediment deposition area and existing kinds of shorelines: This kind

of shoreline was observed in every original rock before Quaternary era in Phu Quocisland and other islands, composition is mostly high stable continental sedimentation,

1.2.2 Climatic and oceanographic characteridies

In general, Phu Quoe area is belonging to tropical monsoon climate with dry and rainyseasons annually Main climatic characteristics computed based on data collected during1992-2003 in the islands are shown as below

‘Temperature: monthly air temperature is presented in table 2 For that annual average

‘temperature is 27.40C; hottest in May (28.70C) and coldest in January (26.10C).

‘Table 2 Monthly and yearly average temperature in Phu Quoc and Rach Gia (°C)

Humidity: varying from 74 87 %, annual average humidi is 81% and minimum value

is les than 50% in dry season and around 60% in rainy season

‘Table 3.Monthly and yearly average and minimum humility (5) at Phu QuoeParameter|1 [2 |3 [4 [8 [6 [7 [8 [5 [1 |i [12 [YearMeanvalve [77 |7? [77 [80% (8 [86 86 [87 [RH 79 [7 [mI

Min value [40 |36 [39 [43 46 60 [61 [65 [60 |50 [44 |39 [36

Precipitation: Yearly rainfall at Phu Quoc is 2983 mm The rainy season starts fromMay to October with about 130 rainy days and total rainfall of 2397 mm, approximately80%, The dry season lasts from November to April next year with total rainfall of only20%, Maximum rainfall is in August and minimum value is in February/anuary Daily

‘maximum rainfall is also in August with value of about 330mm

‘Table 4.Monthly and yearly average and minimum humidity (%) at Phu QuocParameer|1 |2 [3 [4 j5 j6 |7 |8 |9 |w [m |iMonhiy

Wa) |467|386| 651 | 1793 3803 7 | 4114| 40A9 | 4478| 3840| 1956 | 764

ves) 20 [20]21 [21 a3 [a9 [ao [ae [as fio (22 |27

Diresion [E |E BSE [BSW |WBW|W |wisw|W |W |ENW |BNE|ENE

Storms: In general Thailand gulf including Kien Giang province has less storm vents in

‘comparison to East sea and northern part of Viet Nam coasts As statistics in recent 60

‘years (1955-2015), there were fewer than 40 storms hitting to these areas in which therewere only 8 storms attacked Kien Giang coast Storm season usually occurs in lastmonths of a year Despite of less storm, but damages cause by these typhoons were veryserious due to less awareness of local people The Linda storm occurred in 1997 was

‘one example

1.2.3, Hydrological and oceanographic characteristies

aa River system: due to being formed on the small catchment areas, geomorphology andclimate conditior so river system in the Phu Quoc islands is less developed and mostlysmall with very short in length and steeping and later we call springs The flow in thesesprings only exist in rainy season with very small discharge The main springs areDuong Dong, Cua Can, Rach Tram, Cua Lap and Ham Ninh

Duong Dong spring: Its the biggest channel in Phu Quoe originated from the center of

‘4 main island and flowing to the sea in the west coast at Duong Dong estuary This isthe biggest socio ~ economic and tourism center of Phu Quoc In environmental point

of view, the waste water due to all activities is discharged through this channel to causepollution seriously for the coastal and estuarine area of Duong Dong town,

‘Cua Can spring: Itis the s ond rank channel of Phu Quoc island, flowing from the East

to West at Cua Can estuary where saline water is intruded deeply to the land due to verysmall fresh water from upstream, Cua Can is also @ fishing port and very importanteconomic centre of Phu Quoc District

Rach Tram is a third rank channel located at the northern part of the main island, butvery small in size and short in Iength and covered by vegetation, Fresh water exists only

in upper part in rainy season The mouth of Rach Tram is salted by sea water Thedensity of population at this estuary is too high,

Ham Ninh is a spring formed in Ham Ninh island Is also very small channel developed

in west to east direction, The population in this location is high with main activities oftourism and aquaculture

bb, Waye climate; According to long-term meteorological data, Phu Quoc is belonging

to monsoon zone with northeast monsoon from November to April and southwestmonsoon from May to October

Based on observed data of wave and analyzed, it shows that about 40% of wave are

SW-`W; 30% of NE and E directions; 20% of other directions and 10% of calm wave

‘Table 6:The statistical result of wave height and its period at Phu Quoc

Frequency | — XI-I rey V.VH [ VM-X Yearly

(| Hom | Tế) | Mm) | T6) | Hom | 9) | Hem | T@) | Him) | T63)

50 | 02 | 22) 02 | 33 | 05 | as | 04 | 32 033 | 292% | 03 | 24 03 | 25 | 08 | 44 | 07 | 4i | os | 32

os | 32 | 05 | 33 | L2 | 52 | LÍ | so | 083 | đã

1 | 92 |35 | 06 | 36 | l5 57 | 13 | 54 103] 36

¢ Tidal regime

‘The tidal regime in Thai Land Gulf is considered as mixed irregular tide with duration

of ebb and flood tide is approximately the same (11.3-12.0 hours) Tide periods is 24.3hours, Tidal range is approximately 1.2m The highest astronomical tide is appearedfrom September to November and lowest astronomical tide is in April to June,

Table 7.Water level at Phu Quoc (103958 E — 10°13 N) station (1990-2008)

‘Water level (em)Parameter

1[Jm|m|w|v [vi valvmlix| x | xu | xu | year

1.2.4, Social and economic features

Population: As statistical data in 2006, the population at Phu Quoc district was 86.908

people, equivalent to density of 147 people per km” The rate of population growth in

the district is about 15% in 2005 due to the migration from different inland provinces tothis island The distribution of people is uneven and mostly concentrated at the western

‘coasts at Duong Dong and An Thoi towns where the land is of 20.8%, but the population

‘of over 65% in comparison to the entte island

Statistically data on socio-economic in Phu Quoe district is as flowing

+ Urban population: 49,000 people

+ Under aged people: 50.102 people of about 54% of the population

+ Labor in industries: 11.934 employees, mostly working in handicraft and local andlight industries

+ Labor in the service sector: nearly 8,000 mostly in tourism field such as cateringhotels, motels

+ Over 6.000 employees working in agricultural and forestry

Phu Quoc has many favorable conditions for socio-economic development, especially

in eco-tourism With very famous sandy beaches and original forest covered mostly theisland and very sunshine and high temperature around the year, Phu Quoc becomes veryinterested place for ecotourism, Also marine resources, land resources, water resources

are great potential resources for economic development Fish-sauce and pepper arefamous products in Phu Quoc

CHAPTER 2: APPLICATION OF DELET3D TO STUDY STORM SURGE

2.1, Data used for the simulation

2.1.1 Statistical typhoon data

‘The study area is rarely affected by typhoons According to statistics, every 2to 5 years, there is one storm to attack this area Also typhoon intensity when coming to this area

is not so strong With above two conditions, local people seem to be forgotten on

typhoon They are not ready to prevent, so the typhoon is coming, it had eaused the

extremely damages both property and lives for Mekong provinces due to flood andstorm surge both in lands and islands in the areas With above reasons, the study ontyphoon and water surge is very urgent and necessary task for the areas

According to the General Statistics of Southeast Asian coasts, annually Vietnam coastsare subjected about 10 typhoons aquavelent to 33% of total number of typhoons occur

in East sea in which more than 80% hitting to northern and central coasts and only lessthan 20% going to southern coasts including Phu Quoc

‘Typhoon occuring is at the same time of rainy season, from May to October, while inthe southern coasts, it occurs during last quater of the year (October to December) Thetypical paths of typhoon approaching to Viet Nam Coasts are illustrated in figure 4

Table 8 Statistics on typhoon hitting to Phu Quoc and surrounding areas

No [Name ‘Types Time

1 JLUCY, ‘Typhoon 25 NOV-01 DEC, 1962

2 | SARAH Tropical Storm 14-17 FEB, 1965

3 | WENDY Tropical Storm 18-21 DEC, 1965

4 |RUTH ‘Tropical Storm 27-27 NOV, 1970

5 | SALLY Typhoon 30NOV-05 DEC, 1972

6 | THELMA Tropical Storm 1Á-18NOV, 1973

7 JKH Tropical Storm 18-28 DEC, 1974

8 aay ‘Super Typhoon 1-10 NOV, 1989

9 H0 “Typhoon 8⁄22 NOV, 1992

10 | 4 Tropical Storm 24-31 OCT, 1996

n | #87 Tropical Storm 29 OCT-IBNOV, 1996

12 | LINDA Typhoon 31-03 NOV, 1997

BG Tropical Storm 10-11 DEG, 1998

HỘ TẠIW “Tropical Depression ‘01-01 DEC, 1999

IS [32W Tropical Depression (09-11 DEC, 1999

16 | MUIFA Typhoon 14-26 NOV, 2004

17 | DURIAN Super Typhoon 26 NOV-05 DEC, 2006

18 | TWENTYFIVE | Tropical Depression 14-14 NOV, 2012

‘Sourees: tp fw jma go jpfmaima-engma-cente/isme-hp-pub-eg/bestiack hi

‘nup//eathernisys.convarticane!

Characteristics of typical typhoons approaching to the southern coasts including PhuQuoc islands are shown in table 9.

Table 9 Charact isties of typical typhoons approaching to the southern coasts

2006 | 11 |26 | as] 103 | 12] 1000 iia | tor | 80 | is

2006| 11 |26|18| 106 | 1405 | 1000 7 H03 | 161 | 80 | Is

2006 | 11 |26|20| 106 | 1405 | 1000 1H03 | tor | 80 | Is2006| 11 |27| 3 | 109 |1388 | 998 1393 | 232 | 30 | 206

2006| 11 [27] 9 | 108 [1377] 998 | 19 | 25% | 80 | 206

2006| 11 |27|12| 103 [war] 9% Tấ | soo | g0 | 2322006| 11 |27|18| 112 | 186 | 90 | Hồi | 39 | s0 | 258

2006| 11 |30| 6 | ass | 1235| 940 136 | sts | so | a2

2006| 11 |30|12| 135 |1224| 950 T3 | aoa | 80 | 387

206| 12 |1 | 0 | 133 | 1H99, 960 1303 | ae | ao | 3612006| 121 |6 | 136 | 119 | 95 | 1196 | 463 | S0 | 361

2006| T2 |1 |I2| 137 | se] 96 | tie | a8 | a0 | 361

2006| 12 |1 |IR| 134 |H7S| 95 TRÒ | ae | BÚ | 361

2006| 12|2|0 | 135 | HT | 95 THỦ | as | a0 | 361

2006| 12 |2 |6 | 138 [tes] 96 TH | ae | 80 | 3612006| 12 |2 [te] 139 [47 | 960 THỨ | 464 | 80 | 387

2006| T2 |3 |0 | 138 |HA9| 955 | 1140 | 464 | R0 | 387

2006| 12 |3 |6 | 1A7 |[HA2| 955 193 | 464 | 80 | 32

2006| 12 |3 |12| 135 |H27| 955 129 | 464 | wo | 387

2006| 12 |3 [isp asa | H2 | 960 THỦ | 464 | 80 | 3872006| 12|4 |0 | 126 [tie] 97 1HẠ | 412 | s0 | 35

2006| 12 |4 | 6 | 119 | tos] om 1H03 | 42 | 80 | 309

2006| 12 |4 |12| HH [ws] 9O | A07 | W7 | 80 | 309

2006| 12 | 4 | 18] 104 | 1083| 980 10M | 387 | s0 | 309

2006| 12| 5| 0| 10 |1069| 990 | 1070 | 255 | 80 | 2322006|12 [5 |I2|sS [1044 [1006 | 1030 [206 lao

2006|12 [5 [18 [83 |1033 [1008 1013 [206 | so

‘Typhoon LUCY - 1962

LAT LON DATE — | WIND(nots) | Pnimb) | Pe(mb)

65 1391 125/002 ot 1380 1002 6s 1871 11/25/06Z 6 Be 1000

67 52 | 12532 Gl 1345 1000

ca 1335 125/182 5 1326 1000 T5 H17 | 126002 al 1308 995

82 130 117261067 “ 1295 995

87 1285 126/122 $g 1283 995

92 1273 126/182 8 ti 995 9T 1261 127/002 % 1258 %0

87 1009 125/122 30 1003 1004

9s 991 125/182 30 1003 100

Hồ 100 11/26/00Z 1003 | 1001

2.1.2 Water level

‘Water level is used as boundary conditions of Delft3D model and observed water level

at Phu Quoe station which are used for calibration and verification of the model beforesimulating according to proposed scenarios

+ Water level at boundary is taken from global data sources and using one module inDelft3D to generate water level along the open sea boundaries

+ Observed water level at Phu Quoc station is used to calibration and verification themodel The: data will be elaborated later during setting up and simulation,

2.1.3 On land and seabed topography

This data was taken from the project namely KC09.16/11-15 “Marine spatial planningPhu Quoc — Con Dao served for sustainable development” with a map seale of 1/10,000

‘on land and seabed nearby the cosatal trip For deep water, seabed elevation is takenfrom DEM 90m x 90m and general map produced by Viet Nam agencies

2.2, Model description

2.2.1 Hydrodynamic Model

WL/Delft Hydraulic Institute had developed a unique, fully integrated computersoftware namely Delft3D for a multi- disciplinary approach and these software packageare used to compute for coastal, rive and estuary areas It can carry out simulation offlows sediment transports, wave, water quality, morphological developments andecology It has been designed for expert and non- experts alike The Delft3D software

is composed of several modules, grounded around a mutual interface, while beingcapable to interact with another Delft3D- Flow, which this manual is about, is one of

these modules

Deflt3D- Flow is a multi- dimensional (2D or 3D) hydrodynamic (and transport)

result from tidal and meteorological forcing on rectilinear or curvilinear, boundary fittedgrid In 3D simulation, the vertical grid is defined following the sigma co- ordinateapproach,

Storm surge is a long gravity wave with a length scale similar to the size of generatingtropical storm, and last for several hours depending on the size and speed of movement

‘This produces sustained elevation ofthe water surface above the levels caused by normalastronomical tides, however, its behavior is different in deep water and in shallow in thedeep water, far from a coast, the surface wind stress by a tropical creates a rotatingmound, or vortex, of water by diffusing momentum downward The ocean elevation issmall, approximately the hydrostatic uplift response to the low central pressure (theinverted barometer effect) and some minor long term Coriolis effect On entering theshallow water of continental shelf, dynamic effects become pronounced, conservation

‘of the potential vortices ofthe mound requires development of marker divergence Localbathymetry reflection from the coast also contribute to substantially amplify the surgehigh To calculate the extreme water level a hydrodynamic model Delft 3D- FLOW forcontinental shelf is use

Basic equation

‘The hydraulic of the continent shelf in the storm conditions is simulated by solving thesystem of two — dimensional of shallow water equation that consists two horizontal

‘momentum equation and on continuity equation

Conservation of momentum in x-direction (depth and densi

SN, OH gy yg OM gy LÊB, „8U ty

uh yy OM jut ey SE

ara Thay Sap ae Ode) pd

Conservation of momentum in y ~ direction (depth and density averaged)

‘The depth and density averaged continuity equation is given by

Atmospheric pressure gradient

PAA*2 External force by wind \°" "J depth averaged turbulent viscosity

In which:

€ cheesy coefficient 7 water level above a referent level

4 Bottom depth uy depth averaged velocity

F Coriotis parameter Po mass density of water

© Diffusion coefficient (eddy viscosity)

U absolute magnitude of total velocity, Ứ C0 +92)?

is determined by the

x — components of wind shear stress Wind shear stres

widely used quadratic expression, f=-C:”* where 2 air density; Cd wind drag

coefficient; W wind speed at 10 m above the free surface

Governing Equation

As mentioned earlier, CFD is numerical simulation of governing phenomena, It is

jons each model solves Delft3D is able to handle bothimportant to realize what equ:

Cartesian co- ordinates (4:"7) and spherical co -ordinates (4) Transform between

Cartesian and spherical co- ordinates is done with

‘orthogonal curvilinear co-ordinates Both Cartesian and spherical coordinates aresupported In their vertical direction the model offers two vertical boundary fittingsystems the model

Continuity

@

With Q representing the contributions per un wea due to the discharge or withdrawal

of water, precipitation and evaporation

0=], 4„0401P-E

es)

with

4: Source of water per unit volume

we Sink of water per unit volume

: Non-local source term of precipitation

: Non —local sink term due to evaporation