Nghiên cứu phương pháp đánh giá hiệu quả kinh tế các dự án đầu tư xây dựng công trình thủy lợi ở đồng bằng sông cửu long áp dụng cho dự án kênh phú đức thuộc huyện tam nông tỉnh đồng tháp

Declaration
I hereby certify the work which is being presented in this thesis entitled “Modeling
storm surge for the South Central Coast of Vietnam” is an authentic record of my own
work carried out under supervision of Dr. Vu Thi Thu Thuy and Co-supervisor Ass.
Prof. PhD. Nghiem Tien Lam. The master embodied in this thesis has not been
submitted by me for the award of any other degree or diploma.
Date: Aug 15, 2016
Author

Ninh Duy Quỳnh

i


Acknowledgements
I would like to express my sincere gratitude to my advisor Dr. Vu Thi Thu Thuy and
Co-supervisor A/Prof. PhD. Nghiem Tien Lam for their guidance, suggestion and
inspiration.
I would like to express my sincere thanks to Thuy Loi University, professors and
lectures at Department of Marine and Coastal Engineering of Thuy Loi University and
professors and lecturers of the Niche programmer for supporting me throughout my
study progress.
Finally, I would like to express my special appreciation to my friends and colleagues
for their support, encourage and advices. Thank you so much!

ii


CONTENTS
LIST OF FIGUES ........................................................................................................ iv
LIST OF TABLES ....................................................................................................... ix

INTRODUCTION .........................................................................................................1
1. Problem identification and the necessity of the study ........................................1
2. Literature review .................................................................................................2
2.1 International researches on storm surge ............................................................3
2.2 Past studies on storm surges in Vietnam ............................................................6
3. Research objectives.............................................................................................7
3. The scope of research .........................................................................................7
4. Approach and methodology ...............................................................................8
5. Thesis structure ..................................................................................................8
CHAPTER 1: PHYSICAL SETTINGS .......................................................................9
1.1 Geographic conditions ......................................................................................9
1.2 Topographic conditions .....................................................................................9
1.3 Climatic conditions ......................................................................................... 11
1.4 Observation stations and hydro-logic conditions ........................................... 11
1.4.1 Observation stations ...................................................................................... 11
1.4.2 Hydrologic conditions ....................................................................................13
1.5 Oceanographic conditions ..............................................................................14
1.6 Historical disasters of typhoons and storm surges ..........................................15
1.7 Conclusions .....................................................................................................18
CHAPTER 2: MODELLING OF NON-TYPHOON CONDITION ......................20
2.1 Introduction .....................................................................................................20
2.1.1 Introduction model MIKE 21 .........................................................................20
2.1.2 Module MIKE 21 Flow Model (MIKE 21 FM)..............................................21
2.2. Model setup and boundary conditions ...........................................................25
2.2.1 Analysis data and choose scope of model......................................................25
2.2.2 Building mesh model two-way .......................................................................26
2.2. Model calibration ...........................................................................................32
2.2.1 Analysis and choice of time and calibration data model ...............................32
2.2.2 The parameters and model calibration process ............................................34
2.2.3 Results of model calibration ..........................................................................34

2.2.4 Conclusion: ....................................................................................................36
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2.3 Model verification .......................................................................................... 36
2.3.1 The parameter for verification ...................................................................... 36
2.4.2 The result of verification model ..................................................................... 37
2.4 Conclusions .................................................................................................... 38
CHAPTER 3: MODELING OF STORM SURGE ................................................. 39
3.1 Introduction .................................................................................................... 39
3.2 Modeling of typhoon ...................................................................................... 40
3.2.1 Theoretical basis of establishing patterns of wind and barometric pressure in
the storm ................................................................................................................. 40
3.2.2 Wind field model in the storm ........................................................................ 40
3.2.3. Modelling of pressure in storm ..................................................................... 45
3.3 . Model setup and boundary conditions .......................................................... 46
3.3.1 Analysing data ............................................................................................... 46
3.3.2 Set of hydraulic parameters........................................................................... 52
3.4. Model calibration ........................................................................................... 53
3.4.1 Analyze and choose the time and calibration data model ............................. 53
3.4.2 Parameters and model calibration process ................................................... 53
3.4.3 Conclusion ..................................................................................................... 54
3.5 Model verification .......................................................................................... 54
3.5.1 Set up model verification ............................................................................... 54
3.5.2 The result of verification ................................................................................ 56
3.6 Conclusions ...................................................................................................... 56
CHAPTER 4: SENSITIVITY ANALYSIS MODEL................................................ 57
4.1. Role of pressure center in the storm .............................................................. 57
4.1.1 Set of hydraulic parameters........................................................................... 57
4.1.2 Results model ................................................................................................. 59

4.1.3 Results analysis ............................................................................................. 62
4.2. Role of parameters model (B) ....................................................................... 62
4.2.1. Set of hydraulic parameters.......................................................................... 62
4.2.2. Results model .............................................................................................. 63
4.2.3. Results analysis ............................................................................................ 64
4.3 Role of maximum wind speed in the storm .................................................... 64
4.3.1 Set of hydraulic parameters........................................................................... 64
4.3.2. Results analysis ............................................................................................ 66
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4.4 Role of radius maximum in the storm ............................................................66
4.4.1 Set of hydraulic parameters ...........................................................................66
4.4.2 Results model: ................................................................................................67
4.4.3 Results analysis ..............................................................................................68
4.5 Role of wind friction (Cd) ..............................................................................68
4.6 Role of trajectory of storm ..............................................................................71
4.6.1. Set of hydraulic parameters ..........................................................................71
4.6.2 Results model: ................................................................................................73
4.6.3 Results analysis ..............................................................................................75
CHAPTER 5: CONCLUSIONS AND RECOMMENDATIONS ............................76
5.1 Conclusions .....................................................................................................76
5.2 Recommendations ...........................................................................................78
REFERENCES ............................................................................................................79
APPENDIXES

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LIST OF FIGUES

Figure 1: Administrative Map of South Central Coast ................................................... 7
Figure 1. 2 Observation stations in south central coast ................................................. 12
Figure 1. 3: Cau Da station – Khanh Hoa province ...................................................... 12
Figure 1. 4: The monitoring sites of Vung Tau station ................................................. 13
Figure 1. 5: The significant wave height patterns in the East Sea ................................ 14

Figure 2 1: Introduction MIKE 21 ................................................................................ 20
Figure 2 2: Scope of model ........................................................................................... 26
Figure 2 3: Topography of study area ........................................................................... 27
Figure 2 4 Simulated area.............................................................................................. 28
Figure 2 5 Building topography data............................................................................. 29
Figure 2 6 Model boundary conditions ......................................................................... 31
Figure 2 7: Diagram of calibration process .................................................................. 32
Figure 2 8 Calibration station ........................................................................................ 33
Figure 2 9 Comparison of water level at Cau Da observation station .......................... 35
Figure 2 10 Comparison of water level at Vung Tau observation station ................... 35
Figure 2 11 Comparison diagram in Cau Da station ..................................................... 37
Figure 2 12 Comparison diagram in Vung Tau station ................................................. 37
Figure 3 1 Storm surge .................................................................................................. 41
Figure 3 2: Typhoon #21 in 2007 .................................................................................. 47
Figure 3 3: Typhoon #23 in 2009 .................................................................................. 47
Figure 3 4: Wind field model ........................................................................................ 48
Figure 3 5: Data provided for the wind field model...................................................... 49
Figure 3 6: Wind speed in the typhoon in 2007 ............................................................ 51

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Figure 3 7: Wind pressure in the typhoon in 2007 ........................................................51
Figure 3 8: Comparison diagram in Cau Da station 11/2007 ........................................53

Figure 3 10: The parameter of storm #23 in 2009. ........................................................54
Figure 3 11: Wind speed in the typhoon in 2009 ..........................................................55
Figure 3 12: Wind pressure in the typhoon in 2009 ......................................................55
Figure 3 13: Comparison diagram in Cau Da station in 2009 .......................................56

Figure 4 1 The relationship between Vmax and ΔP ......................................................58
Figure 4 2 The positions extract ....................................................................................60
Figure 4 3 Storm surge in Quy Nhon – Binh Dinh .......................................................61
Figure 4 4 Storm surge in Nha Trang – Khanh Hoa .....................................................61
Figure 4 5 Storm surge in Vung Ro – Phu Yen............................................................62
Figure 4 6 Storm surge in Quy Nhon – Binh Dinh .......................................................63
Figure 4 7 Storm surge in Nha Trang – Khanh Hoa .....................................................63
Figure 4 8 Storm surge in Vung Ro – Phu Yen.............................................................64
Figure 4 9 Storm surge in Quy Nhơn – Binh Dinh .......................................................65
Figure 4 10 Storm surge in Nha Trang – Khanh Hoa ...................................................65
Figure 4 11 Storm surge in Vung Ro – Phu Yen...........................................................65
Figure 4 12 Storm surge in Quy Nhon – Binh Dinh .....................................................67
Figure 4 13 Storm surge in Nha Trang – Khanh Hoa ...................................................67
Figure 4 14 Storm surge in Vung Ro – Phu Yen..........................................................67
Figure 4 15 Storm surge in Quy Nhon – Binh Dinh .....................................................69
Figure 4 16 Storm surge in Nha Trang – Khanh Hoa ..................................................70
Figure 4 17 Storm surge in Vung Ro – Phu Yen...........................................................70
Figure 4 18 Typhoon #23 in 2009 ................................................................................71
Figure 4 19 The storm hits Binh Dinh province ............................................................72

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Figure 4 20 The storm hits Nha Trang province .......................................................... 72
Figure 4 21 The storm hits Ninh Thuan province ......................................................... 72

Figure 4 22 Storm surge in Quy Nhon – Binh Dinh ..................................................... 73
Figure 4 23 Storm surge in Vinh Xuan Dai – Binh Dinh.............................................. 73
Figure 4 24 Storm surge in Vung Ro – Phu Yen .......................................................... 73
Figure 4 25 Storm surge in Nha Trang – Khanh Hoa ................................................... 74
Figure 4 26 Storm surge in Cam Ranh – Khanh Hoa ................................................... 74
Figure 4 27 Storm surge in Mui Padaran – Ninh Thuan: .............................................. 74

viii


LIST OF TABLES
Table 1 1 Statistics storm in Vietnam............................................................................15
Table 1 2 Statistics storm in South Central Coast province from 1951 to 2010 ..........17

Table 2 1 Model boundary conditions ...........................................................................30
Table 2 2 the parameters effect to Nam Trung Bo model .............................................31
Table 2 3 Relevance of NASH coefficient ....................................................................34
Table 2 4 Results of model calibration ..........................................................................35
Table 2 5 Results parameter of model after calibration ................................................36

Table 3 1 Wind speed according to the Beaufort wind scale ........................................44
Table 3 2 Parameters of wind field................................................................................48
Table 3 3: The data of Typhoon #21 in 2007 (grade 11) ..............................................49
Table 3 4: Set of hydraulic parameters ..........................................................................52
Table 3 5: The result of model calibration ....................................................................53
Table 3 7: The result in observation station in Storm ..................................................56

Table 4 1 The input parameters of the models ..............................................................60
Table 4 2 The coordinate of positions extract ...............................................................62

ix



INTRODUCTION
1. Problem identification and the necessity of the study
The South Central Coast of Viet Nam is characterized by a long coastline with many
rivers, estuaries , which is good condition for farming, fishing. Its geography, terrain
and natural conditions have strong influence on its geology, climate, hydrology, other
natural resources. This area often suffers a lot of natural disasters such as storms,
floods and drought.
The South Central Coast is an important region in defense and economic strategy.
Many seaports, transportation systems and railways and roads have been built in the
coastal zone to facilitate economic and cultural exchanges between South – North; and
international exchange. However, this region is one of the most vulnerable places to
natural disasters, especially floods (e.g. Large floods occurred in Central and South
Central in: 1952, 1964, 1980, 1990, 1996, 1998, 2003, 2008). In fact, there are at least
8 types of natural disasters and hazards which occur in this region such as: storms,
floods (including flash floods), droughts, landslides, cyclones, salinity intrusion and
erosion of the riverbanks, while there are five phenomena related to typhoons and
storm surges.
According to Hang et al. (2010), on average, Vietnam suffers from 5 to 7 typhoons per
year along its coastal zone. From 1951 to 2006, the activities of typhoons in South
East of Pacific Ocean tend to reduce in the number of weak and average typhoons,
while the number of strong typhoons tends to increase. In West Sea, the typhoons,
which only act in sea, tend to increase, but typhoon’s intensity tends to reduce. In
recent years, the number of typhoons directly impacting on Northern reduces and the
Southern in Vietnam increases. The number of typhoons reduces, but more super
typhoons appear, which causes great damage to people and property, such as Hurricane
Katrina hitting the United States in 2005, Cyclone Nargis hit Myanmar in 2008,

Typhoon Bopha in 2012.
Almost population living in coastal area are often attached by typhoon. When
typhoons hit coastal area, water level increases, and destroying structures and houses

1


nearby coastal zone. When typhoon combines with high tide, water level increase
more and more, and consequently even more serious. Hundreds of people dead or
missing and thousands of people affected by the storm and flood each year. Damage to
property such as lost homes, crops, damaged the social-economic works of up to tens
of billions. The South Central Coast is often threatened by coastal erosion, broken
dike, flooding or salinization caused by storms, especially in the coastal area which is
densely populated and developed economic. Tourism is very vulnerable and at very
high risk.
Therefore, the study of storm surges for South Central Coast is essential. We can
forecast flood for vulnerable areas and the impact during storm landfall. Beside, we
proposed mitigation measures natural disasters, risk of environment in the context of
climate change increasingly unpredictable and the effect of climate change will make
typhoons increased more in the future.
2. Literature review
Storm surge is an abnormal rise of water generated by a storm, over and above the
predicted astronomical tides. Storm surge should not be confused with storm tide,
which is defined as the water level rise due to the combination of storm surge and the
astronomical tide. This rise in water level can cause extreme flooding in coastal areas
particularly when storm surge coincides with normal high tide, resulting in storm tides
reaching up to 6m or more in some cases.
Storm surge is produced by water being pushed toward the shore by the force of the
winds moving cyclonically around the storm. The impact on surge of the low pressure
associated with intense storms is minimal in comparison to the water being forced

toward the shore by the wind.
The maximum potential storm surge for a particular location depends on a number of
different factors. Storm surge is a very complex phenomenon because it is sensitive to
the slightest changes in storm intensity, forward speed, size (radius of maximum
winds-RMW), angle of approach to the coast, central pressure (minimal contribution
in comparison to the wind), and the shape and characteristics of coastal features such
as bays and estuaries. The effects of storm surge very serious. For example, when
Hurricane Katrina approached the US coast in 2005, it generated a storm surge of more
2


than 8 meters in some areas. This led to widespread flooding, including almost all of
the city of New Orleans where the sea defenses couldn't cope with the water level.
More than 1800 people were killed across the US by Hurricane Katrina, many of them
by the storm surge flooding.
In Vietnam, the term "storm surge" as well as studies on the effects of it is new and
very limited. The statistics only indicate the impact of the storm, the damage and the
consequences of them leaving and the reports of the coastal provinces every years
don't analysis the main effects of the damage, therefore very limited in prevention.
2.1 International researches on storm surge
In the world, the calculation of surges and flooding due to storm surges have been
made through the mathematical model or software such as MIKE 21 Flood (Denmark),
Sobek 2D (Netherlands), Delft3D, etc… there have been many waring systems sugers
that developed in many countries in recent times as JMA Storm Surge system (Japan),
KMA Storm Surge (Korea), SLOSH (USA), STORMY (Singapore)...
Pamela Probst, Giovanni Franchello (2012) “Global storm surge forecast and
inundation modeling” specified that storm surge is an abnormal rise of water above the
normal astronomical tides, generated by strong winds and by a drop in the atmospheric
pressure. These atmospheric forcing generates long waves that can be simulated by the
shallow water equations. They used HyFlux2 model to simulate storm surge for 3

storms, iclude:
- Katrina (23-30 August 2005): This is one of the most damaging tropical cyclone
disasters in the history of the United States, Katrina formed over the Bahamas on
August 23 and and crossed southern Florida (first landfall) as amoderate Category 1
hurricane on Saffir-Simpson Scale (Appendix A), causing deaths and flooding. After
Katrina moved westward, entering in the Gulf of Mexico, and began strengthening
rapidly, reaching Category 5 on Saffir-Simpson Scale, with a maximum wind of 150
kts and a minimum of pressure of 902 mbar. After the hurricane weakened to Category
3 and on August 29 it made the second (near Buras, Louisiana) and third landfall (near
Louisiana/Mississipi border) on the northern Gulf coast. Strong winds and an elevated
pressure drop created an extreme storm surge, causing fatalities and damage. Most of
the damage had due to a secondary effect of this surge: the surge caused a rise of the
3


level of Lake Pontchartrain, straining the levee system protecting New Orleans, and on
August 30 significant failures in this system occurred, pouring water into the city
which sits mostly below sea level. After creating death and destruction in Louisiana,
Mississippi, and Alabama, Katrina moved northward into Tennessee and Kentucky and
headed northeast from there, dissipating on August 30. At least 1836 people died, the
most significant amount of deaths occurred in New Orleans, Louisiana.
The results indicate the rainfall amounts from Katrina, though rather high in some
places, were not the main impact of this storm, the main reason is due to storm surge.
The atmospheric forcing obtained is then used in HyFlux2 to simulate the inundation
area and the results show the most inundated area was Gulf of Mexico. Also the
maximum heights simulated by HyFlux2 are consistent with the observations. A
maximum height of 7.22 m is simulated in the region of Pass Christian and a value of
8.4 m has been observed in this area (Graumann et al., 2006). A complete storm surge
analysis is presented in NOAA storm surge report. The observed data shown in this
article are compared with the HyFlux2 simulations. The results of this comparison, for

the area most inundated, are presented in report.
- Nargis (27 April – 3 May 2008)
This is a strong typhoon occurred in 2008 that caused the worst natural disaster in the
recorded history of Myanmar, killing in this region more than 22’000 people according
to Tyagi et al. (2008), while 84’000 people died according to RSMC (2009).
The rainfall effect can influence also the value of maximum water height. The
maximum heights simulated by HyFlux2 are consistent with the values for the
Irrawaddy delta region, with a value of about 3.6 m for this area.
In all comparisons, the maximum heights about water level, wind,… simulated by
HyFlux2 are lower than the observed data. This could be due to the rainfall effect not
included in the hydrodynamic model. For Thetkethaung and Apoung the difference is
more than 4 m, but the value of Apount disagrees with the value provided in Lin et al.
(2010) and comparing the HyFlux2 simulation with this data, the difference is 1.34 m
and not 5.05 m. The last comparison, with the data of Mulein Station (GLOSS Tide
Gauge), shows a close agreement with the HyFlux2 simulation: a difference of only

4


0.29 m is found. Actually no more data have been found for a complete validation,
because in Myanmar few observed data are available. Nevertheless these comparisons
have shown that an additional effort must be done in order to include the rainfall effect
in HyFlux2 code.
- Yasi: Cyclone Yasi is massive tropical cyclones that caused damage to Queensland,
Australia, in 2011. It began developing as a tropical cyclone low northwest of Fiji on
January 29 and started tracking on a westward direction. The low pressure quickly
intensified to a cyclone category and was called Yasi by Fiji Meteorological Service.
Then increase its intensity and began moving west-southwestward, accelerating
towards the tropical
Queensland coast. The landfall happened on February 2 along the northeast coast of

Queensland as a Category 4 on the U.S. Saffir-Simpson scale (Appendix B) midway
between Cairns and Townsville. After landfall, it maintained a strong core with
damaging winds and heavy rain, tracking westwards across northern Queensland.
Finally it weakened to a tropical low near Mount Isa. At the time of writing there are
no verified observations of the maximum wind near the TC centre for a complete
evaluation of the wind field, only some observation of mean sea level pressure are
available, therefore actually no enough observational data are available to a complete
assessment of the results of this TC and the reports was presented a preliminary
analysis.
Jamie Rhome (2013) “Forecasting and Modelling Storm Surge” was used SLOSH
model and computerized numerical model developed by the National Weather Service
(NWS)to estimate storm surge heights(and winds) resulting from historical,
hypothetical, or predicted hurricanes to evaluation storm surges and impact for coastal
area. The author indicates the total water rise is included: surge storm, tides, waves and
freshwater flow.
Tao Shen (2009) “Development of a Storm Surge Model Using a High-Resolution
Unstructured Grid over a Large Domain” showed the storm surge and inundation
simulation results for two scenarios, Hurricane Isabel and Tropical Storm Ernesto used
Description of ELCIRC model. In this study, two separate grids have been generated.
One is the large domain grid for the storm surge prediction purpose covering the
5


Atlantic Ocean from Nova Scotia to Florida; the other is the small, limited domain grid
covering the land parts in the Hampton Roads and Virginia Beach areas for the
inundation prediction purpose and the results showed the storm surge model with a
large domain grid was able to generate reasonable water elevation results during
Hurricane Isabel using only a tidal boundary condition at the open boundary and the
high-resolution inundation model using the water elevations output from the large
domain model as the open boundary condition could generate a reasonable inundation

map.
2.2 Past studies on storm surges in Vietnam
Currently in Vietnam, there are have many research for storm surge, such as:
- Chiến Đ.Đ (2006) “Nghiên cứu tương tác sóng và nước dâng do bão bằng mơ hình số
trị” The report analyzed the interaction between the waves and storm surges based on
results calculated waves and storm surges of Xangsane storm came to on Da Nang
beach in 9/2006 by Suwat model. The report have looked at the same time interaction
between the tides, waves and storm surges, and pointed out that interaction of tides and
storm surges will be increase wave height in center of the storm.
- Chuẩn H.X et al. (2008) “ Đánh giá một số phương pháp tính tốn nước dâng do bão
ở Việt Nam” compared the advantages and disadvantages indicate the method of
calculation of storm surges such as: surveying the statistical method, empirical formula
method , theoretical method... with emphasis on methods using modern models can
calculate and forecast storms in wide range and ensure accuracy if have calibration and
verification model.
- Huy L.Q (2010) “Ứng dụng mơ hình Delft 3D tính tốn nước dâng do bão vùng biển
ven bờ Việt Nam ” use Delf3D model calculate storm surge for all of provinces, the
coastal cities in the Việt Nam, then, assessing the impact to each region.
- Hiển N.X et al. (2012) “Nghiên cứu, tính tốn nước dâng tổng cộng trong bão cho
khu vực ven biển Thành phố Hải Phòng” has analyzed storm surge for 64 typhoon in
the past. In the shoreline, storm surges in the total contribution of many factors,
including tide: surges and atmospheric pressure, wind and wave surges.

6


These results are shown to be the effective, however, the analysis was old and new
research for South Centre coastal is necessary.
3. Research objectives
The main objective of this research is to use sensitivity analysis method to assess the

parameters of storm surge modelling and simulation by MIKE model describe the
water level under no storm and storm condition, thereby making the prediction,
warning of flooding to the coastal region, preventing and mitigating natural disasters
caused by hurricanes, especially for relocation, evacuation of communities coastal
areas in case of danger.
3. The scope of research
The study area includes the coastal provinces from Phu Yen province to Binh Thuan
province, which is located in economic zones: South Central Coastal, Southeast and
Southwest with an area of approximately 35.837 km2, population of about 12.655
million people.

Figure 1: Administrative Map of South Central Coast
7


4. Approach and methodology
The objectives of this study can be achieved by using the numerical modelling
approach with following steps:
a. Collecting related data:
+ Natural conditions, socio-economic.
+ Topographic data.
+ Bathymetric data.
+ Water level.
+ Storm parameter: wind speed, wind direction, atmospheric pressure and
typhoon tracks.
b. Setting up a 2D hydrodynamic model to simulate water level under normal
condition. The model will be calibrated and validated under non-typhoon conditions
using observed water level.
c. Setting up a 2D hydrodynamic model to simulate storm surge. The model will be
calibrated and validated under typhoon conditions using observed water level.

d. Comparing the results from the model under storms and no storm condition.
e. Sensitivity analysis model.
5. Thesis structure
The study has 5 main chapters as following:
Chapter 1: Physical settings.
Chapter 2: Modelling of non-typhoon condition.
Chapter 3: Modelling of storm surge.
Chapter 4: Sensitivity analysis model.
Chapter 5: Conclusions and recommendations.

8


CHAPTER 1: PHYSICAL SETTINGS

1.1 Geographic conditions
The study area is located in favourable geographical location. It’s near Ho Chi Minh
City and South East key economic triangle and also the gateway to the Central
Highlands. All provinces in the region back on Truong Son range and face East Sea.
The region from Binh Dinh province to Binh Thuan province is in the South Central
Coast is adjacent North Central economic zone to the north, Central Highlands and
Cambodia to the west and northwest, South East economic zone to the south, and
South China Sea to the east. In term of South Central Coast geography, the region has
a complex topography of hill, mountain, forest and sea which creates majestic
landscapes and beautiful beaches. This is favourable condition to develop tourism,
especially sea – island tourism, the South Central Coast owning Hai Van Pass, the end
of the North Truong Son mountain range along with South China Sea, Paracel and
Spratly Islands facilitates to develop international ports.
On the other hand, provinces in the South have a part of Mekong delta. In addition,
located at the end of Indochina peninsula, adjacent the southern key economic zone,

Mekong Delta owns the close and important two-way relationship. Situated adjacent
Cambodia and common Mekong River, the region offers favourable conditions to
exchange and cooperate with other countries on the peninsula. Besides, located in the
end of the country’s southwest with 73.2 km long coastline and islands, such as Tho
Chu Island, Phu Quoc Island - exclusive economic zones bordering South China Sea
and Gulf of Thailand, Mekong Delta owns tourism potentials need explored.
Furthermore, the region belongs to the region of maritime transportation, international
air transport between South Asia and Southeast Asia as well as Australia and other
islands in Pacific. This position plays an extremely important role in international
exchanges.
1.2 Topographic conditions
In contrast to most other coastal regions in Vietnam, the South Central Coast's terrain
is not mainly flat. It has a diverse topography with mountain ranges and hills

9


extending not only along the entire border with the Central Highlands but also to the
coast, forming several passes, bays, peninsulas, and beautiful sceneries with beaches
and mountain backdrops. Many of the highest mountains are at or near the border with
the Central Highlands, the highest of which is Ngọc Linh Mountain at 2598 meters.
There are several high peaks near the coast of Da Nang (696m on Son Tra Peninsula),
Binh Đinh Province (up to 874m), Phu Yen Province (up to 814m), Khanh Hoa
Province (up to 978m), and Ninh Thuan Province (up to 1040m). Several mountain
passes function as geographic borders between the provinces of the region, with one or
two provinces between two major passes. Major passes include the Hai Van Pass on
the northern border of the region (Da Nang), Binh De pass between Quang Ngai
Province and Binh Đinh Province, Cu Mong pass between Binh Dinh Province and
Phu Yen Province and Ca pass between Phu Yen Province and Khanh Hoa Province.
The region includes several islands. Some of the larger ones are the Ly Son Islands,

the Cham Islands, and Phu Quy island. The Paracel Islands and the Spratly Islands are
officially administered by Da Nang and Khanh Hoa Province. However, sovereignty
over them is disputed and Vietnam actually controls only some of the Spratly Islands.
The southern provinces of the Mekong Delta displays a variety of physical landscapes,
but is dominated by flat flood plains in the south, with a few hills in the north and
west. This diversity of terrain was largely the product of tectonic uplift and folding
brought about by the collision of the Indian and Eurasian tectonic plates about 50
million years ago. The soil of the lower Delta consists mainly of sediment from the
Mekong and its tributaries, deposited over thousands of years as the river changed its
course due to the flatness of the low-lying terrain.
The present Mekong Delta system has two major distributary channels, both
discharging directly into the South China Sea. The Holocene history of the Mekong
Delta shows delta procreation of about 200 km during the last 6 kyr. During the
Middle Holocene the Mekong River was discharging waters into both the South China
Sea and the Gulf of Thailand. The water entering the Gulf of Thailand was flowing via
a paleo channel located within the western part of the delta; north of the Ca Mau
Peninsula. Upper Pleistocene prodeltaic and delta front sediments interpreted as the

10


deposits of the paleo-Mekong River where reported from central basin of the Gulf of
Thailand.
The Mekong Delta is the region with the smallest forest area in Vietnam. 300,000
hectares (740,000 acres) or 7.7% of the total area are forested as of 2011. The only
provinces with large forests are Ca Mau Province and Kien Giang Province, together
accounting for two thirds of the region's forest area, while forests cover less than 5%
of the area of all of the other eight provinces and cities.
1.3 Climatic conditions
Summer temperatures average above 28°C along most of the coast with slightly lower

temperatures further inland. Winters are significantly cooler with average temperatures
ranging from around 20 to 25°C. Interestingly, the region includes some of the most
arid (Ninh Thuan Province and Binh Thuan Province) as well as some of wettest
climates in Vietnam (Da Nang, parts of Quang Nam Province, Quang Ngai Province),
with the rest being somewhere in between. While average precipitation per year
exceeds 2800 mm in many parts of the three provinces in the north of the region, it is
less than 800 mm in much of Ninh Thuan Province.
Being a low-lying coastal region, the southern provinces are particularly susceptible to
floods resulting from rises in sea level due to climate change. The Climate Change
Research Institute at Can Tho University, in studying the possible consequences of
climate change, has predicted that, besides suffering from drought brought on by
seasonal decrease in rainfall; many provinces in the southern provinces of study area
will be flooded by the year 2030. The most serious cases are predicted to be the
provinces of Ben Tre and Long An, of which 51% and 49%, respectively, are expected
to be flooded if sea levels rise by one meter. Another problem caused by climate
change is the increasing soil salinity near the coasts. Ben Tre Province is planning to
reforest coastal regions to counter this trend.
1.4 Observation stations and hydro-logic conditions
1.4.1 Observation stations
The water level stations in the region is not much, some stations in the river, a number of
stations in the sea, the facilities are not sufficient which leads to lack of monitoring data.

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Figure 1. 2 Observation stations in south central coast

Within the scope of the study using measure data at 02 stations is:
* Observation stations and marine environmental analysis at Cau Da – Nha Trang City
– Khanh Hoa province.

Observation station at Cau Da - Nha Trang city was built in 1968, with volume
2x1.5x2.5m. The water level in here is measured by water-poles, rods and tide gauges.
It is daily observed monitoring water levels and weekly charted to replace the paper
once. Quarterly organization once dredging station aims tide water wells are connected
to the sea.

Figure 1. 3: Cau Da station – Khanh Hoa province
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* Observation stations and marine environmental analysis at Bà Rịa Vũng Tàu
Carry out the monitoring, collecting, updating, synthesizing and analysing of
environmental data in the province in order to detect and announce to the authorities
incidents of environmental pollution on land, coast and sea.

Figure 1. 4: The monitoring sites of Vung Tau station
1.4.2 Hydrologic conditions
The northern part (Da Nang – Ninh Thuan) where the coastline is located in N-S
directions and can be divided into different section by headlands which are forming
bays, lagoons with the mouth directions of E and SE. The shelf is relatively narrow
with depth contour of 200 m lying at distance of ≈ 30 km from the coast. Most rivers
are short with steep slope and low concentrations of suspended matter.
The central part (Binh Thuan - Vung Tau) is where the coastline is oriented in NE-SW
directions; it means the coastline direction is parallel with two main monsoon wind
directions (NE and SW monsoons). The coast can again be divided into several
sections by headlands which form bay with the mouth direction of SE. However, the
coast is relatively less separated in comparison with the northern part. The shelf has a
relative smaller slope compared to the northern part, with the depth contour of 200 m

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located at distance of ≈ 100 km offshore. Almost all rivers are short, suspended matter
concentrations are again relatively low.

Figure 1. 5: The significant wave height patterns in the East Sea
The coast from Ninh Thuan to Tra Vinh was affected during both monsoon phases.
The tidal regime along the study coast is from irregular diurnal tide in the northern part
to an irregular semi-diurnal tide regime in the southern part. Mean high tide amplitude
is approximately 1 ÷ 2 m along Da Nang to Phan Thiet, and about 3 m along Vung Tau
to Ca Mau.
Besides, the main hydro-dynamical processes in South Vietnam waters were driven by
monsoonal wind regime. Remarkable features are the region of strongest upwelling
occurred in Ninh Thuan – Binh Thuan waters during SW monsoon period, and a strong
jet current with low temperature during NE monsoon period which flows from north to
south along Central Vietnam coast. The mechanism inducing water upwelling is
complicated, and not only depends on surface wind stress, but also depends on other
factors like morphology, characteristics of circulation, etc. Intensity of South Vietnam
upwelling is highly related to ENSO phenomena. In case of strong El Nino the
upwelling intensity is weak, whereas, in case of weak El Nino or ENSO Neutral the
upwelling intensity is stronger.
1.5 Oceanographic conditions
In the South Central Coastal, there exist wind currents, steady current and tidal
currents. The tidal currents are of the weak speed and mixed type. The depth
homogeneity of the tidal currents does not express clearly and this shows the tide is a

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result of tidal waves coming from different directions and they have a complex

interaction as known for the case of the tidal oscillation of water level. Since this
region is under the influence of the cold current system in the west of the East Sea the
steady current has dominance among all other components.
1.6 Historical disasters of typhoons and storm surges
Natural hazards include rare earthquakes and occasional typhoons (May to January)
with extensive flooding, especially in the Mekong River delta Almost every year
Vietnam is devastated by storms, floods and typhoons that kill hundreds people and
cause millions of dollars of damage. The problem created by disasters has been
exacerbated by logging, erosion and over development. An average of 430 people was
killed each year by natural disasters between 2007-2011, with property losses
estimated at 1 percent of gross domestic product.
Vietnam's long 3,200-kilometers coastline is battered every year by up to 10 storms,
killing hundreds, even thousands of people. Approximately 71 percent of the
population and 59 percent of the land area are vulnerable to disasters, with floods and
storms as the most destructive occurrences with the highest number of fatalities and
economic damage.
Table 1 1 Statistics storm in Vietnam

Some meteorologist predict that global warming will bring more rain to the region
more rain, stronger typhoons and higher sea levels and make the flooding problem
worse, example:
- Between 1954 and 1999, there have been 212 typhoons landing in or directly
influencing Viet Nam. On average, there are about 30 typhoons originating in the

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