Luận văn thạc sĩ Kỹ thuật và quản lý ven biển: Preventive measures for coastal erosion in Cua Lo, Tam Quang commune, Nui Thanh district, Quang nam province

MINISTRY OF EDUCATION MINISTRY OF AGRICULTUREAND TRAINING AND RURAL DEVELOPMENT

THUY LOI UNIVERSITY

HOANG THI LINH GIANG

MASTER THESIS

HANOI, 2016

MINISTRY OF EDUCATION _ MINISTRY OF AGRICULTUREAND TRAINING AND RURAL DEVELOPMENT

‘THUY LOT UNIVERSITY

HOANG THI LINH GIANG

PREVENTIVE MEASURES FOR COASTAL EROSION INCUA LO, TAM QUANG COMMUNE, NUI THANH DISTRICT,

QUANG NAM PROVINCE

Major: Coastal Engineering and ManagementCode : 62580203

MASTER THESIS

SUPERVISOR: ASSOC PROF DR MAI VAN CONG

HANOI, 2016

I hereby certify the work which is being presented in this thesis entitled, “Preventive

measures for coastal erosion in Cua Lo, Tam Quang commune, Nui Thanh District,

Quang Nam province.” in partial fulfillment of the requirement for the award of theMaster of Coastal Engineering and Management, is an authentic record of my own workcarried out under supervision of Assoc, Prof Dr Mai Van Cong The matter embodiedin this thesis has been submitted to UNDP in Vietnam and DMC under the framework

of the project “Strengthening Institutional Capacity for Disaster Risk Management in

Viet Nam Including Climate Change Related Risks (SCDM Phase II).

Ha Noi, December, 2016

Hoang Thi Linh Giang

First of all 1 would like to acknowledge the sponsors UNDP in Vietnam and DMCunder the framework of project “Strengthening Institutional Capacity for Disaster RiskManagement in Viet Nam Including Climate Change Related Risks (SCDM Phase 11)for the scholarship suppor.

Towe special words of many thanks to Assoc, Prof, Dr Mai Van Cong- my supervisorfor his concer, guidance, enthusiasm, valuable advice and assistance with so muchcare.

1 would like to acknowledge Assoc Prof Dr Tran Thanh Tung and Prof Dr ThicuQuang Tuan who are main co-ordinator of this master program, making valuecontributions to success in Master course I would like to s yy thanks to ProfessorMarcel Stive for his comment on proposed solutions I also want to thank to M.Se.Nguyen Quang Duc Anh from VINWATER for his comments, supports in modelingwork and sug lon, M.Sc Le Duc Dung from VASI for his supports in data and‘model validation.

1 would like to thanks faculty of Marine and Coastal Engineering of Thuy LoiUniversity for providing support in numerous aspects amid the study.

My high appreciation goes to all the lecturers who have taught and provided me withsuch valuable knowledge to my future career both in Vietnam and in the Netherland;

my colleagues, friends and my classmates for their support and assistance.

Finally, I would like to keep the great thanks to my sweet family for their great supportand always being source of encouragement, motivation and energy.

TABLE OF CONTENTS

ACKNOWLEDGEMENTS ‘TABLE OF CONTENT!

LIST OF FIGURES.LIST OF TABLES.INTRODUCTION

1 Rationale of this research2 Research objectives.3 Focus area

4, Research methodology and implementation.5 Structure of the thesis

(CHAPTER I: LITERATURE REVIEW 31.1 Overview of erosion and sedimentation 31.1.1-§omme researches in foreign countries 31.1.2.Coastal erosion and shoreline changes researches in Vietnam 51.1.3 Recent coastal researches in Quang Nam province 91.2.Research method in erosion and sedimentation 121.2.1.Method of mapping- remote sensing 121.2.2 Questionnaire method 121.2.3 Field survey method B1.2.4.Modeling method l31.2.5 Statisical and synthetic analyzing method l3CHAPTER II: OVERVIEW OF STUDY AREA.

2.1.Study area description 42.2.Natural conditions 152.2.1.Climate condition 152.2.1.1 Temperature 152.2.1.2.Rainfall regime 152.2.1.3 Wind regime 162.2.14.Wave regime „

2.2.1.5.Typhoons 19

2.2.1.6.Hydrological regime 2022.2.Geological conditions 22.3.Social-economic features 2B24,Status of coastal erosion and existing coastal protection measures in study areas.232.5.Coastal development 28CHAPTER Ill: ANALYSIS OF COASTAL EROSION PROCESS ANDSHORELINE CHANGES IN THE STUDY AREA s3.1.Causes of coastal erosion in study area 353.1.1 Hypothesis I: Erosion caused by structural properties of the coast 373.1.2.Hypothesis 2: Erosion and shoreline changes caused by sea level rise and theextreme boundary conditions of hydrological factors 37

3.1.2.1-Erosion and shoreline changes caused by sea level rise 373.1.2.2.Bffect of typhoons and storm induced cross-shore erosion 383.1.3.Hypothesis 3: Erosion and shoreline changes caused by human actitities 1

3.2 Analysis of mechanisms for erosion and shoreline changes in the study area 423.2.1 CERC formula 23.2.2 Mike model 463.2.2.1, Data collection 46

3.2.24 Calibration and verification of simulation model, 53.2.3, Evaluation of the hydrodynamic regime in Cua Lo area 373.2.3.1 Hydrodynamic regime of Cua Lo area in winter 583.2.3.2 Hydrodynamic regime of Cua Lo area in summer 6l

3.2.3.3 Hydrodynamic regime of Cua Lo area in flooding, 643.2.3.4 Conclusions 66

CHAPTER IV: POSSIBLE ALTERNATIVE COUNTERMEASURES 68686874.1, The common principles of planning countermeasures,

4.2 Proposed planning countermeasures for study area43, Evaluating of planning countermeasures by modeling,

4.3.1 Extraction locations of the results from Mike 21/3 FM model 74.3.2 Hydrodynamic regime and bed level change of Cua Loarea in summter 784.3.3, Hydrodynamic regime and bed level change of Cua Lo area in winter 82

43.4, Hydrodynamic regime and bed level change of Cua Lo area in ƒlooding 864.3.5 Evaluation of possible countermeasures 90CONCLUSIONS AND RECOMMENDATION

1 CONCLUSIONS.

2 RECOMMENDATIONREFERENCES

Appendix 1; Frequency table in Spring, Summer, Autumn, Winter at Ly Sonstation 100Appendix 2: The result of calibration tidal model 104Appendix 3: The result of verification tidal model 115Appendix 4: Comparision of bed level change at 5 sections 122

LIST OF FIGURES

Fig.2- 1: Study area

Fig.2- 2: Wind rose at Ly Son (1985-2012)

Fig.2- 3: Wave roses in March, April and May at Ly Son stationFig.2- 4: Wave roses in Jun, July and August at Ly Son station

Fig.2- 5: Wave roses in September, October and November at Ly Son stationFig.2- 6: Wave roses in December, January and February at Ly Son station

g.2- 7: River system

Fig.2- 8; Discharge of Truong Giang river in flood season

Fig.2- 9: Existing coastal protection measures in Cua Lo area (Nui Thanh)Fig.2- 10: Geo-textile (Intemet &Google Earth)

Fig.2- 11: Geo-textile was destroyed in the southern of Cua Lo in 12/2013

Fig.2- 12: Approximately 30 m of existing revetments was seriously damage.Fig.2- 13: Large concrete blocks were capsized off the ground

Fig2- 14 Tam Hai revetment, Nui Thanh district, Quangdestroyed after only a short time in use (Internet &Google Earth),Fig.2- 15: Waterway in Cua Lo river mouth(Internet &Google Earth)

Nam provinces were2627Fig.2- 16: Eroded area in Ba Tinh, Nui Thanh, Quang Nam (Intemet &Google Earth)Fig.2- 17: Coastal development (Google Earth)

Fig.2- 18: Average erosion rate in Cua Lo.jon rate in Cua Lo.Fig.2- 19: Average acct

Fig.2- 20: Accretion-erosion in Cua Lo in the period from 1965 to 2014.

Fig.3- 1: Main causes and factors causing coastal erosion and shoreline changesFig.3- 2: Historic tracks of storm events in the vicinity of the research site

Fig.3- 3: Historie relevant tracks of storm events in the vicinity ofthe research siteFig.3- 4: Phu Ninh reservoir (Google Earth)

Fig.3- 5: Representative eross sectionsFig.3- 6: Extend of large domain modelEig.3- 7: Nested detailed (small) modelFig 3- 8: Bathymetry of large model

sl

Eig 3-9: Bathymetry of small model sĩFig.3- 10: Boundary conditions of large model 32FFig.3 1: The location of water level measuring stations 54Fig.3- 12: The calibration result of water level at Son Tra station 35FFig.3- 13: The calibration result of water level at Cua Dai station 5sFig.3- 14: The verification result of water level at Cua Dai station 56Fig.3- 15: The distribution of the characteristic waves of Cua Lo area in winter S8Fig3- 16: The distribution of total currents (speed and direction) when tide going upof Cua Lo area in winter soEig3- 17: The distribution of total currents (speed and direction) when tide goingdown of Cua Lo area in winter 59

Fig.3- 18: Result extracted points from the model 60

Fig.3- 19: Current velocities at points in winter 60Eig.3- 20: The distribution of the characteristic waves of Cua Lo area in summer 62Fig3- 21: The distribution of total currents (speed and direction) when tide going up‘of Cua Lo area in summer 62Fig.3- 22: The distribution of total currents (speed and direction) when tide goingdown of Cua Lo area in summer 6Tp 3- 23: Current velocities at points in summer “Big 3: 24: Water level of Cua Lo area in flooding 6Eig.3- 25: The distribution of total currents (speed and ditection) in flooding 6Š

ig.3- 26: Current velocities at points in flooding 65

Fig: Master plan 1 nFig.4- 2: Dredging for navigation nFig.4- 3: Master plan 2 ”Big 4- 4: Extraction locations of the results from Mike 21/3 FM model nFig 5: The distribution of total currents (speed and direction) whea tide going upand down in summer of master plan | 78Fig4- 6: The distribution of total currents (speed and direction) when tide going upand down in summer of master plan 2 79Fig4- 7: Bed level change in summer of master plan 1 80

Fig 4- 8: Bed level change in summer of master plan 2 81Fig4- 9: The distribution of total currents (speed and direction) when tide going upand down in winter of master plan 1 82Fig.4- 10: The distribution of total currents (speed and direction) when tide going upand down in winter of master plan 2 83Fig 4- 11: The distribution of the characteristic wave in winter of master plan 1 84

Fig.4- 12: The distribution of the characteristic wave in winter of master plan 2 84Fig.4- 13: Bed level change in winter of master plan 1 85

Fig.4- 14: Bed level change in winter of master plan 2 86Fig.4- 15: The distribution of total currents (speed and direction) in flooding of masterplan 1 87Fig.4- 16: The distribution of total currents (speed and direction in flooding of masterplan 2 87Fig 4- 17: Water level of master plan 1 88Fig.4- 18: Water level of master plan 2 88Fig.4- 19: Bed level change of master plan | 89Fig.4- 20: Bed level change of master plan 2 90

Table 3-1Table 3-2Table 3-3Table 3-4Table 3-5Table 3-6Table 3-7:

Table 41

Table 4-2:Table 4-3Table 4 4Table 4- 5

Average erosion rate in Cua LoAverage accretion rate in Cua Lo

List ofthe typical storms in Quang Nam costal areas.ross section 1

Cross section 2

CERC calculation resultsParameters of large model

“The coordinates of measuring stations

Wave height at Ly Son station in season (1985-2012)

Ship size caleutates the navigationPreliminary planning of masterplan ÌPreliminary planning of master plan 2

Extraction coordinates of the results from Mike 21/3 FM modelEvaluation possible countermeasures

93

1 Rationale of this research

Coastal erosion and sedimentation become serious at many coastal sections in theCentral Vietnam in general and Cua Lo, Tam Quang commune, Nui Thanh district,‘Quang Nam province in particular, ‘This causes many adverse consequences on dailylife as well as social economic development, such as house collapsed, public worksdestroyed, shoreline retreated and crop yields reduced This situation triggers local andcentral government to urgently seek for a solution to minimize the erosion andsedimentation problems Proposing possible solution for Cua Lo location, Tam Quang‘commune, Nui Thanh district, Quang Nam province is therefore very important

2 Research objectives

This study comes up with the following objectives:

~ Analysis of erosion causes and determination of driving forces that lead to theaccretion, erosion of the study area

~ Proposing possible solutions for coastal erosion prevention in Cua Lo, Tam Quang‘commune, Nui Thanh District, Quang Nam province.

3 Focus area

~ Focus area of thi study is a coastal section around the Cua Lo river mouth,belonging toTam Quang commune, Nui Thanh district within the geographical limitof 15°3025.19°N - 108°37'44.95°E to 15°287.217N ~ 108941'49.72",

4 Research methodology and implementationResearch methodology and implementation as following.

Research methodology and implementation

5 Structure of the thesis

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

Chapter 1: Li wrature review

Chapter 2: Overview of study areas

Chapter 3: Analysis of coastal erosion process and shoreline changes in the study area

Chapter 4: Possible alternative counter measures

CHAPTER I: LITERATURE REVIEW

1.1 Overview of erosion and sedimentationLLL Some researches in foreign countries

Coastal erosion and sedimentation are natural processes: however, they have become‘anomalous and widespread in the coastal zone of Asia and other countries Zhang et al(2004) confirmed that the erosion is a global problem According to Hegde (2010),most of the coastline in countries around coastal areas was severely eroded The ratesof erosion however, differ with the countries It is well noticed that about 70% of thecoastline of the world is eroding In India, which has ä long coastline of about 7500km including islands, 23% of the coast is eroding, In USA, the rate of erosion variesfrom 0.3m to 0.6 m/year, Louisiana State in USA is losing coastal land at the rate of‘one acre for every 24 minutes, according to U.S.Army Comps of Engineers If this isnot arrested, some 800,000 acres of land is reported to be lost in next about 40 yearsand Louisiana shoreline is expected to recede by about 33 miles A US FederalEmergency Management Agency report of year 2000, states that in next 60 years, 25%‘of homes and other structures with in 150m of shoreline and the shores of Great Lakes‘would fall victim to erosion Bilan (1993) reported that the erosion rate in the northernpart of Jiangsu province in China is serious and as high as 85 m/year, in Hangzhou baythe rate is 40m/year, while in Tianjin itis 16-56 m/year In Japan loses 160 ha of landng 2400 haafter 10 years and 4800 ha after 25 years Shoreline retreat of 2.7m/year has been

every year by erosion, If the situation doesn’t change, Japan will be lo

reported in Mauritius and the coasts of some islands in Fiji have retreated by morethan 30m in the past 70 years,

Erosion becomes more serious in developing countries such as in Asia, especiallySoutheast Asia

According to Jarupongsakul (2006), the rate of erosion around the coastal periphery of‘Thailand is generally from 15 to 25 metres a year But the country’s 2,666.5 kilometershoreline is under serious threat from coastal erosion, which occurring at different

rates along shorelines of the Gulf of Thailand and the Andaman Sea About 485kilometres out of 1653 kilometres in the Gulf of ‘Thailand is severely eroded, whileabout four percent of the shoreline along the Andaman Sea, or 114 out of 1014kilometres, is eroding at what is considered a critical rale The rate of erosion is mostalarming along the Gulf of Thailand, from Trat province in the East to Narathiwatprovince in the South, Besides natural factors, the main reason leading to the erosion isdue to the increase of the shrimp farm to reduce the presence of mangrove forests.Gegar Pras ya (2007) reported that coastal erosion started in the northern coast ofJava Island in the 1970s when most of the mangrove forest had been converted toshrimp ponds and other aquaculture activites, and the area was also subjected tounmanaged coastal development, diversion of upland freshwater and river damming in

Indonesia, Coastal erosion is prevalent throughout many provinees (Bird and

Ongkosongo, 1980; Syamsudin et al, 2000; Tjardana, 1995) such as Lampung,Northeast Sumatra, Kalimantan, West Sumatra (Padang), Nusa Tenggara, Papua,South Sulawesi (Nurkin, 1994) and Bali (Prasetya and Black, 2003) Realizing theserious problems, a lot of money was provided by the Indonesian Government to

combat coastal erosion from 1996 to 2004, but only for Bali Island in order to protect

this valuable coastal tourism base A combination of hard structures and engineeringapproaches (breakwatervjetiesfevetments) of different shapes that fused functionaldesign and aesthetic values, and soft structures and engineering approaches (beachnourishment) was used They succeeded in stopping coastal erosion on Sanur, NusaDua and Tanjong Benoa beaches.

According to Othman (1994), nearly 30 percent of the Malaysian coastline isundergoing erosion A study of national shoreline erosion in Malaysia conducted in1985 showed that more than L972km coastline of Peninsular Malaysia has beenaffected (Chua TE, 1998) Serious erosion areas include half of Kuala Perlis to SungaiUdang, west coast of Johore and northern Kuala Selangor (Abdullah 1992) Inaddition, 85% of the coastline 39.3km from Suga an to Gula has eroded.Sungai Kei

AAs reported by Kast! (2011), shoreline in Koh Kong Province - Cambodia migrationlandwards is 390 m between 1973 and 2011 (10.3 m per year) resulting in the loss of0,60 km2 of mangrove forests The main reason is due to extensive river sand miningin all nearby rivers since 2008 and dam construction since 2010 is correlated in timeWith increased rates of beach barrier migration

1.1.2 Coastal erosion and shoreline changes researches in Vietnam

‘The coastal zone of Vietnam is more than 3260 km long, extending through theterritories of 24 provinces and cities, which include 127 urban and rural districts, 21towns and 6 cities (Ha Long, Vinh, Hue, Quy Nhon, Nha Trang, Vung Tau) At thecoast, a series of interactive processes occur between the land and the sea, betweennatural and human processes, between the dynamic forces of rivers and the sea, ete

Coastal erosion and sedimentation are complicated phenomenon caused by marine

dynamics, Erosion and sedimentation are due to a combination of many factors.Brosion and sedimentation are wo sides of an issue The research of erosion andsedimentation must be bai rated evaluation if the factorsod on a systematic and inteycausing erosion and sedimentation The factors causing coastal and river mouth

erosion and sedimentation are closely related with each other and interact wi th each,other in a unified system, which follows the law of nature and closely controlled byman, creating a kinetic balance among them, When one or some factors change, otheralso change to establish a new balance

In recent years, the process of erosion along the coasts has been occured strongly,caused many adverse consequences on human activities in the coastal areas Manyhouses and public welfare works have been destroyed, lands and crops have beensealed down, Especially in the strongly eroded areas; Cat Hai (Hai Phong), Van Ly,Hai Tricu, Hai Hau (Nam Dinh), Ngu Loc, Haw Loc (Thanh Hoa), Canh Duong(Quang Binh), Phan Ri (Binh Thuan), Can Thanh (Ho Chi Minh), Go Cong Dong,(Tien Giang), Ho Tau, Dong Hai (Tra Vinh), Ngoc Hien (Bác Lieu), ete Coastalerosion is causing shoreline changes and significantly impacting the environment of

the coastal areas Therefore, the study of preventive measures for coastal erosion isextremely important.

According to Pham Huy Tien et al, 2005, coastal erosion has been observed in allcoastal provinces of the Central region, Here 263 erosion sites have been recorded, of‘hich the smallest site covers 1.4 ha, the largest one covers 262.8 ha The total area ofcoastal erosion in the period 1990 - 2003 is 8839 ha Observation and records showthat in the total 263 erosion sites 284 coastal sections and 10 areas have beencompletely eroded In the coastal section from Thanh Hoa to Khanh Hoa there is anerosion site in every 6 km The coastal erosion occurs at different rates The areas withirregular, ruaged landform, with many bays and peninsulas, bedrock, river mouth areascrosion occurs with small extent, low to medium intensity Strong and very strong

erosion occurs in convex coastal sections facing wind and wave direction,with sand

being the main shore-building material, There are up to 268 erosion sections composedof sand, accounting for 93.7% of the total erosion sections The Central coastline fromThanh Hoa to Binh Thuan is 1765 km long, of which 392 km are being eroded(accounting for 22% of the total coast line).The survey results show that the eroded

coastal sections with length over 1000 m account for 41% In the Central region,

erosion occurs nearly all over the coast line, in the territories of all coastal provinces,though with different intensity and rate The areas with strongest erosion areconcentrated in the coastal zone of the Thanh Hoa, Thua Thien - Hue, Quang NamQuang Ngai, Phu Yen.

Studies of phenomena close / open estuaries, lagoons just only significant Focus area in‘Tam Giang-Cau Hai (Thua Thien-Hue) area with the phenomenon of open / close HoaDuan estuary In which, the majority of projects were carried out within the frameworkof international cooperation between Vietnam ~ Netherlands (Cooperation between‘Water Resources University, Ha Noi and Delft University Technology) In general, the

fh projects at Tam Giang ~ Cau Hai Lagoon concentrated in researching natureopen/close regime of estuaries, calculate estuaries stability, salt intrusion with different‘open/close scenarios of estuaries Some research project such as: Tran Thanh Tung et

al (2007); Nghiem Tien Lam (2006); Nghiem Tien Lam etal (2007); Thieu Quang"Tuan (2007); Tran Due Thanh et al (2000, 2002) Sumary, assess the results ofresearch on erosion, deposition of Vietnam coastline and estuaries was presented byAssoc Nguyen Manh Hung in the monographic: "Coastline and estuaries evolution in

Vietnam” (Nguyen Manh Hung, 2010),

In recent years, Central Vietnam has spent thousands of billions to build hundreds ofriver bank protection embankments But before unexpected developments of theclimate, people of central Vietnam have to suffer from hurricanes, severe floodsconsecutively, along with threatening high tides which caused a series of sea dykeseroded or damaged, with serious impact on the lives of people.

In Thua Thien Hue province, many eroded areas have appeared recently with more

than tens of kilometers of coastline in the communes of Phu Vang, Quang Dien,

Huong Tra towns, threatening the lives and property of people Thousands of cubicmeters of soil and vegetation in the coastal areas of Phu Thuan, Phu Hai commune,‘Thuan An town (Phu Vang district), Vinh Hai, Vinh Hien commune (Phu Loc district),‘Quang Cong Commune, Quang Ngan (Quang Dien district) and Hai Duong commune

(Huong Tra town) were washed away in waves and tides The coastline adjacent to the

erosion area is covered with embankments in Genh hamlet (Thai Duong Ha Nam rural,Hai Duong commune), but continue to eroded 10 m deep and 500 m long In Phu Yenprovince, Provincial People's Committee has signed a decision to proclaim a state of‘emergency about coastal erosion in Ro hamlet area, Phu Dong Ward (Tuy Hoa City) inthe lat few years, threatened the lives and properties of dozens of households in theregion Local people said when the sea level fluctuated greatly, 5-7 m high waves were‘d_ serious erosion, rocks werecommon, which destroyed embankments and ¢:

dumped into the sea, which might be dangerous to local people

In addition, some fishing ports and shipping routes into several ports faced serioussedimentation problems in estuari

(Hoai Nhon - Binh Dinh), Da Rang river mouth (Phu Yen), Sa Huynh estuary (DuePho), My A estuary, Dong Hai estuary, La Gi, Phan Thiet and Nhat Le, ee

in Central Vietnam, ie: Tam Quan Bac estuary

The south of Tam Quang estuary (Hoai Nhon- Bình Dinh)

‘The Tam Quan Bae estuary (Hoai Nhon- Binh Dinh) is where 1.400 ships coming andgoing, the largest fishing port in Binh Dinh province and one of the busiest ports inBình Dinh The main navigable channel frequently occur serious accretion, it makesships dit icult to go inside of the harbour and shelter harbor The government of Binh.Dinh Province has invested more than 80 billion implementing the construction ofsafety zone in order to avoid storms in Tam Quan Bac and construction of abreakwater at the southern bank of Tam Quan Bac with 850 meters long.

My A estuary is a mouth of small river of Due Pho district, Quang Ngai province, butit pays a very important role in social and economic development of the area Thechanges of My A estuary is very complicated, it causes many difficulty for

transportation of fishing boats and ships, and even for the life of local people It has

been drastically narrowed over the last decade due to sand and earth deposited at thesea mouth by the river and ocean tides Some 300 boats used to regularly enter andexit My A each day, but now only about 200 small-capacity boats can fit in the narrowJane Bach year, when rough seas narrow local waterways, the government has‘mobilized funds from fishermen to hire dredge the passages, However, after each rainyseason, the estuaries and chann is are filled up again with silt and sand deposits,

‘The conditions are similar at the Sa Huynh Estuary, 20 kilometes to the Sa Huynh fishi

the harbor’s signal light system has also been damaged by sedimentation.

outh of My A.

Passi port, which opened in 2008, have been silted while

The Da Rang River mouth in central coastal Phu Yen Province's Tuy Hoa City hasbeen narrowed as a result of sand encroachment, causing difficulties in the movernentof hundreds of ships In 2012, a fishing ship with a capacity of 16%CV and 10fishermen onboard was caught in shoals atthe river mouth, Around 50 fishing ships‘went through the Da Rang River mouth each day and it took each ship between one to‘wo hours to come into the harbour and even between one and two days for big ships.

‘Over past years deposition has occurred in Cua Tung mouth and erosion occurred atN Hoang terrace The development has negatively influenced tourist and fishing

In Quang Nam province, the farmers living along the coast are still worried day andnight by the threat of collapsing sea embankments, About 10,000 households in thecity of Hoi An coastal (Quang Nam) are familiar with these situations Many houseshere were struck by heavy waves, The lives of tens of thousands of people werethreatened In particular, 300 m embankment of Cua Dai beach had just collapsed oneyear ago, costing approximately 100 billion VND Many houses in the area wereflooded, Meanwhile, in the area of Thu Bon River, located in Hoi An, two‘embankments of Ngoc Thanh -Cam Pho and Thanh Ha were severely eroded The

eroded embankments significantly impacted the lives of people After the flood event,

bout 10,000 houses in Cam An Ward, Cam Thanh, Cua Dai, Tan Hiep Commune (CuLao Cham) had to deal with the effects of erosion

The situation of serious erosion in neighboring coastal estuary in Central Vietnam isbecoming an emergency, it has recently been affecting people's daily activities, both

social and economic, the national security and the defense in the area,

1.1.3 Recent coastal researches in Quang Nam province

‘Quang Nam coasts composes commonly by slight to medium sand, the low groundsurface, so it is easy to be strongly affected by hydrodynamics conditions such as‘wave, sea level rise The above process caused shoreline erosion, sedimentation, movethe channel to the estuary, destroying coastal works, flooding, in the coastal areas,estuaries In order to protect the coastline and estuaries, local government has built a

system of embankments in the southern bank of the Cua Dai river and the southem.

bank of Cua Lo ( Truong Giang river), the embankment along the Au Co road (CuaDai), Tam Thanh embankment, the coastal resorts in Hoi An have also built protection‘embankments However, some positions of the system of embankments at the beachHoi An, Cua Lo have been destroyed: south bank embankment system of Cua Dai hascaused great erosion for An Luong area, the channel at Cua Lo and Cua Dai still

frequently fluctuate Especially, in recent time, erosion of beach Ba Tỉnh (Quang Tam,‘Nui Thanh) become seriously by the exploitation of sand at the beach,

‘Studying and predicting hydrodynamic processes and changes of shoreline, estuary inQuang Nam have been conducted with many different sizes, the most notably which isstate level topic KHCN.06,08: "Study the laws and predict trends deposition-erosioncoastal areas and estuaries Vietnam” (1996-2000); international cooperation projects‘Vietnam-India (2002-2003) tudy, predict the erosion-sedimentation in coastal areas

of Vietnam” with key research areas is Hoi An beach, is presided by Le Phuoc Trinh(Oceanographic Institute) Two themes have focused research on the evolution of the

process of erosion, sedimentat n at the Hoi An estuary The result has set up maps ofterrain and shoreline changes for the Hoi An estuary area, Based on data collected

from themes, scientific researches on the process of hydro-dynamies and terrain

changes was announced Ha Noi National University PhD thesis: "Study of naturalhazards on the basis of geomorphology method to serve the urban development of(1999-2000) by Dao Dinh Bac as a team leaderhas provided documents on natural disasters is erosion and deposition of coastal andcoastal Da Nang-Quang Ngai area

estuary in Quang Nam State-level project: "Apply steps 3, 4, 5 integrated coastalmanagement model for Quang Nam province’ (2008-2010) by Nguyen Tac Anlostitute of Oceanography) presides The study has collected data on the process ofhydrodynamic and erosion, sedimentation in coastal areas in Quang Nam, servescoastal int ited management Science and technology research by Vu Minh Cat, etal,, (2002-2003): “Study of drainage solutions, prevent erosion and sedimentation of‘Vu Gia- Thu Bon estuary” Provincial thesis (2007-2008): "Survey, assess and proposesolutions to protect and restore the ecosystem of coastal wetlands in Quang Nam” byPham Viet Tich chaired, measured 20 sections from Dien Duong to Cua Lo These arevery precious data to support for assessing changes in topography in the study area.Codes of State- level thesis: KC,09.24 / 06-10 (2008-2010): "Scier fie and technicalJustifying for integrated management and sustainable development of the coastal NTBmeet the strategic objectives of sea economic development " by Bui Hong Long(stitute of Oceanography) host and VAST thesis (2008-2009): "Assess the impact of

protection structures to the environment of coastal estuaries NTB" by Le Dinh Mau(Oceanographic Institute) studying, assessing the current situation and the impact of‘bank protection works and estuaries in Quang Nam The research results ofthe projectwere provided on the current situation of erosion-accretion and changes in terrain aswell as the impact of the protection works in Quang Nam Within the framework ofinternational cooperation projects Vietnam - Denmark (2008-2010): "Evaluation of theimpact of climate change on natural conditions, environmental nd socio-economicdevelopment in the Middle Central Vietnam” Institute of Geography (VAST) chaired,in which Quat Nam is a key research area The goal of the project is to contribute to

poverty reduction, environmental protection and community life, including health in

the coastal area through the study of climate change, natural disasters and their effects,

as well as the necessary response: measures However, projects just only focused

research and forecast the climate change and their effects, the process hydrodynamicshas not been studied in detail The directly relevant project to the coastal of Quang‘Nam has been announced e.g Bui Hong Long, Le Dinh Mau (2000); Le Phuoc et al

(2001); Le Dinh Mau (2002, 2005, 2006, 2009, 2012); Le Dinh Mau et al (2004);

Dinh Thi Hoi et al (2013) In adit some studies of the hydrodynamics process in‘Quang Nam to serve the design of protection embankments, estuaries by departmentsin Quang Nam conducted at Cua Dai, Cua Lo, Tam Thanh area in recent years eg.Tran Thanh Tung (2004) in which sediment transport and shoreline changes in CuaDai is computed using UNIBEST model These documents are very important aboutnatural conditions, hydrodynamics for building scientific basis in coast protection, theestuary, serves the planning, sustainable development in coastal zones in Quang Nam.Under the combined effects of natural conditions such as geology, topography, riverhydrology, the wind, flow, waves, water levels, ete and human activities such ascoastal, estuaries protection works, dredging works, mit ing_materials, ete Both

accretion Basie characteristics of erosion and deposition in the coastal area of QuangNam (Le Phuoe Trinh, 2003; Le Phuoc et ai, 2001 and 2003): Focus and drastic insome short coast sections popular in the areas where has bank protection works, the

estuary, which was exploit materials (Cua Dai, Cua Lo, Ba Tinh); alternating eachother in space and time between erosion-corrosion and accumulation-sedimentationHowever, erosion is greater than accretion; quite markedly seasonal nature, in whichthe northeast monsoon caused sương and regular erosion, with southwest wind,erosion and sedimentation only happen in extreme weather conditions such as storms,tropical depressions, ete Cua Dai, Cua Lo estuary showed signs of shifting to thesouth in certain periods (tens of years);

1.2 Research method in erosion and sedimentation

1.2.1, Method of mapping- remote sensing

Comparing maps of the same scale for different time periods is useful in studying ofer mouth evolution Thiscoastline morphological changes by time and coastline and ri

method allows us to study the vast areas, synchronously, objectively and give us anoverall si wge of the coastline evolution in the different time of mapping andphotographing.

1.2.2 Questionnaire method

‘This method was the first time applied in studies of present stage of coast erosion

along the coastline of Vietnam The method is simple, not time-consuming,

inexpensive, and produces timely information Questions in questionnaire notes areoften short, clear, \d easy to understand and answer The answerers (usually

commune officers) only need to have passed at least the secondary school Thequestions are about the composition of the coast (Sand, rock and clay), coastalbathymetry, ranges of erosion, accumulation (width, lengt), occurring period oferosion, accumulation, and types of applied protection measured etc This methodallows us (0 gain the qualitative and quantitative information for each differenterosion, accumulation stretches with small size or occurred in the short time that are‘omitted by the method of mapping and remote sens ng because of low resolution ofmaps and photos also will be pointed out.

1.2.3 Field survey method

‘This is a necessary and indispensable method which is often used after implementingthe first two methods The aim of this method is to check and determine technicalinformation which is not correct or contradiction according to the earlier methods.Furthermore, this method has often been applied for the severe eroding stretches to getadditional data on geology, geomorphology and sediment transport rates.

1.2.4, Modeling method

Mathematical modeling method is one of the most effective methods to simulate thecoastline and river mouth evolution,

1.2.5 Statistical and synthetic analyzing method

All information obtained by the different methods is used as input for the statistical

and synthetic analyzing method The analyzed results are tabulated; from these tablethe places of eroding or accumulation stretch and the accordance importantinformation are noted The re

"with the scals of 1/250000 and after that of 1/100000 and synthesize all the data to find-arch results will be mapped in the evolution diagram

‘out the patterns, reasons and characteristics of coastline evolution,

CHAPTER II: OVERVIEW OF STUDY AREA2.1, Study area description

Nui Thanh district shares @ border with Quang Nam province in the south that was

established in 1984 based on Tam Ky district, and the district border Tam Ky city in

the North, Binh Son and Tra Bong districts in the South, and Nam Tra Mi district in

the East, The interest area is Cua Lo, Tam Quang commune, Nui Thanh distrist withinan extent of 15°30'25.15"N - 108°3744.95"E to 15°287.21"N - 108°41'49.72"E,

‘The district has a 37-km coastline section of beautiful beaches, such as Bien Rang,

‘Tam Tien and Tam Hai There are some existing tourism projects actively such as Le

Domaine De Tam Hai, Cat Vang Tam Tien, Chu Lai Resort Tam Hai is the only

island commune of the district, Nowadays, coastal erosion and sedimentation

processes have ben occurring in a rather complicated manner, causing serious

consequences in Cua Lo areas,

2.2, Natural conditions2.2.1 Climate condition

Vietnam has a tropical monsoon type of climate Quang Nam in general and Nui‘Thanh district in particular are located in the East of Truong Son mountain range andHai Van mountain pass in the South, Therefore, this place is the transition betweenNorthern- and Southern-Vietnam climates Beside Nui Thanh district also has its owncharacteristics in climate because of its topography.

Nui Thanh District has 17 communes and towns, including 8 communes adjacent tothe sea so influenced by marine and continental climates According to data from localhydrometeorology stations, Nui Thanh district climate has the followingcharacteristics:

2.2.11 Temperature

‘The average annual temperature in the area is around 27.6°C The highest in July withaverage monthly temperatures is 31.6°C December and the lowest in January withaverage monthly temperature is only 22.8°C The dry season starts from April and

ends in October On days when the southwest wind blows landward (from June toAugust), the air temperature increases, The cold season lasts from the end ofDecember to March next year The temperature variation is diumal: peak daily

temperature generally occurs dry season, a minimum daily temperature generally

‘occurs cold season,

2.2.12 Rainfall regime

‘The rainy Season lasts from September to December The highest rainfall is October(720 mm) The total average annual rainfall is 2531.5 mm The average number ofrainy days in a year is 140 days, the rainfall in October and November accounts for50.4% ofthe annual rainfall There are an approximately 140-145 rainy days in a year.“The months with most rainy days are October, November, December; each has about20-21 rainy days The months with the least rainy days are March, February, there are5-6 rainy days in each month.

2.5-‘winter months.

Table 2-1: Statistical wind speed (average and maximum) per month in Ly Son (1985-2012)

‘Wind speed Month

(mis) 1H |M ow jv ive |VH|VH|IX |x) xt) xn

average |5I |49 |47 4.1/3.2 127 |27 |27 |34 |50 |64 62maximum |36 |14 |19 16 /25 /16 |12 |18 |27 |28 |26 | 24

Table 2-2: Wind speed statistics (average and maximum) in the direction of Ly Son (1985-2012)

Wind direction

Wind type

N NE |E |SE |S sw |W_ |NWV„„v(ms) |36 |25 [16/16 |24 19 | 23.) 28Vewge (tvs) |57 J54 |25 |35S [36 [25 |29 57With the summer months when the southwest monsoon act the monthly average‘wind speed is small, from 2.5-3.5ms The maximum wind speed recorded at Ly Son is36m/s (level 1 1 1986),direction

ig.2- 2: Wind rose at Ly Son (1985-2012)(Source: “KCO9.17/11-15”)

Land Northeast.don at Quang Nam includes Southeast, Northw

In winter the prevailing wind direction is northeast and northwest with frequencyaccounted for over 40% In the months from winter to summer, the southeast andes northwest and south In thesoutheast wind direction is the prevailing direction bes

summer period includes the main wind direction is southeast, south direction besidessouthwest and northwest, To the transition months from the summer to the winter,‘winds from the northwest and west prevail it is clear seen that the wind regime in LySon is distinct seasons nature, According to statistical calculations see strong windsfrom level 8 or higher mainly occur in the winter months or at the time of the storm,

tropical depression affected area (usually from September to the end of December each

‘year, or may come in January, in February the next year).

Wind regime at Ly Son Island is the basis for calculating and forecastinghydrodynamic processes in coastal areas of Quang Nam,

2.214 Wave regime

‘Sea waves in general and big waves in storms in particular cause damage to coastal‘communities and residential surrounding coastal area Waves are the main cause for

the destruction of coastal structure and shoreline erosion Besides the destructiveimpact directly, wave energy is transmitted through wave-induced currents This is themain factor causing the seabed sediment transport and created the erosion andaccretion zone, Wave conditions change could lead to beach change due to thedifferent erosion processes: back to the shore, bed erosion, inereasing Slope Therefore,the study of the wind impact such as wind direction and its factor were extremely

important to the coast.

According to analysis data from Ly Son Island, NE monsoon starts from October toearly March next year, the strongest in December SW monsoon starts from April to

Fig.2- 4: Wave roses in Jun, July and August at Ly Son station

Fig.2- 6: Wave roses in December, January and February at Ly Son station

(Source: “KC09.17/11-15")

Overall, in coastal areas of Quang Nam, northeast monsoon period, the dominant wave

direction was NE Southwest monsoon period, the dominant wave direction was SE.Wave regime at Ly Son Island is the basis for calculating and forecastinghydrodynamic processes in coastal areas of Quang Nam in general and Nui Thanh inparticular.

2.2.1.5 Typhoons

‘Typhoons usually occur from September to December, they are most appear in

October and November, they usually attach heavy rain caused flooding The annual

average typhoon often occur 8-10 typhoons impacting directly or tropical depression

affecting the region Due to unexpected developments of the weather, there are five

appearing storms and tropical depressions and they have affected the area very early in

May and June.

22.1.6 Hydrological regime

The local river system includes Tam Ky river, Truong Giang river, Ba Tue river, Tran

river, ete Those rivers originate from the West, Northwest eastward flowing down to

the sea through An Hoa river mouth and Cua Lo river mouth, The river basins are

small, from 50 lo 100 kmỂ, The river lengths are from 20 to 40 km, with steep

channels, and flow rate varying with the seasons Currently, the rivers are contained inthe upstream areas to build water reservoirs such as Phu Ninh reservoir in Tam Kyriver, Thai Xuan reservoir in Trau river.

Fig.2- 7: River system

(Result of Viemam Academy for Water Resources)

ig.2- 8: Discharge of Truong Giang river in flood season(Result of Vietnam Academy for Water Resources)In particular the two largest rivers flow through Nui Thanh district are:

‘Truong Giang river: A river runs alongside the coast of Quang Nam flow to the seathrough the Tam Xuan 1 commune, Tam Xuan 2 commune, Tam Anh commune andTam Tien commune, Tam Hoa commune, Tam Hiep commune and Tam Giang‘commune, Nui Thanh town connection An Hoa river mouth with Cua Dai river mouth,Hoi An, The downstream sections of these rivers are relatively wide

‘Tam Ky river: the confluence of 10 small springs, derived from the west, flows fromWest 1o east and out on tô a main line at Xuan Binh - Phu Tho, Tra Tam commune Nui‘Thanh district, then from the Northwest - Southeast flow through Hoa river mouth A

catchment area is about 800 km’,

“The district's rivers converge to the east created turbulence area, built the dunes andcreated the pond rammer in Tam Quang commune, Tam Anh Nam commune, Tam‘Anh Bac commune, Tam Hoa commune, Tam Giang commune, Tam Hai commune,‘Tam Tien commune Diurnal tide occurred in October about 15 days, and the rest areimegular semidiurnal tide, The average water level is 1.2 m, spring tide is from 1.20 2

am, neap tide is 0.5 m The average flow speed is 0.2 to 0.3 mis, the maximum speed is2.5 m/s, Storm surge heights can be up to 1.5 ~3 m.

Due to the characteristics of the regional climate, water discharge of rivers varied withseason, was remained in upstream and water discharge in downstream was let down,2.2.2 Geological conditions

“The study area has two stratigraphic layers:

Early cambria metamorphic rock layer: This was type of crystalline schist with dark grayand bluish This stone was distributed in Northeast cape of An Hoa, Hon Dua island.

The characteristics of these rocks were similar to rocks of A Vuong layer.

Basalt eruptions rock and Pliocene - Pleixtocen voleanic sedimentary rock layer: This‘was already weathered basalt The upper part has been turned into yellow dit ~ feralt

The thickness of this soil layer was weathered nearly 40 m Under this layer of

weathered rock was dark brown laterite rock and it all cohered This laterite layerexposed on the surface in many places due to seawater corroded weathered soilsabove These rocks wer distributed in cape of An Hoa, Hon Dua island, With a highdegree of weathering, basalt has been classified into Pliocene - Pleixtocen age by

geologists (Source: Geological map of Vietnam, continent part, a ratio of 1: 500,000

by Tran Due Luong, Nguyen Xuan Bao, editor, 1986).

Quarternary deposit rock layer: Pleistocene deposit This sediment distributed narrowstrips, extended along rivers, small streams, formed mainly white - gray sandy,‘gray due to it was mix with organic impurities and powdered clay This type was pale

yellow sand, it used to be sand dunes, ancient sand dike but today it is affected by

wind, waves and it is accumulated and distributed mostly in the area of Tam Haicommune, According to Tran Nghỉ (1997), this sand was derived from here, due to asystem of Tam Ky river -Trau river flow out in the time Pleixtocen (Q12-3) Themineral composition is mainly quartz sand, feldspar, mica, urmalin, mud, clay, layeredunclear and thickness from 3 - 4 m,

2.3 Social-economic features

Founded in 1983, Nui Thanh district at that time was a town with 12 communes Afternearly 32 years of construction and development, Nui Thanh district has been

gradually urbanized and is on its way towards the fourth grade city in 2020, Nui Thanh

District currently has 17 communes and towns with a population of over 140,000people This district has seaport, airport, national highway 1A, a tain station and aNorth-South rail running across Especially, Nui Thanh is located in key regions of‘Chu Lai open economic zone and two industrial complexes: Trang Ton and Nam ChuLai with hundreds of companies.

In recent years, along with the development of the country, that the economy of Nui“Thanh district has gradually integrate with the national economy has ereated conditionsfor development a mult-sector economy and encouraged all sectors and individuals toinvest in production and business On May 12.2008, Quang Nam provincial People'sCommittee issued decision 4219 / QD-Committee approving the overall planning ofurban construction Nui Thanh distrit After more than 6 years of implementing decision

4219 (from 2008-2015), Nui Thanh district has changed, the industrial patk and

services are formed, attracting investors and creating jobs for local workers local andsurrounding areas The residential projects, ecotour m, upgraded roads, coneretization,infrastructure systems, electricity, roads, schools and health development are relativelysynchronized, creating a new image for the district Nui Thanh.

2.4, Status of coastal erosion and existing coastal protection measures in studyareas

Coastal protection and protection in estin Fig.2-9.

lary areas have applied at Cua Lo area shown

Fig.2- 9: Existing coastal protection measures in Cua Lo area (Nui Thanh)

(Le Dink Mau, et al, 2015)

In 2009, the system consists of 9 geotextile bags (Geo-textile) had been built to protect,the shoreline, However, they was completely destroyed by wave after a short time.Systems of coast protection forest (forest of casuarinas) were unable to prevent thedestruction of the shore by wave action,

Fig.2- 10: Geo-textile (Internet &Google Earth)

Fig.2- 11: Geo-textile was destroyed in the southern of Cua Lo in 12/2013

(Le Định Mau, et al, 2015)

In 2010, Quang Nam province has invested in the revetment construction in essentialplaces in Tam Hai commune When put into operation in 2012, the phenomenon of

erosion was reduced living life of local people is more stable However, the influence

of 13 typhoons in 2013 that a segment revetment in the end of the dikes about 30 mWere waves, storm damage and Tam Hai commune has petitioned the province to

reconsider In addition, Tam Hai is about 2.4 km of Thuan An and Binh Trung Village

need to build revetments to keep the land without deepening inland about 10m every

Fig2- 12: Approximately 30 m of Fig2-13: Large concrete blocks were

existing revetments was seriously capsized off the ground

Fig.2- 14: Tam Hai revetment, Nui Thanh district, Quang Nam provinces weredestroyed after only a short time in use (Internet &Google Earth)

‘The accumulation of sediment in the north of Cua Lo had been affecting water traffic,

it made transportation more difficult,

Fig.2- 15: Waterway in Cua Lo river mouth (Internet &Google Earth)

‘A rather large area was lost from Ba Tinh to Bai Lang in Tam Quang commune.‘According to local people, Ba Tinh and Bai Lang landmarks are quite beautiful with

100 m white sandy beach that connect to shoreline However, at this moment, thebeach has been eroding severely, and some places are vulnerable to landside,

16: Eroded area in Ba Tình, Nui Thanh, Quang Nam (Internet &Google

Earth)

An Hai Dong village, Tam Quang commune is eroded severely, deepening inlandabout 20 m as the cleft shape The cleft shape has 10m length, counting from beach tooffshore, creating traps that are very dangerous for people and animals.

In landside position, the dangerous zone is in back of Ky Ha port and Tam Quangmarket, The coastline moves deeply inland in Casuarina forest, threatening thestability of local people and coast guard in zone 2.

In Thuan An village, salt water intruded far from the village about 100m, so localpeople have to re-locate deeply inland, influencing property and crops The protectionforest that local people planted to prevent waves, but some typhoons is lost dozens ofhha, and local people cut down to create ponds, so the village is easier to be attacked,As a result, the smallest width in the village is only about 320 m.

2.8 Coastal development

As can be seen in Google Earth images from Fig.2-17 that taken over the years andaccording to research results of the Vietnam Academy of Science and Technology, thenorth bank of Cua Lo always tends to accrete, which further pushes Cua Lo southward,According to survey results over a period of 30-40 years, Cua Lo has moved south

about 4 km In period from 1965-2014, coastline and estuaries in the region Cua Lo

have been subjected to continuous erosion and accretion, Many segments of thecoastlines have been changed strongly While the north-west coastline in Cua Lo andthe cast of Tam Hai commune tended to accretion, the south segment coastline in TamHai commune and Ba Tinh beach tended to erode.

‘Along the southern coast of Cua Lo, the coastline was severely eroded deeply toward adune, of approximately 15-30 m height Erosion strongly makes Casuarina forests here

gradually sparse, with the shrimp on sand also contributes to Casuarina forest

destruction in Tam Hai commune In 2009, a system consisting of 9 geotextile bags(Geo-textile) has been built to protect the shoreline The geotexdle bags were spacedaout 50 metres apart, each bag was about approximately 25 m long, on along neatly600 m coastline However, the embankment system was completely destroyed by waves

after a short time The coastline has eroded seriously and will continue to be eroded ,approximately 30 m per storm During storm No 9/2013, the erosion of coastline

Coastline in 2002 Coastline in 2010

Coastline in 2011 Coastline in 2014Fig.2- 17: Coastal development (Google Earth)

‘The complex phenomena of sedimentation, erosion taking place in this area is verycomplex (table 2-3, table 2-4)

‘The shoreline aceretion trends: the Northwest shoreline of Cua Lo in Tam Hoa nd

‘Tam Hai commune, the west shoreline of North and East of Tam Hai commune Theshoreline erosion trends: the shoreline of Tam Hoa commune, the southeast shoreline