Research hydrodynamics to serve layout design of beach nourishment project for the mui nai beach, ha tien, kien giang province master thesis major coastal engineering and management code 62 58 02 0

THUY LOI UNIVERSITY --- PHAM THI HAN RESEARCH ON HYDRODYNAMICS TO SERVE LAYOUT DESIGN OF BEACH NOURISHMENT PROJECT FOR THE MUI NAI BEACH, HA TIEN, KIEN GIANG PROVINCE THESIS OF MASTER

THUY LOI UNIVERSITY -

PHAM THI HAN

RESEARCH ON HYDRODYNAMICS TO SERVE LAYOUT DESIGN OF BEACH NOURISHMENT PROJECT FOR THE MUI

NAI BEACH, HA TIEN, KIEN GIANG PROVINCE

THESIS OF MASTER DEGREE

HA NOI - 2016

MINISTRY OF EDUCATION

AND TRAINING

MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT

THUY LOI UNIVERSITY -

PHAM THI HAN

RESEARCH ON HYDRODYNAMICS TO SERVE LAYOUT DESIGN OF BEACH NOURISHMENT PROJECT FOR THE MUI

NAI BEACH, HA TIEN, KIEN GIANG PROVINCE

Major: Coastal Engineering and Management Code: 62-58-02-03

THESIS OF MASTER DEGREE

SUPERVISOR: Assoc.Prof.Dr TRAN THANH TUNG

HA NOI - 2016

MINISTRY OF EDUCATION

AND TRAINING

MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT

DECLARATION

I guarantee the work which is being presented in this thesis entitled, “Research on

hydrodynamics to serve layout design of beach nourishment project for the Mui Nai beach, Ha Tien, Kien Giang province” in partial complete of the requirement for the

award of Master thesis of Coastal Engineering Management, is an authentic record of

my own work carried out under supervision Assoc.Prof.Dr Tran Thanh Tung The matter embodied in this thesis has not been submitted by me for the award of any other degree or diploma

Ha Noi, December 16, 2016

Pham Thi Han

Finally, I would like to express my special appreciation to my friends and colleagues for their support and encourage I would like to express deep gratitude to the members

of my family

1.2Brief description of the study area 15

CHAPTER 2 SETUP HYDRODYNAMIC AND WAVE MODEL FOR STUDY

2.2Data usage for model setup, calibration and verification 24

3.2.4 Criteria of the legal framework and implemented project beach nourishments

43

3.2.5 Criteria for planning, protection, exploitation and using of coastal resource 43

3.3 Design the Mui Nai beach nourishment project 44

3.4 Computation lifetime for the Mui Nai beach nourishment project 45

3.4.1 Estimation of annual alongshore sediment transport for study area 45 3.4.2Computation lifetime of the Mui Nai beach nourishment project 51

CHAPTER 4 DESIGN BEACH NOURISHMENT IN COMBINATION WITH SUBMERGED GEOTUBE FOR THE MUI NAI BEACH 56 4.1 Design draft layout for submerged geotube 56

4.1.4 The parameters design layout of submerged geo-tube for beach nourishment 60

4.2 Simulation waves pattern with and without submerged geotube 62

4.3 Simulation flow pattern with and without submerged geotube 74

4.4 Propose layout for beach nourishment in combination with submerged

Figure 2 2Points setting automatic equipment to observe water level, WL1, under the

Figure 2 3 The locations of the sediment sampling area Mui Nai - Ha Tien 26Figure 2 4Water level at rear beach of Mui Nai to 18 hours of June 6, 2016 to 18

Figure 2 5 Grid and computation domain of wave and tidal models (large domain) 32Figure 2 6 Bed topography of wave and tidal models 33Figure 2.7 Comparison of measured and calculated water levels of the Phu Quoc gauging stations from May 6, 2010 to May 20,2010 35Figure 2 8Comparison of measured and calculated wave height at Mui Nai station,

Figure 2.9Comparison of measured and calculated water levels, Phu Quoc gauging stationfrom September 2, 2010 to September 6, 2010 36Figure 2 10Computational domain of the Mui Nai hydrodynamics model 37Figure 2 11 Grid mesh II and domain of hydrodynamics model 37Figure 2 12 Topography of hydrodynamics model for study area 38Figure 2 13Comparison of measured and calculated water levels at Mui Nai beach,

Figure 3 1Monthly wind rose average month, the period from 2009 to 2016 years, Phu Quoc gauging station (Source: WindFinder.com GmbH & Co KG) 41Figure 3 2Monthly wave rose average month, the period from 2009 to 2016 years, Phu Quoc gauging station (Source: WindFinder.com GmbH & Co KG) 41Figure 3 3The scope of dry beach: width 50m, elevation +0.5 44Figure 3 4The scope of submerged beach: width 40m, slope of 1/20, bed elevation at

Figure 3 5Definition of the angle of wave propagation with respect to the coast 46Figure 3 6Schematization of triangular beach fill layer 51Figure 3 7Lifetimes as function of total fill volume 55Figure 4 1 Solution submerged built by geotube to sand pump (Source: Internet) 57 Figure 4 2 Plan view of submerged geotube (Source: Google earth) 59Figure 4.3 Frequency line of synthesis level at point 139 (104027 'A, 10025' B) My Duc, Ha Tien town, Kien Giang province (Source: 14TCN1613 – 2012) 60Figure 4.4Layout of submerged geotube for the beach nourishment project 62Figure 4 5The boundary conditions in wave model 64Figure 4 6Location of points on section extracted to calculation results for wave

Figure 4.7 The grid in case with and without submerged geotube 66Figure 4 8Wave height at MC1 section, simulation scenarios without geotube 66Figure 4 9Wave height at MC2 section, simulation scenarios without geotube 67Figure 4 10Wave pattern in 4 simulations scenario, without submerged geotube 69Figure 4 11Wave height at MC1 section, scenarios with submerged geotube 69Figure 4 12Wave height at section MC2,scenarios with submerged geotube 70Figure 4 13Wave mode the scripts of the case submerged geo-tube 71Figure 4 14 Cross-shore profiles in central section computed by DELFT3D-model

Figure 4 15Shows the time development of the total beach fill volume by time 73Figure 4 16Water levels at Ha Tien station, 2015 and period of highest spring tide in

Figure 4 17The boundary conditions in hydrodynamics model 75Figure 4 18The location to extract the hydrodynamics data 76Figure 4 19Water levels at boundary, from 12th Nov to 20th Nov 2015 77Figure 4 20The area outside submeged geotube of case current status 77Figure 4 21The area outside submeged geotube of case with submerged geotube 78Figure 4 22The area outside submeged geotube of case current status 78Figure 4 23The area outside submeged geotube of case submerged geotube 79Figure 4 24The area inside submeged geotube of case current status 79

Figure 4 25The area inside submeged geotube of case with submerged geotube 80Figure 4 26The area inside submeged geotube of case current status 80Figure 4 27The area inside submeged geotube of case with submerged geotube 81Figure 4 28The point between submeged geotubes of case current status 81Figure 4 29The point between submeged geotubes of case with submerged geotube 82Figure 4 30The point between submeged geotubes of case current status 82Figure 4 31The point between submeged geotubes of case with submerged geotube 83Figure 4 32Current speed at measuring point with wave direction West before and

Figure 4 33Current speed at measuring point with wave direction southeastbefore and

Figure 4 34Currents speed corresponding to the scripts of the status quo plan 85Figure 4 35Current speed in the scripts of case with submerged geotube 86

LIST OF TABLES

Table 1 1Comparison about the number of projects, the frequency and volume of material used for beach nourishment in some countries 7Table 1 2Comparison of common parameters beach nourishment project between a

Table 2 1Coordinates of stations observing wave and water level 25Table 2 2Description of hydro-dynamics survey 27Table 2 3Quantity of taking suspended sediment and bottom sediment 27Table 2 4Water level characteristics at rear beach Mui Nai, Ha Tien town 28Table 2 5Results of characteristic wave at WV1 station, averaged for each day 29Table 2 6Characteristic of wave at WV1 station, the real beach resort of Mui Nai 29Table 2 7Analysis of 12 samples suspended sediment in the Mui Nai beach 30Table 2 8The synthesis of mechanical characteristics for 16 samples bed sediment in

Table 3 1Statistics waves offshore at Phu Quoc Island from 2005 to 2015 (wave

Table 3 2Brief description of the beach nourishment area 44Table 3 3Statistical analysis of data offshore wave Phu Quoc Island in 2005-2015

Table 3 5Input data of sediment and other main parameters 50

Table 3 7Input data for calculation lifetime 53Table 3 8Output data for lifetime of project 54Table 4 1Synthesis of the scripts for wave model 63Table 4 2In put data of the scripts for wave model 64Table 4 3Description of extraction points on wave model 65Table 4 4Wave height at Section MC1, MC2, without geotube 68Table 4 5Wave height at Section MC1, MC2 with submerged geotube 70Table 4 6Wave climate of winter season North Sea (180days; October to March) 72Table 4 7Synthesis of the scenarios for hydrodynamics model 74Table 4 8Input data of the scenariosfor hydrodynamics model 75Table 4 9Current speed according to the scripts 84

INTRODUCTION

1 The necessity of study

The coastal eco-tourism zone of Mui Nai (Ha Tien town, Kien Giang province) is situated in the southwest of Vietnam, with special topography and it has an important role in the economic - social development, security defense and security of Kien Giang province in particular and tourism Southwest region in general

Geographical coordinates:

From 104040’-105032’40’’ East longitude;

From 9023’50’’- 10032’30’’ North latitude

Figure 1 The research area (Source: Collect data) The study area is located in the west sea, shielded by Mui Nai in the South (Mountain Lights) about 8 km west of the island are some of Cambodia, more than 30 km away from Phu Quoc island We can say the project area is shielded almost connected with the sea on both sides, creating a gentle waves mode than in other beach area of Vietnam Besides, here the tidal magnitude reaches a modest value, from 1.1m to 1.2m

The coastal eco-tourism zone of Mui Nai beach comprises two beaches: a front beach

and a rear beach The area has gently sloping beaches, charming landscape and very

suitable for bathing needs and tourism organizations However, the recent years, under

the impact of waves and currents, large amount of sand on the beach of Mui Nai lost;

the other hand due to the effects of sea level rise phenomenon has made the beach area

here are much narrower, sometimes increase tide, the sea level has risen to foot of

dike, no tourists bathing and recreation It had a large impact to the tourism

development strategy of Mui Nai in particular and Kien Giang province in general

Before the urgent need for improvement and upgrading of beach resort in Mui Nai

beach, Ha Tien town, Kien Giang province, there are no reports, recommendations,

proposals from planners or scientists to provide reasonable solutions to improve and

upgrade of Mui Nai beach yet

Figure 2 Location map of the study area (Source: Google earth)

Being aware of the urgency of these issues, the student has selected study with the

theme: "Research on hydrodynamics to serve layout design of beach nourishment

project for the Mui Nai beach, Ha Tien, Kien Giang Province" The research aims

to identify an overall picture on hydro-dynamics regime of the research area and to

simulate design plans in term of hydrodynamic for the Mui Nai beach nourishment

project, review the solutions layout design related to beach nourishment in

combination with submerged geo-tube Also analyze and evaluate the effectiveness of

the solutions layout design, choosing the most reasonable design plan that can be

StudyArea

Gulf of Thailand

Ha Tien town

applied in practice for the study area

Facing this urgency situation, the layout design of beach nourishment project to improve and upgrade of the beach area for beach nourishment, thereby creating new shore is essential because:

a) Solution makes basis scientific to implement layout design of beach nourishment project for improving and upgrading are completed to supplement sand for beach replenishment, creating space for tourists to beach with entertainment activities

b) It serves as a prerequisite for the development of tourism here; turn Mui Nai beach into a major tourist area of Ha Tien in particular and Kien Giang province in general c) It ensures the safety of the infrastructure inside, under the effect of waves, currents and sea levels rise

2 Research objectives

The main objective of this thesis is to simulate the hydrodynamics regime for the study area using a numerical model (MIKE 21FM), and use simulation results as scientific basis for improving and upgrading the Mui Nai beach via a beach nourishment project + Improved landscape and safety for tourists;

+ Reduced loss of sand after implementing beach nourishment project;

+ Maintained natural features of the beach area

3 Study method

3.1 Subject

Research on hydrodynamics regime by numerical models to serve design layout of beach nourishment project for the study area

3.2 Methodology of the thesis

- Data collection and analysis;

- Field investigations and surveys;

- Numerical modeling (MIKE21 FM, HD module and SW module)

4 Thesis outline

Besides the introduction, conclusion and recommendations, the thesis is consisted of 4

chapters as following:

Chapter 1 Overview of beach nourishment and study area

Chapter 2 Setup hydrodynamic and wave model for the study area

Chapter 3 Beach nourishment criteria and design beach nourishment for the Mui Nai beach

Chapter 4 Design beach nourishment in combination with submerged geo-tubes for the Mui Nai beach

CHAPTER 1 OVERVIEW OF BEACH NOURISHMENT AND STUDY AREA

1.1 Introduction of beach nourishment

1.1.1 Beach nourishment, a basic concepts

Beach nourishment is a soft solution to protect sea shore by using suitable material source (known as beach nourishment material) to expand the existing beaches by pouring directly or indirectly materials for this beach area

A coast is considered to be stable when the amount of sediment provides coastal is balanced with the amount of sediment lost (due to sediment transport alongshore, horizontal, human exploitation ) Therefore, when the supply of sediment smaller erode the coastline and vice versa To minimize the coastal erosion, we usually focus

on two solutions: the first solution is to reduce the amount of sediment lost by sediment transport alongshore by design hard structure cross-shore to prevent sand and decrease wave or planting mangroves; the second solution includes beach nourishment and sand by - pass to increase the amount of sediment supply to the coast area

So in essence the solution generally by pouring the material directly on the beach but completely submerged under water, within breaking wave zone Material for beach nourishment should be put on the shore with low-energy waves and long period In this solution, the beach width increased significantly, which increase supply of sediment to the coast is eroded to progress conditions balance of sediment Therefore beach nourishment must be carried out in a certain period time, this period is called beach nourishment period

Nowadays, there are two forms of beach nourishment, which is direct beach nourishment and indirect beach nourishment In beach nourishment the material is poured directly on beaches, usually using the appropriate motor vehicles (cars, bulldozers, etc) and razed to the material or using ship suck – puff to spray until the material reaches the expected beach elevation, width and shape

Unlike beach nourishment, shore-face nourishment is the method applied in large wave energy and erosion speeds greater the beach nourishment methods often use in

order to reduce the loss of material due to beach nourishment caused sediment transport alongshore and horizontally Therefore, with the beach area with small wave condition, the solution using direct beach nourishment is more efficient, reducing the economic costs

Beach nourishment is describes in the figure below:

Figure 1 1Beach nourishment (left) and shore-face nourishment (right)(Source:

Internet) Specifically, the review study of H Hanson, et al [10] about "soft construction" solutions showed that there are clear differences in the frequency of beach nourishment and material used to beach nourishment between the nations Table 1.1 below provides information on the number of beach nourishment projects, beach nourishment frequency and volume of material used for beach nourishments in 2002 From the data, we see that the Spain and the Netherlands are the two countries that used the solutions beach nourishment among European countries However, solutions beach nourishment solutions in these two countries were different While beach nourishment in the Netherlands was performed with large-scale projects, there are more number of projects, but with smaller-scale in Spain

Table 1.1 shows the Quantitative Statistics about number of projects, the frequency and volume of material beach nourishment in each country since the started beach nourishment as the 2002 However, to see more clearly the difference between countries, table 1.2 presents a more detailed comparison of the common parameters of the beach nourishment project between some nations

Table 1 1Comparison about the number of projects, the frequency and volume of

material used for beach nourishment in some countries

as France and Italy that number is quite small So this shows that, except for the Netherlands, raising beach activities in other countries is relatively small and is not commensurate with the total length of the coast can be beach nourishment

Referring to the volume of material beach nourishment used annually under 1 meter length of coastline (AVN) we see that: this value in the Netherlands and Spain approximately the same and at around 40 m3/year/m length of beach nourishment This indicates that, in the Netherlands and Spain, materials used beach nourishment more lost or are these countries more efforts to compensate for the material lost beach nourishment Consider return cycle beach nourishment (ARI) we see that: the period beach nourishment in countries such as the Netherlands, Spain, France and Denmark is about 5 years, while in countries such as Italy and Germany is about 25 years on

used volume material of beach nourishment project much less is expressed in value AVP (the average volume of materials using for all projects beach nourishment)

Table 1 2Comparison of common parameters beach nourishment project between a

The average volume of material

beach nourishment/1m length

coastline were beach nourishment

(m3)

The average volume of material

beach nourishment for project beach

nourishment (m3)

The average number of times beach

nourishment /project beach

nourishment is uses for many different purposes and below will present the usual situations beach nourishment is applied

- Apply to the narrow coast or erosion coast but width of coast is not enough to protect the inside area the risk of flooding due to storm waves and sea level rise;

- Handling, emergency overcoming erosion caused by storms;

- Reduce the erosion speed for beach nourishment area and the areas downstream projects beach nourishment;

- Handling of erosion caused by impact of hard structure on a large area or handling and overcoming erosion occur in the hard structure;

- Expanding the beach to serve the play activities, rest at the beach;

- Improving the protection of the natural coast dunes to against flooding for inside area when have impact of storms and sea level rise;

- Maintain position shoreline to serve the purpose of management, exploitation and use sustainable coasts;

- Respond to the phenomenon such as climate change and sea level rise

1.1.2.2 The Netherlands

In the Netherlands, beach nourishment are started applicable since 1970, in this period about 200 new projects and old projects about beach nourishment was performed at 35 locations with a total volume of material to beach nourishment used up to 110 x 106

m3 From 1991 to now, the volume of medium material for beach nourishment around

6 x106 m3/ year

The Netherlands has a lot of experience in protecting the coastal from the effects of flooding at the western part of the country have altitude lower than the average sea level The majority of the Netherland coastline has faced with encroaching sea condition during a long time In the past, the erosion was processed and decrease in a number of positions with the application of hard structures to prevent sediment transport alongshore However, downstream of these structures, coastal erosion has occurred The Netherlands has used hard structure in protecting the beach However, the historic 1953 floods in the southern region has created a change in the coastal protection policy in the Netherlands

Important step of this trend in 1990 was carried when assessing the feasibility of the technical and economic results of adopting measures beach nourishment for sand coast erosion This priorities for restoring and enhancing the protection of the natural dunes

to prevent wave overtopping Beach nourishment was considered as the main solution

in the coastal protection in the Netherlands after the policy the protection and conservation of the coast was carried in 1990

The design layout parameters includes: the volume of material beach nourishment; beach nourishment performance; beach nourishment period; cross-section; source material beach nourishment, etc

In the Netherlands, the shoreline position is determined based on the measured volume

of sand (based on annual beach cross-section) Beach nourishment has designed with a purpose to offset the loss of sediment caused by the natural process coast dynamics in

a certain period time Materials of beach nourishment is calculated by taking the volume of sediment average annual has loss (taking the average for the ten years prior) multiplied by the beach nourishment period Then material of beach nourishment is added from 10-20 % of the material was calculated (depending on the conditions of each beach nourishment position)

Safety conditions against flooding also are checked regularly every year based on the measurements of the cross-section the beach Elevation of the sand used to beach nourishment is determined based on the actual annual survey The structure had done during 1965 with the cross-section apart from 200 – 250 m along the entire Dutch coast

1.1.2.3 Japan

Japan is an island country with a approximately 30000 km coastline Due to the specific features of topography, geology and system transport infrastructure and services, residential at the coastal areas with high security requirements a majority of structure coast protection are built from the 90’s and before the use of hard structures However, in recent years, due to the impact of a series of dams built on main river systems, the source of river sediment supply to the coast reduced dramatically due to

retained in the reservoir This caused a serious shortage of sediment to the coastal strip around the estuary and cause serious erosion of coastal areas

In the beach nourishment design, requirements for beach nourishment materials adopted first purpose This beach nourishment solution is applied to the beach have small wave and often combined with hard structure is functions keeping the material for beach nourishment

Motivation to design beach nourishment: Material beach nourishment and contribute

to stable beach coast beach culture medium positioned acting as sediment supply to the area is the lack of sand downstream without beach nourishment Generally, applicable activities beach nourishment for small coast and grain size of sediment is much changed This method has the advantage of flexible and harmonious with the natural processes

Technology built beach nourishment in Japan is using cars and bulldozers to pouring directly sediment on the coast Measures using vessels suck, puff is only use in some projects With some other projects with floodplain, using much laparotomy types ship

In Japan, most beach nourishment project are supported by the government budget or the coastal provinces directly The management and exploitation have control of state government and local The private enterprise is not direct financial investment for the protection of the coast, which is only use through a special tax if the business manufacturing jobs related directly to coastal protection structures present

1.1.2.4 Italy

Italy has about 7500 km of coastline, more than half of which geology is alluvial sediments and are now faced with state of erosion and the area of the coast limited region in a serious Coastal protection is an important issue for Italian, a country that is destination resort with over 90 million beach tourist arrivals in the country and Western Europe

In Italy, the solution beach nourishment to the coast against erosion is conducted since

1969 During this period, about 50 projects beach nourishment has implemented in 36

106 m3 Most of these projects are of scale 100 - 150 x103 m3 Except for some scale projects such as dunes along Venice Strip:7.6 x106 m3; beach nourishment in the river mouth Po: 1.4 x 106 m3

large-Almost all the beach nourishment projects in Italy are making by form of beach nourishment combined with hard structure These the projects are purpose at addressing some issues the following: Mitigation of coastal erosion in small range; Expanding the tourist beach resorts and small scale; protecting some sections related to infrastructure in the south of Italy

1.1.3 Beach nourishment in Vietnam

The solution beach nourishment "soft structure", with the "flexibility" in preventing erosion, shoreline stabilization has applied successfully in many countries around in the world However, this solution has not applied in Vietnam

Beach nourishment combined with hard structures measures to improve the efficiency

of beach nourishment, which hard structure had the effect of reducing the loss of sediment horizontal and alongshore Hard structures: submerged breakwater, artificial reefs, etc

The solution against coastal erosion by hard structures measures has been applied quite often in our country, so we had some experience in that problem The traditional solution structure have been used mainly in the coastal strip is now the bank protection

by concrete or stone structures with detailed design guidelines newly updated in 2012 However, if the use of shore protection measures "hard structure" in the tourist activities (e.g cases protecting coast by use concrete structures at Doi Duong beach, Binh Thuan province) or potential tourism activities will disrupt the natural landscape, reducing the environmental friendly tourism If the design layout structure are incorrect, would quickly destroy by regularly suffered the direct impact of these factors waves, winds in the area

In recent years, coastal protection solutions using geotextile tubes forming "soft structure" has also been applied in some sections of coastline erosion in Hoa Duan (

Thua Thien Hue); Tam Hai (Quang Nam); Doi Duong (Binh Thuan); Loc An (Ba Vung Tau)

Ria-Beach nourishment as erosion prevention solutions, stabilizing the shoreline have forms "non-structural" or also known as structural measures "soft" has been applied successfully in many countries with the first marine science and technology advanced

in the world Beach erosion prevention and embellish the coast had not studied applied

in Vietnam although we had many reclamation projects, but mainly built inside the bays and material mostly rocky beaches and have combination with hard structure In Vietnam, in recent years, some beach regeneration project, reclamation in the tourist areas, resorts and coastal areas have just started For example, the reclamation project

in Do Son peninsula, Hai Phong, Quang Ninh Tuan Chau island, the reclamation project Da Phuoc, Da Nang city, the reclamation Can Gio project, Ho Chi Minh City, etc

Can Gio project was started in 2007 with a design total area of reclamation of 600 hectares, in which 200 hectares will be reserved for internal sea and beaches, 400 hectares to develop service projects tourism and residential areas

The improvement and upgrading of the tourist areas in Vietnam has not been focused, due to many reasons such as capital investment, scientific and inadequate technical level, etc Currently, only some areas such as Bai Chay Beach, Tuan Chau and Bai Tu Long Bays (Quang Ninh), Sam Son beach (Thanh Hoa), Nha Trang beach, are being properly concerned with the implementation layout design layout to improve and upgrade beach study area

Figure 1 2Dike in Mui Ne, Binh Thuan (Source: Google Earth)

In previous years, Tuan Chau beach, despite being a beautiful beach, with views of the

Ha Long bay, the UNESCO World Heritage, but also somewhat inconvenient due to narrow and low quality of mud sand on the beaches Thanks to the investments in the improvement and upgrading of this beach, the Tuan Chau beach now has a new appearance The beach is wider, sprayed with clean white sand; the sand has smoothly screened before put into use Tourists are comfortably frolic on the wide beach with white sand In addition, Tuan Chau beach has been expanding services to create satisfaction for arriving tourists

Nha Trang beach needs upgrading and improving because the beach area no longer meets the demand for entertainment while ensuring environmental sanitation and urban landscape The improvement and upgrading of the beach must be consistent with the overall planning of development economic - social, increase efficiency, ensure the beauty of landscape and environment for each region and minimize negative impacts to Nha Trang

In Sam Son, Thanh Hoa there are also plans to improve and upgrade the beach to serve the tourists in summer 2016 The Provincial Committee has approved the policy assigned to Joint Stock Company FLC Group to perform spatial planning at the beach area, Sam Son town, Thanh Hoa province

Measures to improve and upgrade the beach in Vietnam mainly are "hard measures",

so there is less experience on “soft measures” Beach nourishment is "flexible" in

keeping sand, shoreline stability for serves to improve and upgrade of beach tourism region has been successfully applied in many countries around the world This solution combines with structure to promote the advantages of both “hard” and “soft” measures However, this solution has not been applied extensively in Vietnam

1.2Brief description of the study area

1.2.1Geographical location and natural conditions

Kien Giang province in the Mekong Delta - the Southwest of the country: the North by the Kingdom of Cambodia; the South near Ca Mau and Bac Lieu province; Eastern and Southeastern of province border An Giang, Can Tho City and Hau Giang Province; West by the Gulf of Thailand

The province is located from 90 23 '50'' - 100 32' 30 '' north latitude; from 1040 26 '40'' -

1050 32' 40 '' east longitude;

North of Kien Giang province bordering Cambodia, 56.8 km long border; south of Bac Lieu and Ca Mau provinces; west by the Gulf of Thailand with a coastline of 208 km; respectively adjacent eastern provinces of An Giang, Can Tho City and Hau Giang Province

Kien Giang has 15 administrative units districts: Rach Gia city, Ha Tien town, the districts of Kien Luong; Giang Thanh, Hon Dat, Tan Hiep commune, Chau Thanh, Giong Rieng, Go Quao, An Bien and An Minh and Vinh Thuan, U Minh Thuong and Phu Quoc, Kien Hai

Figure 1 3Location of Ha Tien town, Kien Giang province

Ha Tien is a small town located in the northwest of the province of Kien Giang (formerly located in the province of Ha Tien district and then Rach Gia province) North bordering Cambodia with 13.7 km long border, the eastern and southern borders Kien Luong district, the West by the Gulf of Thailand with a coastline of 22 km Ha Tien is a narrow coastal strip of land with a rich terrain as bays, plains, mountains, rivers, caves and islands, etc

Mui Nai is located in the southwest of the country and south-west of the Mekong Delta Eastern and south-eastern borders of the provinces of An Giang, Can Tho, the south by the Ca Mau and Bac Lieu, the west by the Gulf of Thailand, north bordering Cambodia, with length borders 56.8 km

Ha Tien is where the distances to the ASEAN countries are relatively short; these countries are having economic growth rate highest in the world Ability of develop with Cambodia through the gate and create a relationship with Thailand through road transport system

Figure 1 4The rear beach of Mui Nai beach, Ha Tien Town, Kien Giang Province

(Soure: Survey) Mui Nai beach is the gateway to the sea of some Mekong Delta provinces to several countries around the world This is a very important location for the development of outward-oriented economy, suitable with the policy of the Party and State

Mui Nai beach of Ha Tien town is one of three "rare" area of the Mekong River Delta From more than 300 years ago, Mui Nai was called Loc Tri and renowned as one of ten beauty of Ha Tien town For many years, this area has become a major tourist destination attracting many tourists to visit beach and resort On an area of 17 hectares, Mui Nai beach have 11 business tourism operators

1.2.2 Topography, geomorphology characteristics

a Topography characteristics

The study area is mountainous terrain on the coastal plain

Coastal areas in Kien Giang province has relatively flat topography and low altitude in common areas from 0.3 to 0.5 m Particularly through Ha Tien town high topography, interspersed with hilly, altitude in the region of 0.8 to 1.2 m Seabed terrain is flat and gentle slope Accretion takes place strongly in Rach Gia Bay area and many other areas such as tourist resorts of Mui Nai

Topography and geomorphology of the study area will be the basis for the research design of the project layout, offering suitable technical solutions to serve the beach nourishment project

b Geomorphology characteristics

Among study area, there are 16 stratigraphic units, which the presence of intrusive rocks, eruptive, sediment Young Holocene sediments (Q12) are distributed in a narrow area, but very diverse in origin: rivers, marshes, bays, oceans

The region is full of mountainous terrain types, hills, plains, beaches, islands and archipelagos Ha Tien - Kien Luong characterized by the landscape of the massif, rocks erupting cone, like the coast of Mui Nai, and geomorphology karst landscape with towering limestone blocks, distribution pyramid isolated on Freeze Cave system distributed in different heights, with many stalagmites, stone columns, stalactites with interesting shapes Hollow strip worn by the sea meets the typical average have 4.5 meters high - the traces of climate change in the past engraved on limestone cliffs

1.2.3 Hydro-marine conditions of study area

1.2.3.1 Hydrological conditions

Tidal waters of Ha Tien and Mui Nai general in particular influenced by semi-diurnal East Sea; also influenced by the diurnal tide from the Gulf of Thailand Tidal of Ha Tien sea area prone to mixed diurnal During the day there are two peaks, 2 feet, but the catastrophe completely dominate and neither diurnal Means two peaks differ significantly but each approximately 2 feet Only small tidal amplitude ranges from 0.7

to 1.0 m This timetable form time to maintaining low water levels create favorable drained spending In January, the highest level on day care to high expectations (15 lunar), down on the day the upper and lower amplitude mystical about 0.2 to 0.5 m The lowest water level is no clear cycle oscillations for two boundaries

The wave regime of the region is affected by two distinct seasons, with NE, SW monsoon In which the wave direction SW is most active from May to September, the wave height may reach 5 meters and in the summer (June and July) The average sea temperature reached 29.2 0C, often never to below 24 0C

The flow in Ha Tien coastal area is formed the combination of by the tidal current, wind and river flow stream The average flow speed is quite large, from 30 to 50 cm/s

1.2.3.2 Climatic – meteorological conditions

The climate, hydrology resort in Mui Nai characterized hydrology climate is tropical monsoon, hot and humid throughout the year, the average temperature from 27.5 0C Celsius to 27.7 hours of sunshine in the years around 2400 hours, average humidity 81–82 % The year is divided into two distinct seasons including rainy season and dry season The rainy season from May to November, the dry season from December to April next year The average rainfall is over 2100 mm/year The area has two main wind directions northeast and the southwest monsoon

1.2.4Social and economic features

a Economic conditions

Ha Tien town is located in Long Xuyen quadrangle, has borders with Cambodia, both

on land and at sea, from Cambodia's Kampot province about 60 km and 20 km of the city of Kep, which is very convenient in economic development with Cambodia

through border gate, creating a relationship with Thailand through waterway and aviation

For the development of tourism, Ha Tien and hinterland are popular destinations of Vietnam travelers in general However, very few international visitors have been to this place Thus solution is needed to enhance regional economic development through tourism activities development this areas

Research about infrastructure in poor areas, greatly hinders socio-economic development in the region In the future, along with the renovation and synchronous infrastructure of the industrial centers and economic zones, coastal cities need to spend adequate funds to invest in developing infrastructure systems for the deep-lying, remote and island areas

By 2020, construction of Ha Tien town into a tourist center of services, development of urban type III, is the closest connection points along the Phu Quoc island district; renovation and expansion of the port in Kien Luong, Hon Chuong and Binh Tri; urban development, such as Hon Dat, Chau Thanh, Song Doc, Nam Can, Ghenh Hao form

an urban system along the coast; urban construction, the town on the island as of Duong Dong, An Thoi and Kien Hai create a strong base for development combined with security and defense, firmly safeguard the waters south west of the country

CHAPTER 2 SETUP HYDRODYNAMIC AND WAVE MODEL FOR STUDY AREA

2.1Model descriptions

MIKE 21 is a modeling system developed by DHI Water & Environment The objective of this section is to provide the user with a detailed description of the flow and transport model equations, numerical discretization and solution methods and model validation

MIKE 21 is based on a flexible mesh approach and it has been developed for applications within oceanographic, coastal and estuarine environments The modeling system may also be applied for studies of overland flooding

The system is based on the numerical solution of the two/three dimensional incompressible Reynolds averaged Navier - Stokes equations invoking the assumptions of Boussinesq and of hydrostatic pressure Thus, the model consists of continuity, momentum, temperature, salinity and density equations and it is closed by

a turbulent closure scheme

The spatial discretization of the primitive equations is performed using a cell-centered finite volume method The spatial domain is discretized by subdivision of the continuum into non-overlapping elements/cells In the horizontal plane an unstructured grid is used while in the vertical domain in the 3D model a structured mesh is used In the model 2D the elements can be triangles or quadrilateral elements In the model 3D the elements can be prisms or bricks whose horizontal faces are triangles and quadrilateral elements, respectively

2.1.1Hydrodynamics model (MIKE 21 FM HD module)

2.1.1.1 The theoretical basis of the hydrodynamics model

MIKE 21 Flow Model FM is a new modeling system based on a flexible mesh approach The modeling system has been developed for applications within oceanographic, coastal and estuarine environments

MIKE 21 FM is composed of following modules:

 Hydrodynamic Module

 Transport Module

 ECO Lab Module

 Particle Tracking Module

 Mud Transport Module

 Sand Transport Module

The Hydrodynamic Module is the basic computational component of the entire MIKE

21 Flow Model FM modeling system providing the hydrodynamic basis for the Transport Module, ECO Lab Module, Mud Transport Module, Particle Tracking Module and Sand Transport Module

The Hydrodynamic Module is based on the numerical solution of the 2D shallow water equations - the depth-integrated incompressible Reynolds averaged Navier-Stokes equations Thus, the model consists of continuity, momentum, temperature, salinity and density equations In the horizontal domain both Cartesian and spherical coordinates can be used

The spatial discretization of the primitive equations is performed using a cell-centered finite volume method The spatial domain is discretized by subdivision of the continuum into non-overlapping element/cells In the horizontal plane an unstructured grid is used comprising of triangles or quadrilateral element An approximate Riemann solver is used for computation of the convective fluxes, which makes it possible to handle discontinuous solutions

2.1.1.2 Model equations

The local continuity equation is written as:

The two horizontal momentum equations for the x- and y-component, respectively:

Where t is the time; x, y and z are the Cartesian co-ordinates; η is the surface elevation;

is the still water depth; h = η + d is the total water depth; u, v and w are the velocity components in the x, y and z direction; f = 2Ωsinφ is the Coriolis parameter; g is the

gravitational acceleration; ρ is the density of water; νt is the turbulent (or eddy) viscosity; pa is the atmospheric pressure; ρo is the reference density of water S is the magnitude of the discharge due to point sources and (us,vs), is the velocity by which the water is discharged into the ambient water

2.1.1.3 Application areas

The application areas are generally problems where flow and transport phenomena are important with emphasis on coastal and marine applications, where the flexibility inherited in the unstructured meshes can be utilized

2.1.2 Wave model (MIKE21 FM SW module)

2.1.2.1 The theoretical basis of the wave model

Mike 21SW is a state of the art third generation spectral wind –wave model developed

by DHI The model simulates the growth, decay and transformation of wind –generated waves and swells in offshore and coastal areas

Mike 21SW includes two different formulations:

 Full spectral formulation;

 Directional decoupled parametric formulation

The fully spectral formulation is based on the wave action conservation equation Komen et al (1994) and Young (1999) The directional decoupled parametric formulation is based on the parameterization of the wave action conservation equation The parameterization is made in the frequency domain by introducing the zero and first moment of the wave action spectrum The basic conservation equations are formulated in either Cartesian co-ordinates for small-scale applications and polar spherical co – ordinates for large-scale applications

The discretisation of the governing equation in geographical and spectral space is performed using cell- centred finite volume method In the geographical domain, an unstructured mesh technique is used The time integration is performed using a fractional step approach where a multi-sequence explicit method is applied for the

propagation of wave action

2.1.2.2 Model equations

Mike 21SW includes two different formulations:

 Full spectral formulation;

 Directional decoupled parametric formulation

The directionally decoupled parametric formulation is based on a parameterization of the wave action conservation equation Following Holthuijsen et al (1989), the parameterization is made in the frequency domain by introducing the zero and first moment of the wave action spectrum as dependent variables Mike 21 SW it is not necessary to set up a number of different orientated bathymetries to cover varying wind and wave directions

The governing equation in Mike 21 SW is the wave action balance equation formulated in either Cartesian or spherical co-ordinates In horizontal Cartesian or spherical co-ordinates, the conservation equation for wave action reads:

Where N(x,σ,θ,t)is the action density; t is the time; 𝑥��⃗ = (𝑥, 𝑦) và 𝑦 = (𝜙, 𝜆)is the Cartesian co-ordinates; is the propagation velocity of a wave group

in the four- dimensional phase space , σ và θ; và S is the source term for energy balance equation ∇ is the four- dimensional differential operator , σ và θ

2.1.2.3 Application areas

Mike 21SW is used for the assessment of wave climates in offshore and coastal areas

in hind cast and forecast mode

A major application area is the design of offshore, coastal and port structure where accurate assessment of wave loads is of utmost importance to the safe and economic design of these structures

Mike 21SW is also used for the calculation of the sediment transport, which for a large part is determined by wave conditions and associated wave induced currents The wave - induced currents is generated by the gradients in radiation stresses that occur in the surf zone

Mike 21SW can be used to calculate the wave conditions and associated radiation stresses The long-shore currents and sediment transport are using the flow and sediment transport models available in the MIKE 21 package For such type of applications, the directional decoupled parametric formulation of MIKE 21 SW is an excellent compromise between the computational effort and accuracy

2.2Data usage for model setup, calibration and verification

2.2.1 Observation periods and location

Construction Engineering Institute has conducted the task of observation of oceanographic factors including waves, currents, water levels and sediment at the beach of resort Mui Nai, Ha Tien Town, Kien Giang Province Data is recorded in June 2016 when the southwest monsoon is dominant Basically, the factors are simultaneously observed

Tide was continuously observed for three days in June 2016

(c c cσ cθ)

v= x, y, ,

v

v

Wave was continuously observed for 6 hours per day and for three days in June 2016

2.2.1.1 Location of observation station and taking samples

The observation factors includes: waves, water levels, sediment bottom and suspended sediments Therefore, there are basically three monitoring stations and 1 group of sediment sampling locations Specifically, wave station WV1 and current station FL1 are arranged close to each other, located on the cross-section in the middle of thebeach, about 300 meters from shore The station observing water level WL1 is located at the toe of marina in front of Ta Pang motel Location and coordinates of station WV1 / FL1 and WL1 are given in Figure 3.1 and Table 3.1

Table 2 1Coordinates of stations observing wave and water level

Coordinates Station WV1/ FL1 Station WL1

East longitude 104026’35,53” 104026’45,0”

North latitude 10023’12,69” 10023’14,4”

According to the research proposal, wave characteristics are observed at a fixed point

in the surfzone and continuous measuring in 3 days However, based on the actual conditions of equipment transportation and hiring boats, the observation process is adjusted Due to difficulties in transporting automatic equipment continuously and accessories, the survey team can only carry equipment to measure wave height Therefore, wave was observed about 6 to 8 hours per day (in 3 days)

The location for setting equipment to observe water level at the tourist port This position is satisfied in term of stability, easy observation and protection as well as the least impact to the activities of visitors Moreover, this position is always flooded even

if the water level down to the lowest Figure 2.1 illustrates position of installing the equipment

Group of sediment sampling locations included fifteen points, distributed over four cross-sections with regular intervals along the beach from North to South, as shown in Figure 2.3

Figure 2 1 Location of points observing waves WV1, currents FL1 and water level

WL1 on satellite image

Figure 2 2 Points setting automatic equipment to observe water level, WL1, under the

wharf in front of Ta Pang motel

Figure 2 3 The locations of the sediment sampling

2.2.1.2 Factors of the survey

Three oceanographic factors are observed that include wave characteristics, the current (speed and direction) and the water level Wave height and wave period are measured

at the sea at the water depth of 3 m

Near the location, a boat was arranged to measure speed and observing current direction Tidal fluctuation was observed by self-recording machines; results are based

on national elevation datum The number of oceanographic surveys is summarized in Table 2.2

Table 2 2 Description of hydro-dynamics survey

Contents Stations Period of survey Description

Wave 1 From 7 to 9 June,

2016

The device is set by 4 Hz mode,

6 hours per day x 3 days x 2 devices

Water level 1 From 6 to 9 June,

2016

The device is set under the regime of

15minutes/observation in 3 daysTable 2 3 Quantity of taking suspended sediment and bottom sediment

Contents Locations Period Description

Bottom sediment 15 3 days Bottom Sampling using

Wildco Grab

Suspended sediment 12 3 days

Suspended sediment sampling using depth-average method

To analyze the characteristics of suspended sediment for sediment transport calculation, four sections along the coast to take suspended sediment samples with density of three locations per section Besides, in order to assess the nourishment material to calculate for beach nourishment, on these section bottom sediment samples were taken at 4 locations per each section Table 2.3 shows the number samplings of

2.2.2 Water levels observation and field measurement

Results of measurement tide water level:

The water level observations at foot of the bridge of beach Mui Nai in 3 days time measure are summarized and illustrated in Figure 2.4

Figure 2 4 Water level at rear beach of Mui Nai to 18 hours of June 6, 2016 to 18

hours of June 9, 2016 Reviews tide water level measurement results: Overall, water level at the Mui Nai beach is quite similar to Ha Tien town, but with different amplitude

Table 2 4 Water level characteristics at rear beach Mui Nai, Ha Tien town

Characteristics Water level (cm)

Table 2 5 Results of characteristic wave at WV1 station, averaged for each day

Days Wave height Hs (m) Wave period T1/3 (s)

Table 2 6 Characteristic of wave at WV1 station, the real beach resort of Mui Nai

Characteristics H s Time H m0 Time

From the measurements carried out calculations of waves includes: the maximum wave height and minimum wave height and medium wave height as shown in Table 2.6

Through the data collected, we can see the frequency 4 Hz ensures the meter is required Matlab code of Verhagen (2013) was use for statistical characteristics of the wave; calculation results relatively reasonable

Using measured water level data to calibrate is recommended instead of curve fitting if the water level monitoring data fully In addition, the values Hm0, Tmean, Tm and Tpeakshould be calculated by means of wave spectrum with some parameters specified

2.2.4 Suspended sediment

Analysis results of samples suspended sediment in the Mui Nai beach area at 4 sections long shore, as shown in Table 2.7 below

Table 2 7Analysis of 12 samples suspended sediment in the Mui Nai beach

Numbers The concentration of

Suspended sediment (mg/l) Sampling locations

2.2.5 Bed sediment sampling

Analysis result of bed sediment samples Dn50 in the area Mui Nai in 4 sections along shore, is presents in Table 2.5 below

The average value calculated from the average diameter D50 of 8 samples is 161 µm

So, material to beach nourishment should have D50 about 180 to 200 µm