Using landsat vegetation indices in quantifying coastal mangrove in thai thuy district thai binh province

MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT
VIETNAM NATIONAL FORESTRY UNIVERSITY

STUDENT THESIS PROPOSAL
Title

Using Landsat Vegetation Indices in quantifying coastal

mangrove cover in Thai Thuy District, Thai Binh Province
Major: Natural Resources Management
Code: D850101

Faculty: Forest Resources and Environmental Management

Student: Tran Duy Binh

Student ID:1253092057

Class: K57 Natural Resources Management

Course: 2012 – 2016

Advanced Education Program
Developed in collaboration with Colorado State University, USA
Supervisor: Dr. Nguyen Hai Hoa
Co-supervisor:

Ha Noi, 10/2016


ACKNOWLEDGEMENT

This thesis would not have been possible without the support and help from my
teachers, friends, families and several people. I would like to express our special
appreciation of following people who supported me with my sincere gratitude:
I would like to express my sincere thanks and appreciation to my supervisor Dr. HaiHoa Nguyen for his untiring and excellent guidance, valuable suggestions in my dilemmas.
His comments and advices have helped me to finish my thesis.
I am also thankful to Prof. Lee MacDonald for his enthusiasm in guiding me to
construct thesis proposal. His comments and criticism on my proposal helped me to present
better final thesis.
Further, I would like to thank the Department of Natural Resources and Environment
in Thai Thuy district for support and giving me the chance to study in Thai Thuy District.
Besides, I also thank the local authorities and farmers in three communes namely: Thuy
Truong, Thuy Xuan and Thuy Hai for providing valuable information and data of the area.
I wish to thank the Center of Laboratory and Practice of Vietnam Forestry University
for providing me with survey instrument (GPS Garmin) for field survey. I also thank my
friends for their enthusiastic help in the process collected data in field survey.
Last but not least, my everlasting gratitude goes to my parents who always
encouraged and supporting me all the time.


CONTENTS
ACKNOWLEDGEMENT
CONTENTS
ACRONYMS
LIST OF TABLES
LIST OF FIGURES AND DIAGRAMS
CHAPTER I. INTRODUCTION ....................................................................................... 1
CHAPTER II. LITERATURE REVIEW .......................................................................... 5
2.1. GLOBAL MANAGEMENT OF COASTAL MANGROVES ...................................... 5
2.2. COASTAL MANGROVES MANAGEMENT IN VIET NAM .................................... 8
2.3. MANGROVE CHANGE AND METHODS ................................................................ 10

2.4. SIGNIFICANCE OF STUDY ...................................................................................... 10
CHAPTER III. OBJECTIVES, CONTENTS AND METHODOLOGY ..................... 12
3.1. GOAL AND OBJECTIVES ......................................................................................... 12
3.1.1. Overall goal ............................................................................................................... 12
3.1.2. Research objectives.................................................................................................... 12
3.2. RESEARCH CONTENTS ............................................................................................ 12
3.2.1. Investigate spatial distribution characteristics and management schemes of coastal
mangroves in Thai Thuy District, Thai Binh province. ....................................................... 12
3.2.2. Quantify changes in coastal mangrove extents in Thai Thuy district during 2001 2016 ..................................................................................................................................... 13
3.2.3. Identify key drivers of changes in coastal mangrove extents in Thai Thuy district
during 2001 – 2016. ............................................................................................................. 13
3.2.4. Propose solutions for better management of coastal mangroves in Thai Thuy district. .... 13
3.3. METHODOLOGY ....................................................................................................... 13
3.3.1. Secondary data collection: ........................................................................................ 13
3.3.2. Quantification of coastal mangrove changes ............................................................ 13
3.3.3. Field data collection .................................................................................................. 17
3.4. Calculation of Vegetation indices ................................................................................. 18
3.4.1. NDVI calculation ....................................................................................................... 18
3.4.2. Difference Vegetation Index (DVI): ........................................................................... 19
3.4.3. Ratio-based Vegetation Indices: ................................................................................ 19
3.4.4. IPVI:........................................................................................................................... 20


3.4.5. SAVI: .......................................................................................................................... 20
CHAPTER IV. NATURAL AND SOCIOECONOMIC CHARACTERISTICS ........ 21
4.1. NATURAL CHARACTERISTICS .............................................................................. 21
4.1.1. Geography ................................................................................................................. 21
4.1.2. Terrain ....................................................................................................................... 21
4.1.3. Climate ....................................................................................................................... 22
4.1.4. Land condition in Thai Thuy ...................................................................................... 23

4.2. SOCIOECONOMIC CHARACTERISTICS ................................................................ 23
4.2.1. Social characteristics ................................................................................................. 23
4.2.2. Economic characteristics ........................................................................................... 24
4.2.3. District production and commercial results .............................................................. 26
4.3. COASTAL MANGROVES .......................................................................................... 26
CHAPTER V.RESULTS AND DISCUSSION ................................................................ 28
5.1. SPATIAL DISTRIBUTION AND MANAGEMENT OF COASTAL MANGROVES.... 28
5.1.1. Spatial distribution of coastal mangroves ................................................................. 28
5.1.2. Management schemes of coastal mangroves ............................................................. 29
5.2. HISTORICAL CHANGES IN COASTAL MANGROVE EXTENTS ....................... 31
5.2.1 Mangrove extents using various vegetation indices ................................................... 31
5.3. KEY DRIVERS OF COASTAL MANGROVES CHANGES .................................... 36
5.4. SOLUTIONS FOR BETTER COASTAL MANGROVES MANAGEMENT ............ 38
CHAPTER VI. CONCLUSION AND FURTHER STUDY........................................... 40
6.1. CONCLUSION ............................................................................................................. 40
6.2. EXISTANCE AND FUTHER OF STUDY.................................................................. 41
REFERENCES
APPENDIX


ACRONYMS
FAO – Food and Agriculture Organization
JICA – Japan International Cooperation Agency
GIS – Geographic Information System
MONRE – Ministry of Natural Resources and Environment
MARD – Ministry of Agriculture and Rural development
GPS – Global Positioning System
UNICEF – The United Nation Children’s Fund

LIST OF TABLES
Table 3.1: Landsat and Sentinel Data used for detecting changes in coastal mangroves. ... 14
Table 3.2: Equation of Vegetation Indices used for mangrove mapping ............................ 14
Table 4.1: Climate characteristics ........................................................................................ 22
Table 4.2: Traffic system in Thai Thuy district. .................................................................. 24
Table 4.3: Key indicators of Thai Thuy district economy during 2005 – 2010. ................. 26
Table 5.1: Values of Vegetation indices calculated from 2001 to 2016. ............................. 31
Table 5.3: The result of table comparing the percent of accurate in 5 vegetation index (%) ... 33
Table 5.4: Changes in mangrove extents different periods: 2001– 2006; 2006 – 2011; and
2011 – 2016. ........................................................................................................................ 35


LIST OF FIGURES AND DIAGRAMS

Diagram 3.1: Flow chart of mangrove classification using Landsat images from 2001- 2016. ... 15
Figure 5.1: Spatial distribution of coastal mangrove species in Thuy Truong, Thuy Xuan and
Thuy Hai communes, Thai Binh province. ........................................................................................ 29
Fig. 5.2. Difference between the area of mangrove in Thai Thuy district by using 5 vegetation
indices. .................................................................................................................................................... 32
Fig.5.3 Mangrove area by using Landsat image and Sentinel image. ............................................. 34
Fig. 5.4. The maps show that LULC change using NDVI in Thai Thuy district during three
periods (2001-2006, 2006-2011, 2011-2016). ................................................................................... 36


CHAPTER I
INTRODUCTION
Vietnam has a coastline of 3260 kilometers, creating an appropriate environment for
mangroves development. According to Forest Trends- a non-profit organization based in
Washington DC – Vietnam’s mangrove extent account for around 2% of the world’s total,
ranked 2nd only after the Amazon river basin. They play an important role for the environment

and people’ livelihood such as: providing various ecosystem services including carbon
storage; wood for building, setting traps, firewood; shelters for fishes and other marine
species; shoreline stability and erosion prevention. A large part of Vietnam’s population lives
in coastal regions, where mangroves play a major role in their livelihoods. Apart from
providing homes, jobs, food for millions, mangroves also attenuate wind-induced waves,
current and storm surges so it protects coastal inhabitants from extreme events such as
tsunamis and storms. Currently, there are 30 provinces and cities in Vietnam mainland that
have coastal mangrove forests and wetland. The mangroves vegetation is divided into 4
zones: North-eastern coast from Ngoc cape to Do Son cape (Zone I), Northern delta from Do
Son cape to Lach Truong river (Zone II), Central coast from Lach Truong to Vung Tau cape
(Zone III) and Southern delta from Vung Tau cape to Ha Tien (Zone IV) [1]. Total mangrove
extents in Vietnam reduced dramatically from 1943 to 2000 due to natural disasters, wars and
unprecedented human exploitation activities [2].
Protecting and regenerating mangroves in coastal regions have been becoming an
extremely important task of the Government, local authorities, organizations and individuals.
The coastal mangroves extents of Thai Thuy district, Thai Binh province is not out of this
trend. For many years, they have been protected carefully. This is achieved because the Thuy
Truong commune set up a specialized forest protection task force with 6 members and some
equipment. Mangroves in Thai Binh have a high biodiversity level with many terrestrial and
marine species. They not only help create a formidable forest that withstands typhoons and
1


waves but also form a marine ecosystem. It is also the main source of income for local people.
Coming to Thuy Truong- a coastal commune of Thai Binh that was usually affected by floods
and storms- can we see the effectiveness of mangroves? This commune has about 3.7
kilometers of sea dike and before 1994, it was often threatened by high sea waves. However,
nowadays, with 1,300 hectares of mangrove running along this dike system (the widest area
can be up to 1.8 kilometers), it has become very safe after many typhoon seasons. Especially
the 2nd and 8th typhoon in 2005, with wind speed at over 10 degrees which destroyed the

concrete dike systems in Hai Phong and many nearby provinces, but the one in Thuy Truong
survived. Apart from protecting the sea dikes, Thai Binh’s mangroves also ensure the safety
of more than 3,000 hectares of aquaculture ponds.
Realizing the impact of tides and storms, Thai Binh has launched hundreds of
mangroves plantation campaign to counter typhoons and climate change, and has planted tens
of thousands of hectares of trees. In particular, Thai Thuy district has the largest forest area,
with about 4.700ha stretches over 27km along the coastline. To promote afforestation, coastal
communities have sought to allocate forest land to household management and afforestation.
Accordingly, the growers enjoy the planting and care funding from the district and commune,
and they would enjoy all the marine resources brought from the forest, so people are actively
involved in this project. The district’s Resources and Environment department continues
advising and implementing of the Law on Mineral (2010), the Law on Water Resources
(2012) and different guiding decrees from both National and regional levels. At the same
time, they also effectively execute coordination regulations, checking and handling sand
mining activities on the river bed between Hai Phong and bordering districts: Tien Hai, Dong
Hung, Kien Xuong. In the 4th quarter of the year 2014, this agency was scheduled to complete
the environmental evaluation criteria (the 17th criteria) for 12 communes that finished the
project before October and November of 2014; guided communes to implement the Decision
No.2070/QĐ-UBND of the province’s People’s committee referring to the regulation of
2


charges hygiene and Decision No.15/2014-QĐ-UBND referring to some mechanisms and
policies to support the collection and processing of domestic waste in the province of Thai
Binh. Leaders and local governments would often advocate and encourage people to increase
production while protecting the environment and the mangroves itself.
Several proposed vegetation change detection methods are based on the same image
pre-processing to create a time-series dataset, requiring a geometric and radiometric image
correction. Coppin & Bauer (1996) and Milne (1988) reported the main methodological
approaches for vegetation change detection can be distributed into four broad categories:

linear procedures (difference and ratio images); classification routines (post-classification
change, spectral pattern change); transformed data sets (vegetation indexes, principal
components analysis-PCAs); and others, such as regression analysis, knowledge-based expert
systems, or neural networks (Sader et al. 2003). Several literature reviews such as suchoney
and Haack (1994); Nordberg and Evertson (2004, 2005) reported the most efficient
methodologies in accuracy and cost saving performances were image differencing and PCA
techniques. The image differencing technique is based on a cell-by-cell subtraction between
different images in a time-series. This technique applies differences between remotely sensed
images of vegetation characteristics, and indexes derived from image radiance or reflectance
differencing as NDVI (Normalized Difference Vegetation Index) or change vector
differencing (Schowengerdt 1997). The NDVI differencing method uses estimated NDVI as
the normalized difference between near infrared (NIR) and visible red (RED) bands, which
discriminate vegetation from other surfaces based on green vegetation chlorophyll absorption
of red light for photosynthesis, and reflection of NIR wavelengths (Tucker 1979). The NDVI
differencing technique was widely applied for both human-induced and natural forest cover
change detection as land cover conversion, forest harvesting, revegetation, or afforestation
that includes natural forest expansion and human-induced landscape restoration (Lyon et al.
1998, Wilson & Sader 2002, Sader et al. 2003, Lunetta et al. 2002, 2006, Nabuurs et al. 2007,
3


Podeh et al. 2009). In addition to the standardized techniques for pre-processing and
differencing images, the most important step for vegetation change detection analysis is
discrimination between real changes and seasonal or inter-annual variability, represented by a
threshold between these factors, which is generally determined by applying the standard
deviation (SD) from the NDVI differencing image (Hayes & Sader 2001, Coppin et al. 2004,
Desclée et al. 2006, Sepehry & Liu 2006, Pu et al.2008).
Recognizing the importance of coastal mangrove management efforts, we decide to
perform this research: “Using Landsat Vegetation Index in Quantifying Coastal Mangrove
Cover in Thai Thuy District, Thai Binh Province.”

4


CHAPTER II
LITERATURE REVIEW
2.1. GLOBAL MANAGEMENT OF COASTAL MANGROVES
Todays, there are many problems related to the environment and the ecosystems that are
being concerned by many people in the world. Thus, every countries and organizations in the
world especially care much about the management of mangroves and then understanding the
role of mangroves that is very essential for humans. In many places around the world,
mangroves plays an extremely important part in the protecting environment as well as
providing the most important value for human’s life but the mangroves extents are being
narrowed. That’s one of the urgent matters that must be dealt with quickly. Therefore, there
are many policies, projects and methods related to sustainable development of mangroves
management in the world.
The coastal mangroves in the world play a very significant role to these countries.
Firstly, mangroves protect the environment and prevent the bad effects from global climate
change. They slow down the flow, reduce wave’s elevation, change wind’s velocity and
dispersal tide thanks to dense roots system in the surface lands of some plants such as
Rhizophora apiculata, Bruguiera gymnorrhiza, Sonneratia….Secondly, according to UnderSecretary-General and UNEP Executive Director Achim Steiner:” Mangroves provide
ecosystem services worth around 33,000 ÷ 57,000 USD per hectare per year. Adding to that
their superior ability to store carbon that would otherwise be released into the atmosphere and
it becomes clear that their continued destruction makes neither ecological nor economic sense.
On the other hand, mangroves provide nutrients, accommodation for an immense number of
marine species such as red snapper, grey mullet, sharks and stingrays. The scientists estimate
that 30% of the fishes caught in south east of Asia were supported by the mangroves. Thirdly,
mangroves ecosystem are very diversified and rich. It is the residence and feeding grounds of
many rare reptiles such as crocodile and sea turtles. Moreover, due to the complexity network
5

of roots that help preventing erosion ,protecting coastal from the effects of natural disasters
like storms, tsunami, tornado…Interlacing roots system in the surface land that keeps
sediment, contributes to the rapid increases of lands reclamation to sea. On the other hand,
mangroves are barriers that keep pollutants and heavy metal from rivers flow to the sea and
protect coastal organisms. Fourthly, according to modern research, mangroves play a big part
in the storing process of carbon in almost every coastal country in the world. The scientists
estimate that the amount of carbon that is synthesized and stored in mangroves is around 1.5
ton C/ha/years. Studies of FAO have shown that the world lose 1% of its mangroves area each
year with the gross area destroyed of about approximately 150,000 ha due to human activities
such as building shrimp farms and urban areas.
In Southeast Asia, for example in Myanma, Ayeyawady Delta a place where mangroves
was badly damaged and the aquaculture activities may also be affected. And if mangroves is
not secured, it will be comprehensively ruined in the mid of 2020s.This not only affects
ecosystem but it also affects the regional economies. Therefore, JICA has sent a team of
scientists to do research on integration mangroves management through public participation
in The Ayeyawady Delta. The results of the research have contributed to propose a reasonable
plan: “The mangroves management plan (2005-2044) aim at supporting the survival of
mangroves”. Unfortunately, May 2008, Hurricane Nargis reached Myanmar and caused great
damage to the project’s area includes mangroves, the community and infrastructure. Because
of this storm, the project was interrupted for 8 months and it was under renovation as of 2011.
Another country in Southeast Asia where some projects have been made with the major
content of mangroves management and conservation is Philippines. It is a wonderful place to
focus on the management, restoration and the protection of the mangroves. However the
success of the project is very different. It contains evidence of a project in Philippines that
have more than 50 percent of the number of seedlings die because of the wrong position or
neglected as well. That’s because they did not use GIS system in their research and arbitrary
6

choose a position to plant trees. Thus in Thailand, there are some projects such as: “The
restoration of mangroves carried out in the coastal area of Thailand”. This project used GIS
system for the purpose of managing, controlling distribution and protecting recently
mangroves and extension, improving people’s awareness of conservation issues. Thanks to
this project, they directly approached three main goals: Management, Protection, Awareness.
In Cameroon, Africa, the mangroves are threatened by some of the development
pressure as well as sustainable management and the mining activities of local people that are
living there. Therefore, in recent time, there have been many projects of world’s organizations
that have been formed useful for these mangroves. Particularly, the Food and Agriculture
Organization of the United Nations has a project with the title: “CBSP-Sustainable
community-based management and conservation of mangrove ecosystems in Cameroon”.
This project aims to strengthen protection and reducing degradation in the area by the support
of the authorities in association with the local community. Not only that, this project include
the activities that develop and conduct a campaign to protect mangroves ecosystem at national
level. On the other hand, it will focus on preparation and sustainable implementation of
mangroves management.
Moreover, nowadays the application of unsupervised classification in remote sensing is
highly valued. A typical example is the “Changes in Mangrove/Saltmarsh Ecosystems and
Their Upscale to Regional Levels in a Changing Climate in 2014. This project’s goal was to o
characterize and quantify the effects of climate change on the relationships between landscape
patterns and ecological processes in these important coastal ecosystems. The project used to
NDVI and MODIS image. The second project used Landsat TM imagery and NDVI
differencing to detect vegetation change: assessing natural forest expansion in Basilicata,
southern Italy of Giuseppe Mancino, Angelo Nolè in 2013. In this project, they used to
Landsat TM and NDVI to detect vegetation change.

7

2.2. COASTAL MANGROVES MANAGEMENT IN VIET NAM
Viet Nam is a coastal nation with an overall length of 3,200 kilometers. Viet Nam is
the world’s second largest country when by mangroves extents (FAO, 2001). The role of
mangroves is very important in the world, especially in Viet Nam, mangroves directly
affected human’s life and ecosystem. The first role of mangroves to Vietnam’s human is
providing foods. There are many foods that are provided from mangroves like: seafood,
honey, sugar, etc... Not only that, but in Vietnam, mangroves also provide many rare
medicinal plants that prevent diseases and has the researched ability to cure some previously
incurable diseases caused by virus. For a longtime, the mangrove trees have been used as a
traditional medicine to cure many common ailments. For example: cây Đước (Rhizophora
apiculata) is used to cure burnt and soft wounds; cây Muống biển (Lpomoea-pes-caprae)
helps reducing fever, relieving headache; cây Cúc tần (Pluchea pteropoda) helps curing
stomachache. The next role of mangroves to Viet Nam is providing wood products. The
species of tree in genus Avicennia, genus Rhizophoraceae with the different of conditions
ecosystem, size and occasionally this causes different uses to appear. For example: In Ngoc
Hien (Ca Mau), Rhizophoraceae forest has reserves about 210m3/ha, some areas have large
reserves of about 450-600m3/ha. Their products can be used for industrial, household
appliances, roofing…
Moreover, mangroves bring a lot of benefits to Viet Nam through ecotourism and
scientific researches. Mangrove is the nation’s most precious ecotourism resources. Vietnam
in recent years, tourists have the trends to go on a sightseeing tour of mangroves and research
mangroves. Thanks to these activities, the profit from tourism sector has been slightly higher.
Finally, mangroves also provide residence and breeding sites for many species. Because
mangroves are located between sea and mainland so ecosystem has high biodiversity.
According to Vu Trung Tang and Phan Nguyen Hong, there are nearly 43 various species of
fish that is living in mangroves in Viet Nam. There are also some terrestrial species that is
8


living in mangroves such as: otter, tiger cat, vervet monkey…especially the species of

migratory birds that are threatened with extinction.
Nowadays, in most coastal countries around the world and Viet Nam, the mangroves
extents are being narrowed and destroyed overtime, especially during the period 1943-2000.
In Viet Nam, from 1943 to 1945, the area of mangroves was about 430 thousand hectare but
now, in fact they have lost about 80 percent in only half a century by some reasons such as
conflict between conservation and economic development.
The decline of mangroves resources is a great loss not only for aquatic species but also
for the quality of life of people in the region. Therefore, forestation plants reinforcement are
especially good for human’s life and aquatic species such as mangroves prevents the ravages
of tsunami and erosion. They also protect dike, restrict saltwater intrusion, provide foods for
aquatic species and contributes to the climate equable. A heavy dependency on this coastal
resource requires close cooperation of government and community. Mangroves management
in Viet Nam is shared between the Ministry of Natural Resources and Environment
(MONRE) and the Ministry of Agriculture and Rural Development (MARD). MONRE has
jurisdiction over land and water, namely land use planning, surveys and mapping, land
registration. While MARD has jurisdiction over trees and fisheries, but there are some
restrictions between government and community which lead to the government encourages
organizations, scientific research that engage in activities related to mangroves management
to improve the lives of people. Some of the non-government organizations such as the
Denmark Red Cross, the Japan Red Cross, Great Britain Children’s Fund that invested in
mangroves management in Viet Nam and there are some projects at national level such as:”
Research on enhancing community ability in conservation, restoration and management of
coastal wetland ecosystems – Professor Phan Nguyen Hong”; “ Monitoring Program:
Environment and Socio-economic issues and responses in management of mangrove
rehabilitated. Research sites – Tien Hai & Thai Thuy Districts – Thai Binh Province”.
9


2.3. MANGROVE CHANGE AND METHODS
According to some reports, evaluating mangroves condition and dynamics is still very

difficult for the Forest Protection Service and other government officials. In Vietnam, to
investigate the information on the overlay area, the mangrove extents, they have to rely on the
data collected through previous periods had or the households reporting it to the higher level
of management by traditional manual method. These methods are time-consuming and often
have low accuracy. Today, there are many tools and methods applied by scientists and
researchers to manage coastal mangroves and remote sensing is one of the most dominant
methods. It is used to monitor natural resources of multiple levels: global, national and
regional. Using remote sensing method combined with geographic information system (GIS)
and global positioning system (GPS) help to assess the changes in the coating quickly and
accurately. According to Cihlar, classification of vegetation cover from satellite imagery has
been widely applied, these achievements are recognized at a global scale (Cihlar, 2000) [3].In
China there were some studies analyzing multi-temporal and multispectral in remote sensing
image analysis Landsat ETM + in Guangzhou province. The research has combined Landsat
TM and Landsat ETM+ and has accurately tracked changes of 7 types of covers with over
89% accuracy and Kappa coefficient was averagely 0.79 (Fan et al, 2007) [4].
The research of Sangavongse used Landsat TM to study vegetation cover changes in
the city of Chiang Mai, Thailand in the period 1988 – 1991 and found that the use of
supervised classification methods brought greater precision than other methods under the
condition that the study site is large enough (Sangavongse., 1995) [5].

2.4. SIGNIFICANCE OF STUDY
In Vietnam in general and in Thai Thuy district, Thai Binh province in particular,
mangrove is not only a source for supplying of products for everyday life, serve the needs of
exporting marine products but also is an extremely important element thanks to its ability to
keeps water, soil conservation, wind and waves break, climate regulation, improve the
10


environment, absorbing CO2 and disaster prevention. The reductions of mangrove extent and
quality in the past decades have been considered one of the main causes of increasing in

floods, landslides, and affect the lives of coastal residents. Protecting and developing forests
has been considered one of the important tasks to contribute to the sustainable development of
the country. However, there are still questions that have yet been answered properly, can these
mangrove forests be managed and monitored properly. According to the document recorded,
the area of mangroves in Thai Thuy has gradually increased over the years because of the
actions taken by the government in cooperation with the environment organizations.
Therefore, the monitoring of forests and forest management in a strict order for it not to be
falling is extremely important to the Thai Binh and especially Thai Thuy and assessing the
level of volatility of mangroves here over the years is extremely necessary. Currently, only a
few studies of remote sensing applications, such as of Nguyen Thi Cuc and Tran Van Dat on
the development of mangroves under the fluctuation of environmental factors and rising sea
levels and a number of studies that only classified and assessed at the given time, resulting in
low accuracy and not a correct assessment of forest cover.
In recent years, progress in in remote sensing and GIS has allowed the formation of
new methods and technologies to study forest dynamics through different periods of time. It
opens an opportunity to solve many fundamental problems related to forest management. Our
study aims to study the dynamic of mangroves over time, from which to assess the
distribution and structure of mangroves and offer solutions to improve the efficiency of
management in study area.

11


CHAPTER III
OBJECTIVES, CONTENTS AND METHODOLOGY
3.1. GOAL AND OBJECTIVES

3.1.1. Overall goal
This study aims to provide a scientific foundation of quantifying and monitoring
changes in extents of coastal mangroves, which contribute to better manage mangroves in

Vietnam.

3.1.2. Research objectives
Objective 1: To assess the status of coastal mangroves and management schemes in
Thai Thuy district, Thai Binh province.
Objective 2: To quantify the extents of coastal mangroves using different Landsat
vegetation index in Thai Thuy district, Thai Binh province.
Objective 3: To quantify the spatial changes in mangrove extents in certain periods of
time in Thai Thuy district, Thai Binh province.
Objective 4: As the findings in Objective 1, 2 and 3, this study proposes to:
+ to provide lessons learnt from a case study in Thai Thuy district;
+ give lessons learnt from management schemes of coastal management;
+ provide lessons learnt from spatial changes in mangrove extents lessons learnt from
using Landsat vegetation index for mangrove mapping.

3.2. RESEARCH CONTENTS

3.2.1. Investigate spatial distribution characteristics and management schemes
of coastal mangroves in Thai Thuy District, Thai Binh province.
Investigate spatial distribution characteristics of coastal mangroves;
Management schemes of coastal mangroves.

12


3.2.2. Quantify changes in coastal mangrove extents in Thai Thuy district
during 2001 - 2016
Construct a thematic map of coastal mangrove extents each year, including 2001,
2006, 2011 and 2016.
Monitor quantitative dynamics of coastal mangroves in selected periods: 2001 - 2006,

2006 - 2011 and 2011 - 2016.

3.2.3. Identify key drivers of changes in coastal mangrove extents in Thai
Thuy district during 2001 – 2016.
Identifying key drivers of coastal mangrove increase during 2001 – 2016;
Defining key drivers of coastal mangrove reduction during 2001– 2016.

3.2.4. Propose solutions for better management of coastal mangroves in Thai
Thuy district.
Strengthening forest allocation policies in relation to coastal mangroves;
Promoting mangrove management and conservation activities;
Raising public awareness and participation in coastal mangrove management.
Propose solutions to improve management coastal mangroves in study site.

3.3. METHODOLOGY

3.3.1. Secondary data collection:
Review the documents from the previous research, legal documents, and the
documents of basic investigation of the local government about field study.
To assess the status of coastal mangrove management and mangrove structures, the
study conducted the interview with People’s Committee of district .and People who are living
nearby mangroves. In addition, forest rangers, forestry officials and, local security guards are
also interviewed to obtain the additional information of coastal mangroves, such as mangrove
species names, historical spatial distribution

3.3.2. Quantification of coastal mangrove changes
In this study, Landsat imageries in 2006, 2010, 2013 and 2014 with a 30-m spatial
resolution are used to coastal mangrove changes as shown in Table 3.1
13

Table 3.1: Landsat and Sentinel Data used for detecting changes in coastal mangroves.
Resolution
ID

Image codes

Date

Path/Row
(m)

1

LE71260462001272SGS00

29/09/2001

30

126/46

2

LT51260462006310BJC00

06/11/2006

30

126/45

3

LT51260462011148BKT00

28/05/2011

30

126/46

4

LC81260462016114LGN00

23/04/2016

30

126/46

5

S2A_OPER_MTD_L1C_TL_

17/01/2016

10

SGS__20160117T083907_A002
975_T48QXH

Sources: earthexplorer.usgs.gov and scihub.copernicus.eu
To calculate the mangrove covers, this study has used the list of vegetation indices as
shown in Table 3.2
Table 3.2: Equation of Vegetation Indices used for mangrove mapping
Name

Equation

References

SR/ RVI
DVI

Jordan (1969),
DVI=RNIR-RRED

Tucker (1980),

NDVI

Rouse et al. (1973),
Claudio Parente (2013)

IPVI

SAVI

Crippen (1990),

(

)(

)

(

)

Huete (1988),

Mapping status of mangroves in different year (2001, 2016, 2011, 2016)
Mapping the status of coastal mangroves and their distribution in different years are
used this study. Process of mapping the status of mangroves and classifying a single image is
illustrated in Diagram 3.1
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Landsat image selection

Pre-processing images

Composite band

Crop selected image

Ground truthing

Image classification: calculate 5
vegetation index
Accuracy assessment

Thematic map: 2001, 2006, 2011, 2016

Post classification

Final thematic maps each year

Coastal mangroves changes: 2001, 2006,
2011, 2016.

Diagram 3.1: Flow chart of mangrove classification using Landsat images from
2001- 2016.
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Mapping coastal mangroves each year is described as the following:
Step 1: Landsat image processing
Image clustering channel: Collected image data includes individualspectral channels,
thus raise the need to conduct image channel collection to serve the image interpretation. This
is the first work in the process of interpreting image to serve the purpose of mapping the
current mangroves status. When collected from satellites, images are obtained in the form of
various black and white spectral bands. Therefore, to facilitate image interpretation and
increased accuracy, we often conducted color combinations for remote sensing.
Improving image quality: After combination, remote sensing image can be enhanced
by the addition of a colored band (Band 8 for Landsat 8) to increase the image resolution.
Geometric correction: Before the analysis, image processing, satellite image need to
be geometric corrected to limit positional error and terrain differences, so that the image is

close to the terrain. Results interpretation depends on the accuracy of the image. Therefore,
this is a very important task for the next steps.
Correction: The purpose of the correction process is to convert the scanned images
from coordinates of the pixel columns to geodetic coordinates (geographical coordinates or
flat coordinates). This work is to eliminate errors caused by pixel position angle of the image
and limiting the number of pixels by high terrain differences.
Cropping images: Because the study area forms only a part of the image, it is
necessary to cut separating the study area. A file containing the study area boundaries are
used to cutting areas of research topics from newspaper photographs.

Step 2: Analysing and processing of remote sensing images
Calculate vegetation indices: NDVI, DVI, IR, SAVI, IPVI. This method used to calcuated
the vegetation indices. After that, comparing 5 vegetation indices and chose the most of
vegetation indices to quantify changes in mangroves coastal in Thai Binh province.

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Thus, the mangroves as well as other groups of subject (population, water, agricultural
crops, bare land, shrubs) will be separated from the other groups. In addition, subjects using
expert knowledge, Google Earth images (2001, 2006, 2011 and 2016), combined with the
classification results from step 1 to identify groups of coastal areas in image classification.

Step 3: Image interpretation
In order to implement the process of image interpretation, the study constructed
interpretation training patterns for each entity covered class, to help facilitate the setting and
choosing a later train to be fast and accurate. The evaluation of the correlation of the training
patterns are extremely important because they show the ability to overlap, causing errors in
the objects classification phase.

Step 4: Evaluating accuracy and image processing after sorting
Assessing accuracy after image sorting: Used to assess the quality of the interpretation
of satellite images or compare the reliability of the results of the different methods in remote
sensing image classification.
Handling after sorting: After sorting photos, to perform the process of treating postclassifications to create layers capable of outputting map by generalizing information:

Step 5: Constructing thematic maps of coastal mangroves each year
The rule to calculate the relationship between the scale of the map with the resolution
is to divide the sample rate for the 1000 to find the size (unit: m). The formula for calculating
the ratio between resolution map was developed as follows:

Map scale = resolution (m) * 2 * 1000

3.3.3. Field data collection
Field survey: Objects that are not coastal mangroves, including as wetlands, wet and
bare soils, shrimp ponds, paddy field, shrubs, grass, build-up areas, are classified as non-

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mangroves. Besides, in the study site where study also investigates mangrove structures to
identify how dense mangroves are in the study site.
In addition, a set of questionnaires was conducted to know where coastal mangroves
were in this area in the past, whether existing coastal mangroves have been planted or
regenerated, and whether policies in relation to coastal mangrove management and
development are in use this area. These kinds of data are used for mangrove classification and
identifying drivers of coastal mangroves changes.
With assistance of GPS Garmin 78x, study collected 230 points for later classification,
including 79 points for coastal mangroves, wetlands (48 points), shrubs and grass (29 points),
shrimp ponds (60 points), build-up areas (14 points)

3.4. Calculation of Vegetation indices
3.4.1. NDVI calculation
Change detection in land use alterations during the analysis period (2001-2016) was
analyzed using the NDVI differencing technique following Singh(Singh A (1989). First, we
calculated NDVI following the general normalized difference between Band TM4 (near
infrared - NIR) and band TM3 (visible red - RED) from the two Landsat TM pre-processed
images (2001 to 2016 - eqn. 1):

The resulting images were subtracted to assess the ΔNDVI image with positive (NDVI
increase) and negative (NDVI decrease) changes on a 30 x 30 m pixel resolution (eqn. 2):

The NDVI difference image was also tested to determine its goodness-of-fit to a normal
distribution. Mean, mode, median, standard deviation, and specific statistical indexes were

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