ACKNOWLEDGEMENT
I am indebted to my respected Advisors, Dr. Pham Thanh Hai and Ass - Prof.
Hoang Thanh Tung who work as lecturers in Department of Hydrology and Water
resources in Thuy Loi University for their continuous guidance, advice and expedience
from the proposal preparation to thesis finalization. Their constructive comments,
untiring help, guidance and practical suggestions inspired me to accomplish this work
successfully.
Besides, I am especially grateful to other lecturers in the Department of
Hydrology and Water resources who supported me in terms of the data collection and
gave me useful advices for my thesis.
I remember all those who have contributed directly or indirectly to
successfully completing my study.
Finally, I must express my very profound gratitude to my family for providing
me with unfailing support and continuous encouragement throughout my years of
study and through the process of researching and writing this thesis. This
accomplishment would not have been possible without them. Thank you.

Hanoi, November 11th 2016

Vu Hoang Tung

1


DECLARATION
I hereby declare that is the research work by myself under the supervisions of Dr.
Pham Thanh Hai and Assoc. Prof. Dr. Hoang Thanh Tung. The results and conclusions
of the thesis are fidelity, which are not copied from any sources and any forms. The
reference documents relevant sources, the thesis has cited and recorded as prescribed.
The results of my thesis have not been published by me to any courses or any awards.
Ha Noi, November 11th 2016

Vu Hoang Tung

2


ABSTRACT
Flooding is one of the major natural hazards in the city of Hue. This city is frequently
affected by flooding and most of the low-lying areas in the city are flood-prone areas.
Annually, the losses of people and property caused by flooding in Hue city are very
much. This has a great influence on the local’s life and inhibits the socio-economic
development of the city. Therefore, in order to minimize losses of life and economic, a
detailed and comprehensive flood hazard assessment is necessary for both flood
control and mitigation works. The objectives of this research were (i) to simulate flood
flow in the city by using 2D hydrodynamic model MIKE 21 FM, (ii) to develop a
hierarchical structure through the analytic hierarchy process (AHP) to define and
qualify parameters that contribute to flood hazard, (iii) to map the flood components
using the geographic information system (GIS), and (iv) to integrate these three
methodologies and apply them to the Huong river basin in the Hue city to create flood
hazard index map. In addition, based on the sea level rise scenarios for Hue city in
2030, this study also calculated and created flood hazard index maps corresponding to
B1, B2 and A1 scenarios. Three flood components were considered, including flood
depth, flood flows velocity and flood duration. Flood maps were thenc drawn based on
the data collected from institutes, inheriting the results of studies in the past, and
documents related to historical flood events, climate change in Hue city. The results
show that high level of flood hazard tends to broaden over the low, medium and high
emission scenarios. In the high emission scenario (A1), the high flood hazard zone
covers 45.3% of the study area. While the medium and low hazard zones covers 19.6%
and 17.5%, respectively. It is concluded that integration of hydrodynamic model, AHP
and GIS in flood hazard assessment can provide useful detailed information for flood

risk assessment, and the method can be easily applied to other areas where necessary
data is readily available.

3


Abbreviation
WRI

World Resources Institute

GDP

Gross Domestic Production

CCFSC

Central Committee for Flood and Storm Control

AHP

Analytical Hierarchy Process

GIS

Geographical Information System

FHI

Flood Hazard Index


IPCC

International Panel on Climate Change

UNFCCC

United Nations Framework Convention on Climate Change

GDP

Gross Domestic Product

FDI

Foreign Direct Investment

WMO

World Meteorological Organization

DHI

Danish Hydraulic Institute

DEM

Digital Elevation Model

CBDRM


Community-Based Disaster Risk Management

ADPC

Asia Disaster Preparedness Center

4


TABLE OF CONTENTS
CHAPTER I INTRODUCTION……………………………….................................8
1.1 General introduction...............................................................................................8
1.2 Description of the study area .................................................................................9
1.3 Description of the Huong River ...........................................................................10
1.4 Hue city in the context of climate change ............................................................11
1.5 Problems and need of study .................................................................................18
1.6 Objectives of the study .........................................................................................21
1.7 Scope of study ......................................................................................................21
CHAPTER II LITERATURE REVIEW…………………………………………....23
2.1 Flood hazard mapping ..........................................................................................23
2.2 AHP method .........................................................................................................25
2.3 Flood hazard index ...............................................................................................27
CHAPTER III METHODOLOGY…………………………………………………..30
3.1 Conceptual framework .........................................................................................30
3.2 Overview of the research .....................................................................................31
3.3 Flood hazard mapping ..........................................................................................31
3.4 Flood hazard index identification ........................................................................37
CHAPTER IV DATA COLLECTION AND ANALYSIS………………………….44
4.1 Data collection .....................................................................................................44

4.2 Data analysis ........................................................................................................44
CHAPTER V RESULTS AND DISCUSSION……………………………………...49
5.1 Hydrodynamic model parameters ........................................................................49
5.2 Flood hazard mapping ..........................................................................................57
5.3 Flood hazard index ...............................................................................................61
5.4 The impacts of flood on Hue city in the contexts of climate change ...................62
5.5 Community-based disaster risk management (CBDRM) ....................................71
CONCLUSION AND RECOMMENDATION……………………………………...75
References……………………………………………………………………………...78

5


LIST OF TABLES
Table 1.1: Flood season in the Huong river ..................................................................11
Table 1.2: The change of average temperature in the recent decades ...........................13
Table 1.3: Scenario of temperature change in future in Hue.........................................13
Table 1.4: Scenario of rainfall change in future in Hue city .........................................17
Table 1.5: Scenarios of sea level rise in the future of Hue city (cm) ............................17
Table 3.1: Saaty Rating Scale ........................................................................................38
Table 3.2: Random inconsistency indices (RI) for different number of criteria ...........40
Table 4.1: Pairwise comparison of flood depth categories respect to flood hazard ......47
Table 4.2: Pairwise comparison of flood duration categories respect to flood hazard .47
Table 4.3: Pairwise comparison of flood velocity categories respect to flood hazard ..48
Table 4.4: Pairwise comparison of components respect to flood hazard ......................48
Table 5.1: Result of Mike21 FM calibration flood event in 1983 .................................52
Table 5.2: Hydrodynamic parameters after calibration process ....................................54
Table 5.3: Result of Mike21 FM verification, flood event in 1999 ..............................55
Table 5.4: Flooded area in districts in Hue City............................................................58
Table 5.5: The change of flood depth between climate change scenarios with ............64

Table 5.6: The change of flood hazard levels by area ...................................................70
Table 5.7: What community should do and should not do in each stage of flood
management ...................................................................................................................73

6


LIST OF FIGURES
Figure 1.1: Trend of average temperature in July (1986-2006) ....................................12
Figure 1.2: Trend of average annual temperature in period 1986-2006 ........................12
Figure 1.3: Trend of average rainfall change in September – November .....................15
Figure 1.4: Trend of average rainfall change in July ....................................................15
Figure 1.5: The maximum daily rainfall in 10 past decades .........................................16
Figure 1.6: Administration Map of Thua Thien Hue Province .....................................22
Figure 2.1: Structure of FHI study methods ..................................................................23
Figure 3.1: Framework for flood risk assessment and risk management ......................30
Figure 3.2: Overview of the research ............................................................................31
Figure 3.3: Study area ....................................................................................................34
Figure 3.4: Steps for model calibration and verification ...............................................35
Figure 3.5: Diagram for converting qualitative indexes to quantitative value ..............40
Figure 3.6: Applying AHP in identifying flood hazard index at the Huong river ........42
Figure 4.1: Surface topography of the study area .........................................................45
Figure 5.1: Topographic Mesh ......................................................................................50
Figure 5.2: Checking cross-sections ..............................................................................51
Figure 5.3: Observed and Calculated discharge at Cross-section 1 ..............................53
Figure 5.4: Observed and Calculated discharge at Cross-section 2 ..............................53
Figure 5.5: Observed and Calculated discharge at Cross-section 3 ..............................54
Figure 5.6: Observed and Calculated discharge at Cross-section 1 ..............................55
Figure 5.7: Observed and Calculated discharge at Cross-section 2 ..............................56
Figure 5.8: Observed and Calculated discharge at Cross-section 3 ..............................56

Figure 5.9: Flood depth map at the Huong river – Hue city in 1999 ............................57
Figure 5.10: Flood flows velocity map at the Huong river – Hue city in 1999 ............59
Figure 5.11: Flood duration map at the Huong river – Hue city in 1999 ......................60
Figure 5.12: Flood Hazard Index map at the Huong river – Hue city in 1999 .............61
Figure 5.13: The change of flood depth in climate change scenarios ...........................64
Figure 5.14: The change of flood velocity in climate change scenarios .......................66
Figure 5.15: The change of flood duration in climate change scenarios.......................67
Figure 5.16: The change of flood hazard index in climate change scenarios ...............69
Figure 5.17: Disaster management cycle.......................................................................72

7


CHAPTER I
INTRODUCTION
1.1 General introduction
Over the last decades, flood has become a real threat that human have to face due to its
severe impacts on economy, society and people. According to the World Resources
Institute (WRI), 20.7 million people are affected by river flooding each year, 56% of
people at risk of being impacted by river flooding live in three countries: India,
Bangladesh, and China. These combined with the next 12 largest impacted populations
- in Vietnam, Pakistan, Indonesia, Egypt, Myanmar, Afghanistan, Nigeria, Brazil,
Thailand, Democratic Republic of Congo, Iraq, and Cambodia - account for 80% of
the people at risk world-wide. In addition, an average of $96 billion in global Gross
Domestic Product (GDP) is exposed to river flooding each year. And these numbers
are expected to increase gradually in the next years because of population growth,
urbanization, and climate change. As a result, it will increasingly put people at risk.
Floods in Viet Nam are well-known phenomena and occur in all regions of the
country, especially in the Central Coast region (CCFSC 2006). As an example, the
Central Viet Nam’s flood of November 1999 killed 780 people, affected around 1

million residents, and sunk and damaged more than 2,100 boats. This flood caused
damage worth US$364 million (CCFSC 2006). Being a coastal province in Central of
Vietnam, Thua Thien Hue province has been suffering from floods impacts annually.
Especially, in the context of climate change, catastrophic floods are increasing in term
of frequency and magnitude, and taking a high death toll, assets and infrastructures.
Therefore, the measures in flood risk management and mitigation for Thua Thien Hue
province are very indispensable and need to be researched strictly. One of the effective
approaches which are being used widely in flood risk management is flood hazard
assessment. This approach showed its capacity to apply in practice and it is a useful
tool to facilitate in flood risk management and mitigation.

8


Flood hazard assessment in a river basin can be performed by overlaying maps or/and
identify indexes. Each certain area has a hazard value. The value can be utilized in
analyzing, estimating and comparing among different areas in order to support for
making decision. Thus, realizing the impacts of floods on Thua Thien Hue province in
general and Hue city in particular, this research studies “Identify the flood hazard
index in the Huong river basin – Hue city area”. The result of this project will be
foundation for identifying the flood risk index and evaluating flood risk in the area,
and support to help decision makers in making flood prevention plans for Hue city.
1.2 Description of the study area
Thua Thien Hue is a province in the North Central Coast region of Vietnam. The
province is located at the latitudes 16°14'- 16°15' north, longitudes 107°02' - 108°11'
east. Area of the province is 5,053.990 km2; population is 1.115.523 people according
to statistics in 2012. It borders Quang Tri province to the North and Da Nang to the
South, Laos to the West and the East Sea to the East. The province has 128 km of
coastline, 22,000 ha of lagoons and over 200,000 ha of forest. The province comprises
4 different zones: a mountainous area, hills, plains and lagoons separated from the sea

by sandbanks. The mountains, covering more than half of the total surface of province,
with height ranges from 500 to 1480 m. The hills are lower, between 20 to 200 m, and
occupy about a third of the province’s area, between the mountains and the plains. The
plains account for about a tenth of the surface area, with a height of only up to 20m
above sea level. Between the hills are the lagoons which occupy the remaining 5% of
the province’s surface area.
The climate in Thua Thien Hue province is similar to Central Vietnam in general – a
tropical monsoon climate. In the plains and in the hills, the average annual temperature
is 25oC, but in the mountains only 21oC (statistical yearbook 2004). The annual
precipitation in the province is 3200 mm but there are important variations. Depending
on the year, the annual average may be 2500 to 3500 mm in the plains and 3000 to
4500 mm in the mountains. In some years the rainfall may be much higher and reach
more than 500 mm in the mountains.

9


The sale of goods and services in the province is 10930.6 billion VND accounting for
0.9% of total sale of goods and services in the whole country. This is compared with
12.7% of Hanoi and 23.5% of Ho Chi Minh City. The province has more than 120 km
of coastline, which provides for a seafood industry which produces over 40,000
tons/year consisting of over 500 species of fish.
Hue is the city of Thua Thien Hue province. The city is the center of culture, politics,
education, science, tourist… Area of the city is 71.68 km2. Population in 2012 is
estimated as 344,581 people. Hue city is located in downstream of the Huong River
and Bo River, average height is about 3-4 m above sea level and is often submerged
when a heavy rain occurs in the upstream of the Huong River.
1.3 Description of the Huong River
The Huong river basin is located from 15o29’ – 16o35’ of the North latitude to
105o07’-107o52’ of the East longitude, with the basin area of 2830 km2. The river

length is 86.5km included 28 distributaries. The upstream of the Huong River is called
as Ta Trach River which derives from a high mountain area of Bach Ma mountain
range. The Ta Trach River connects with the Huu Trach River at the Tuan confluence.
From the Tuan confluence, the main flow is called the Huong River.
The river then flows in the general direction of southeast to northwest, passing the Hue
city, and before flowing into the sea, the Huong River goes through the Tam Giang –
Cau Hai lagoon. Tam Giang - Cau Hai is the largest lagoon in the South East Asia,
with an area of 22,000 ha, and a length of 68 km along the coastline of the province.
Finally, the river flows to the sea at the Thuan An and Tu Hien mouths. Besides the
Thuan An and Tu Hien estuaries, the lagoon systems have some smaller river mouths
linking to the sea.
As same as other rivers in the Central of Vietnam, flood season in the Huong river
basin is not so long, only about 4 months: from September to December with the
amount of water accounting for 70% - 75% of total volume of annual flow. Therein,
November has the largest amount of flood and often account for 30% - 35% of total
volume of annual flow. Although flood season is short but many large floods occurred
10


in the Huong River such as floods happened in 1953, 1975, 1983 and 1999. These
floods often lasted in 5-7 days.
Table 1.1: Flood season in the Huong river
Station

Flood discharge in flood season (m3/s) with P = 75%

Average
discharge

IX


X

XI

XII

Ta Trach

40.9

90.9

204

73.6

39.9

Binh Dien

40.5

84.0

165

39.0

28.6


Co Bi

62.6

83.6

161

58.7

34.1

(P is flood frequency)
In recent years, many large floods happened in the Huong River. According to
statistics, from 1977 to 2005, 34 large flood events which exceeded alarming level III
(H > 3m) occurred in the Huong River. Observed data at the stations in the Huong
River indicated that there were 4 extreme flood events happened in last 50 years: 1999,
1953, 1975 and 1983 corresponding to 5.81m, 5.50m, 5.32m and 4.92m of water level.
In summary, the Huong River plays an important role in development of livelihood,
economy and society in Thua Thien Hue province. However, the Huong river basin is
also vulnerable and susceptible to natural disaster (especially to flood inundation) and
impacts of climate change. In recent years, Thue Thien Hue province and the Huong
river basin has been affected by many natural disasters such as: storm, heavy rain,
flood and drought with high intensity and frequency, caused many losses of people and
socio-economy, damaged cultural heritage and property of local residents.
1.4 Hue city in the context of climate change
1.4.1 Climate change in Hue city
a. The change of temperature from the past to now
The trend of temperature change is estimated based on series of observed data from

1931 to now. Analytic results showed that in this period, the average annual and
11


monthly temperature has inconsistent change and does not show a clear trend.
Basically, average annual temperature tends to increase slightly (0.10C – 0.20C) from
period 1931 – 1940 to 1971 – 1980, however, from the late periods until now,
temperature tends to decrease 0.20C – 0.30C. (Phong, 2014)

Figure 1.1: Trend of average temperature in July (1986-2006)
(Source: Climate action plan Responding to Climate Change From 2014 – 2020)

Figure 1.2: Trend of average annual temperature in period 1986-2006
(Source: Climate action plan Responding to Climate Change From 2014 – 2020)
The scenario for the temperature change in the future
In general trend, average seasonal and annual change is likely to increase in the future
with minimum increase of 10C in 2050 (corresponding to low emission scenario B1)
occurs in the summer. The maximum increase of average seasonal and annual
temperature can reach to 3.70C in 2100 (corresponding to high emission scenario A1).

12


Thus, the average temperature tends to rise more in the spring and winter while it rise
a little in the summer. In terms of extreme value, the lowest temperature in winter
(corresponding to B2 scenario) increases 1.20C in 2050 and 2.20C in 2100, while the
highest temperature increases 2.20C in 2050 and 3.20C in 2100. Besides, in 2100, the
number of days with maximum temperature above 350C may increase 10 days –
20 days per year (corresponding to medium emission scenario B2). (Phong, 2014)
Table 1.2: The change of average temperature in the recent decades

Decades

Average temperature in Hue
Average
temperature in
January

Average
temperature in
July

Average annual
temperature

1931-1940

19.8

29.0

25.1

1941-1950

20.8

29.3

25.3


1951-1960

20.1

29.3

25.2

1961-1970

19.9

29.8

25.3

1971-1980

20.0

29.4

25.3

1981-1990

1938

29.3


25.1

1991-2000

20.2

29.1

25.0

2001-2010

19.9

28.9

25.0

Table 1.3: Scenario of temperature change in future in Hue
Season

2050

2100

2050

Seasonal average
Winter (XII-II)


1.4-1.80C

1.6-3.70C

Spring (III-V)

1.2-1.60C

1.6-3.70C

Summer (VI-VIII)

1.0-1.40C

1.0-3.10C

13

2100

Extremely temperature (B2)
Minimum: 1.0-1.20C

2.0-2.20C

Maximum: 1.2-2.20C

2.2-3.20C

Minimum: 1.7-20C


2.7-3.20C


Autumn (IX-XI)

1.0-1.60C

1.3-3.70C

Average annual

1.2-1.60C

1.6-3.70C

Maximum: 1.0-1.20C

2.2-3.20C

Minimum: 1.0-1.70C

2.2-3.00C

Maximum: 1.0-1.70C

2.0-3.20C

b. The change of precipitation from the past to now
According to observed data, annual rainfall in Hue city is relatively high compared

with other regions with the annual rainfall from 2700 mm to 2800 mm. The extremely
high total rainfall occurs in some years (for example: rainfall in 1999 was up to 3093
mm). Regarding to distribution of rainfall over time, rainfall usually concentrates
mainly in October and November. In some years, rainfall in one of 2 months accounts
for 60% to 80% annual rainfall (for example the rainfall in November 1999 is 2452
mm while the annual rainfall is 3093 mm).
According to statistics, rainfall in Hue has a considerable variation over the decades
and it does not show a clear trend. The average annual rainfall tends to decrease from
the decade 1961-1970 to 1981-2000(from 2842 mm down to 2575 mm), but then
increase gradually in the next 2 decades. The most significant increase is more than
500 mm in 1991-2000 compared with the previous decade. It is worth noting that even
though the average annual rainfall increases but rainfall in July (dry season) in the
period 1991-2000-2010 has a strong downtrend, and rainfall in September, October
and November (rainy season) tends to increase compared with 2 previous decades.
Compared with the period 1961-1970, the average rainfall on July in the decade 20012010 decreases 23% while the rainfall in November increases 27%.
Regarding to rainfall intensity, in the past few decades, the intense rainfalls appear
more and more and always happen in October and November. Heavy rainfall occurs in
some days, for example, on 2nd November 1999, a rainfall with 978 mm happened,
accounted for 20% the total rainfall that year.
In summary, the average annual rainfall in the decade 2001-2010 is larger than the
previous decades since 1961 but we cannot confirm about the trend of average annual
14


value. Only one thing we can confirm is that the rainfall in October and November has
always reached extremely levels, accompanied by intense rainfalls and tend to rise in
October and November while the rainfall on July – dry season tends to decrease.
(Phong, 2014)

Figure 1.3: Trend of average rainfall change in September – November

(Source: Climate action plan Responding to Climate Change From 2014 – 2020)

Figure 1.4: Trend of average rainfall change in July
(Source: Climate action plan Responding to Climate Change From 2014 – 2020)
15


Figure 1.5: The maximum daily rainfall in 10 past decades
(Source: Climate action plan Responding to Climate Change From 2014 – 2020)
The scenario for the precipitation change in the future
According to forecast, the average annual rainfall in Hue city may increase 3% - 4% in
2050 and 6% - 10% in 2100. The average rainfall in the spring, summer and autumn
may increase while the rainfall in winter may decrease.
It is worth noting that the rainfall decreases in the dry season with the maximum
decrease is 6% in the middle and 10% in the end of the decade. The rainfall in autumn
(from October to December) has the largest increase with the maximum increase is up
to 16% in 2100 while the highest rainfall in the year concentrates in this stage. As a
result, flood and drought in Hue city is likely to become more serious in the future. In
addition, the maximum daily rainfall in Hue may increase about 20% compared with
corresponding value in the period 1980-1999 and even the abnormal rainfall can
appear with the rainfall rises twice as the record rainfall at present. (Phong, 2014)

16


Table 1.4: Scenario of rainfall change in future in Hue city
Season

Average rainfall change
2050


2100

Winter (XII-II)

Increase 2-4%

Increase 0-6%

Spring (III-V)

Decrease 2-6%

Decrease 4-10%

Summer (VI-VIII)

Increase 4-6%

Increase 4-14%

Autumn (IX-XI)

Increase 4-10%

Increase 4-16%

Average annual

Increase 3-5%


Increase 6-10%

(Source: Climate action plan Responding to Climate Change From 2014 – 2020)
c. Sea level rise
Sea level rise scenario for Hue city is taken to the forecasting figures for the region
from Ngang mountain pass to Hai Van mountain pass. The change of sea level in the
future is compared with the average sea level in the period 1980-1999.
According to the table below, sea level tends to increase in the future. In 2020, 2050
and 2100, sea level could rise at the highest level of 9 cm, 28 cm and 94 cm. Besides,
the error in forecasting between low emission scenario and high emission scenario
tends to increase over time. This shows that the uncertainty of the forecast in future is
larger and larger. (Phong, 2014)
Table 1.5: Scenarios of sea level rise in the future of Hue city (cm)
Scenarios
of
emission

Year
2020

2030

2040

2050

2060

2070


2080

2090

2100

B1

7-8

11-12

16-18

22-24

28-31

34-39

41-47

46-55

52-62

B2

8-9


12-13

17-19

23-25

30-33

37-42

45--51

52-61

60-71

A1F1

8-9

13-14

19-20

26-28

36-39

46-51


58-64

70-79

82-94

(Source: Climate action plan Responding to Climate Change From 2014 – 2020)

17


1.4.2 The impacts of flood on Hue city in the contexts of climate change
The main types of natural disaster in Hue city includes typhoon, flooding, drought,
whereas flooding is considered as the most dangerous natural disaster and causes the
most damage to Hue. In recent years, under the influences of variations regarding
temperature, rainfall, floods tend to serious, complicated and unpredictable.
Floods usually occur in rainy season and mostly concentrated in the period from
September to December annually. Total of flow during flood season accounts for
about 65% of the total annual flow. According to observed data, there are 3.5 floods in
average annually which are equal or higher than flood alarming level II occurred in the
Huong river.
Normally, the flood duration is about 3-5 days in average. The longest period of a
flood ups to 6-7 days. The average time for transferring flood from upstream (Thuong
Nhat) to downstream (Kim Long) with the distance of 51 km is about 5-6 hours. The
severity of a flood (flood duration and flood depth) depends on many factors such as
rainfall in upstream, rainfall in Hue city, tide and sea level rise (due to storms or the
rising of earth’s temperature).
Thus, under the impacts of climate change, in recent decades, floods in Hue city tend
to become more complex, less predictable and more dangerous. (Phong, 2014)

1.5 Problems and need of study
Vietnam is a coastal country with a long coastline and located in the tropical monsoon
climate region, Vietnam has suffered impacts of floods annually. Since ancient times,
Vietnamese people regarded flooding as one of the four biggest dangers to people,
along with fires, robbers and invaders.
In order to control flooding, a large system of river and coastal dykes has been
constructed. For many centuries, these flood control measures achieved results all over
the country. However, this structure approach is now under pressure because the
conditions inducing flooding are intensifying, both at local and global level (CCFSC,
2006). For example, increasing population, rapid urbanization, high demand for
natural resource exploitation, environmental pollution, and degradation are coupled
18


with global threats, such as climate change (Tran et al. 2008). In addition, due to the
limitation of current fund in Vietnam, non-structure measures are more concentrated
and given preference over the structure measures. One of the most effective nonstructure measures currently is flood risk assessment. Flood risk assessment will be a
background for planning and coping with floods.
Being the central of Thua Thien Hue province, Hue city is located in intersection of
traffic routes from North to South and East-West economic corridor connecting
Thailand, Vietnam and Laos. It is also where has interference about society – economy
– culture of 3 regions North – Central – South. With the importance of a central urban
where experienced many historical events, Hue city has been had outstanding
development in socio – economy, infrastructure, culture, tourism,… In recent years,
infrastructure, new urban areas have been invested continuously and this made the
appearance of Hue city become more modern and civilized.
In the context of climate change, Thua Thien Hue province in general and Hue city in
particular is suffering from many impacts of climate change. The ultra-weather events
tend to become more severe in terms of both frequency and magnitude. The direct
consequences caused by climate change in Hue city in recent years are the occurrence

of many events such as flood, storm, drought and deep freeze. These events have
influences on social and economic development. Whereas, flooding is considered as a
top threat to coastal cities like city of Hue. This was demonstrated via the historical
flood events, such as the flood events in 1953, 1975, 1983, 1999… And now, the
severe flood events are still happening more and more powerful under the impacts of
climate change.
The flood event started from 20 to 26/9/1953 caused 500 casualties, swept away 1290
houses, 80% of the crops were lost.
A big flood occurred from 15-20/10/1975 took a heavy toll of people and property.
The flood event in 1983 lasted for 8 days with the flood peak discharge observed at Co
Bi, Binh Dien and Thuong Nhat station corresponding to 2850 m3/s, 4020 m3/s and

19


1470 m3/s. The flood caused 252 dead, 115 people were wounded, 2100 houses were
collapsed, and 1511 houses were swept away.
The flood event 11/1999 happened for 6 days (1/11 – 6/11), was a very large flood.
The flood peak discharge observed at Ta Trach, Binh Dien and Co Bi stations
corresponding to 7000-8000 m3/s, 5500-6000 m3/s and 3500-4000 m3/s. The flood
caused widespread inundation and flood damage was enormous. Flood level in the
upstream up to 1.4 m, more than 90% residential areas living in the delta were
submerged for 4-9 days. From 1/11 to 12/11, there were 372 dead and missing, total
damage was estimated as 1,762 billion VND. Transportation sector had the most
damage of 600 billion VND, followed by Agriculture sector of 307 billion VND and
Fishery sector of 110 billion VND.
According to predictions of experts, Hue city will be one of areas where has to suffer
from many impacts of climate change in the process of socio-economic development.
Vulnerability caused by climate change to Hue city is considered more serious than
other regions in the province due to population density and the level of infrastructure

investment is very high, especially, Hue city is planning to become a nuclear urban in
the future. However, the problems related to climate change are still new and have not
been perceived deeply and implemented specifically to local authorities and residents.
Although, the local authority has made great efforts in urban management,
environmental protection and disaster damage mitigation, but the role of the city
authority in adaptation and mitigation of climate change impacts is not clear. Facing
with negative effects of climate change requires the local authority need to assess
properly the situation and existing capacity in responding, then recommends suitable
solutions to minimize the negative impacts caused by climate change.
Facing with the problems as mentioned above, this study will identify one of the most
important components in Flood risk assessment in the Huong river basin: Flood hazard
index. Flood hazard index represents the level of flooding impacts. It is combination of
all hazard parameters such as flood depth, flood duration, velocity of flood flow…
Base on the index, the hazard zones are determined. The impacts of flood on local
people, social-economic development in whole study area can be reduced by the
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structure and non-structure measures. However, the structure and non-structure
measures also need detailed calculations and estimations in order to mitigate the
influences of flood in the economical and efficient way.
1.6 Objectives of the study
The general objective of this study is to support to flood control and mitigation works
in the Hue city.
The specific objectives of the study are:
1. Simulate flood flow: Simulation and estimation magnitudes, drainage process, and
flooding flow along the river.
2. Create flooding maps: Developing flood depth, flood velocity, flood duration maps
for the river basin.
3. Identify flood hazard index: quantify factors which contribute to the damaging

potential of flood hazard to serve for flood risk assessment.
1.7 Scope of study
The scope of the study is limited within the Hue city of Thua Thien Hue province. To
arrive at the objective, the following tasks will be carried out:
- Collecting and analyzing data, information about hydrology, topography, socioeconomy…
- Selecting suitable model for simulating a flood processes in the Huong River.
- Calibrating and verifying the selected model.
- Developing flood hazard mapping based on results of the above model and analysis.
- Applying Analytical Hierarchy Process (AHP) method and ArcGIS software to
develop flood hazard maps and calculate flood hazard index.
- Assuming scenarios in context of climate change to estimate the impacts of flood to
Hue City in the future.

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- Recommending some non-structure measures to help local residents in coping with
flooding.

Figure 1.6: Administration Map of Thua Thien Hue Province

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CHAPTER II
LITERATURE REVIEW
Flood hazard assessment including the integration of GIS and hydraulic model as well
as identifying indexes related to flooding by applying weight methods have been
described and studied by many researchers. These approaches are also estimated as
effective approaches in flood hazard assessment currently. In order to determine

theoretical base for this research, some available references have been reviewed. This
chapter summarizes the review of related literature as following structure:

Literature
review

AHP method

Flood hazard
mapping

Flood hazard index

Figure 2.1: Structure of FHI study methods
2.1 Flood hazard mapping
Gardiner (1990), as cited by Omran et al. (2011), indicated that, the morphometric
characteristics of basins have been used to predict and describe flood peaks and
estimation of erosion rate. Indeed, the relationship between basin morphometric and
flooding impact have also been investigated. Morphometric studies include the
evaluation of streams through measurement of stream network properties, which are
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calculated based on such characteristics as drainage density, water allocation ratio,
stream frequency and overland flow. However, it is difficult to measure the details of
drainage elements in the field due to their extent throughout rough terrain over vast
area. Thus, in order to solve the task, the author applied GIS techniques to extract the
stream networks as well as analysis morphologic characteristics of the basin. The aim
of this research is to produce a potential flood hazard map based on geomorphic
parameters and to estimate the risk degree of individual sub-basin in the study area.

According to Marfai and Njagih (2002), flood is recognized as one of two hazardous
phenomenon which has the most serious damages to people and economy in Turialba
City in Costa Rica annually. Therefore, the authors found that it’s necessary to do risk
assessment in order to know how much would be the damage if the flood hazard
occurs. In the research, the authors considered flood hazard assessment as an
indispensable part in flood risk assessment, beside flood vulnerable assessment. In this
part, he used ILWIS software to generate the flood hazard maps corresponding to
various return periods. These maps then were used to serve for risk assessment and
cost estimation for study area.
Karagiozi et al. (2011) conducted their research in Laconia Prefecture in Peloponneus,
Greece. In the research, flood hazard assessment was implemented by using
hydrological models in a GIS environment taking into account the geomorphologic
characteristics of the study area. For each basin, the morphologic characteristics such
as area, mean slope, mean elevation and total relief were calculated. These factors then
were combined by using GIS to produce a final flood hazard map.
According to Ripendra (2000), flood hazard mapping and risk assessment in Nepal is
still rudimentary. Most of the flood protection works were carried out at the local scale
without proper planning or without considering the problem at river basin scale. Apart
from piecemeal approaches on a limited scale, no pragmatic efforts in comprehensive
flood risk assessment and flood hazard mapping have been done. Therefore, in his own
study, he prepared flood vulnerability, flood hazard and flood risk maps by integrating
the hydraulic model HEC RAS and GIS with the case study of Lakhandei River basin.
The results of the research are the flood vulnerability, flood hazard and flood risk
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maps with the assessment for each elements. The author then emphasized to the
important role of community as well as stakeholders in flood management and made
the action plan for flood mitigation in study area.
2.2 AHP method

Siddayao et al. (2014) combined Analytical Hierarchy Process (AHP) method with
Geographical Information System (GIS) for flood risk analysis and evaluation in the
town of Enrile, a flood-prone area located in northern Philippines. AHP

results

showed the relative weights of three identified flood risk factors, and these results
were validated to be consistent, using a standard consistency index. Using the GIS
software, the factor weights from the AHP were incorporated to produce a map with 5
levels of estimated flood risks. Using such a GIS weighted overlay analysis map as
guide, local residents and other stakeholders can act to prepare for potential flooding,
promote appropriate land-use policy that will minimize threat to lives due to flooding.
According to Chen et al. (2011), flooding is one of the major natural hazards in
Taiwan and most of the low-lying areas in Taiwan are flood prone areas. Thus, a
comprehensive decision making tool for flood control planning and emergency service
operation is necessary in order to reduce losses of life and economy. A research about
flood risk assessment was then carried out by him. The research objectives were to
develop a hierarchical structure through the Analytic Hierarchy Process (AHP) to
provide preferred options for flood risk analysis; map the relative flood risk using the
Geographic Information System (GIS), and integrate these two methodologies in flood
risk assessment. The results of research indicated that integration of AHP and GIS in
flood risk assessment can provide useful detailed information for flood risk
management, and the method can be easily applied to most areas in Taiwan where
required data sets are readily available.
A flood hazard assessment using AHP and mapped by GIS has also been applied for
the Yasooj River, Iran (Rahmati et al. 2015). The aim of this research is to identify
potential flood hazard zones. The decision factors for flood hazard of the AHP matrix
include distance to river, land use, elevation and land slope. The set of criteria were
integrated by weighted linear combination method using ArcGIS 10.2 software to
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