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Assessment of integrated flood management strategies in the Lower Dong Nai – Sai Gon River Basin,
Viet Nam

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Paper 3-4-2

ASSESSMENT OF INTEGRATED FLOOD MANAGEMENT STRATEGIES
IN THE LOWER DONG NAI – SAI GON RIVER BASIN, VIET NAM
NGUYEN ANH DUC1; KLAAS-JAN DOUBEN2; TANG DUC THANG3 AND
VU MINH THIEN1
1

2

Viet Nam National Mekong Committee, Ha Noi, Viet Nam
UNESCO-IHE Institute for Water Education, Delft, the Netherlands and Waterboard Brabantse Delta,
Breda, the Netherlands
3
Southern Institute for Water Resources Research, Ho Chi Minh City, Viet Nam

ABSTRACT
The paper presents a comprehensive study on integrated flood management strategies in the
Lower Dong Nai-Sai Gon River Basin situated in the southwest of Vietnam. The basin has the
country’s highest economic development rate. It houses Vietnam’s largest population centre
(Ho Chi Minh City) and has the largest concentration of industrial output. As a typical flat and
low-lying riverine-estuarine transition area, it is flood prone and faces increasing damages as a
result of re-occurring flood events, both from rivers as well as storm surges from the sea. In
general, the existing flood defence structures with a relatively low safety standard are small and
situated in a scattered order over the river basin. In the past the area experienced large scale
flooding, which brought about serious damages to private houses and properties, public
facilities, agricultural crops and livestock.
Flood management strategies in Ho Chi Minh City should initially be based on a ‘holistic
approach’. This approach considers the catchment as a whole, not only in terms of the
geographical and functional interdependencies involved, but also the inter-relationships between
land and water. Not just economic developments are considered, but also socio, environmental
and institutional developments. The development of flood management strategies should be
implemented by associating water-related sciences, environmental sciences with social sciences
as well as by coordinating and combining physical and mathematical modelling tools, involving
experts in all sections and public participants.
Firstly, the flood damages and impacts are assessed by using results of a 1-D
hydrodynamic model (SOBEK). Different (steady-state) scenarios for future flooding situations
have been taken into account, considering both upstream runoff as well as tidal dynamics.
Secondly, flood management strategies have been developed on the basis of the abovementioned assessment results. Various starting points for flood management strategies for
different geographic areas have been defined, such as: ‘keep floods away from people’, ‘keep
people away from floods’ and ‘accept floods and clean up afterwards’. In total eight different
strategies have been defined, based on three conceptual approaches: (i) different principles of
structural measures; (ii) compatibility between structural and non-structural measures; and (iii)
spatial distribution and pre-feasibility of various measures. Thirdly, the proposed strategies have
been assessed and compared by using a specific set of criteria in order to determine preferred
strategies, which could be suitable for further analysis. The strategies can be roughly divided
into three main categories: favourable, less favourable and non-favourable. The advise on
favourable strategies is composed by taking existing environmental conditions (ecologically,
socially and economically) of the study basin into consideration. The ‘storage and confinement’
strategy has been evaluated to be the most promising solution.
The flood issues in the Lower Dong Nai-Sai Gon River Basin can be substantially

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managed and mitigated by some promising integrated management strategies, which are the
combination of various structural measures and their appropriate non-structural measures.

INTRODUCTION
The Lower Dong Nai - Sai Gon River System (Figure 1) is situated in the southwest of Vietnam
and has the country’s highest economic development rate. It houses Vietnam’s largest
population centre (Ho Chi Minh City) and has the largest concentration of industrial outputs. At
the same time, the river basin continues to diversify its agricultural sector with products ranging
from basic staples like rice and maize to raw materials for the local industry (Claudia et al.,
2001). As a typical flat and low-lying riverine-estuarine transition area, it is flood prone and
faces increasing damages as a result of re-occurring flooding events, from rivers as well as
storm surges from the sea and as a result of local precipitation (Figure 1). In general, the
existing flood defence structures are small and situated in a scattered order over the river basin
(Japan International Cooperation Agency (JICA), 1996). The dike systems are discontinuous
and contain a relatively low safety standard (Sub-Institute for Water Resources Planning
(SIWRP), 2001). Upstream of Ho Chi Minh City, two large reservoirs have been developed in
the recent past (Dau Tieng and Tri An). In the past the area experienced some exceptional
floods, with return periods ranging from 1 - 25%, which caused serious damages to private
houses and properties, public facilities, agricultural crops and livestock (Table 1). During the
flood season, the drainage possibilities of different rural and urban areas are severely affected,
since the drainage system has no sufficient capacity to adequately discharge the flood waters
and it is not well maintained.
Despite many efforts from various governmental agencies on different levels, floods and
their consequences still remain as one of the biggest issues in the Lower Dong Nai - Sai Gon
River Basin. To solve the flood problems substantially is a challenging task, which needs broad
and profound studies.

DAU TIENG RESERVOIR
CHAU THANH
TAY NINH

DAU TIENG

TRI AN RESERVOIR
BEN CAU

TAN UYEN
GO DAU HA
TRANG BANG

THU DAU MOT STATION

BIEN HOA

CU CHI

LEGEND

DUC HOA

River - Canal

HO CHI MINH CITY

Reservoir

PHU AN STATION

Water Level Station

MOÄ
C HOÙ
A

City, Town

NHA BE STATION

Road
BEN LUC STATION

VUNG TAU WATER LEVEL STATION

TAN AN

SOUTH CHINA SEA

Figure 1. The Lower Dong Nai – Sai Gon River System

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Assessment of integrated flood management strategies in the Lower Dong Nai – Sai Gon River Basin,
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Table 1.Historical flood damages (JICA, 1996 and SIWRP, 2001).
Year
(Frequency)
1952
(1%)
1978
(10%)
2000
(25%)

Damages
House
(unit)
7,598

Road
(km)
13

Paddy crops
(ha)
31,270

Cereals

1,834

20.5

8,110

203

1,100

32

6,500

100

120

The objective of this paper is to develop and assess various flood management strategies to
reduce flooding risks, potential damages and losses in the Lower Dong Nai – Sai Gon River
Basin and to explore their pre-feasibility by analyzing hydraulical, environmental and
economical impacts in a broad scope.

METHODOLOGY AND APPROACH
Flood management strategies in Ho Chi Minh City should initially be based on a ‘holistic
approach’. This approach considers the catchment as a whole, not only in terms of the
geographical and functional interdependencies involved, but also the inter-relationships between
land and water. Not just economic developments are considered, but also socio, environmental
and institutional developments. The development of flood management strategies should be
implemented by associating water-related sciences, environmental sciences with social sciences
as well as by coordinating and combining physical and mathematical modelling tools, involving
experts in all sections and public participants.
The flood management strategies in the Lower Dong Nai-Sai Gon River System have
been developed within a contemporary concept which states that ‘Floods cannot and should not
be eliminated, and every future flood-related development should be compatible with the entire
environmental system of the Lower Dong Nai – Sai Gon River System. Flood management
strategies should cover all potential flood stages and should be developed to efficiently respond
before, during and after floods’.
Flood management strategies have to comply with relevant aspects of social-economic,
physical and ecological conditions in the Lower Dong Nai – Sai Gon River System. Therefore,
various starting points for different geographic areas have been defined (Figure 3) (Petry, 2002):

‘Keep the floods away from people’;

‘Keep people away from floods’; and

‘Accept floods and clean up afterwards’.
After analysing flooding risks, potential damages and losses for future flood situations
(based on historic GIS data), flood management strategies have been derived, primarily based
on the combination and complementarity of structural and non-structural measures, taking
effectiveness and technical and socioeconomic pre-feasibility into consideration (Green et al.,
2000).
In order to explore the flooding situations in the Lower Sai Gon – Dong Nai River Basin,
12 different scenarios have been defined (see Table 2). These scenarios include different
upstream (discharge) and downstream (tidal level) boundary conditions, considering the effects
of climate change and other recent and future developments in the study area. A 1-D
hydrodynamic model (SOBEK-RURAL) (see model schematisation in Figure 2) has been
employed to simulate the hydraulic impacts of the flood management strategies. Flood scenario

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hydraulic impacts of the flood management strategies. Flood scenario No. 10, which
corresponds to the upstream (discharge of 0.1 exceedance frequency) and downstream (high tide
+ sea level rise) boundary conditions and mid-term future developments in the study basin.

Figure 2. SOBEK schematization of the Lower Dong Nai - Sai Gon River Basin

Figure 3. Zoning of starting points for the development of various flood management strategies
The purpose of structural measures is to keep floodwater away from people. The
implementation of structural measures will modify the flow of floodwater and alter the physical
characteristics of the floods (Petry, 2002). They comprise ‘discharge control’, ‘water level
control’ and ‘embankment and levees’ measures.
Non-structural approaches, as defined by the International Commission on Irrigation and
Drainage (ICID) (1999), comprise activities, which are planned to eliminate or mitigate adverse
effects of flooding without involving the construction of flow-modifying structures (i.e. land use

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Assessment of integrated flood management strategies in the Lower Dong Nai – Sai Gon River Basin,
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effects of flooding without involving the construction of flow-modifying structures (i.e. landuse planning, preparedness and emergency and relief).
Table 2. Measures selected for various flood management strategies
Tide level

High tide (or spring tide)
High tide + sea level rise
High tide of 2%
Storm surge

Tide water level
exceedance
frequency
100%
100%
2%
0.1%

Flood discharge exceedance frequency
1%
0.5%
0.1%
Scenario 01
Scenario 02
Scenario 03
Scenario 04

Scenario 05
Scenario 06
Scenario 07
Scenario 08

Scenario 09
Scenario 10
Scenario 11
Scenario 12

RESULTS
In total eight different strategies have been defined (see Table 3), based on three conceptual
approaches:

different principles of structural measures (discharge control, water level control and
confinement);

compatibility between structural and non-structural measures;

spatial distribution and feasibility of various measures.
Table 3. Measures selected for various flood management strategies
No

Measure
1

5

3

Strategy
4 5

6 7 8
Structural measures
Reservoirs and discharge control works in Dong Nai X
X X
X
River
2.
Reservoirs and discharge control works in Sai Gon X
X X
X
River
3.
Detention areas in East Vam Co River
X
X X
X
4.
Dike – embankment system for entire river system
X
5.
Dike – embankment system for important areas (*)
X X X X
6.
Floodplain excavation for the river system
X
X X
7.
River channel widening for the river system
X
X X
II.
Non-structural measures
1.
Land use planning (floodplain management)
a.
Floodplain regulation
O
O X X O X X O
b.
Zoning and land use by-laws
O
O X X O X X O
c.
Building codes
2.
Preparedness
a.
Flood forecasting
X
O
X X
X
b.
Emergency response planning and training
c.
Local social structure strengthening
d.
Public participation
X
X X X X X X X
e.
Flood proofing
O
O O
3.
Emergency and relief
a.
Flood emergency response planning
b.
Response measures
X
X X X X X X X
c.
Flood fighting
X
X X X
d.
Recovery measures
O
O O O O X O O
Note: X: Compulsory for the strategy
O: Optional for the strategy
(*) Important areas: Ho Chi Minh City, Bien Hoa City, Thu Dau Mot town and some small towns.
I.
1.

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The various strategies have been assessed and compared with a specific set of criteria,
derived from studies like Hooijer et al. (2002) and Silva et al. (2001) (i.e. costs, excavation
works, land use, environmental impacts, implementation time, etc.) in order to determine
preferred strategies, which could be suitable for further analysis. The quantitative and
qualitative assessment results for the eight proposed strategies are presented in Table 4.
Table 4. Assessment results for flood management strategies
No

Crirterion

Unit
1

1
a

b

c

2
3
4
5
a

Effectiveness (∆H)
Sai Gon river
River zone
Transition zone
Tidal zone
Dong Nai river
River zone
Transition zone
Tidal zone
East Vam Co river
River zone
Transition zone
Tidal zone
Absolute Costs
Excavation work
Embankment work
Land use or
land occupation
Rural

2

3

Strategy
4
5

6

7

8

metre
metre
metre

0.27
0.65
0.70

na
na
na

0.55
0.02
0

0.67
0.04
0

0.27
0.65
0.71

1.04
0.67
0.69

1.56
0.18
0

0.89
0.54
0.64

metre
metre
metre

2.72
1.18
0.18

na
na
na

0.64
0.05
0

0.94
0.1
0

2.72
1.18
0.19

3.40
1.19
0.18

1.68
0.10
0

3.44
1.09
0.18

metre
metre
metre
million US$
million m3
million m3

0.52
0.12
0.02
1,845
3.0
2.1

na
na
na
866
174
121

0.18
0.03
0
915
129

0.45
0.04
0
581
98.5

0.52
0.26
0.08
1,983
27.5
19.2

0.68
0.26
0.08
2,900
157
19.2

0.64
0.02
0
1,630
401
121

0.81
0.20
0.08
2,560
126
19.2

km2

346
27
129
9.5
346
475
166
(86)
(86)
(86)
b
Urban and sub-urban
km2
5
5
5
5
6
Technical feasibility
++
++
+
+
++
+
+
7
Environmental impacts
+
*
+
*
8
Time
++
++
++
++
++
++
++
Note: na: not applicable 346 (86) Italic text represents for the temporary land use or occupation
i. ‘Effectiveness’ is presented by average values of water level reduction (in metre)
ii. ‘Absolute Costs’ are calculated in Present Value, with an assumed discount rate of 10% (for the
period from 2005 to 2050).
iii. ‘Technical feasibility’: (++) most feasible; (+) feasible; (*) moderate; (-) less feasible; (- -) not
feasible
iv. ‘Environmental impacts’: (++) very positive; (+) positive; (*) moderate; (-) negative (- -); very
negative
v. ‘Time until the desired effect occurs’: (++) very short; (+) short; (*) moderate; (-) long time; (- -)
very long time

The strategies can be roughly divided into three categories: favourable, less favourable
and non-favourable. The advise on favourable strategies is composed by taking existing
environmental conditions (ecologically, socially and economically) of the study area into
consideration. The ‘storage and confinement’ strategy (no. 5 with reservoirs, detention, dikes
and embankments, and various non-structural measures) seems to be the most promising
solution to mitigate flooding in Lower Dong Nai - Sai Gon River System (Figure 4 and Table
4).
In addition, it can be concluded that all non-structural measures can be applied for each
strategy in practice. For this study, in order to distinguish the characteristics of each strategy,

6

356
(86)
5
+
*
++

Assessment of integrated flood management strategies in the Lower Dong Nai – Sai Gon River Basin,
Viet Nam

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relevant and closely related non-structural measures accompany certain structural measures. For
example, the ‘reservoir building’ measure should accompany the ‘flood forecasting’ measure,
and the ‘floodplain excavation’ measure should be associated with ‘land-use planning’
measures.
Table 5 presents more detailed information for the criterion ‘Environmental impacts’. The
information was obtained from a JICA study (1996) and literature (Petry and Boeriu, 2005 and
Douben, 2006).
The ‘Initial Environmental Examination’ (IEE) is carried out instead of a detailed
‘Environmental Assessment’ as a result of lacking data. However, the IEE roughly reveals that
the ‘reservoir building’ measure might give an overall positive impact, whilst ‘dredging and
excavation works’ implicate an overall negative impact and the ‘dike-embankment system’
might give a moderate impact to the existing environmental system. These qualifications
however, should be considered as a very rough estimation of potential environmental impacts.
The actual environmental consequences of a flood management strategy can only be quantified
after a detailed and thorough analysis.
Table 5. Initial Environmental Examination for proposed structural measures
Measure

Reservoir

Dredging and
excavation
works

Positive impact








Negative impact

flood reduction
food security (increase
of agricultural
production)
domestic water supply
hydropower supply
fisheries
reduction flood water
levels
soil material for
construction








loss of land (360 km2)
resettlement ( 41,500 people)
loss of wild lands and wildlife habitat
scouring of river bed below dams
decrease in floodplain agriculture
conflict demands for water use



affect sensitive habitats or valuable
fisheries resources
alteration of bottom surface, which
may be unfavourable to flora and
fauna
upland disposal of dredging material
could modify terrestrial habitat
impacts of possible land disposal on
surface run-off
sediment pattern changes
separation of river environment into 2
sides – outside and inside river
frequent improvement as a results of
section failure, settlement
reduction of natural storage for
floodwaters
flow of water in tributaries constrained
exacerbation flood problems for other
parts of rivers
increase flow velocities, reduced
shelter in the channel bed





Dike –
Embankment
system

Protection by keeping
people away from floods
and tidal movements









Overall
environmental
evaluation
‘Positive’

‘Negative’

‘Moderate’

DISCUSSION
The assessment results indicate that the implementation of the ‘storage and confinement’
strategy (no. 5) will reduce peak water levels significantly for a flood event that occurs with

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0.1% exceedance frequency, as well as the consequences of flooding, hence potential losses and
damages. Although considerable reductions occur of flooding impacts in the riverine and
transition zones will be achieved, in many developed areas such as Ho Chi Minh City and Bien
Hoa City, the pre-established protection levels still are not met fully. Additional measures (e.g.
drainage works, local dike and embankment systems) need to be studied and implemented as
well.
Ho Chi Minh City is located in the transition and tidal zones of the rivers. Therefore,
improvement and implementation of a continuous dike-embankment system with appropriate
sluices and gates are certainly needed to protect the area against floods with 0.1% exceedance
frequency and to satisfy the principle of ‘Keeping floods away from people’. The continuous
dike-embankment system will also need to be implemented in some other important areas, such
as Bien Hoa City and Thu Dau Mot town.
Along the Sai Gon, Dong Nai and East Vam Co rivers, in which important agricultural
areas are located, it is proposed to build embankment systems to protect these areas against
floods with 1% exceedance frequency. In remaining agricultural areas in floodplains, it is
proposed to locally build summer-embankment systems to protect these areas against annual
floods, with full consideration of the functions of floodplains in- and outside the summerembankment system during floods. Appropriate sluices and gates need to be built in order to
drain inundation water back into the river.
Local heavy rainfall also significantly contributes to urban inundations, and therefore
exacerbates the adverse inundation consequences during and after floods. Hence, effective
drainage systems, accompanied by pumping stations are necessary.

Figure 4. Spatial presentation of Strategy 5 ‘storage and confinement’.
The implementation of non-structural measures is required to satisfy the principle of
‘Keeping people away from floods’ and ‘Accept floods and clean up afterwards’. They will play
a main role for flood management strategies in many areas, where the above mentioned
structural measures do not solve flooding issues substantially, are not justified by cost-benefit
analysis and/or are not preferred due to adverse environmental consequences. Flood forecasting
and warning, flood emergency response planning and flood response measures will need to be
implemented all over the river zones. However, their performance (including maintenance)

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Assessment of integrated flood management strategies in the Lower Dong Nai – Sai Gon River Basin,
Viet Nam

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should be optimised in the river and transition zones, where most of the rural and urban areas
are located, in order to minimise the potential damages and losses. Land-use planning measures
will be used for the rural and sub-urban areas as well.
As a result of lacking environmental system data, together with non-accurate hydrological
data, the inter-relationships between land and water can be considered as the most important
uncertainty of the study. Therefore, further (implementation) studies should consider the basin
as a whole, not only in terms of the geographical and functional interdependencies involved, but
also the inter-relationships between land and water as well as socio-economic and institutional
development.

CONCLUSIONS
A comprehensive study on integrated flood management strategies in the Lower Dong Nai-Sai
Gon River System is presented. Flooding issues in these basins might be substantially managed
and mitigated by some promising integrated management strategies, which are a combination of
various structural measures and appropriate non-structural measures. Despite of some
constraints and limitations, the paper will certainly contribute to the ongoing development of
flood management studies in the Lower Dong Nai – Sai Gon River System.

REFERENCES
Claudia, R., Nguyen, C.C. and V.H. Nguyen, 2001. Water Allocation and Use in the Dong Nai River
Basin in the Context of Water Sector Reforms. Workshop IWRM, Manglang, Indonesia.
Douben, N., 2006. Flood Management. Lecture Notes, UNESCO-IHE Institute for Water Education,
Delft, The Netherlands.
Green, C.H., Parker, D.J. and S.M. Tunstall, 2000. Assessment of Flood Control and Management
Options, WCD Thematic reviews, 1999. World Commission on Dams Secretariat, South Africa.
Hooijer, A., Klijn, F., Kwadijk, J. and B. Pedroli, 2002. Towards Sustainable Flood Risk Management in
the Rhine and Meuse River basins, Main results of the IRMA SPONGE research program. NCR
Publication 18-2002. Netherlands Centre for River studies, Delft, The Netherlands.
International Commission on Irrigation and Drainage (ICID), 1999. Manual on Non-structural
Approaches to Flood Management. New Delhi, India.
Japan International Cooperation Agency (JICA), 1996. The Master Plan Study on Dong Nai River and
Surrounding Basins. Water Resources Development. Nippon Koei Co. Ltd., Tokyo, Japan.
Nguyen, A.D. and N. Douben, 2004. Integrated flood management strategies: a case study in the Lower
Dong Nai - Sai Gon River System, Vietnam. In: Douben, N. and A.G. van Os (Eds.) (2003).
Proceedings of NCR days 2003: Dealing with floods within constraints. NCR-Publication 242004, Netherlands Centre for River Studies, Delft, The Netherlands, pp. 64-65.
Petry, B., 2002. Coping with floods: complementarily of structural and non-structural measures. Volume
I, Proceedings 2nd International Symposium on Flood Defence. Beijing, China, pp 60-70.
Petry, B. and P. Boeriu, 2005. Environmental Impact assessment. Lecture Notes, UNESCO-IHE Institute
for Water Education, Delft, The Netherlands.
Silva, W., Klijn, F. and J. Dijkman, 2001. Room for the Rhine branches in the Netherlands, what the
research has taught us. Institute for Inland Water Management and Waste Water Treatment and
WL | Delft Hydraulics, Report no’s 2001.031 and R3294. Arnhem/Delft, The Netherlands.
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Economic Area, Ho Chi Minh City, Vietnam (in Vietnamese).

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