Luận văn assessment of flood control alternatives for dong tham muoi region south vietnam

analysis of the physical constraints, present situation, and in future consideration, In order to get above purposes the determination of inundation depth, inundated area and inundatio

ASSESSMENT OF FLOOD CONTROL ALTERNATIVES FOR

DONG TIIAP MUQI REGION, SOUTII VIETNAM

by

Neo Van Quan

nbmitted in partial ful Gllment of the requirements for the

Degree of Master of Engineering

Examination Committee: Prof Ashim Das Gupta (Chairperson)

Dr Mukand Singh Babel (Co-chairperson)

Dr Roberlo Sulil Clemente

Dr Sutat Weesakul

Nationality; Vietnamese Previous Degree! Bachelor of Water Engineering

Hanoi Water Resources University VieUun

Scholarship Donor: Government of Denmark (Danida), Vietnam

Asian Listitute of Technology School of Civil Lngineering

ThaiLand May, 2006

Abstract

Dong Tháp Muoi region is a hollow part of Mekong Delta in Vietnam Flood causes a lange inundation arva in this region every year Tl affeels to waler resources, environmen ecosystems, and socio-cconomic activities of people More on specific, flood inundation affect directly to agricultural production ‘Therefore, this study deals with the assessment of flood control alternatives in order to determine damage reducing on agricultural sector to find the best alternative which bring securing fong-Lerm benefits in agricultural production in region

‘Three possible altematives are proposed, through the assessment based on the most affective net benefits and whase cost of construction is acceptable for implementation for selection, Allcrnatives based on critics! analysis of the physical constraints, present situation, and in future consideration,

In order to get above purposes the determination of inundation depth, inundated area and inundation time in cateulation for he scenarios are very important in damage assessment, Therefore, this study, the VRSAP model was applied to calibrate for the Hood L996 and to simulate for the flood 2000, with expect to determine inundation depth and inundation time in

‘Lien riever, Vam Co river and the existing channel systems in calculation cases The GIS tools were used to simulate and determine inundation area after getting water lavel from calewation of VRSAP model

Benefit-cost analysis of plarmed flood control alternatives indicates thal scenarios Dredging An Phong - My Hoa chamets aud Building up Sluice al the end of channel is found

as the most effective flood cantrol alternatives, The combination flood control construction alternatives and damage reducing on agricultural production from flood inundation is recommended for implementation, with discount rate L0% is calculation result Benefit/Cost ralio of 2.91

Calculation results of relationship between present value (P) and interest rate (i) the results are determined that, with change of discount rates as 6%, 8%, 12% and 14%, the corresponding Benefit/Cost ratios are 3.26, 3.08, 2.75 and 2.61, respectively and internal rate

of rctumn of IRR 34.2% which is concluded that the selection is zconomically justified

Acknowledgement

Firstly, T would like to express my deepest gratilude lo my adviser Prol Ashim Das Gupla and my co-adviser Dr Mukand Singh Babel for their advices and encouragements throughent the poriod of this study

Very sincere thanks and appreciation are due to Dr Sutat Weesakul and Dr Roberto Sulit Clemente who serves as the member of the examination commiliee for this helpful stiggestions arel comments,

I would like to express my deep gratitude to Prof, Dao Xuan Lloc, who help me a lot helpful suggestions of this stndy and 1 also gratefully acknowledges the kin cooperation and help of Eng, Neuyon Thai Quycl, who help me to understand and use VRSAP model

I thank to secand base Water Resource University and my friends who help me complete data collection Dong ‘thap Muoi region, Mekong delta in Vietnam | also would like to thank to

my classmates m ATT and my friends in Vieinam for their kind helps during the study

Sincere gratitude is due to WAterSPS, MARD — DANIDA - Vietnam for providing scholarship for me to study in the Water Lingineering Management field, in School of Engineering Technology, at ATT

Finally, [am profoundly grateful to my parents, my sisters, my brother, and my uncle tor their

xcouragemcnt in this sludy

love and continuous

2 Rational of the Study

1.3 Statcment of the Problem

1.4 Objectives of Study:

1.5 Scope of the Study

LITERATURE REVIEW

2.1 Flood Routing Model

2 Geographic Infannation System Application in Water Resources

2.3 Approaches and Methods for Assessment of Plocd Control Plarming

RESEARCH METHODOLOGY

3.1 Approach for Research

3.2 Theoretical Consideration VRSAP Model

3.2.1 Schematization for hydraulic computation 3.2.2 Governing equations

3.3.5 Root mean square crrer

3.4 Are view GIS in Simulation of Flood Mundation

TẾ

16 16

RESULTS AND DISCUSSTION

5.1 Dala Analysis

5.1.1 Rainfall data 5.1.2 Runoff data 5.2 VRSAP Model Sclup, Calibration and Verification

5.2.1 Establish schematization of river network for VRSAP model 5.2.2 Run model,

5.2.3 The simulation for historical flood year 2000

libration and verification

5.3 Development of Flood Innndation Maps

5.4 Calculation Results Inundation Area and Damage Reducing

COSTS AND BENEFITS CACULATION

6.1 Culeulation Methodology and Calenilation Content

6.2 Proposed Construction Prograrn

LIST OF FIGURES

Figure 1.1: The administration map Mekong River Delta, Vieltarn and the study area

Figure 1.2: Schematic representation of flow systems in dong Thap Muoi region

Figure 2.1 Literature review of hydraulic and assessment flood control planning,

Figure 3.t: Mothodotagical framework for as

Figure 5,2: Calculated and observed at Tan Chau station on Tien river flood 1996

Figure 5,3: Calculated and observed at Moc Hoa station on Vam Co river flood 1996

Figure 5.4: Caloulated and observed at Hung ‘hanh station Phuoe Xuyen channel 1996

Figure 5.5: Calculated and observed at Tan Chau station on Tien river flood 1999

Figure 5.6: Calculaled and observedt al Moc Toa station on Vain Co river flood 1999

Figure 5.7: Caloulated and observed at Ilung ‘hank station on Phuoe Xuyen channel 1999 Figure 5.9: Water level (Scenario 1) at some nodes along Tien river of flood 2000

Figure 5.10: Water level (Scenario 1) at some nodes along Vami Co tiver of flood 2000

Figure 5.11: Water level (Scenario 1) some nodes along Phuoc Xuyen channel flood 2000

Figure 5.12: Tlustraien of agricultural cultivation periods and water level

Figure 5.13: Illustration to separate field cells

Figure 5.14: Simulation flood inundation map on 30/Aug before have flood control

Figure 9.15: Situation fload inundation map on 01/Nov before lave Sood control

Figure 5.16: Simulation flood inundation map on 30/Aug for Sub-scenario 3 (Scenatio 2)

Figure 3.17: Simulation fload immdation map on 01/Nov for Sub-scenario 3 (Scenario 2)

Figure 5.18: Simulation flood inmdation map on 30/Aug for Sub-scenario! (Scenario 3)

Figure $.19: Sitnulation flood inundation mnap on 01/Nov for Sub-secnariol (Secmatio 3)

Figure 6.1: The stages of constriction for immplsmentation plan in Scenario?

Figure 6,2; The stages of construction for implementation plan in Scenario3

Figure 6.3: The relationship between present & interest rates

LIST OF FIGURES

Figure 5,20: Flood inundation map on 30/Aug before flood cantrol (Scenariol) 85 Figure 9.21: Flood imundalion map on O1/Nov before flood control (Scenario 1) 86 Figure 5.22: Hood inundation map on 30/Aug for Sub-1 (Scenario 2) 87 Figure 3,23: Flood inundation map on 01/Noy for Sub-1 (Scenario 2) 88 Figure 5.24: Hood inundation map on 30/Aug for Sub-2 (Scenario 2) go Figure 5,25: Flood inundation map on 01/Nov for Sub-2 (Scenario 2) 90 Figure 5.26: Flood inundation map on 30/Ang for Sub-3 (Scenario 2) 91 Figure 5.27: Flood inundation map on 01/Nov for Sub-3 (Scenario 2) 92 Figure 3.28: Flood inundation map on 30/Aug for Sub-4 (Scenario 2) 93 Figure 5.29: Flood inundation map on @1/Nov for Sub-4 (Scenario 2) 94 Figure 5,30: Flood inundation map on 30/Aug for Sub-1 (Scenario 3) 95 Figure 5.31: Flood inundation map on O1/Nov for Sub-1 (Scenario 3) 96 Figure 5.32: Hood inundation map on 30/Aug for Sub-2 (Scenario 3) 97 Figure 3.33: Flood inundation map on 01/Nov for Sub-2 (Scenario 3) 98 Figure 5.34: Flood inundation map on 30/Aug for Sub-3 (Scenario 3) 99 Figure 5,35 Flood inundation map on 01/Nov for Sub-3 (Scenario 3) 100 Figure 5.36: Flood inundation map on 30/Aug for Sub-4 (Scenario 3) 10L Figure 5,37: Hood inundation map on 01/Nov for Sub-4 (Scenario 3) 102 Figure 3.38: Flood inundation map on 30/Aug for Sub-5 (Scenario 3) 103 Figure 5.39: Mood inundation map on O1/Nov for Sub-5 (Scenario 3) 104 Figure 5.40; Flood inundation map on 30/Aug for Sub-6 (Scenario 3) 105 Figure $.41: Flood inundation map on O1/Nov for Sub-6 (Scenario 3) 106 Figure 5.42: Flood inundation map on 30/Aug for Sub-7 (Scenario 3) 107 Figure 3.43 Flood inundation map on 01/Nov for Sub-7 (Scenario 3) 108

vi

LIST OF TABLES

Table 4.2: The information of agriculturat production in region lọ

Table 5.7: Flood water level at 30/August (Summer-Antumn) before and after have flood

‘Table 5.8: Hood water level at 01/Nov (Spring-Winter) before and after have flood control

‘Table 5.9: Elood water level at 30/August (Summer-Antumn) before and after have flood

Table 5.10: Flood water level at OL/Nov (Spring-Winter) before and affer have flood control

Table 5.11; Summarize calculation results of inundation arca in Sumimer-Auturnn scason

Table 5.12; Summmurize calculation results of inundation arca in Winler-Spring scason afler

‘lable 5.13: Calenlalion resnlts of imundation area in Stwnmer-Atttrmn season after completed

"Table 5.14: Calculation results of flood immdation area in Winter-Spring season after

Table 6.4: Scenario3: Altematives for floodwater drainage in internal field by channel

Table 6.5; Investment throughout the stages for seenatio 2 58 Table 6.6: Itvsstrnenl tnoughoul (he stages for scerratio 3 58

‘Table 6.7: Calculation results of flood inundation area in Summer-Antumn season of Sub- scenariol (scenario 2) before and after have stages construction 63

LIST OF TABLES

Table 6.8: Calculation resulls of flood inundation area in Winter-Spring scason of Sub-

soenariol (scenario 2) before and after have stages construction 64

Table 6.29: Summarize calculation results Mnilial investment cost and cconomic damage

reducing on sccnario2 aftcr have stages construction 65

‘Lable 6.30: Summarize calculation results initial ivestment cost and economic damage

rodlucing ort sccnario3 aller lưve stages construction 66

‘rable 6.31: Summarize calculation results of Economic Benefits and Costs Analysis for alb

Table 6.32: Shows the cash flow in Investment, Operation and Maintenance (O&M), and

‘lable 6.S4: Summarize calculation and comparisons results for altemative A & alternative 3

72

"able 5.3: Max water level calculation results along rivers and channels before & after have

‘Table S.4: Max water level calculation results along rivers and channels before & after have

Table 5.5: Max flood water level at field cells before and after have flood control alternatives

LIST OF TABLES

Table 6.12: Calculation results of flood inundation arcu in Winler-Spring season of Sub-

‘The Cash flow in Investment, (O&M), and Benefits of Sub-2 The cash flow in Investment, (O&M), and Benefits of Sub-3 The cash (ow in Investment, (O&M), and Benofits af Sub-4 The cash flow in Investment, (O&M), and Benefits of Sub-5 The cash flow in Investment, (O&M), and Benefits of Sub-ó

‘The cash flow in Investment, (O&M), and Benefits of Sub-?

Calculation result of benefits/costs of altemative A, with i — 6%

Calculation result of bensfils/costs of allemalive B, with i= 6%

Calculation result of benefits/costs of altemative A, with i— 8%

Calculation result of bencfits/costs of alternative B, with i— 6%

Calculation result of benetits/costs of alternative A, with i= 12%

Calculation result of benefits/costs of alternative B, with i— 12%

Calculation result of bensfils/costs of allemalive A, with i= 14%

Calculation result of benefits/costs of altemative B, withi = 14%

Chapter 1

INTRODUCTION

1.1 Background

The Mekong River (Figure 1.1) is one of the historic rivers of Asia, ranking twelfth in the list

of longest rivers of the world It flows along the borders of six countries: China, Myanmar, Laos, Thailand, Cambodia and Vietnam A large delta in South of Vietnam, the Vietnam’s Mekong delta comprise of provinces: Long An, Dong Thap, Tien Giang, Ben Tre, Tra Vinh, Vinh Long, An Giang, Can Tho, Kien Giang, Hau Giang, Soc Trang, Bac Lieu and Ca Mau as shown Figure 1.3 This delta is subdivided into four main regions: (a) Dong Thap Muoi, (b) Long Xuyen Quadrangle, (c) Bassac and Mekong (the region located between the Mekong and Bassac river), and (d) west Bassac River region (the area on the west side of Bassac River between Long Xuyen and Mekong River) as shown in Figure 1.2

Map of Subvided Region Mekong River Delta, Vietnam

Figure 1.1: Vietnam map and Figure 1.2: Map of subdivided region in Mekong

the study location River delta, Vietnam

Figure 1.3: Schematic representation of flow systems in dong Thap Muoi region

A large area in the northern part of Viet Nam's Mekong Delta (Dong Thap Muoi) is flooded

annually when the water level in the main channels rises above the river, canal banks and particularly, the floodwater overflow border Vietnam-Cambodia Flooding has serious

negative impacts on production and livelihood of the people In the past, the flooded areas

were almost unproductive or planted with floating rice of low yield Since the 1980s, as the

result of many projects funded by the Government to exploit the Dong Thap Muoi area, water

control structures have begun to promote development with a new perspective Double or

triple cropping patterns using high yielding varieties are new concept and have practiced in

the flooded area

Annually, floods still cause serious losses in terms of production, infrastructure damage and

human lives In recent years, 1994, 1995, 1996, more than hundreds of people were flood victims Particularly flood in 2000 is still vivid memory Total losses amounted to hundreds

of million dollars This results as permanent threat to the communities, where people are

living in low-lying lands The low-lying land in the delta is usually fertile that has been

exploited for the agricultural purposes Inundation occurs causing great damage for the

lowland inhabitants whose economy mainly depends on agriculture activities from flooding.

This is a flood plain (closed floodplain systems) and contains agricultural area, which accounls about 72% of Dong Thap Muoi region whore agrieillurc is the mainstay of ceonomy Nevertheless, ood has positive cffcels, for cxaupls, floodwaters carry sediments

to enrich the rice fields, increase aquaculture production, and leach toxic ions from acidic sails

Flood controls in the Mckong Delta in general have been the focus of many studics by various Vietnamese and international agencies particularly in Dong ‘hap Muoi region While the main problem is to minimize the impact and maximize benefits of flood and inundation using flood control planning siill in obscure

According to Vietnam's atlas, the Dong Thap Muoi region is located between 10°35'-1 °00'N 1aitmide and 105°20'-106700T: longitude It is surrounded by Cambodia in North, Tien River

in the West and South, Van Co River in the Fast TL covers the lund of Long An, Dong Tháp and Ticn Giang Provinces as shown in Figure 1.3 The slope is from North-West to South- East, the land surface of 1.0 to 3.5m Total area of the region is 7,088.6 knr,, with agricultural area of 510,379.2 ha (72%) and it includes three provinees as:

Sone of the characteristics of these regions are described as follows:

a) Water quality: Fresh water is available for the whole year ‘Tidal effect in the dry season: The semi diumal tidal {twice daily) is dominant with amplitude of 1.0m and a high tidal water level of 1 Sm and coming along sonic nuain rivos as Tin riover and Varn Co river

bj Flooding: Annual inundation for periods of up to five months (fom fuly to November) Tigh food occurs al the end of Seplember and first of October, with water level from 3.7 lo 3.12m compurcd with Hon Dau datum (at Vung Tau beach) During thal fime, 90% of the area is submerged

6) Existing charmels and hydrandic structures: oxcopl for the main rivers namely the Tion river, Want Co river and Phuoc Xuycn channel, the horizontal channel systerus and the parallels channel system with Tien tives,

1.2 Rational of the Study

‘The natural limitations are deciding factors to oxploit land resources of this region such as flood inundation, alum soil and salt intrusion particularly in coastal belt, Recognizing the high potential for agricultural development in the region, the Government of Vietnam accorded a high priority to this region for the design and construction of flood protection and flood drainage project These activilies for flood controt andl potential development in region have

been partially implemented, based on calculation results ftom historic flood 1996 Ths purposes of these projects are lo minimizing the flood ¢ffecl.on agricultural soctor in Dong Thap Muoi region

Although they brought economic benefit due to agricultural productions and improved drainage in region Ilowever, it has been observed that there are many limitations, after the particularly historical flood 2000

1.3 Statement of the Problem

Flood and inundation are annual events, which might affect the infrastructure, house, and specifically agricultural production, It not only interrupts socio-economic activities but also bring negative impact in natural environment

The flood inundation in the Dong Thap Muoi region is mainty due to overflow across the Vietnam — Cambodia border In addition, a part of the floodwater in the Dong Thap Muoi originates from the rainfall within the region itself The [loodwater in the Dong Thap Muai is being drained out fo the Ticn River and Varn Co River Also, the flood drainage system is ot adequate enough to drain effectively that results high inundation depth causing permanent threat to the communities Some sluices have improved the flood control, but now their effects are limited because of development efforis to date, and their physical conditions đo not pornit stable and effsctive operation Spocially, the historical flood of 2000 was very high, so they were not fully effective as they planned, In addition, the Govemment of Victham built Tan Thanh-Lo Gach Dyke in order to control the overilow across Vietnam-Cambodia border and this system was effective in earlier days to protect the agricultural field from severe inundation

In recent years with climatic variability and extremity, the flow and water level upstream of Viemam Mekong River Delta and Cambodia border is increasing during the rainfall season and in addition, the Dyke (Tan Thanh-L.a Gach) is scriously downgraded and ths bed level of

natural channcl systems is raiscd duc to siltation These factors impact the agricultural

development in the region To address this, the project has been implemented with the flood control alternatives based on flood year 1996 ‘I'he flood event of year 2000 was severe with

discharge of floodwater across the border of 12,000 m/s compared to 8,270 m/s (1996

event) (Vietnam yearbook 2001) and the resuftant damages were higher

With the limitations shown after historical flood 2000, the Government of Viemam have assigned the Ministry of Agricultural and Rural Development to establish flood control aliernatives in Dong Thap Muoi region with purpose of economic potential development in this region in order to secure cultivation of two Lice crops per year The objectives are

‘The proposal for the flood control alternatives are given in detail in the next section, In order

to know the economic effectiveness of each altemative, an assessment and analysis of cost and benefit of each alternation is needed

To dctcnminz depth, arca of inundation and the damage to agricultural sector for

different flood control alternatives

‘To compare and assess the economic effectiveness of the proposed flood control

allornatives, Conclusion aud recommendations for implementation of flood control alternatives

1.5 Scope of the Study

The scope of the study inchades:

”

Collection of relevant dala and information raatrly from the secondary sources:

Development of spatial database for the study area, using Geographic Information

§ tòl

Calibration and verification of VRSAP model using Mood year 1996 and flood

1999 respectively

Simulation for flood year 2000 using calibrated VRSAP model

Lstimation of depth, area and duration of inundation, with/without flood control

sccnarios

Calculation of investinent cost for flood control construction scenarios

Calculation of economic losses reduction in agricultural sector corresponding to

different Mood contro! scenarios

Recommendations for alternatives to solve the problem of inundation in future

Chapter 2

LITERATURE REVIEW The literatures relevant to flood inundation and its impact on society were studied and discussed in this chapter This chapter is sub-divided into three sections according to the

proposed objectives of the study as shown in figure 2.1

+

Studies of flood control in the study

area and related basin

Figure 2.1 Literature review of hydraulic and assessment flood control planning

2.1 Flood Routing Model

The VRSAP model has been used in a number of water control studies in Viet Nam on both

low flow saltwater intrusion, and flood flow, such as: salinity intrusion studies in the Mekong

Delta supported by the Australian Government through the Interim Mekong Committee from

1981 to 1991; eco-development planning and pre-feasibility studies of water control in the

Quan Lo - Phung Hiep area of the Mekong Delta supported by the Mekong Secretariat and

Canada's CIDA; the UNDP-supported Mekong Delta Master Plan project studied by

NEDECO of the Netherlands, 1990-1993, In this project the VRSAP model was used to simulate the flood flow and the low flow including salinity intrusion, the study of flood control planning for the Mekong Delta, a high priority study of the Vietnamese Government,

flood flow and low flow-salinity intrusion studies in the Saigon-Dong Nai Basin; the drainage

studies of storm-generated rain water in the Nhieu Loc Thi Nghe canal system and water resources development projects in the Mekong Delta and the Saigon-Dong Nai Basin

Khue (1978) developed VRSAP model based on the solution of the full Saint-Vernant equations using the implicit finite difference scheme that take the cross-sectional data in average of the segment Later in 1980s, VRSAP model was added with a subroutine that calculated salinity intrusion This model has been widely used in recent water resources planning projects, especially in recent topographic and hydraulic data and calibration for the flood, 1996 in Vietnam part of Delta

Lya, D.A and Goodwin, P (1987) examined stability and convergence characts

four point implicit finite differerice schemes dus ta Preissinann which has boon wisely used in open channel flow modcling, The analysis is nnadc for a general lincar hyperbolic systear ofn first order equations but is restricted to the homogeneous or frictionless case In particular the affects of a weighting factor in space, as well as in time was considered

Mien (1998) developed KOD modcl for flood computation in the Victnam Mckong River Delta, The model is based on the full St Vernant equations for unsteady flow in the river channel and equations for flow over structure, The solution is based on explicit scheme,

Dalla (2000) applied Distributed Iydrotogic model for the simulation of the flood inumdation paramelers and for land warnings for any predicted rainfall cvenl in Japan The physically based distributed hydrologic model considers five major components of hydrological cycle, they are interception, and evapotranspiration, Liver flow, Overland flow, Subsurface flow and Gromnd water flaw In this madel, for river flow, diffusive approximation of St Venant’s momentum equation is considered and an inmplicil finite difference scherns is used Lo solve the equation tor river network Similarly, tor overland flow also diffusive approximation of the St Venant’s momentum equations are considered and the equations are solved by using an implicit finite difference scheme

Nhan (2000) developed HYDROGIS model, and used for flood and salinity intrusion forecasting, in the Mekong Delta, The model is based on the full Saint Vernant equations Upstream boundary conditions was based on the forecasted flow at Pakse Downstream conditions was forecasted tidal waler level in the river mouth A comprohansive interface was developed for data entry and presentation

Suphat and Nguyen (2000) developed a hydrologic-hydraulic modeling approach to simulate the rainfall runol? process and the Nlow in the large river basin The rainfall runoff models was first developed for the subcatchment of the river basin, which are combined to form a large river basin This model was used to generate the runotf being modeled as lateral flow to the hydrodynamic model in which the main streams in the basin are schematized

Gupta, Babel and Ngoc (2003) used VRSAP model to simulate the flood phenomena in the Mekong Delta, Information on depth, duration, and spatial extent of inundation and estimation of damages caused by floods are needed for plaming proper fload mitigation measures

2.2 Geographic Information System Application in Water Resources

Recently, as a results of development of technologicel science, many flood damage estimation models were developed with aid of tlood simulation models based on high techniques such as Geographical Information System (GIS) These models simulate a tlood event with spatial distribution of extent of flood, a criterion of new approach by aid of GIS and RS Spatial information management and spatial analysis help managers for making decisions on

structural, non-structural floods mitigation measures

‘Thapa ef al (1992) described about the GIS assisted watershed management in the upper Pokhara Valley in Nepal They studied the deteriorating condition of the watershed and performed the spatial analysis using GIS as a tool The spatial analysis focused on the identification of the locations under severe threat to environmental degradation and zoning of the land unit's were done in accordance with their physical suitability

Leipnik ef al (1993) explained about the implementation of GIS for water resources planning and management, GIS is dosignod to store information about, the location, topology and attributes of spatially referenced objccis and many dala base queries arc performed through it,

‘They have deseribed in detail about the stages in the implementation of GIS, and understanding of these stages help in using GIS in water resources planning and management effectively

Dutta et al (1998) presented the methodology for flood damage assessment using GIS and Distributed Ilydrology model and a case study in Ichinimiya River Basin, Chiba, Japan The TIS Distributed Iydrologic Model (Iha el al, 1996); which include four major component such as overland flow, river flow, unsalurated zone flow, and saturated zene flow, was uscd in this study for Dood modeling He also described the method to develop flood damage assessment model with consideration of three categories in term of land use pattern as urban damage and damage to service by using various hypathetical damage functions which were devclopod by Bhavragri ø af, (1965), Beradon (1973) and Ropgs (1974)

Ieping et af (1998) presented the implementation of GIS technology on Urban Lood Dynamic Sitnulation Model The main characterises of Urban Flood Dynamic Simulation Model are simulation of the detailed flood process, therefore, the results can be applicd in many aspects such as flood loss calculation, flood hazard map, regional planning, flood insurance, flood control planning, etc

2.3 Approaches and Methods for Assessment of Flood Coniral Planning

‘rhe Red Commission for Flood control and Management (1973) made a study on the flood control planning in Red River Delta and concluded that to protect Hanoi and downstream areas fiom flooding in case do historical flood as occured in 1971 it is necessary to divert flood in to the sea through Day River Basin Based on the land use condition on the basin as well as structural conditions such as barrage and dikes and sluices along the Hloodways, the study indicated that the maximum discharge that the l'ay Basin can carry to the sea is 4800

m/s

Horn (1987) Use an approach to establish priorities for future flood eontrol planning and

applied to hydrologic sub basins in the New Jersey Data on historical flood losses, flood potential, and current and prior flood control planning efforts were compiled and entered into flood contro) database, accessed through a computer database management system The selection of indicator variables, characterizing flood control planning need, was considered along with a system of the ranking and weighting these variables for assignment of planning prierity numbers to the sub basins, This approach provided an adequate screcning mechanism for establishing an initial list of planning candidates, although more subjectve factors must then be used for further evaluation

Ouslllstte, 1.cblane and Rousscll (1988) The coonomic yicld af a Naod-plain zoning program was measured by cost-benefit analysis The methodology entails the use ofa probabilistic hydro economic model to evaluate expected flood damages with and without zoning The application showed that this type of program, albeit cost-effective overall, may be umacceplable for various Teasons to the various parties involved

Nefeco (1993) carried out the study on optimal use of resources of Mekong Delta in Vietnam The study defined the water abstractions and [heir distribution over the delta and the tow Now ported for different Jand use scenarios The study looked at surface and ground water resources as well as consumptive use of water for drinking water supply and for imrigation of agricultural land “he water requitement was calculated for the dry season only

Ty (1995) developed a new perspective of sustainable development for the Mckong Basin development plan his report listed five key issues of development planning: (1) Active participation of the riparian countries, (2) Continmity and consistency of the basin planning work, 3) Advanced technotogy and lilzst achievernents in basin nalural plarming, (1) A soil fourdation af the basin development knowledge, and (5) Core human resonrees clements for the basin development planning

Tamd (2002) Feonomical integration of pormanent and emergoney flood contrel options is a long-standing problem in water resourecs planning management, A two-stage lincar progranuning formulation of this problem was proposed and demonstrated, which provides as axplicit economic basis for developing integrated floodplain management plan The approach minimized the expacied value of flood damage and cosls, given a flow or stage f

distribution A varicty of permanent and cmergency foadplain management optio

examined in the method, and interactive effects of options on flood damage reduction can be represented ‘he approach was demonstrated and discussed for a hypothetical example Limitations of the method in terms of forecast uncertainty and concave additive damage function forms was discussed along with exlansions for addrossing these more difficult situations,

Bradsn and Douglas (2004) assessed the dawnsiream economic consequences of devetoprent

designs lasing benefit transfer method ta promote greater once-site water retention TL

concluded that once-site retention provides many services, For residential propetties, the economic value of those service was on the order of 0-0.5% of the market valne depend on the difference that retention makes to downstream flood exposure, For water quality improvernants, the incroasos range up to 15% of the market value for watarside residences whore clarity of the water quality was greatly improved The inercascs were much less for improvements that are much less visible, properties that property value on average for all properties in the flood plain, ‘I'he public sector realized additional benefit through smaller bridges, culverts, and other drainage infrastructure and through incrsased recharge Cilies and industries may avoid costly upgrades to waste water trcatmmenl facilities if taw [aw increase

Hayes, Amasce (2004) An interdisciplinary team consisting of representatives from state

government amd academia has dovelopod an inrovative flood risk maragernent plan thal combines a large-scale nonstructural hazard mitigation plan with portions of a federally authorized plan previously developed by the U.S Amy Corps of Engineers Separate alements of the féderally authorized plan were considered for inclusion in the alternative plan based on the estimates of each elements marginal benelfU cost ratio, potential environment impacts, and level of consistouey with cwtenl policy The plan involved relrofitting approximately 1,500 residential and nonresidential structures in the 100- year floodplain and require development of a structure-by-structure flood proofing benefit’cost analysis computer program At less the half the cost, the alternative plan achieved flood risk management goals ina significantly more cosi-cflcetive manmcr for an cnvironmenlally sonsilive arca

Chapter 3 RESEARCH METHODOLOGY

This chapter describes systematic procedures for achieving the objectives of the study Figure 3.1 shows the methodological framework for assessment of flood control planning using

analytical approach

‘Assessment of the present situation in stuly axea

~ Flood and inundation problems:

= Dearages in agricultural sector development

‘Assessment af Flood Contral Planning

~ Situation of iandetion

~ Agnonltural sertav development

~ Soenurio anul reduction of flood control

Siunleian 2000 flesd Change Seensnios im

flood control phianing,

Compare and assess daxuges of inundation and effectiveness in flood control planning options to agricultural sector ]

Conclusion and Recommendation

Figure 3.1: Methodological framework for assessment analytical flood control planning

10

3.1 Approach for Research

The proposed methodological framework is comprised of two main components

ve Application of Vietnam River System and Plain Model (VRSAP model) tor flood routing

ce Application of tool for development of food inundation taps by using Acrview GTS software, and simnulaling flood inundation from results of the VRSAP model

vo Estimation of damage and economic effectiveness to agricultural sector for

different flood control alternatives

3.2 Theoretical Consideration VRSAP Model

Khue (1978) developed VRSAP model, for simulation one-dimensional motion of water and substance (salinity, bio-chemical material, etc) An implicit finite difference scheme for solving one-dimensional Saint-Vernant equations and advection dispersion equation are applied for comptsx network of rivers and canals

3.2.1 Schematization for hydraulic computation

In VRSAP model, river, canal and floodplain system are divided into segments, nodes, and storage cells for hydraulic computation

River segments link together at nedes, Nodes arc intcrscetion points of onc er several river segments, Each segment links two nodes: the upstream node (d) and the downstream node (c) Segments are described by representative cross section while plain cell by area corresponding

to land level

In the network, nodes are code by natural numbers, form 1 to KK (NN are total number of niodes) The coding is principally arbitrary and free from ths place of nodes on the plane One nods may accept cilhor given discharge Q,, inflow (-) or oul How () or givan water level 7,

as boundary The cdge of an amputated branch is also onc nonal node, where the inflow discharge is Qe 0

Segments arc basiv finilc differenee clernents of the problem, the Saint - Vernant cquation system will be used to every segment, the water balance condition at nodes links them to form

an equation system for the whole network

3.2.2 Governing equations

For a general network flow may exist in river network, flow in or out or storage cells So, ane has to deal with throc types of aquation: Partial differential cqualious for a main river branches, ordinary differential equations for storage celis and equation for hydraulic structures Apart from these, it is also needed to add junction conditions in some location of the network to keep the flow contimmity

1H

a) Main elver

Unsteady flow can be expressed by the two governing equations, they are continuity and momentum equations, and are non-linear VRSAP model is based on the solution of the full fledge Saint - Vernani equalions, The governing equations are used as follow

w = cross section area (m')

B = canal width at fiee surface (m),

Be canal width, including storage area, averaged over the segment (mm), or storage width

q =lateral flow per unit length

C =Chezy”s resistance coefficient (m"7/s)

b) Equation for storage cells:

This is the continuity cquation for storage cells

a

Where V is the water volume, Q is in and ont, going discharges

12

¢) Equation for hydraulic structures and junction conditions:

The flow must be conservative, so at confluences or tribufaries the sum of all discharges must

be zero At hydraulic structure, flow rate is defined by the empirical formula

Where Zl, Zhi are the upstream and downstream water levels and @ is characteristic parameter of structures A structure may be modeled by onc of two ways asa spillway and a sluice The discharge, passing through a spillway is calculated as:

The discharge through sluic

9=m A2g\jZ 2 for free Dow 8)

%œs 42g42 Z, for submerged flow G39)

Where mm, ,s,e, are empirical coefficients for the structure, b is the width ofthe

can be determincd as follows:

spitway, is he wel area of the sluice

3.2.3 Method of solution

‘To get numerical solutions, the considered river network is split into river branches, separated

by nodes A node is point in a river system, A confluence or tributary is a node For a hydraulic structure in river, it is associated with two nodes Upstream and downstream nodes are defined due to different water levels

‘The numerical method is based on the implicit 4 points method for river branches instead of high-resolution numerical methods, implicit finite difference scheme for storage cells and linking discharge of hydraulic structures

4) Finite difference scheme for river branch’ s equation:

a=x,<x,<.<64 26, Coax, x

Where , (iHk, ,1) arc location of cross section Using difference scheme for any function f

are given below equations

13

For cell & with waler level 7, surlace area F ()™ the discharge between nodes k andj g

©) The exchange of water between river, channel and plain cell

VRSAP distinguished two types of the exchange of the river flow and flood plain area

Separated, conditionally connceted ecll:

‘This type is applied for the exchange, limited by small canal system or structure There is water level difference between canal system and plain so that equation can be written as:

Qr—+ thV2£Z Z# @-19

Where,

Qk: discharge of rice-tield

2; wate level in riec-cd

Zy Water level In channel

©pzncd Adjaccmt CcH:

This type is applied for the cells freely connected with a segment of river or canal Waler level in the plains equals to thal in the canal system, Submerged arca of eull affeck divcelly lo flow area in governing equations for this case, equation is

B,=canal width, including storage arsa, averaged over the segment (m),

or storage width;

F =lolal submerged arza of ects atong the river

f2 =1ength of river segmant where cell is comscted (11)

3.3 Statistical Criterion

The degree of accuracy in calibration ofany mathcmatical model can be checked by statistical

evaluation of the observed and computed data The following criterion are used to check the

P represents the computed values

Q =represents the observed values

n— the sample size

STDP is the standard deviation of the computed data

STO is the standard deviation of the observed data

G-19)

3.4 Arc view GIS in Simulation of Flood Inundation

A GIS, a system that is capable of assembling, storing, manipulating and displaying geographically referenced information, A GIS can perform complex operations on goographical information This technology arc used in this thesis

cstimation of effected depth imundation, duration and arca inundation in different flood control alternatives scenarios during flood time GIS spatial analysis technique are used for this work as using the GIS tool for development of flood immdation maps by using Acrview GIS software, from simulation resulls of Ihe VRSAP model

“The application tools of Acrview GIS software are shown detail in chapter five

lô

Chapter 4

DATA COLLECTION AND METHODOLOGY

4.1 Data Callection

1 Hydrology data

The all available hydrological data in the study area are collected and shown in the table 4.1

below and location of all station is described in figure 4.1 below

‘Table 4.1: The data collection of stations in study area

2 HEIRAGS Goma tive | Darla

3 Waterlevel (hourly) Cao Lanh ‘Tien River oe Tôn, season

6 vet a Moc Hoa West Vam Co river mm _—

7 MaRS enh tage camel | Pug tose

9 Rainfall (daily) Vinh Thmg West Varn Coriver _— 90 season

13 Discharge (daily) EastVamCo Kast Vam Co river _

I6 Tidal evel (hourly) BmhDai Hamu Tatang river PT ng 1000.2000.”

17 Tidal level hourly) Ben Trai Co Chien river ma 3000

Figure 4.1: The location of all stations of study area

Gauging network in Dong Thap Muoi region

Keatie (0-9 Enea He (2b)

os

West Yam Ce ca East Van Ca (0-0

= Water level station -

2 Bathymetric data: Cross section data, which are measured along the rivers of Tien river,

Vam Co river and Channel systems are collected from the Institute Water Planning in South Vietnam

3 Map: The collection Topography map (1/50.000) (use to develop DEM) and Land Use map (1/50.000), are collected from secondary sources as; Water Resources University and

also download to get DEM 90m from free Internet

4 Agricultural documents: Collected Agricultural report of Dong Thap Muoi region in 2001 and agricultural damage of region in flood 2000, are collected from the Institute Water Planning in South Vietnam and second based Water Resources University, The information of agricultural production in region as given table 4,2 below

18

Table 4.2: The information of agricultural production in region

(Sources: Agriculteral report in 2001 for provinces in Dong Thap Muvi region)

4.2 The Methodology of Research

Summary of esearch methodology are shown in the flowchart 4.2 below:

19

Figure 4.2: Methodological framework detail of thesis are summarize as shown below

Hydraulic motiel (VRSAP Model)

- Input data R, H, Q, Cross section data

- Moitel calibration flood 1996

- Model verification flood 1999

‘Simulation of historical flood 2000

le scenarios in different flood control alternatives

Out put results by simulation water Level

Water depth gid fom

DEM and Hydraulic model

GIS tool (map query, map calculation, image classiSeation, ete

| Land use map |

Floodarea shape Ble with change allematives

Affected crop and land types under water depth

in September and October

§.1.2 Runaif data

‘There are four stations measuring daily discharge in region, 8 stations hourly observed data of water level and 3 stations hourly of tidat level

5.2 VRSAP Model Setup, Calibration and Verification

Like other hydrodynamic models, VRSAP model requires data at boundaries: Flow data at upstream, rainfall data, tidal level and water level at station and cross section, Due to availability of the data for Dood 1996, 1999 and historical 2000, dala using flood 2000 for simmilation, flood in 1996 are used for model calibration and the data of the flood 1999 are used for verification,

5.3.1 Establish schematization of river nctwork for VRSAP model

In VRSAP model, river, canal and floodplain system are divided into segments, nodes, and

s for hydrautic computation

Segments are described by representative cross section while plain cell by area corresponding,

to land level One node may accept cithor given discharge Q,, inflow 4) of out flow ©) or piven water level Z as boundary The edge of an amputated branch is also one normal node, where the inflow discharge is Q, = 0

fh segment finks hve nodes: the upstream node (d) and the downstream nade (c)

‘There was a schematization of the Mekong rive systems in Vietnam Mekong delta, which was sel up and this schernatization is now accepted and is susd broadly for simulation the river system of Mekong river system

Based on above large schematization in this study also will be used but it have to added and developed some nodes as well as segments of main channel system to meet with requirement

of this study region (ong ‘hap Muoi)

‘The Establish Schematization of river network for VRSAP model in Dong Thap Muoi region

is shown in Figure 5.1 in (T-Appondix A)

of the model are chosen such a way’ as fo achieve the model stability

conditions

§.2.2 Rua mode!, calibration and verification

a) After completing input data for model, run model and output to compute results are carried out ‘The Model calibration is carried out to find the model parameters ‘he mode! parameters ate considered in VRSAP model as channct roughness The data of foods in 1996 are used for mode] calibration and the data of the flood 1999 arc for model verification

The modc! calibration is catried out firstly with the investigation on the channel bottom roughness, Different values of roughness are applied the same to all channel sections to find out the most suitable value After that, difference channel sections are fine turned with the variations of boltorn roughness lo gel the best fil with observation data al the check poinls, which are Tan Chau on the Tien tiver (node 1), Mo Hoa on Vem Co river (node 93) and Hung Thanh on Phuoc Xuyen river (node 235), The bottom roughness that gives the best fit for computed and observed water levels at checkpoints, is found to be range from 0.024 to 0.05, which are suitable with experiment values of rougimess of rivers

b) The results for calibration of flood 1996 and verification 1999 from run VRSAP model is shown the below

% From simulation results of model calibration for food 1996, as shown in Figure 5.2,

Figure 5.3 and Figure 5.4 below Based on cvaluation stalistical criteria crrov of calculated and observed water level at check points such as Peak difference (2 max)

and Efficiency Index (ET) their crrors results are evaluated: @) max al Tan Clau is

0.05m and Elis 0.95, (3 max at Moc [Loa is 0.016m and Li] is 0.97, @ max at Lung

‘Thanh is 0.107m and #1 is 0.91

Similarly, for evaluation of simulation results for verification by Mood 1999 is carvicd aul The calculated and observed water levels at checkpoints for flood 1999 are shown in Figure 5.5 to Figure 5.7 below

Efficiency Index (EI) are calculated @ max at Tan Chau is 0.045m and EI is 0.89,

© max at Moc Hoa is 0.025m and EI is 0.96, and @ max at Hung Thanh is 0.077m

and EI is 0.92 Looking at the flood hydrograph at three stations and based on calculation statistical criteria error, the verification result is suitable in Dong Thap

Muoi region, thus the calibration and verification results of VRSAP model for flood in

1996 and 1999 are acceptable The evaluation statistical criteria are represented in Table 5.1 (I-Appendix A)

Figure 5.3: Calculated and observed at Moc Hoa station on Vam Co river flood 1996

23

(Chservetedtand edaated water level at Hung Thanh station flood 1996

1 188 DS NE Gee GSS 1006 1170 ee ad er ta 2409 Z8IE 2672 20/0 3/7 3l7 36Z:13806 agyg TM

=

Figure 5.4: Calculated and observed at Hung Thanh station Phuoe Xuyen channel 1996

Result of calibration for flood depth showed that the peaks are fitted well with observed value

at three stations, though the shapes of the graphs are not the matches properly, especially at Hung Thanh station However, looking at the flood hydrograph at three stations and based on

calculation statistical criteria error, the results are seems in acceptable limit

Observed and calculated water level at Moc Hoa station flood 1999

5.2.3 The simulation for historical flood year 2000 in flood control alternatives

With the expected damage, reduction by annual ffood inundation, and in order to increase the agricultural production of region, options are flood control alternatives, having main purpose

ax protection against early floods in August to ensure the sale harvest of the Summer-Auturnn

crop Inmprovernant of the drainage conditions at the ond of the flood scason to advance sowing of the Wintcr-Spring crop This allows sufficient time for the cropping cycle

1 The proposed flood control alternatives are considered as table below

Scenario 1 Without Mluod contro] measures

Scenario 2: Alternatives for floodwater drainage in ficld internal by Horizontal

channel systems

Sub- Scenario 1 Dredging of the Hong Ngu channel with bed widih B=40m, H=-4m, m=1.5

and building up Sluice to remove floodwater at the end of channel

” Bredging and Widening of the Dong TienTagrange channel with bed ‘width

Sub- Scenario? B 30m, Ho -3.5m, m 1.5 and butlding up Sluice for both of blocking the

| saline water intrusion and removing floodwater at the end of channel Dredging and Widen of the can Phong My ‘wilh bedd

Sub- Scenario 3 width B-14m, H—3m, m-1.5 and building up Shuce gate for buth of blocking

the saline water intrusion and removing floodwater al the énd of channel Dredging and Widening of the Nguyen Van Tiep channel with bed width

Sub- Scenario4 g=15m, H=-3n1 and building up Shiice gate for both of blocking the saline

water inirusion and removing floodwater at the end of channel

Scenario 3 Alternatives for Noodwater drainage in internal field by channel

systems parallel with Tien river

_ Building up the flood preventing Dyke Tan Thanh-Lo Gach (elevation |6.5m at

Sub- Scenario 1 Hong Ngu and | 5.5 at Vink Hung) Dredging and Widening of the Tan Thanh-

vs man ams» LO Gach channel B= 32m ai Hong Neu, B= 24m at Vink Hung, ALO)

Sub- Scenario] Dredging and Widening of the 2Thang 9 channel with bed width B=30m, H

3m m=1.0 and building up Shuice at head of channel for flood control

‘Sub Scenario 3 Dredging and Widening of the Khang Chien channel with bed width B 300,

H=-3m, m=1 and building up Sluice at head of channel Sub- Scenario 4 Dredging and Widening of the Binh Thanh channel with bed width B 20m,

H -3m and lnulding up Sluice at bead of channel

Sub- Scenario § Predging and Widening of the Thong Nhat channel vith hed width R=20m,

TH—-âm, m1 auyi building up Sluice at bead of channel

‘Sub Scenario 6 Dredging and Widening of the Song Trang chanel with bed width

H=-3m, me=1 amd building up Sluice at bead of chramel

‘Sub Suemario 7 Dredging and Widening of the Lai Tam channel with bed width B=20m, =

3m and building up Shuice at head of channel

‘The proposal to building up of sluice at head and the end of channel

This simulation result of flood 2000 for each sub-scenario is used for development of the flood inundation maps to estimate depth, area and time of inundation and determine the damage to agricultural sector

Also, to assess the economic effectiveness of the different flood control alternatives based on costs that have to invest in flood control with a value to reduce economic damage of flood in Dong 'Thap Muoi region

The hydraulic modcling would provide information for water levcls at different locations throughout the study area, correspond with different flood control altematives his information would be used to assess the damage-cost related to the different inundation scenarios based on land use data and vatue of agricullurat products,

bẻ 3

2 The calculation results

With purpose: Protection against early floods in August and to ensure the safe harvest of Summer-Autumn crops Improvement of the drainage conditions at the end of the flood season to advance sowing of the Winter-Spring crop This allows sufficient time for the cropping cycle

Determine the maximum water level in that region in order to get information of

flood peak and peak time to concern to cultivation period On the other hand, also

rely on this simulation result and some characteristic as: terrain, main channel route,

road route to separate field cells in study region (as given below)

“» Determine water level at the end of August and first of November in order to

determine damage for Summer-Autumn crop and Winter-Spring crop against before

and after have flood control alternatives

a) Results of simulation WL at nodes on main rivers (before have flood control)

Phe 2uyen channel

“The simulation results at some nodes

before have flood control altematives