Improving environmental monitoring plan for thua thien hue coastal zone, vietnam pham hong ng

Thua Thien-Hue coastal zone, and its Tam Giang-Cau Hai lagoon Thien-in particular, is known as the largest brackish water system Thien-in South East Asia.. INTEGRATED ENVIRONMENTAL ASSES

M.Sc Thesis HE 146

June2003

Pham Hong Nga

The research is done for the partial fulfilment of requirements for the Master of Science degree at the IHE Institute for Water Education, Delft, The Netherlands.

UNESCO-UNESCO-IHE Institute for Water Education

Prof B Petry (!HE)

Dr Randa M Hassan (IHE)

Dr Joost Stronkborst (RIKZ)

Dr Mindert de Vries (WL)

Supervisors

Dr Randa M Hassan (IHE)

Dr Joost Stronkborst (RIKZ)

Mr Maarten Scheffers (RIKZ)

Master of Science Thesis

by Pham Hong Nga

For Thua Thien-Hue Coastal Zone, Vietnam

Environmental Engineering

DELFT

The fmdings, interpretations and conclusions expressed in this study do neither necessarily reflect the views ofInternational Institute for Infrastructure, Hydraulic and Environmental Engineering, nor of the individualmembers ofMSc committee, nor of their respective employers.

Thank you all very much, indeed!

And, I thank my family, especially my parents and my parents in law, my husband P T.Tung, my little son Ti An for their everlasting love, sacrifice and support and overall, for the way they overcome all the difficulties during such long period I have to be away.

Thanks must be given to my terrific friends, big Huong, small Huong, Thuy, Lam, Giang, Vu, Ahmad, Jim in particular and all others of HEb family Their wonderful friendship helps me keep going on well throughout the study.

I would like to express my appreciation to Mr Johan van Voorthuize Mr Le Van Thu, Dr Robbert Misdorp, Mr Hans Pos, Mr Nga, Mr Son, Ms Thu, Ms Hanh and other staff of VNICZM offices

in Hanoi and Hue for kindly sharing me their knowledge, experience and information.

I am greatly indebted Hanoi Water Resource University, especially Prof Dr Le Kim Truyen, Prof

Dr Ngo Dinh Tuan, Dr Vu Minh Cat, Dr Do Tat Tuc, Dr Le Dinh Thanh, Dr Nguyen Van Thang, Dr Pham Hung and all my colleagues in Environmental Division for supporting my study

in many ways.

I am grateful to CICATprojectfor providingfinancial support.

My sincere thank is given to my mentor, Dr Randa M Hassan, for her constant assistance and support my study in many ways I also wish to extent myfeeling of gratitude to all other members of IHE, especially the Department of Hydraulic Engineering, Prof Bela Petry, Ir Ronand de Heer and Ir Mick van der Wegen for their academic guidance and thoughtful encouragement in everyday life.

First of all, I would like to express my great gratitude to my supervisors Dr Joost Stronkhorst and

Mr Maarten Scheffers as well as advisor Dr Mindert de Vries Without their valuable guidance and closefollow-up, this work could not have come into reality.

This M.Sc thesis forms the completion of my study at IHE, Delft, The Netherlands I would like to take this opportunity to express my acknowledgment to many people who help make last one-and-a- half-year become successful timefor me.

Key words: ICZM, DPSIR, monitoring strategy, monitoring indicators

Besides, the existing monitoring strategy is further improved by statistically revising theefficiency of sampling locations, replicates and frequency

However, in order to have a truly effective monitoring program, an integrated assessment must

be carried out to revise the critical needs for monitoring In order to do so, DPSIR Pressure-State-Impact-Response) conceptual model is applied, covering major issues of localconcern, such as growing population, agriculture, fisheries and aquaculture, tourism and sealevel rise The output of the assessment is a set of environmental and social indicators, whichare, in fact, needs for monitoring

(Driver-Therefore, an Integrated Coastal Zone Management (ICZM) program has been developed forThua Thien-Hue coastal zone in order to response to emerging threats In particularly,monitoring has been gained much attention due to its key function as provision of data andinformation for other actions of whole ICZM cyclic process taking place

This study is to propose relevant improvements for existing monitoring strategy ofThua Hue coastal zone in Vietnam Thua Thien-Hue coastal zone, and its Tam Giang-Cau Hai lagoon

Thien-in particular, is known as the largest brackish water system Thien-in South East Asia It has highlyimportant environmental and economic roles The lagoon provides valuable habitat of diverseand sensitive aquatic ecosystem Moreover, because of its favourite geographic locations andnatural conditions, this coastal zone has to support a range of economic activities, such asfisheries and aquaculture, tourism along with some agriculture, industry and shipping, most ofwhich are resource-based activities On the other hand, Tam Giang-Cau Hai lagoon is subject tofar complex and unstable hydrodynamic and morphological processes Due to the combination

of all these drivers, this region undergoes undesirable changes and degradation, which seriouslythreat the local sustainable development

Chapter 2 ENVIRONMENT~ DESCRIPTION

5.1 Needs for Monitoring Improvement 5-1

5.3 Improvement of Monitoring Location, Replicates and

Chapter 5 PROPOSAL ON MONITORING STRATEGY IMPROVEMENT

Chapter 4 INTEGRATED ENVIRONMENTAL ASSESSMENT

3.1.3 Monitoring for coastal zone in The Netherlands 3-4

3.2 Review on Monitoring Program CCP2002 in Thua Thien-Hue Coastal zone 3-11

3.2.2 Definition of monitoring objectives and requirements 3-12

Chapter 3 LITERATURE OVERVIEW ON MONITORING

Appendix A List of Resource People

Appendix B Monitoring Record of CCP2002

Appendix C Reference Values

Appendix D Replicate Calculation by Statistical Method

Appendix E Databank Set-up for Monitoring Program in Thua Thien-Hue Coastal Zone

List of References

5-235-245-25

at each location

Table 5.4 Replicate calculation (for fish sampling)

Table 5.5 Proposed replicates for biological monitoring

Table 5.6 Minimum observation periods (in days) for six semi-diurnal

tidal components

Table 4.10 Estimated impacts in some Asian countries for selected magnitudes

of sea level rise in case of no adaptation measures in 100 years 4-25Table 4.11 Residue of pesticides in water column of Tam Giang-Cau Hai lagoon 4-32Table 4.12 Residue of pesticides in sediment of Tam Giang-Cau Hai lagoon 4-32Table 4.13 Residue of pesticides in soil in Phu Hiep (Hue) 4-33Table 4.14 Heavy metal concentration in Thua Thien-Hue coastal zone 4-33

Table 4.16 Yearly sediment of river runoff discharging into the lagoon system 4-39Table 4.17 Daily sediment transport through lagoon inlet 4-40

Table 5.2 Replicate calculation (for water quality sampling) 5-22Table 5.3 Anexample on allocation of number of replicates for each campaign

4-164-21

4-134-134-144-154-15

Table 4.3 Fisheries catching capacity in Tam Giang-Cau Hai lagoon

Table 4.4 Gross fisheries production in Tam Giang-Cau Hai lagoon

Table 4.5 Aquaculture in Tam Giang-Cau Hai lagoon area

Table 4.6 Expected expansion of the aquaculture area for the coming period

Table 4.7 Offshore fisheries development in Thua Thien-Hue province

Table 4.8 Summary of fisheries and aquaculture development

in Thua Thien-Hue over the last period

Table 4.9 Annual number of visitors in Thua Thien-Hue

Table 4.2 Total estimated annual amount of chemical agent usage in Thua Thien-Hue 4-10

3-153-164-9

Table 3.4 List of sampling location for water quality

Table 3.5 Sampling biological monitoring program

Table 4.1 Annual average yield of some main crops in Thua Thien-Hue

Table 3.1 Evolvement of monitoring concept and goal over time 3-1Table 3.2 Anoverview on particular monitoring substances and

Table 3.3 Vietnam National Monitoring Network along the coastline and nearshore sea 3-9

2-42-52-162-162-172-18

Table 2.1 Monthly average rainfall at Phu Bai station, Thua Thien-Hue

Table 2.2 Monthly wind speeds and dominate wind direction

Table 2.3 Distribution of zooplankton in Tam Giang-Cau Hai lagoon

Table 2.4 Distribution of zoobenthos in Tam Giang-Cau Hai Lagoon

Table 2.5 Monthly changes in the number of fish species in the lagoon

Table 2.6 List of waterfowl observed in Tam Giang - Cau Hai lagoon system

Figure 4.7 Fisheries and aquaculture development in Thua Thien-Hue province 4-16

Figure 4.13 Estimated occurrence of extreme water level at present and

Figure 4.14 Environmental pressures of global warming, esp sea level rise 4-27Figure 4.15 Historical flood occurred in Thua Thien-Hue in 1999 4-28Figure 4.16 Temporary and spatial variation of BODs and COD 4-30Figure 4.17 Overall tendency of COD concentration in the lagoons 4-30Figure 4.18 Nutrient as N concentration performance in Tam Giang-Cau Hai lagoon 4-31Figure 4.19 Tendency of phosphorus in the lagoon water 4-31

Figure 4.21 Correlation of phosphorous concentration and weight of phytoplankton 4-36Figure 4.22 Monitoring site for waterbirds at 0 Lau estuary 4-37

Figure 5.1 Major issues of concern in Thua Thien-Hue coastal zone 5-2Figure 5.2 Distribution of sampling location for water quality 5-16

3-184-24-54-74-84-114-14

Figure 3.6 Location of cross-section profiles at Tu Hien inlet

Figure 4.1 The DPSIR framework for reporting on environmental issues

Figure 4.2 Pressure of population growth in ThuaThien-Hue coastal zone

Figure 4.3 Population and infrastructure distributioninThuaThien-Hue

Figure 4.4 Main economic activities in ThuaThien-Hue

Figure 4.5 Environmental pressures of agriculture

Figure 4.6 Images of aquaculturallots in the lagoons

Figure 1.1 Geographic location of study area: Thua Thien-Hue, Vietnam 1-2Figure 2.1 Administrative map of Thua Thien - Hue province 2-2Figure 2.2 Bottom geometry of TamGiang-Cau Hai lagoon system 2-6

Figure 2.4 Hydrological system in ThuaThien-Hue province 2-9

Figure 2.6 Cross-section profiles at ThuanAn (left) and Tu Hien (right) in 2002 2-11Figure 2.7 pH variation from season to season at different locations of the lagoon 2-13Figure 2.8 Temporal and spatial variation of salinity in TamGiang-Cau Hai lagoon 2-14

Figure 3.3 Overview on monitoring sites for the water compartment in the Dutch

Figure 3.4 Monitoring station network in the coastal and nearshore zone

Figure 3.6 Location of cross-section profiles at ThuanAn inlet 3-17

A coastal zone is commonly defined as the interface or transition zone of land and sea,including the part of the land affected by its proximity to the sea and the part of the oceanaffected by its proximity to the land (Sorenson and McCreary, 1990) In TT-Hue province, thistransitional strip of land and sea includes vast areas of plain and sandy beach, 120 km shoreline,22,000ha lagoon, several estuaries, coastal wetlands and a nearshore sea up to the depth ofapproximately 40m.

Thua Thien - Hue has a great tourism potential The provincial capital, Hue city, was the formerimperial capital of Vietnam from 1802 to 1945 It has been inscribed in the list of UNESCOWorld Heritages since December 1993 Besides, there are many beautiful landscapes such as theTam Giang - Cau Hai lagoon system, and many beautiful beaches named Thuan An, Lang Coand Canh Duong along a coastline of 120km long All these features make this area become one

of the most attractive tourist places in Vietnam

Thua Thien - Hue province, the study area, is located in the Coastal Central Area of Vietnam(Figure 1.1) The geographic coordinates of the province are 16°00'-16°45' North latitude and107°03'-108°12' East longitude The total area of the province is 5,009krrr', and the population

is more than one million The provincial economic bases mainly on the small industries andhandicrafts, tourism and services, agriculture, forestry and aquaculture and fishery

However, in ICZM Strategy of Thua Thien-Hue as well as in Monitoring Action Plan of thecoastal zone, the need for monitoring has not been yet fully addressed Therefore, this study is

to work out the answer to "Why do we want to monitor" and thereby, the existing monitoringprogram can be improved Therefore, this M.Sc study will be a great help for future monitoringactivities ofThua Thien-Hue coastal zone

This M.Sc study is to take into consideration a component of the Coastal Cooperative Program

2002 (CCP2002) between Vietnamese and Netherlands governments, which is to strengthen thecapacity of Thua Thien-Hue province, Vietnam, on Integrated Coastal Zone Management(ICZM) Among its tasks, monitoring is considered by the provincial authorities in IT-Hue as avital activity through ICZM cyclic process In the frame of CCP2002, an ICZM Strategy andMonitoring Action Plan has been elaborated and implemented since August 2002

1.1 BACKGROUND

INTRODUCTION

Figure 1.1 Geographic location of study area: Thua Thien-Hue, Vietnam

As other coasts in Vietnam and worldwide, Thua Thien-Hue costal zone is of greatenvironmental and economic roles Firstly, for environmental role, with such complex andspecialized features, this coastal area contains some highly diverse and productive ecosystems,such as marine algae, sea grasses, inundated forest, migratory and non-migratory birds,waterfowls, fisheries and abundant population of aquatic living organism More importantly, itprovides the shallow water area as spawning sites of many water birds and fisheries Secondly,regarding to the economic role, with such favourable biophysical conditions, together with theease of communication and navigation, this coastal zone provides very high potential foreconomic development of Thua Thien-Hue province The economic activities taking place in

Therefore, a key question arisen hereby is how to conserve the natural values and meanwhile, toboost economic development as well as to enhance the living standard of local communities.

4 main constrains:

Low education and low living standard;

Lack of public awareness about the values of coastal and marine resources and aboutthe sustainable development;

Lack of a comprehensive or integrated environmental management, only simple sectoral

Natural disasters and environmental hazard;

Increasing conflicts of different uses

The potential impacts caused by range of all those socio-economic and physical drivers havebeen recognised by the governmental and local authorities In the ICZM Strategy Reportelaborated by IT-Hue People's Committee in 2002, the most emerging threats and constrainsthat limit the sustainable development of the province have been clearly addressed as follows

Beside the demographic drivers, the coastal area of Thua Thien-Hue is also subject to physical(natural) drivers: morphological processes, extreme events, natural hazards and global climatechange, e.g sea level rise The previous studies have showed that the lagoon system undergoeserosion of shoreline and sand dune, freshening of lagoon water, shallowing of lagoon depth,reduction of nutrient flux from river discharge and so on These factors very much threat thebrackish ecosystem health and human safety

However, the coastal zone in Thua Thien-Hue is currently experiencing intense and sustainedundesirable changes due to a range of driving forces, including demographic and natural-process-related The primary attention must be given to local demographic driving force, which

is increasing economic activities taking place in the coastal zone as above mentioned along withhighly dense population Apparently, the coastal resources and coastal space are limited.Therefore, the conflict of different economic sectors is always the case leading to unsustainabledevelopment in the region unless there is a proper holistic management planning On the otherhand, serious ecosystem degradation, water pollution and natural resource loss have beenwidely occurred in the local area due to overexploitation and effluent discharge Therefore, thehuman health and human well-being is critical issues of concern

this area are mainly resource-based activities, including coastal fisheries, aquaculture,agriculture, tourism along with some industries and shipping

Regarding to Task 3, the Coastal Co-operative Program CCP2002 is an extra support, whichmainly focuses on strengthening the ICZM activities in Thua Thien-Hue province In the frame

of CCP2002, a primary environmental monitoring program for Thua Thien-hue coastal zone hasbeen designed and implemented since August 2002 This monitoring program is of greatimportance because for the first time, the province has a comprehensive database on coastalzone environment, which can be considered as one of the best information source availablecurrently

Nevertheless, in the Strategy and Action Plan for this monitoring program, the needs formonitoring, e.g "Why to monitor", was not yet fully addressed Therefore, the second majortask of the study is to propose relevant improvements for the existing monitoring program based

on the set of environmental indicators developed by DPSIR approach with the intention ofachieving "best needed information" goal

• Problem recognition: identifying issues and problems and establishing correspondingobjectives and criteria; identifying stakeholders, and ensuring their participation in themanagement process;

• Policy development: analysing existing planning programmes, institutional arrangementsand management tools to determine whether they may be useful in addressing the issues

• Collection of information needed: collecting and analysing existing data and evaluating theneed for further research and information; establishing monitoring systems and integrateddatabases

• Decision-making: supplying information for programme evaluation to policy makers

Additionally, at present, in Vietnam, the Vietnam Netherlands (VN) - ICZM project 2000-2003

is operating at national level in Hanoi as well as at provincial level in three VN-ICZM pilotprovinces, namely Nam Dinh in the north, Thua Thien-Hue in the central and Ba Ria-Vung Tau

in the south This project is to promote vertical integration by initially undertaking the tasks ofplanning phase, such as:

Apparently, the provincial authorities have recognised that the most promising approach isunderlined by an Integrated Coastal Zone Management (ICZM), which replaces theconventional sectoral management In order to achieve it, it is crucial to have a clearunderstanding of the interaction and the cause-effect relationship of the local human andenvironmental systems by carrying out an integrated assessment based on "best availableinformation", which is the first major task of this study In order to do so, one of theadvantageous approaches for environmental integrated assessment is selected, which is so-called Driver-Pressure-State-Impact-Response (DPSIR) framework developed by the EuropeanEnvironmental Agency [EEA, 1999] The implementation of DPSIR approach will help todevelop a set of environmental indicators, which can answer "what is happening" or evenfurther, "does it matter" type questions of the environmental managers and policy makers totake any effective responses Furthermore, based on these indicators, more effort is needed tomove from a position of "best available information" towards "best needed information"

Chapter 1 Introduction

Additionally, the study intends to recommend the application of GIS and other supplementarysoftware in the development of a database for monitoring data management However, time isconstrain, it is able only initiate the set up of structure of main menu The results are enclosed inAppendix D for references but not discussed in details in the report.

Regarding to the monitoring program improvement, this study is to work out the answer toquestion "Why to monitor" and based on which, propose some improvements on monitoringnetwork design Due to time constrains and limits of data, the study will not cover cost analysisnor laboratory analysis procedures

Moreover, the integrated assessment is to work out the causes and consequences ofenvironmental changes of the lagoon system, for which some recommendations on differentresponse options will be reviewed, but not in details, only monitoring will go further in thefollow-up discussion

This study is to take IT-Hue coastal zone into its consideration, which is one of the pilot sites ofthe integrated coastal zone management project between Vietnam and The Netherlands(VNICZM) As discussed earlier, however, there are no exact natural boundaries of a coastalzone, unlike the watershed Usually, the extension of a coastal area varies in different researchworks, further to the ocean or further inland, depending on their interests This study isconcerned about management issues and thus, coast-hinterland interaction is more emerging.The environmental integrated assessment will be carried out for the selected area in order toanalyse and to detect the potential negative impacts on human and ecosystems However, theeconomic loss expressed in term of monetary is not covered for the time being

1.4 SCOPE OF THE STUDY

3 To improve the strategy of current monitoring program with:

• A list of the indicators that need to be measured;

• A clear description of the sampling locations;

• Relevant sampling replicates and frequency

2 To develop a set of environmental and socio-economic indicators for Thua Thien-Huecoastal zone;

1 To carry out an integrated assessment on environmental quality;

The main objectives of this M.Sc study are:

1.3 OBJECTIVES OF THE STUDY

• Initially apply Visual Basic and GIS Arcview for databank set-up (see Appendix E).

• Improve monitoring program based on conceptual and statistical analysis;

• Apply a conceptual model for integrated assessment, which is so-called State-Impact-Response framework;

Driver-Pressure-• Study literature;

• Interview resource people, including policy makers, local officials, and project consultantsabout the issues of concern in Thua Thien-Hue coastal zone;

These approaches will be carried out through several methodologies, including:

• Develop a frame of a databank package for monitoring data management;

• Propose relevant improvements on current coastal monitoring program: what, where andwhen to monitor;

• Develop a set of environmental indicators, which are used in environmental managementand policy making;

• Assess the causes and impacts of environmental changes of the coastal zone recently andtheir trends in the future;

• Analyse the available data to understand the geographical and major physical characteristicsofThua Thien-Hue province and its coastal zone in particular;

• Discuss the available data on historical changes of the coast morphology; any available data

on water quality, salinity and biology of the coastal area, lagoons, river estuaries andaquaculture areas; some meteorological data: temperature, rainfall; and information aboutsocio - economic activities

• Study extensively and intensively literature related to integrated assessment applied to acoastal zone; and related to environmental monitoring development in general and for thecoastal zone inparticular

The objectives of the study will be achieved by following approaches:

1.5 METHODOLOGY AND APPROACH OF THE STUDY

Chapter 1.Introduction

Tam Giang-Cau Hai lagoon system alone covers an area of about 22,000 ha, which is thebiggest lagoon in South East Asia with highly diverse aquatic ecosystem Part of the lagoon

2.1.2 Tam Giang-Cau Hai lagoon system

In spite of historic sites and traditional cultural values, Thua Thien-Hue province is alsohighlighted by its coastline of more than 120km and such diverse lowland features, includingvast Tam Giang-Cau Hai lagoon systems along and several wetlands This study is particularlyinterested in this brackish water complex and also the surrounding lowland plain and sand dunewith total area of about 216 km", which belongs to 6 administrative districts, namely: QuangDien, Quang Dien, Huong Tra, Phu Yang, Phu Loc and Hue City This lagoon and tidal inletsystem has a crucial role for the provincial economic development because it directly concernswith navigation, aquaculture and fishery, tourism and services, which are the main contributions

to the provincial budget

Thua Thien-Hue province is located between 16°00'-16°45' North latitude and 108°12' East longitude (Figure 2.1) in the narrow strip of Central Vietnam It is 660km fromHanoi in the north and 1060km from Ho Chi Minh City in the south With a total area of 5,009krrr'; a population of more than one million and Hue city, a famous ancient capital [Dien P B.,

107°03'-et aI., 2001], the province is considered as an economic and cultural centre of the middle part ofVietNam

2.1.1 General

2.1 TOPOGRAPHY

This part is to brief general environmental conditions in Thua Thien-Hue coastal zone, which isbasis of all the analysis in the next parts and next chapters The information and data presentedhereby have been collected from the reliable authorized sources: National EnvironmentalAgency in Hanoi, Thua Thien-Hue People's committee, Thua Thien-Hue EnvironmentalDepartment, Ministry of Agriculture and Rural Development, Ministry of Fisheries, HanoiWater Resource University, VN ICZM Office in Hanoi and CCP2002 office in Hue, previousM.Sc studies in IHE, etc

ENVIRONMENT DESCRIPTION

OF THUA THIEN-HUE COASTAL ZONE

The evaporation of the area is about 900 mmlyear (Hue: 974 mmlyear; A Luoi: 855 mmlyear).High monthly evaporation occurs in the dry season with 100 mmlmonth As a result, during thisperiod, the freshwater budget decreases and the lagoon salinity increases Conversely, in the wetseason, the monthly evaporation decreases to 50 mmlmonth or less.

The mean relative humidity in the delta (Hue) and in the mountainous area (A Luoi) are 83%and 87%, respectively The highest humidity occurs in November at these locations are 89%and 93%, respectively The lowest humidity occurs in July at these locations are 73% and 79%,respectively (Tuan N D., et al., 2002)

The average temperature in Thua Thien-Hue province varies from 19.5°C in January to 29°C inJune The maximum and minimum temperatures ever observed are 41.3°C and 8°C respectively.Overall, temperature amplitude during a year is about 9-10°C and mean annual temperature is25°C (Hoi T D., et al., 2001)

Thua Thien - Hue province is located in the tropical monsoon area with cool and dry winter andhot and wet summer

2.2.1 Temperature, humidity and evaporation

2.2 CLIMATE

Eventually, the system is influenced by both, marine and inland flow conditions Interaction ofthe tides and salt water from the sea through Thuan An and Tu Hien inlets with inland flowdischarges of the rivers cause highly dynamic characteristics of its hydraulic and morphologicalbehaviour, which is to be discussed more in details later

The lagoon is a complex system comprised of a series of coastal lagoons that are separated fromthe sea by narrow sand dune barriers Over its total length of 68km, it receives flows of mostrivers in the province and discharges to the sea through two narrow tidal inlets, namely Thuan

Aninlet and Tu Hien inlet

The lagoon extends from 0 Lau river mouth in the north-west to Vinh Long mountain in east with a length of 68 km It occupies 4.3% ofThua Thien - Hue province area or 17.2% ofthe area of Hue delta It consists of Tam Giang, Thanh Lam (Sam,AnTruyen), Ha Trung, Thuy

south-Tu and Cau Hai lagoons

around 0 Lau estuary is being proposed by the Government of Vietnam and AsianDevelopment Bank (ADB) as a Marine Protected Area and a RAMSAR site for its unique interms of landscape and biodiversity

The area is affected by monsoon systems: the north east monsoon season in winter and thesouth-west monsoon season in summer These monsoons in the area are changed by thetopographic condition of the province.illsummer, the wind is from the east direction with speed

of 1-1.5 mis, where the SW wind is dominant offshore with an occurrence of 56% and speed of 1-7 mls The occurrence of calm condition is 30%. illwinter, dominant winds are Nand NWwith an occurrence of 30% and speed of 1.6 3mls Strong winds in winter may reach 17-18 mls Observed data at Thuan An in 1988 indicated NE and N winds were dominant in February

with an occurrence of 80% of the NW wind in March was 42% Table 3.2 shows the wind speedand direction through the year that are measured at Hue station as an inland station and Con Costation on Con Co island

Winds have a significant effect on the waves, sediment transport in the shore and surface flowcirculation inside the lagoon, contributing to the morphological processes and change of bio-ecological system

Source: Tuan N D., et aI., 2002

is very unevenly distributed during a year A year can be divided into two distinct seasons: thewet season (flood season) from September to December contributes 70-80% to the total annualrainfall; the rest (20-30%) is distributed for 8 months, from January to August (see Table 2.1).The distribution of rainfall and consequently the river runoff, which are the decisive factors forthe water quality performance in the lagoon, must be taken into account when designing thesampling program

2.2.2 Rainfall

Chapter 2 Environmental Description ofTT- Hue Coastal Zone

Moreover, it is important to bear in mind that in the longer run, the severity and damage of thesenatural disasters will be increased due to sea level rise So far, the systematic observation onwater level of the area has not yet been established in order to study the potential impact of thisglobal phenomenon occurred in Thua Thien-Hue coastal zone But, according to a number ofpublications issued by IPCC (1996), Tom G., Huan N.N., et al in VV A (Vietnam Vulnerability

The high floods from the upstream and high storm surges at the sea due to typhoons can result

in severe destruction of the sea dykes and breach river dykes and cause flooding and inundation

of the coastal lowland areas More seriously, every year, these typhoons and tropicaldepressions are natural disasters that claim a number of human lives and their properties, such

as house, fishing boat, crops; destroy infrastructure and so on For the environmental concern,typhoons, floods and storm surges cause erosion of the sand barriers and changes of themorphology of the lagoon systems and inlets

During the last 30 years, 50% of the typhoons were accompanied with storm surges of 1m ormore; 30% of the typhoons caused storm surges of 1.5m or more, and occasionally, a fewtyphoons have coupled with a storm surge exceeding 2.5m On 15 October 1985, the typhoonCecil of 12 Beaufort scale hit the area causing storm surge of 2.25m (VJWRR, 2000; Le BacHuynh et aI., 1999)

Typhoons are normally accompanied with violent winds, gust bumps, high rainfall and storm

surges The maximum wind speed during a typhoon is 15-20 mls on average Highest observed wind speed is 38 mls.

Vietnam is located in the north-west of the Pacific Ocean, where the highest number oftyphoons occur every year During the last 100 years, 493 typhoons and tropical depressionshave approached the coastal provinces of Vietnam, among which 87 (18%) hit Thua Thien-Hue province In average, there are 0.87 typhoons hitting the province every year Theoccurrences of typhoons are from June to November and highest in September and October(64%)

2.2.4 Typhoons, tropical depressions and storm surges

Table 2.2 Monthly wind speeds and dominate wind direction

Figure 2.2 Bottom geometry of Tam Giang-Cau Hai lagoon system (LamN.T., 2002)

The water body system of the Tam Giang - Cau Hai lagoons spread over an area of 216km2

with a length of 68km It has an average volume of 300 millionrrr', or over 400 million m3 incase of flood water discharging into the system The system can be divided into four differentbasins, namely Tam Giang, Thanh Lam, Thuy Tu and Cau Hai Based on some studies on ThuaThien-Hue and its coastal zone [Cu N H, 1995; Hoi N C., 1996, Hoi T D., 2001], a briefdescription of the lagoon geometric features is summarized as follows (see also Figure 2.2)

Apparently, the study area is strongly subjected to the river system of Thua Thien-Hue Thetotal catchment basin of the rivers in Thua Thien-Hue, discharging into Tam Giang-Cau Hailagoon system, is about 4,000km2, including0Lau river, Dai Giang river, Cau Hai river, Nongriver, Truoi river and the largest one, Huong river (Figure 2.4) These rivers commonlyoriginate in the mountainous area of the province and flow on quite steep slope of 20-29%before entering the lower delta Therefore, such condition along with deforestation and landclearing, which undergo stress in many area, can cause severe flash flood.

2.3.3 River system flowing to the lagoon system

The main inlet is the most dynamic and variable one, which is named as Thuan An inlet (Figure2.3) The channel of the inlet is 600m long orientating NNW-SSE Thuan An inlet has a normalwidth of 350m and a maximum depth of 11m inside the lagoon

The normal dimension ofTu Hien inlet is 200m wide and 3m deep.InOctober 1994, one monthbefore its closure by nature, it had only 50m wide with maximum depth of 1m However, afterthe flood event of November 1999, the inlet is 600m and 4-8m deep Itis narrowed by theextension of the updrift barrier south-westward InMarch 2001, its width was reduced to about150m after just 16months (Lam N.T., 2002) The flood delta ofTu Hien inlet inside the Cau Hailagoon is at the depth of 0.4-0.5m and divided into three parts by narrow 1m - deep - channels

At present, Tam Giang - Cau Hai lagoon has two tidal inlets at Thuan An and Tu Hien Forcenturies, the system used to have only Tu Hien inlet In1404, Thuan An inlet was opened sothe system had one more inlet Since then, Tu Hien inlet has been gradually narrowed andThuan An inlet becomes the main inlet of the system The distance between these inlets is40km

• Thanh Lam lagoon covers an area of 16.2km2•It includes Sam and An Truyen lagoons Atthe north-eastern part of the lagoon, the average depth of the lagoons is 1.5m There is anebb channel north-westward with a depth of 2-5m However, at the opposite side, the north-western part, the lagoon bottom is quite flat and shallow with an average depth ofO.5m

In the flood season, from September to December, high rainfall on the hilly upstream of thebasin usually immediately causes flood in the rivers and inundation in the lowland and coastalarea eventually Effects oftides on the water levels in the rivers are dimmed by the floods Theinundation in the area becomes more serious due to narrowing of the inlets and the sand barriersthat obstruct the flood evacuation On the other hand, the extreme condition of flood dischargesand water levels can result in breakthrough of the sand barrier at weak points and may changethe locations and the orientation of the inlets that leads to morphological instability of thecoastal system as a whole.

The distribution of the river runoff is very uneven during a year, in accordance with rainfall It

is concentrated in the flood season from September to December with 70% or more of theannual flow

Huong river, with 3 tributaries: Huu Trach, Ta Trach and Bo rivers, is largest and mostimportant in the area: total basin area of 3,000km2, river network density of 0.75kmlkm2; thebasin's average slope of about 11-12%, average sediment concentration of 150g/ m3, but 70-80% of total sediment transport occurs in the flood season In the upstream of Ta Trach river, areservoir of 500 million m3 are being constructed in order to secure the operation of thehydropower plant with a capacity of 30,000kW and to guarantee irrigation for 5,000ha of ricefields

Figure 2.3 Image of ThuanAn inlet (CCP 2002)

Chapter 2 Environmental Description of Thua Thien-Hue Coastal Zone

Wave action is one of dominant driving forces in Thua Thien - Hue coast The wave conditionsare directly influenced by the wind conditions that are distinguished of two main monsoon2.4.2 Wavesand longshorecurrent

Figure 2.5 Tidal level at the inlets (CCP, 2002)

Nov loth2002Time

2.4.1 Tides and tidal currents

The coast of Thua Thien - Hue province is exposed directly to the open sea in the relativelyshallow area of the Gulf of Tonkin The length of Thua Thien - Hue coast is 120km aligned in

NW - SE direction

Chapter 2 Environmental Description of Thua Thien-Hue Coastal Zone

Figure 2.6 Cross-section profiles at Thuan An (left) and Tu Hien (right) in 2002 (CCP 2002)

Distance (m)

Distance (m)

30.0 20.0 10.0 -2000L - ~ 0.0

100.0 60.0 80.0

The shoreline of Thua Thien-Hue is about 120 km long in the NW-SE direction According toprevious surveys [Anh N T., et aI., 1998-2000, Hoi T D:, et aI., 2001, Tung T T., 2001,CCP2002], the shore has a relatively mild slope at the depth of 0+5m and quite steep of 10+15m(Figure 2.6 and see also Appendix A) The distance of the 10-m depth contour to the shoreline isl.2+ 1.5km, nearest is 100m The beach material is composed of 98% of sand with diameterfrom 0.05+2mm; the rest is fine gravel with diameter of2.5+3mm

2.5.1 Shoreline

Wave induced longshore currents are the main factor of the sediment transport in the surf zone.The direction of the longshore currents is quite stable in a monsoon season which is north-

westward in summer and south-eastward in winter The velocity of the longshore currents is

from 0.3-1m1s and highest in winter during north-east monsoon season.

During severe conditions of a violent typhoon, the wave height can rise to 7 - 8m However, thedata of wave period is not available

In the summer monsoon season, dominant waves are SW and SE offshore and SE nearshore.According to the observed data in 1998, the occurrence of E waves at Thuan An is 93% withwave heights from 0.2-1m (Anh N T., et al., 1998-2000)

In the winter monsoon season from September to March, dominant waves are E and NE

nearshore and N offshore Observations in February 1998 shows that the occurrence of NE

waves at Thuan An are 99% with the fluctuation of the wave height are from 0.25 up to 3m(Anh N T., et al., 1998-2000)

seasons: the north-west monsoon in winter (so-called winter monsoon) and the south-west

monsoon in summer (so-called summer monsoon)

Iili Ingeneral, pH value of the whole lagoon varies from 6.0 to 8.0 [Hoi N c., et aI., 1996;CCP, 2002], which is within the range required by Vietnam standard TCVN 5943-1995.However, it is still not fully safe for aquaculture usage because pH varies quite significantly inrainy and dry season (in the order of 1.5 or 2) (Figure 2.7), which is not favourite for the aquaticspecies at all According to Hoi N C., et aI (1996), for the aquacultural or conservationpurpose, the pH should not vary more than 1 for all year round.

Water temperature Water temperature in the lagoon ranges from l5+30°C, which is suitable foraquatic life In general, all the results of the past studies show that there is no significantvariance of temperature in time and space of the whole lagoon system, which is also quitefavourite for aquatic life

The status of lagoon water quality is reviewed based on outputs of several surveys, research and

a part of EIAs of some hydraulic constructions in the local area (Hoi N C., et al, 1996, Hoi T.D., et al, 2001, Tuan N D., et aI., 2002) Especially, the output of the current monitoring inThua Thien-Hue is used as a vital and most up-to-date source of information about the localenvironmental condition

2.6.1 Water quality

This part is just to overview some basic characteristics of water quality and ecosystem in thelagoon, more in detail will be discussed later in Chapter 4 along with integrated assessment.2.6 WATER QUALITY AND BIODIVERSITY

The sand barrier from Loc Dien at 0 lau river mouth to Thuan An is composed of two sanddune systems overlapping each other But from Thuan An to Linh Thai, the sand barrier hasrelatively homogeneous structure

The sand barriers include sand dunes, sandbars and beaches extending in parallel to shoreline, which can be divided into four parts [Hoi T D., 2001; Lam N T., 2002]:

120km-The sand barrier from Dien Huong commune to Thuan An has a length of 60km, anaverage width of 4.5km, and an average height ofless than 10m The height of the sandbarrier increases from north to south The maximum height is 32m at Hai Duongcommune;

The sand barrier from Thuan Anto Linh Thai has a length of 37km, an average width

of 2km, and an average height of 10m The height of the sand barrier increases from 2m

at Thuan An to 20m at Phu Dien;

The sand barrier from Linh Thai to Tu Hien inlet has a length of 2km, an average width

of 300m, and an average height of 2.5m;

The sand barrier from Tu Hien to Loc Thuy is 3km long and 2-2.5m high

2.5.2 Sand barriers

Chapter 2 Environmental Description of Thua Thien-Hue Coastal Zone

I. Significant variation of salinity from season to season Similarly to pH, this fact quiteadversely affect on the aquatic species; and

Figure 2.8 shows the general temporal and spatial variation of salinity in Tam Giang-Cau Hailagoon system during a year based on the record in2002 [Lam N T.,2002], one year after thehistorical flood event Based on this figure and other researches [Hoi N C., et aI., 1996; Hoi T.D., et aI.,2001; Lieu P K.,2002], three main issues of concern are drawn as follows:

Zone 1- 0 Lau estuary ambient (upper part of Tam Giang lagoon): ranging from freshwater (S <0.5 %0)to slightly brackish (S=0.5-5%0)

Zone 2 - from Dam market to An Gia commune (middle part of Tam Giang lagoon), rangingfrom freshwater - slightly brackish - medium brackish

Zone 3 - the rest of the lagoon, rang is wider: slightly - medium (5-18%0)- salty brackish 30%0),depending on the season

(18-In Thua Thien-Hue coastal area, the rainfall is mostly concentrated in October and Decembercausing heavy flood in the lagoon system from river discharge During this period, the water inthe lagoon turns to be almost fresh with salinity of about0%0.In December and January, rainfalldecreases and tidal current is intruded further into the lagoon and increase the salinitysignificantly In February and March, the salinity increases up to 10%0or more, depending onthe distance from the inlet and tidal regime The highest figure of salinity up to 25%0is usuallyoccurred from July to September According to the classification of salinity in Venice (1958)and the result of the past studies (Anh N T., et aI., 1998-2000, Hoi T D., 2001), the wholelagoon can be roughly divided into several zones in term of salinity as follows:

Salinity Apparently, salinity is one of most important factors to decide the presence and spatialdistribution of seawater, brackish or freshwater species However, the lagoon is influenced bymany factors, such as river discharge, tide, inlet opening and closing and rainfall

Figure 2.7 pH variation from season to season at different locations of the lagoon

Nov Oct

Sep Aug

Biodiversity and aquatic products of Tam Giang lagoon depend on the stability of the lagoonenvironment, including salinity, nutrient sources, relevant water quality, and so on Recently,there was a significant change of ecosystem in the lagoon due to inlets open resulted fromhistorical flood in 1999 According to the most recent surveys (Tuan N D., et aI., 2001,SAPROF Team for Japan Bank, 2002; CCP 2002), the presence of biological diversity in thelagoon is divided into 5 categories:

in the lagoon and 12.2%0at the inlet Apparently, such gap of salinity through watercolumn, which can also be a natural phenomenon, create undesirable habitat for aquaticspecies

Figure 2.8 Temporal and spatial variation of salinity in Tam Giang-Cau Hai lagoon

(Lam N T., 2002)

• Saline sampling location

*Maximum in the dry season

• In March 2000 " Minimum in the dry season

• Average in the flood season

Chapter 2 Environmental Description of Thua Thien-Hue Coastal Zone

Fishes A total of 135 species offish belonging to 88 genera, 47 families and 17 orders has beenrecorded as shown in Table 2.5 Among them, perch (Perciformes) is observed as mostdominant in number of species (42.9%), of genera (36.3%) and of families (36.2%) The secondmost dominant fish is carp (Cypriniformes) with 14.1% of species and 18.2% of genera.

The distribution of zoobenthos is also affected by salinity, and it is summarized in Table 2.4

Zoobenthos A total of 53 species of zoobenthos have been identified including Polychaeta with

23 species (43%), Mollusca with 17 species (32%) and Crustacean with 13 cpecies (25%) Ofthose, 39 species appear at the estuary of the Huong river, constituting 74% of the total species

Similarly to the diversity of the phytoplankton in the lagoon system, the species composition ofthe zooplankton within the system is also highly diverse due to changes in salinity withfreshwater and seawater Salinity is the primary factor affecting the distribution andcomposition of the zooplankton in the lagoon, which is summarized in Table 2.3

Zooplankton A total of 34 species of zooplankton has been identified, of which Copepoda wasdominant (82%) with 28 species; followed by Cladocera (15%) with five species and Rotatoria(3%) with one species In addition, some larvae of Bivalvia, Gastropoda and Polycheata havealso been observed

According to the observation of CCP 2002, it has identified about 17 undesirable species, out ofwhich 7 species are considered as toxic algae They present mainly at the aquacultural areas,such as SamAnTruyen and Vinh Giang

Nevertheless, in general, the average density of phytoplankton, which is based mainly on twogroups of Dinoflagellates and Diatoms, is 9,700 cellslliter The estuary of Huong river hosts thelargest population size and the highest diversity of phytoplankton of the whole lagoon areathroughout the year (63,500 cellslliter as highest) For the other river estuaries, the figuresobserved density of the plankton are 5,422 cellslliter and less than 5,000 celllliter at 0 Lau rivermouth (upper part of Tam Giang lagoon) and Truoi river mouth at Cau Hai lagoon, respectively

In general, the diversity of plankton algae tends to gradually decrease with a distance from theriver mouth The population size and the diversity of the phytoplankton in the lagoon systemfluctuate seasonally mainly due to changes of salinity

Phytoplankton It has been identified that there are totally 346 species of phytoplankton in thelagoon, belonging to 5 phyla of Cyanophyta (32 species), Heterokonrophyta (136 species),Dinophyta (48 species), Chlorophyta (93 species) and Euglenophyta (37 species) (CCP 2002)

4 Fishes; and

5 Waterfowls

Distribution of the fish in the lagoon also shifts with the seasonal changes in salinity as shown

in Table 2.5 The diversity of fresh water fishes in the lagoon increases from 8 to 35 species dueSource: SAPROF Team, 2002

Salinity

(S,o/oo)

- Namalycastis longicirris

- Grandidierella vietnamica - Dam market

5::;S::;8

- Dendronereis arbirifera - Thuy Tu lagoon

- Nephthys oligogranchia

- Neanthes japonica

- Ceratorenereis mirabilis - Thuan An inlet

- Nepthys californiensis - Hoa Duan inletS> 18

- Anomalocardia producta

- Mactra quadragularis

Table 2.4 Distribution of Zoobenthos in Tam Giang - Cau Hai Lagoon

Source: SAPROF Team, 2002

- Vietodiaphtomus hatinhensis - oLau river mouth

- Metis

- HarpacticusTable 2.3 Distribution of Zooplankton in Tam Giang - Cau Hai lagoon

Chapter2 Environmental Descriptionof Thua Thien-Hue CoastalZone

Although Table2.6lists all the water birds available in the Tam Giang-Cau Hai lagoon system,they are, in fact, observed mainly in 0 Lau and Dai Giang estuaries and partly in Thanh Lamlagoon Generally speaking, in winter, the population of waterfowl increases, such as500 grey-leg geeses, up to2,000-3,000black coots, etc.

Waterfowls There is a record of about 70 species of birds around the lagoon, of which 34species are migratory The birds that have been reported are listed in Table2.6.However, non

of these birds are listed in Red List ofIUCN (2000)or Red Data Book of Vietnam There seems

to be some discrepancies between the criteria, but occurrences of critical habitat for birds need

to be confirmed in the later stage of the monitoring program

On the other hand, approximately 8 species of euryhaline freshwater fish (e.g Cyprinuscentralus, sheat-fish, crucian carp) and60species of euryhaline sea fish (e.g cardinal, ponyfish,grassfish, thomfish, grey mullet, goby and bar-tailed flathead) seem to be available in thelagoon throughout the year These fish are not susceptible to the seasonal changes in salinity.Source: Source: SAPROF Team,2002

Table2.5Monthly Changes in the Number ofFish Species in the Lagoon

With respect to the marine fishes in the lagoon, 116 species can be observed in August,decreasing to about 60 species in October About 40 species of sea fish, such as selachian,pointer, grouper and golden spinefoot, leave the lagoon because of the huge discharge of riverflows.Inthe post - flood period (from December to August), the amount of marine fish speciesincreases steadily due to the intrusion of the tide into the lagoon, reaching a maximum in aboutAugust (Table 2.5)

to a large supply of freshwater from the rivers during rainy season, e.g from September toNovember Conversely, the distribution of freshwater species is significantly reduced fromNovember when the salinity steadily goes up

Source: SAPROF Team, 2002

6 Choi choi nho Little ring~lover Charadrius dubius

7 Choi choi khoang co Kentish Elover Charadrius alexandrinus

13 Nhan bung trang -Bam swallow - Hirundo rustica

-14 Chia voi yang _Yello_~wag!ail Motacilla flava

Chapter 2 Environmental Description ofThua Thien-Hue Coastal Zone