Luận văn analysis of boundary conditions and concept design for port dong lam thua thien hue province vietnam

Figure 32 cumulative probablity of exceedance versus wave height for offshore and nearshore wave data.. Figure 68: sediment transport during monsoon and typhoon events - offshore port...

DESIGN FOR PORT DONG LAM, THUA THIEN-HUE

PROVINCE, VIETNAM"

Prof rH Ligteringen Delft University of Technology W.A.Broersen

Dr Ir.J Van de Graaff Delft University of Technology

Ir DJLR Walstra Delft University of Technology Date:

Ir.T Elzinga Royal Haskoning

Port Dong Lam x une ety

PREFACE

What lies in front of you is the result of the Master Thesis, the final step before graduation

in Civil Engineering at Delft University of Technology (DUT) This project is about the analysis and modelling of boundary conditions and the conceptual design of Port Dong Lam, Thua Thien-Hue Province, Vietnam The work was executed in cooperation with Royal Haskoning - departments Rotterdam, The Netherlands and Ho Chi Minh City, Vietnam

Royal Haskoning provided me a working space and put all their information, knowledge and advice at my disposal, for which | am thankful As well, | want to show my gratefulness to the members of my graduation committee for guiding me during the process:

Prof ir H Ligteringen Delft University of Technology, chait Ports & Waterways

Or ir J Van de Graaff Delft University of Technology, chair Coastal Engineering

Ir DJLR Walstra Delft University of Technology, chair Coastal Engineering

Ir M Westra Royal Haskoning (NL), department Coastal & Rivers

Ir T Elzinga Royal Haskoning (NL), department Maritime

Besides | want to thank my overseas supervisors in Vietnam for providing information and advice:

Ir M Coopman Royal Haskoning (VN), department Maritime

Ir M Klabbers Royal Haskoning (VN), department Maritime

Last but not least | want to show my appreciation to my friends, roommates and fellow

students Special thanks go to my family, Mischa and my close friends Loek, Paul, Cyriel and Jan Without their support the mountain to climb would have been a few steps higher

At the end of this project | can say that | have really expanded my knowledge and skills,

both technically and pragmatically Moreover, my self-awareness has reached a higher level which is priceless with regard to my future The struggle to achieve this was tough and | would like to quote a fellow student to describe this journey:

(Andesgebergte) Aangekomen in Argentinié staat vervolgens een viiegtuig klaar, die kun je

nemen, naar welke plek op aarde dan ook Bas van Son (2009)

Wouter Broersen Delft, 28 mei 2010

28/05/2010 II MSc Thesis — W.A Broersen

Port Dong Lam x une ety

From the production plant, the clinker bulk is transported to a storage facility by truck From here the material is transported to the seaport by means of a conveyor belt The coal

is transported by the same modalities but vice versa

In the first phase (up to 2015) about 2 million ton per year bulk material is expected to be handled at this port In the second phase (2015 - 2035) this amounts about 4 million ton per year of bulk material Following the increasing demand for concrete, a doubling of the production is expected in 2035 This results in a throughput of almost 8 million ton per year

in the third project phase (2035 and up)

Objective

The objective is to design a port with sufficient capacity to handle the predicted cargo flow and which offers acceptable conditions for the ships to enter The effective berth and hinterland capacity have to be determined such, that turnaround times are within limits To create safe conditions, the vessels need to have enough space for manouevring in the wet port area These manoeuvres can be seriously disturbed by wind, wave, currents and siltation on the long term To ensure the workability of the port these effects have to be limited

Analysis

Port capacity

To determine the effective berth capacity the queuing theory is applied In phase 1 and 2

one clinker and one coal berth satisfy with effective capacities of respectively 700 and 175 t/h respectively In phase 3 two clinker and two coal berths are needed with the same loading/unloading rates Clinker is loaded with a radial loader and coal is unloaded with a pneumatic unloader

Boundary conditions

To get insight in the environmental boundary conditions, field data is collected and

analysed thoroughly In Vietnam the wind climate is governed by the South-East Asian monsoon system, with a dominant SE direction and strong NNE winds The wave climate is

Having frequent waves from the NNE and SE, littoral transport is generated in north- and southward direction Nevertheless, the northward transport is clearly dominant Currents are heading SE for most of the time

Port dimensions

To reduce the breakwater length, it is decided for the tugs to make fast outside the

breakwaters As a consequence, almost 4% of downtime can be expected, since tugs cannot

operate when Hs 2 2m Once the vessel has entered the harbour the stopping manoeuvre can be started, which requires an inner channel length of 290 m The turning circle allows for the turning manoeuvre for which a radius of 290 m is reserved In the mooring basin, ships are forced into the right position to make safe berthing possible This requires a width

of 210 m and a quay length of 652 m Note that these basic dimensions are determined for

project phase 3 (4 berths), considering a 15,000 dwt design vessel

Layouts and evaluation

Four different layouts are developed for phase 3 of the project Two of them are dismissed

in an early stage, because of unfavourable conditions The other two layouts — the ‘coastal’ and ‘offshore’ alternative, are evaluated with a cost-value approach In this approach the value of each design is assessed by means of a MCA

‘The following criteria are taken into consideration: navigation, tranquillity at berth, coastal impact, sedimentation, ease of cargo handling, safety and flexibility Regarding navigation

and wind, wave and current hindrance, no significant differences are found It turns out

that the most important difference is found in the coastal impact The coastal alternative will cause erosion along 7.5 km of coastline with a maximum retreat of 100 m Instead, the offshore alternative affects ‘only’ 3 km with maximum retreat of 70 m

The other element of the cost-value approach is the costs The investment costs for the coastal alternative are 64.1 MS, which include the dredging works, breakwater and quay construction The costs for the offshore port amount 77.5 M$, which entails the dredging works, breakwater, jetty quay and trestle construction The relative low costs for the coastal alternative are achieved by applying the cut-and-fill balance; the dredged sand is used as breakwater foundation, Maintenance dredging costs are 1.75 M$ and 0.9 M$ for respectively the coastal and offshore alternative

To finish the cost-value approach the value/costs ratio is taken for both port layouts The

coastal alternative (1.11) turns out to be a better port layout than the offshore alternative (0.95)

Downtime assessment

The total downtime amounts 5.4 %, which is entails the following contributions:

© Wave height exceedance tugs: 3.9%

* Wind speed exceedance moored vessels 1.5%

————

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28/05/2010 VI MSc Thesis — W.A Broersen

Port Dong Lam um neat tne

2.6.2 Water level setup

2.6.3 Sea level rise

2.12.2 Littoral transport under normal conditions

2.12.3 Littoral transport under extreme conditions

Port Dong Lam um neat tne

B OTHER WIND AND WAVE SOURCES

€.2.1 _ Calculation of maximum wave heights

2.2 Calculation of wave heights at port site

D EXTREME VALUE DISTRIBUTIONS

D.1 EXTREME WIND SPEEDS

0.2 EXTREME WAVE HEIGHTS ~TVPHOON GENERATED

Calculation of sediment transport

Calculation input and output G3 MIKELITPACK-LITDRIFT

General

Hydrodynamic model Sediment transport model

J.1 CAPITAL DREDGING Costs

J.2 MAINTENANCE DREDGING COSTS ~ COASTAL PORT

J.3 MAINTENANCE DREDGING COSTS ~ OFFSHORE PORT

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‘TABLE OF FIGURES

Figure 1: planned port site in Google Earth image 5

Figure 2: transport system for clinker export and coal import

Figure 3: rivers and lagoon system in Thua Thie-Hue province

Figure 4; bathymetry near Thua Thien-tiue Province obtained from C-map

Figure 5: bathymetry near port site obtained from C-map

Figure 6: cross-shore C-C’

Figure 7: different water levels in a mixed tide

Figure 8: measurement of the water level at the project site,

Figure 9: schematization of wind setup =

fieure30: schematiiadon ofthe fetch for wind-setup calculation

schematization of wave setup

Figure 14; Asian summer and winter monsoon system, so

Figure 15: typhoon Cecil, landed in Vietnam at the 15th of October, 1985,

Figure 16: wind climate according to the China Sea Pilot

Figure 17: NOAA wind roses for the six data locations,

Figure 18: wind rose (1)

ime series of wind speed in 1998, imulativeexceedance frequency versus ind speed Figure 21: top 50 of tropical depressions hitting central Vietnam between 1959 and 2009

Figure 22: NOAA wave roses for the six data locations

Figure 23: time series of wave height in 1998

Figure 24: wave rose (wave height, direction and frequency)

fave rose (wave period, direction and frequency fave height versus frequency exceedance

Figure 32 cumulative probablity of exceedance versus wave height for offshore and nearshore wave data 41 Figure 33: Typhoon ED (1990) coming from ESE (112.5%) direction and showing the dominant wave fron 3 Figure 34: currents in the South China Sea Source: UKHO (1978)

Figure 35: locations of current measurements (about 600 m offshore) Source: TEDIPORT,

irrent rose for vertical 2, Source: local measurement by TEDIPORT

/drographical survey area (drawing scale 1 : $0,000)

Figure 38: bed sample of location MD9

Figure 39: net sediment transports along the coastal barrier from Thuan An inet to Uh Thal

Figure 40: cross-shore distribution of sediment transport for 1/10 years typhoon condition

Figure 41: cross-shore distribution of sediment transport for 1/50 years typhoon condition

'0ss-shore distribution of sediment transport for 1/10 years monsoon condition

Figure 45; geotechnical cross-section indicating four different soil layers

Figure 46: throughput time scheme 7

Figure 47: transport system to and from the new sea port

Figure 48: schematized port system and the Erlang-k distribution,

Figure 49: example of a portal scraper

Port Dong Lam

): example of a radial loader for clinker loading

-xample of a continuous unloader for coat unloading Figure 52: example of a stacker-reclaimer.,

: example of a conveyor belt (non-enclosed

langular shape of storage areas, example of an open storage

: example of a covered warehouse

‘ad between production plant and Port Dong Lam, Figure 58: make fast and pilot boarding outside the breakwater

Figure 59: increase of drift angle during entering of the port

Figure 60: basic manoeuvring width of a sailing ship,

Figure 61: channel depth contributions

fequired space for operations in mooring basin

uur port layouts

Figure 64: cross-shore distribution of sediment transport during 1/10 years typhoon,

Figure 65: sediment transport during typhoon event - coastal port

Figure 67: cross-shore distribution of sediment transport during 1/10 years monsoon

Figure 68: sediment transport during monsoon and typhoon events - offshore port

fraction around breakwater head ~ coastal port

): diffraction around breakwater head ~ offshore port

Figure 71: coastal impact - coastal port

Figure 72: coastal erosion - coastal port

Figure 73: pact - offshore port

ost-shore sediment detribution curing 3/10 monsoon storm without and with coasine growth 106

Figure 80: sand spit and land reclamation ~ coastal port wast,

Tigure 83:longlidnal cros-sedion of the main breakoater(ưet pieture] and the secondary breakwater

pave eights and water depths rom SWAN model ~ coastal por : cross-section 1 and 2 (founded on sand spit) ~ coastal port

Figure 86: cross-sections 3 and 4 —coastal port

Figure 87: example of a marginal quay

Figure 88: dredging works -offshore port

Figure 89: sand spit - offshore port

Figure 90: longitudinal cross-section of offshore breakwater

Figure 91: wave heights and water depths from SWAN model - offshore port

‘oss-sections 1 and 2 ~offshore port

ile ot tty cua, cote vo the aid bya ea Figure 94: cost estimate offshore port

Figure 95: final port design “

Figure 96: Asian summer and winter monsoon system

Figure 97: wind rose Source: HMS, Con Co Island

Figure 98: wave rose, Source: HMS of Con Co Islan

Figure 99: tabular wave data from Global Wave Statistics, Northeast direction

Figure 100: top 50 of tropical depressions hitting central Vietnam between 1959 and 2009

Figure 101: dimensions of cyclone winds

Port Dong Lam um neat tne

Figure 102: F/R versus Umax (m/s)

solo Wave hee at eetant Co Wave eight at ope adios

letermination of distant r between landfall and port sit

Figure 105: definition of X, x’ and Y

Figure 106: example calculation: determination of Hr 7MR

Figure 107: Weibull distribution fitted to wind speeds of 33 m/s and up

Figure 108: distinction between tropical storms and typhoons »

Figure 109: Weibull distribution fitted to wave heights of 6.61.m and up

Figure 110: Weibull fitted to wave height of 33 m and up

Figure 111: currents in the South China Sea Source: UKHO (1978)

Figure 112: computational grids used in the SWAN model

Figure 113: land boundary, computational grid and bathymetry for grid 2

Figure 114: k-factor per wave height and direction

Figure 115: grid 2 and its bathymetry

Figure 116: wave attenuation for wave condition 20,

Figure 117: grid 1 (most coarse) in modelling of extreme waves

Figure 118: wave power P per unit beach length (left) and the alongshore component of P (right

Figure 119: linear relation between Sx ( J) and P( P, ) based on measurements

Figure 12

ee MD

athymetrie survey by TEDIPORT

Figure 121: cross-shore coastal profile “

Figure 122: all velocity by Van Rin (1984) and Delft Hydraulics

Figure 123: measured and approximated tidal current velocity

Figure 124: measured and approximated water level h

Figure 125: wave height, wave period and sediment transport in 1998

Figure 126: wave helght, wave period and sediment transport (i) between 1957 and 2008

Figure 127: accumulated sediment transport (m3) from 1997 to 2009

Figure 128: results of the sensitivity analysis

Figure 129: LITLINE model setup with indicated boundary conltions

Figure 130: offshore port schematization

Figure 131; coastal port schematization

Figure 132: definition of coastline characteristics

Figure 133: extended cross-shore profile

Figure 134; capital dredging cost5

28/05/2010 XIV MSc Thesis — W.A Broersen

Port Dong Lam um neat tne

TABLE OF TABLES

Table 1: fetch schematization and wind setup calculation i

Table 2: wind speed and direction and the corresponding frequencies of occurrence

Table 3: typhoon induced wind speeds

Table 4: wave height and direction and the corresponding occurrence frequencies,

Table 5: wave period and direction and the corresponding occurrence frequencies

Table 6: wave steepness’ for the different wave climates

Table 7: typhoon generated extreme waves

Table 8: monsoon generated extreme WAVES 8 SEN

Table9:wase hoÌd sổ điGllerend thg somgsponsdng:aguendecdi'oeourroiee

Table 10: calculation of typhoon wave periods under extreme contditions

Table 11: offshore typhoon conditions for wave model

Table 12: nearshore typhoon wave conditions for structural design

Table 13: nearshore typhoon wave conditions for littoral transport calculation

Table 14: calculation of monsoon wave periods under extreme conditions

Table 15: offshore monsoon conditions for wave model

Table 16: nearshore monsoon wave conditions

Table 17: current velocity and the occurrence frequency (%) in vertical 2 Source: TEDIPORT

Table 18: sediment characteristics for MD1 to MDY7

Table 19: total toral transport per year and per 12 yearby CERC formula

Table 20: total littoral transport per year and per 12 year as calculated by LITPAC

Table 21: input for typhoon induced sediment transport

Table 22: input for monsoon induced sediment transport

Table 23: determination of coal volume

Table 24: cccupancy, mean walting time and mean tuearound the In Phase 2

Table 25: occupancy, mean waiting time and mean turnaround time in Phase 2

Table 26: occupancy, mean waiting time and mean tumaround time in Phase 3

Table 27: required storage areas for clinker storage facility

Table 28: required storage areas for coal storage facili

Table 29: required number of berths, transport and storage capacities

Table 30: characteristics of clinker and coal vessels

Table 31: calculation results of channel width

Table 32: calculation results of channel depth

Table 33: calculation result for inner channel depth

Table 34: summary of water area dimensions

Table 35: determination of weight factors

‘Table 36: wave diffraction factors for coastal port

Table 37: wave diffraction factors for offshore port

Table 38: coastline growth in time for coastal port

Table 39: coastline growth in time for offshore port

Table 40: MCA result 7

Table 41: calculation of sand spit volume

Table 42: required volumes of concrete and natural rock coastal pot

Table 43: material availability and costs

‘Table 44: placing and total costs per m3

Table 45: Costs of Xbloc armour units és

Table 46: Total costs of breakwaters — coastal port

Table 47: cost estimate coastal port

Table 48; total costs of breakwater - offshore port

Table 49: NPV maintenance dredging operations - coastal port

a

Table 50: NPV maintenance dredging operations - offshore port

Table 51: Cost-Value Approach

Table 52: wind speed and direction with corresponding occurrence frequencies

‘Table 53: wave height and direction and the corresponding frequencies of occurrence

‘Table 54: top 50 typhoons between 1959 ~ 2009 and corresponding wind speeds

Table 55: top 50 typhoons and corresponding wave heights

“Table 56: distant r, ratio r/R, ratio Hr/HR, Hsanax and Hs; max_ site

Table 57: example calculation: characteristics of typhoon Xangsan:

Table 58: example calculation: results for typhoon Xangsane

‘Table 59: example calculation: actual wave height Hs;site (in m)

Table 60: top 10 monsoon storms in terms of wave height

Table 61: example of a SWAN wavecon file

‘Table 62: SWAN input and output for offshore - nearshore wave translation

Table 63: extreme offshore wave condition

Table 64: offshore - nearshore wave translation in normal conditions,

Table 65: extreme offshore and nearshore condition

Table 66: wave height versus period and the corresponding occurrence frequency

Table 67: kr versus wave height and wave period

Table 68: Ksh versus wave height and wave period

Table 69: nb versus wave height and wave direction

Table 70: eb versus wave height and wave direction so

Table 71: wave height and period and the corresponding tora transpor

Table 72: total littoral transport per year and per 12 year calculated by CERC formula,

Table 73: result of sediment transport for one random event

Table 74: total littoral transport per year and per 12 year as calculated by LITPACK

Table 75: berth calculation phase 1

Table 76: berth calculation phase 2

Table 77: berth calculation phase 3

Table 78: breakwater calculation ~ coastal port

Table 79: breakwater calculation ~ offshore port

Table 80: maintenance dredging costs - coastal port

Table 81: maintenance dredging costs - offshore port

Port Dong Lam um neat tne

TABLE OF EQUATIONS

Equation 1:water level rise due to low atmospheric pressure

Equation 2: calculation of wind shear stress and water level gradient

Equation 3: Hs -Tm relationship

Equation 4: CERC formula,

Equation S: basic sediment transport formula

Equation 6: formula to calculate v_eff

Equation 7: formula to calculate channel width,

Equation 8: formula to calculate channel depth

Equation 9: calculation of quay length for one berth

Equation 10: calculation of sedimentation volume

Equation 11: calculation of PV (Present Value) i :

Equation 12: Bretschneider equation for maximum wind speed (m/s) in tropical depressions

Equation 13: calculation of effective radiv:

Equation 14: Young's equation

Equation 15: JONSWAP relationship

Equation 16: example calculation: effective radius,

Equation 17; example calculation; equivalent fetch,

Equation 18: example calculation: wave height Hs;max (In m)

Equation 25: calealation ofthe probably of exceedance of U20 for the peak-overthreshold approach

Equation 20: Calculation of U10 from Weibull equation

Equation 21: requirement for deep water wave conditions

Equation 22: basic CERC formula

Equation 23: explicit CERC formula

Equation 24: calculation L0

Equation 25: calculation L

Equation 26: calculation k,

Equation 27: calculation ©

Equation 28: Snel's Law and calculation of phi

Equation 29: refraction factor

Equation 30: conservation of energy in waves

Equation 31: shoaling factor

Equation 33: calculation dimensionless bed shear stress eo ee Equation 34: vertical turbulent diffusion equation

Equation 35: suspended sediment transport

Equation 36: calculation of all velocity

Equation 37: calculation of kinematic viscosity

Equation 38: continuity equation for sediment

28/05/2010 xvill MSc Thesis — W.A Broersen

Port Dong Lam a Uae ent

REPORT

Analysis of boundary conditions and concept

design for Port Dong Lam, Thua Thien-Hue

Province, Vietnam

Port Dong Lam x une ety

1 INTRODUCTION

11 Study Background

Dong Lam Cement Factory ~ one of the largest privately owned cement companies in

Vietnam - is developing a new clinker plant in Thua Thien-Hue Province As well, three other

shareholders including a bank and other trading companies are involved

Next to the location of the plant there is a limestone quarry which provides the main

ingredient for production process The produced clinker will be exported from the province

and it will require coal for the production To make this possible a new dedicated seaport is

required to allow for up to 15,000 dwt clinker vessels and up to 7,000 dwt coal vessels, This

new seaport terminal is to be constructed several kilometres from the quarry plant on the

coastal stretch North West of the city Hue (see Figure 1) In the first phase (up to 2015)

about 2 million ton per year bulk material is expected to be handled at this port In the

second phase (2015 and up) this amounts about 4 million ton per year of bulk material,

After 2035 the production of the plant will be doubled, resulting in a throughput of 8

million ton per year

Port Dong Lam ROYAL HASKONING

The clinker bulk will be transported from the plant to a storage facility by truck over a

specially-build new road From there the material is transported to the seaport by means of

a conveyor belt The coal is transported the other way around This is shown in Figure 2

From the port, the clinker is exported to a grinding plant in Ho Chi Minh City, where it is

grinded into cement

lo STORAGE

Figure 2: transport system for clinker export and coal import

1.1.1 Port location

The port is to be located on the beginning of a coastal barrier, which is about 30 km away

from Thuan An inlet of the Tam Giang - Cau Hai lagoon — shown in the upper right corner in

Figure 2 This lagoon is located in Thua Thien-Hue province which is one of the six provinces

in the region of the North Central Coast The province borders the Quang Tri Province to

the north, the city of Da Nang to the east, the Quang Nam Province to the south, and the

Xekong Province of Laos to the west

1.1.2 Metocean conditions

In Vietnam, the monsoon system is the governing force of the wind and wave climate

Besides, typhoons find their origin in the Western Pacific Ocean and propagate towards the

Vietnamese coast The most affected areas by typhoons are the coastal provinces of the

North and Central regions This means that wave conditions are strong and that severe

ee ee

Port Dong Lam x une ety

wave conditions can be expected Together with the sandy beaches this can lead to

significant erosion and accretion, which has to be studied when building port structures,

1⁄2 Study Scope

Paragraph 1 shows that an extensive transport system is required in between the clinker

and grinding plant to enable the transport of clinker and coal bulk In this study the focus is

on the port design, which forms a very important element The design of the conveyor belt

and storage facility is not considered in this study Only the required capacities are

determined

When designing a port four important conditions should be fulfilled:

* The port entrance at the seaside should be safe and well accessible

* The port basins and quays should provide adequate space for manoeuvring and

berthing of the ships

*_ At the quay sufficient loading and unloading capacity should be available

* The hinterland connections should be efficient and have enough capacity

In Paragraph 1.1.2 it was stated that knowledge and understanding about the metocean

and morphological circumstances in the port surroundings is crucial to make a proper port

design The study objective can be outlined as follows:

The objective is to design a port with sufficient capacity to handle the predicted cargo flow

and which offers acceptable conditions for the ships to enter and for the surroundings This means that wave and current disturbance and sedimentation of the harbor basin have to be limited as well as the morphological impact on the coast

Before any design can be initiated, information has to be known on the coastal,

bathymetric and climate conditions As well data is required about the water level, wind,

waves and currents Moreover, the sediment characteristics and littoral transport have to

be known and quantified to be able to make a proper port design As well, the soil conditions have to be known for foundation of the structures These data sources can be found in Paragraph 2.1 to 2.13

1.3.2 Modelling

To determine the nearshore wave climate, littoral sediment transport and coastal impact,

numerical models will be setup using SWAN and MIKE LITPACK The results from the wave modelling study form the input for the morphological model In both models, normal and extreme conditions are considered The results of the wave and morphological model can

be found in Paragraph 2.9 and 2.12 respectively For more details the reader is referred to

Appendices F and G

13.3 Transport capacities

Based on the predicted cargo forecasts the required number of ships per year can be determined From this the number of berths, loading and unloading capacities, conveyor belt capacity and the storage areas can be calculated This is described throughout Paragraph 3.1 to 3.3

13.4 Port dimensions

By means of design guidelines the principal dimensions of the port can be formulated, taking into consideration the environmental boundary conditions The principal port dimensions are understood as the approach channel, mooring basin, turning circle and the quay length These basic dimensions can be found in Paragraph 4.2 to 4.5

1.3.5 Layout đesign and concept selection

The port layouts are designed based on guidelines in Paragraph 5.2 and 5.3, The following elements are considered:

Port Dong Lam x une ety

To avoid misunderstandings while reading this report, one important remark is made:

* All compass directions are relative to the North, unless stated differently

2 ENVIRONMENTAL BOUNDARY CONDITIONS

2.1 Introduction

In this chapter the collected field data is described and analysed thoroughly A large part of

the data has been obtained from a local survey, executed by the Vietnamese engineering

company TEDIPORT Normal and extreme conditions are considered, which enables the determination of the serviceability of the port and the design of the port structures The

following boundary conditions are studied:

* Offshore wave climate

* _ Nearshore wave climate

The central coast of Vietnam is characterized by an abundance of small and medium size

estuaries and lagoons formed at the mouth of rivers that discharge the steep hinterland

More than 60 rivers meet the South China Sea along 1500 km of coastline Rivers usually

are short and steep with gradients generally steeper than 1:100 The coast is predominantly sandy as a result of high fluvial sediment input during flood periods which nourish the mainland beaches and sandy barriers that form across estuary mouths and tidal inlets Mainland beaches and barriers are typically steep and narrow and are dominated by cross-

shore sediment transports The sediment of the beaches and barriers is rather coarse In

the south of the Central coast, the coast line is dominated by rocky headlands or by

sheltered bays behind headlands; sand deposition is limited to pocket beaches and river

Port Dong Lam x une ety

In the period May till August, when the continental high pressure area diminishes, the

summer monsoon sets in and causes winds from the SW Wind speeds are normally lower

than in the winter months, up to 11 m/s In this warmer period, average monthly temperatures are 29°C in July, reaching up to 41°C occasionally The relative humidity is

lower, sometimes down to 50%

The annual rainfall ranges from 1500 mm to 4000 mm The rainy season is during the South

monsoon, from May to September; about 70 percent of the precipitation occurs in those

months, The central region receives its maximum rainfall during tropical storms in

20 meters above sea level, The lagoons occupy the remaining 5 percent of the surface area

Figure 3: rivers and lagoon system in Thua Thie- Hue province

* http://www.weatheronline.co.uk (meteorological service in the United Kingdom)

2.5 Bathymetry

With C-Map data” a bathymetry has been created using QUICK-IN in DELFT3D (Figure 4) An island, named Con Co, can be recognised together with some shoals further offshore The contour lines show an inclined pattern, in which the continental shelf of North Vietnam can

be recognised

100m

Figure 4: bathymetry near Thua Thien-Hue Province obtained from C-map

In Figure 5 a close up bathymetry is shown, also obtained from C-Map The 20, 30 and 50 m water depth isolines are clearly visible

? Obtained from Jeppesen Marine

28/05/2010 10 MSc Thesis — W.A Broersen

2.5.1 Cross-shore profile

In Figure 6 the cross-shore profile C-C' — as indicated in Figure 5 - is shown from -50 m up to

‘the dune at +5.0 m The first part is almost linear with a slope of 1:70 Further offshore, a

shallow area is found with a minimum water depth of -16.5 m Next, the profile continues

linearly towards deeper waters with a slope of 1:200 m

2.6 Water levels

The sea level is frequently subject to fluctuations, mainly due to astronomical and

meteorological forces The tide causes water movement in a regular pattern and is the only component that can be well predicted Meteorological influences - such as water level setup due to low pressure, wind and waves ~ have an irregular character and cannot be predicted Historical data about storms should provide an answer here Besides, sea level rise has a long-term influence on the water level

In Paragraph 2.6.1 the tide is described and in Paragraph 2.6.2 the water level setup is calculated, In Paragraph 2.6.3 the sea level rise is discussed

2.6.1 Tide

The tidal regime at the future port location is mixed; i.e irregular semidiurnal, in which semidiurnal constituents prevail This normally means two high (one Higher High Water and one Lower High Water) and two low (one Higher Low Water and one Lower Low Water) tides in a day See Figure 7

Tidal Period

Lower Water

Tidal Day

Data on the tide were collected from four sources:

* Local measurement at the port site

* Measurements (Hydro Meteorological Station at Cua Viet)

© British Admiralty Charts (UK Hydrographic Office)

* Global Inverse Tide Model (Oregon State University)

Port Dong Lam x une ety

Looking at the measurement in Figure 8 the tide reaches a maximum on 09/19/2008 of 41

cm, which is a spring tide - knowing that full moon was on the 09/15/2008 As well, at 09/19/2008 the lowest water level during the spring tide is measured, which is -48 cm These water levels are measured with respect to National Datum (ND), which is equal to

the mean sea level

The maximum water level during spring tide — which is called Higher High Water Spring

(HHWS) - is considered as normative for design The minimum water level during spring tide

~ which is called Lower Low Water Spring (LLWS) — is considered as Chart Datum (CD) The

HHWS becomes now 41 + 48 = 89 cm w.r.t CD Mean sea level (MSL) is 48 cm w.r.t CD

Time series plot of hourly water level at Dong Lam station

(Period 2: From 10h 12” September to 6h 24" September 2008) w.r.t National Datum

Figure 8: measurement of the water level at the project site

2.6.2 Water level setup

For the design of the port structures with a lifetime of 50 years, the maximum water level

has to be known in this period In statistical terms, this is a water level with a probability of exceedance of once in 50 years As already stated in the introduction, the water level setup consists of the following contributions:

For the Vietnamese coast the most severe storm surges are induced by typhoons For a

statistically correct calculation, this means that the once in 50 year typhoon conditions have to be considered Here a simplification is made by taking the most severe typhoon conditions which occurred in the last 50 years This was typhoon Harriet in 1970 with the

following characteristics:

© Wind speed (U10) = 52.4 m/s

* _ Atmosperic pressure P= 925 hPa

With this data the water level setup can be calculated

Atmospheric pressure

Low atmospheric pressure gives a water level rise, because surrounding waters are pushed down by high pressure areas For open water domains, Equation 1 gives the relationship between the rise in water level (in m) and the atmospheric pressure (in hPa) In the formula, 1013 is the normal atmospheric pressure (= 1 atm = 1.013 bar = 1013 hPa) For a value of 925 hPa, this gives a water level rise of 0.9 m

km is taken, which is the average fetch in typhoons (see Appendix C) This results in a wind setup of 3.3m

28/05/2010 14 MSc Thesis — W.A Broersen

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Equation 2: calculation of wind shear stress and water level gradient

Figure 10: schematization of the fetch for wind-setup calculatioi

m—-——————— ————— - ? Fetch 1 is not shown over its full length of 55,400 m

Table 1: fetch schematization and wind setup calculation

Now the storm surge amounts:

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nmax = maximum wave setup (m)

Figure 11: schematization of wave setup

Figure 12: calculation of wave setup

CIRIA, CUR, CETMEF (2007) proposed a chart from which the wave setup at the shoreline can be read for uniform sloping beaches To do so, the beach slope, the deep water wave height HO and the fictitious deep water wave steepness H0/LO have to be known From the wave model in Paragraph 2.9.2.1 it follows that HO = 17.0 m with a return period of 50 years The steepness of this wave is 0.045 (-) The beach slope turns out to be 1:70 — deduced from Figure 6 Now the wave setup becomes 1.7 m

2.6.4.1 Mean sea level

* MSLis 0.5 m w.r-t CD (rounded off)

2.6.4.2 Extreme water level

In Figure 13 the different water level contributions are schematically presented Summation gives a 1/50 year water level of:

This value is very large because all contributions are added up In practice, the event that all the contributions occur at the same time has a low probability A probabilistic approach can offer a more realistic solution in this situation, but will not be applied here Instead a factor

of 0.75 is introduced to obtain a more realistic result The approximated 1/50 year water

level becomes then: 0.75 * 7.1=5.3 mw.r.t CD

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2.7 Wind data

In Vietnam, monsoons winds are the governing force of the wind climate Extreme wind conditions are induced by typhoons Several data sources have been collected, in which a distinction is made between normal and extreme conditions The normal wind conditions (Paragraph 2.7.2) are necessary to determine downtime as a consequence Extreme conditions (Paragraph 2.7.3) have to be known in order to calculate extreme wave heights

2.7.1 Background

2.7.1.1 Monsoon winds

In Figure 14 the South-Asian monsoon system is shown, indicating the different origin of

the summer and winter monsoon In summer the wind is coming from the Southwest which

reverses in winter to Northeast

Figure 14: Asian summer and winter monsoon system

Wind data were collected from several sources and are listed here:

* National Oceanic and Atmospheric Administration (NOAA, USA) - 12 year data

* China Sea Pilot (UKHO, 1978) — 130 year data

* Hydro Meteorological Station at Con Co Island (Vietnam) ~ 20 year data

The three data sources were well studied and the NOAA data source proved to be the most

applicable because omnidirectional data is provided Besides, there is also wave data

available from the NOAA which is favourable In Paragraph 2.7.2.2 the NOAA wind data is

described extensively As the data covers ‘only’ 12 years of measurement, the 130 year data

from the China Sea Pilot is used as a check, The wind data from Con Co Island can be found

in Appendix B.1

2.7.2.1 China Sea Pilot

The China Sea Pilot describes wind measurements on ships which are carried out for over

130 years In the North western part of the South China Sea, monsoon winds are coming

from the NE in autumn and winter Typically, wind speeds do not exceed Beaufort 7 (14 - 17

m/s) In spring and summer, the dominant directions are SE and SW Winds speeds are

lower, not exceeding Beaufort 5 (8 - 11 m/s) The wind patterns in the different seasons of

the year are shown in Figure 16

July (summer) October (autumn)

Figure 16: wind climate according to the China Sea Pilot

2.7.2.2 NOAAdata

In the years from 1997 to 2008 this data has been measured by satellite, equipped with

weather radar systems and acoustic sensors Wind speed (U10 in m/s) and direction are

determined every 3 hours and has been provided at six locations (see Figure 17) The

It must be noticed that a relatively coarse grid is used for the measurement and calculation

of the wind fields As a consequence, data can be inaccurate close to land boundaries, because of the fact that parts of inland wind fields are taken into account in the data

a