DETERMINATION OF DEPTHS OF CLOSURE
ALONG THE KELANTAN COAST
NOR HISHAM BIN MOHD. GHAZALI
UNIVERSITI TEKNOLOGI MALAYSIA
iii
In the name of Allah, the Compassionate, the Merciful
Dedicated to my loving wife Noriah Abu Bakar for sharing my life and
dreams, to my father and my mother for their relentless faith in me, and my sons
Hazim, Nadim and Aqil Zuhair for their unconditional love.
iv
ACKNOWLEDGEMENT
All praise be to Allah the Merciful, the Benevolent to Whom all will return
and Whose knowledge is infinite, eternal.
I would like to first thank my supervisor Associate Professor Dr. Ahmad
Khairi Bin Abd Wahab whose guidance, counsel and support were critical to the
direction, focus and completion of this thesis.
I am indebted to my employer the Department of Irrigation and Drainage
Malaysia and the Public Services Department Malaysia for providing me the
opportunity and the financial means to pursue this study, and especially to Ir. Tan
King Seng, Director of Coastal Engineering Division for his personal and professional
support.
My thanks extend to Khairol Azuan Bin Adam of the National Hydraulic
Institute of Malaysia for his assistance, comments and advice on numerical modelling
and the staff of the Coastal Engineering Division, Department of Irrigation and
Drainage Malaysia for their immense support.
And not in the least, my deepest and eternal gratitude to my wife Noriah
Binti Abu Bakar whose strength, love and encouragement were beacons in all my
pursuits.
v
ABSTRACT
The design of beach-fill in beach nourishment works requires knowledge of the
cross-shore sediment transport process. By the theory of equilibrium profiles, beachfill material will be redistributed across the shore profile up to a seaward limit known
as the depth of closure or Dc.
The determination of the depth of closure is a key
component of beach-fill design and is measured in the field from the study of
periodical surveys over the same beach profiles. The Hallermeier equation which
relies on the incident pre-breaking wave height is the only analytical means to predict
the depth of closure. This study has examined the applicability of the Hallermeier
equation in predicting depth of closure for the coastline of Pantai Sabak, Kelantan
using nearshore waves which were transformed from offshore waves through
numerical modelling. The predicted depth of closure was compared against measured
depth of closure at 13 profiles that were surveyed in 1998, 1999, 2000 and 2004. The
widely-accepted Standard Deviation of Depth Change (SDDC) and Fixed Depth
Change (FDC) methods to determine Dc were both explored and the Dc for monsoon,
annual and 5-year events were investigated. The research found that along the study
shoreline at Pantai Sabak, more than one closure point can occur across the same
profile over the seasonal and annual period. Hallermeier’s equation overpredicts
annual Dc by 43% and affirms previous findings that the predictive equation
determines an upper limit value of Dc. Within the limitations of the survey data
available, the annual depth of closure at Pantai Sabak can be equated to 1.5 times
H0.137.
vi
ABSTRAK
Pengetahuan mengenai proses pergerakan ampaian rentas pantai adalah
penting dalam kerja-kerja merekabentuk penambakan pasir pantai. Berpandukan teori
keseimbangan profil, pasir penambakan dijangka akan diangkut dan diendapkan ke
seluruh profil pantai sehingga satu lokasi kedalaman yang dinamakan kedalaman
tertutup atau Dc. Penentuan kedalaman tertutup merupakan salah satu komponen
penting dalam rekabentuk penambakan pasir dan ianya diperolehi melalui kajian ke
atas data ukur bersiri yang diperolehi daripada profil-profil pantai yang sama.
Persamaan Hallermeier yang bergantung kepada keadaan ombak sebelum pecah
merupakan satu-satunya kaedah analitikal yang ada untuk menentukan kedalaman
tertutup.
Kajian ini telah menguji kesesuaian persamaan Hallermeier ini dalam
meramalkan kedalaman tertutup bagi Pantai Sabak, Kelantan dengan menggunakan
ketinggian ombak di kawasan dekat pantai yang diperolehi melalui permodelan
numerikal yang berasaskan ombak lepas pantai.
Kedalaman tertutup yang dikira
dengan menggunakan persamaan Hallermeier telah dibandingkan dengan kedalaman
tertutup yang dianalisa di 13 profil pantai yang diukur dalam tahun 1998, 1999, 2000
and 2004.
Kaedah Persisihan Piawai Perubahan Kedalaman dan Perubahan
Kedalaman Tetap telah digunakan untuk menentukan Dc bagi keadaan tengkujuh atau
monsun timur-laut, tempoh tahunan dan untuk tempoh 5 tahun. Penyiasatan ini telah
mendapati bahawa lebih daripada satu kedalaman tertutup boleh wujud dalam profil
yang sama.
Ramalan Dc tahunan dengan menggunakan Persamaan Hallermeier
didapati tinggi dengan lebihan purata 43% dan ini mengesahkan hasil kajian-kajian
terdahulu yang menyatakan bahawa persamaan ini boleh menentukan nilai had teratas
untuk Dc. Tertakluk kepada data ukur yang terhad di Pantai Sabak, kedalaman tertutup
tahunan boleh disamakan dengan 1.5 kali ketinggian ombak H0.137.
vii
TABLE OF CONTENTS
CHAPTER
TITLE
DECLARATION
ii
DEDICATION
iii
ACKNOWLEDGEMENT
iv
ABSTRACT
v
ABSTRAK
vi
TABLE OF CONTENTS
vii
LIST OF TABLES
xii
LIST OF FIGURES
xiv
LIST OF ABBREVIATIONS
xix
LIST OF SYMBOLS
xx
LIST OF APPENDICES
1
PAGE
INTRODUCTION
xxii
1
1.1
Introduction
1
1.2
Background of the Problem
2
1.2.1 Erosion Control and Beach Nourishment in Malaysia
2
1.2.2 Study Shoreline
3
1.2.3
5
Beach Nourishment Design and Depths of Closure
1.3
Objectives of the Study
7
1.4
Benefits of the Study
7
2
LITERATURE REVIEW
2.1
Introduction
2.2
Cross-shore Sediment Transport and Equilibrium
8
8
Beach Profiles
8
2.3
Definition of Depth of Closure
9
2.4
Methods of Determination
12
2.4.1
Predictive Methods
12
2.4.2
Depth of Closure from Profile Surveys
15
2.4.3
Depth Change Criterion
16
2.5
Application of Depth of Closure
18
2.6
Depth of Closure – Malaysian Context
19
2.7
Summary
21
3
RESEARCH METHODOLOGY
23
3.1
Introduction
23
3.2
Scope of the Research
24
3.3
Research Methodology
27
3.3.1 Data Sets
27
3.3.2
Primary Data Collection
28
3.3.3
Numerical Modelling
29
3.3.4
Analysis
30
3.4
4
3.3.5 Depths of Closure from Beach Profile Data
30
3.3.6
31
Depth of Closure from Empirical Formulae
Summary
FIELD DATA ANALYSIS
31
33
4.1
Introduction
33
4.2
Study Area
34
ix
4.3
Environmental and Climatic Conditions
35
4.4
Data Sets
36
4.5
Beach Profile Survey
36
4.5.1
Survey #1 - 1998
37
4.5.2
Survey #2 - 1999
37
4.5.3
Survey #3 - 2000
38
4.5.4
Survey #4 - 2004
38
4.5.5 Survey Data Selection
38
4.5.6
42
4.6
Sediment Data
42
4.7
Wave
44
4.7.1
UKMO Design Wave Analysis
45
4.7.2
Measured Waves
50
4.8
Tidal Heights
52
4.9
Wind
54
4.10
Summary
55
5
NUMERICAL MODELLING
57
5.1
Introduction
57
5.2
Model Description
57
5.3
Numerical Modelling
59
5.3.1
Model Area and Orientation
59
5.3.2
Wave Breaking Conditions
59
5.4
6
Survey Data Filtering
5.3.3 Calibration
61
5.3.4
66
Prediction of Nearshore Waves from Wave Model
Summary
77
DETERMINATION OF DEPTHS OF CLOSURE
79
x
6.1
Introduction
79
6.2
Depth of Closure – Scope and Criteria
80
6.2.1
Definition
80
6.2.2
Algorithm for Determination of Dc from Profile Surveys
81
6.3
Predicted Depth of Closure, Dl,t
84
6.4
Monsoon Dc (1998-1999 surveys)
84
6.4.1
Profile Descriptions and Application of Algorithm
84
6.4.2
Monsoon Dc at Ch.3100 and Ch.2700
84
6.4.3
Monsoon Dc at Ch.2300 and Ch.1900
87
6.4.4
Monsoon Dc at Ch.1500, Ch.1200 and Ch.800
88
6.4.5
Monsoon Dc at Ch.400, Ch.200 and Ch.00
91
6.4.6
Monsoon Dc at Ch.-400, Ch.-900 and Ch.-1400
95
6.4.7
Summary for Monsoon Dc
97
6.5
Annual Dc (1999-2000)
100
6.5.1
Profile Description and Application of Algorithm
100
6.5.2
Annual Dc at Ch.3100
101
6.5.3
Annual Dc at Ch.2700
102
6.5.4
Annual Dc at Ch.1500
103
6.5.5
Annual Dc at Ch.1200
104
6.5.6
Annual Dc at Ch.800
105
6.5.7
Annual Dc at Ch.400
106
6.5.8
Annual Dc at Ch.200
107
6.5.9
Annual Dc at Ch.00
108
6.5.10 Annual Dc at Ch-400, Ch.-900 and Ch.-1400
109
6.6
Summary for Annual Dc (1999-2000)
111
6.7
Time-interval Dc (1999-2004)
113
6.7.1
Profile Description and Application of Algorithm
113
6.7.2
Five-year Dc at Ch.3100
114
6.7.3
Five-year Dc at Ch.2700
115
xi
6.7.4
Five-year Dc at Ch.1500
116
6.7.5
Five-year Dc at Ch.1200
117
6.7.6
Five-year Dc at Ch.800
118
6.7.7
Five-year Dc at Ch.400
119
6.7.8
Five-year Dc at Ch.200
120
6.7.9
Five-year Dc at Ch.00
121
6.7.10 Five-year Dc at Ch.-400, Ch.-900 and Ch.-1400
122
6.8
Summary of 5-year Dc (1999, 2000 and 2004)
124
6.9
Comparison of Event and Time-Interval Dc
126
6.10
Measured Dc vs. Hallermeier’s Equation
127
6.11
Simplified Dc Equations
129
6.12
Observation
131
CONCLUSIONS AND RECOMMENDATIONS
133
7.1
General Conclusions
133
7.2
Suggestions for Future Research
135
7
7.2.1
Dc Criteria and Survey Techniques
135
7.2.2
Wave Data
135
7.2.3 Profile Surveys and Bar Migration Phenomena
136
7.2.4
136
Determining a predictive formula for local Dc
REFERENCES
APPENDICES A - E
138
142-174
xii
LIST OF TABLES
TABLE NO.
TITLE
PAGE
4.1
Profile Survey Data Register
40
4.2
Starting And Ending Points Of Selected Survey Dataset
(13 profile lines) off Pantai Sabak, Kelantan
41
4.3
Statistics of UKMO Wave Dataset
47
4.4
Tidal Levels Along Study Shoreline (meters, LSD)
53
4.6
Mean High Water (meters, LSD)
53
4.7
Difference between MSL and MLW at Study Coastline
54
4.8
Difference between MSL and MHW at Study Coastline
54
5.1
Results of Wave Model Calibration
63
5.2
Location of Offshore Points in Model Grid for Extraction
of Wave Parameters
Predicted Wave Heights At 10 M Depth Based On Offshore
wave of H0.137 = 2.9 m and Tm = 6.3 secs
74
Predicted Wave Heights at 10 m depth Based On Offshore
Wave of H0.027 = 3.13 m and Tm = 6.54 secs
75
6.1
Depths of Closure (SDDC) for Monsoon Event 1998-1999
99
6.2
Depths of Closure (FDC) for Monsoon Event 1998-1999
99
6.3
Annual Dc (May 1999 – May 2000)
111
6.4
Five-year Dc (1999, 2000, 2004 surveys) for beach-fill
design
125
5.3
5.4
67
6.5
Outer Closure Depths Dco (MLW) from Profile Plots
127
6.6
Effective Dc and Predicted depth of closure, Dl,t , MLW
128
6.7
Dc from simplified equations compared with effective Dc
130
6.8
Dc from simplified equation compared to Dco
130
xiv
LIST OF FIGURES
NO.
1.1
TITLE
PAGE
Study Area - 4.5 km of Shoreline From Pantai Dasar Sabak
to South of Kg. K.S.P. Besar (Sungai Pengkalan Datu)
4
Evolution of Beach-fill based on Theory of Equilibrium
Profile
6
Zonation Of Seasonal Beach Profile (Hallermeier 1978,
1981); extracted from Rijkswaterstaat (1987)
10
3.1
Research Model
26
4.1
Location of Study Area
34
4.2
Close-up of Study Area from Kg. Pantai Dasar Sabak
to Kg. Senok
35
4.3
Profile Lines At The Study Area
39
4.4
Distribution of sediments along Pantai Sabak 1998, 1999
and 2004 (d50 averaged across all chainages)
43
Distribution of bed sediments along Pantai Sabak 1998-1999.
Negative chainages are south of the breakwater
43
4.6
Distribution of bed sediments along Pantai Sabak 2004
44
4.7
Location of Wavebuoy And UKMO Wavedata Source
Relative to Kelantan Coast.
45
Offshore Significant Wave Heights at 6.39N 102.92E;
28/05/1999 – 30/07/2004
46
4.9
Histogram of UKMO Waves
47
4.10
Wave Height vs. Wave Period for UKMO Offshore
Wave Records 1999 to 2004
48
1.2
2.1
4.5
4.8
xv
4.11
H0.137 Wave from 1999-2000 UKMO Wave Data
49
4.12
H0.027 Wave from 1999-2004 UKMO Wave Data
50
4.13
Wave Buoy Measurements at E19236.3 N33957
(Kelantan Cassini) off Pantai Sabak, Kelantan Coast;
30 June to 13 July 2004.
51
Comparison of Offshore (UKMO Data) and Nearshore
Waves Measured at the -12 m LSD Contour
51
Location Of Water Level, Current and Wave Stations At
Study Area.
52
Wind Rose for UKMO Offshore Wind Data (20 m Above
MSL)
55
Orientation of rectangle model layout for the input
(offshore) wave approach conditions N330o, N0o, N30o,
N60o, N90o and N120o
58
Sensitivity of kN parameter and location of breaking wave
based on waves in July
62
Water level measurements at Pantai Sabak during calibration
period
64
Wave Model Calibration – Wave Heights (for offshore waves
from 0 to 120 degrees)
64
Wave Model Calibration – Wave Directions (for offshore
waves from 0 to 120 degrees)
65
5.6
Location of extraction points in wave model
67
5.7
Wave Refraction Diagram; H0.137 = 2.9, Tm = 6.3 sec;
North approach.
68
Wave Refraction Diagram; H0.137 = 2.9, Tm = 6.3 secs;
N30o approach.
69
Wave Refraction Diagram; H0.137 = 2.9 m, Tm = 6.3 secs;
N60o approach.
69
Wave Refraction Diagram; H0.137 = 2.9 m, Tm = 6.3 secs;
N90o approach.
70
Wave Refraction Diagram; H0.137 = 2.9 m, Tm = 6.3 secs;
N120o approach.
70
4.14
4.15
4.16
5.1
5.2
5.3
5.4
5.5
5.8
5.9
5.10
5.11
xvi
5.12
Wave Refraction Diagram; H0.027 = 3.13 m, Tm = 6.54 secs;
North approach.
71
Wave Refraction Diagram; H0.027 = 3.13 m, Tm = 6.54 secs;
N30o approach.
71
Wave Refraction Diagram; H0.027 = 3.13 m, Tm = 6.54 secs;
N60o approach.
72
Wave Refraction Diagram; H0.027 = 3.13 m, Tm = 6.54 secs;
N90o approach.
72
Wave Refraction Diagram; H0.027 = 3.13 m, Tm = 6.54 secs;
N120o approach.
73
Predicted Maximum Wave Heights at 10-m depth ACD
contour along Pantai Sabak, Kelantan.
76
Predicted Wave Heights at 10-m depth (ACD) contour along
Pantai Sabak, Kelantan averaged over all directions
77
6.1
Monsoon Dc at Ch.3100
85
6.2
Monsoon Dc at Ch.2700
86
6.3
Monsoon Dc at Ch.2300
87
6.4
Monsoon Dc at Ch.1900
88
6.5
Monsoon Dc at Ch.1500
89
6.6
Monsoon Dc at Ch.1200
90
6.7
Monsoon Dc at Ch.800
91
6.8
Monsoon Dc at Ch.400
92
6.9
Monsoon Dc at Ch.200
93
6.10
Monsoon Dc at Ch.00
94
6.11
Monsoon Dc at Ch.-400
95
6.12
Monsoon Dc at Ch.-900 (slope 1:400)
96
6.13
Monsoon Dc at Ch.-1400; closure is not defined with
SDDC method at Ch.-1400
97
5.13
5.14
5.15
5.16
5.17
5.18
xvii
6.14
Comparison of SDDC and FDC methods in determining
Monsoon Dc
100
6.15
Annual Dc at Ch.3100
101
6.16
Annual Dc at Ch.2700
102
6.17
Annual Dc at Ch.1500
103
6.18
Annual Dc at Ch.1200
104
6.19
Annual Dc at Ch.800
105
6.20
Annual Dc at Ch.400
106
6.21
Annual Dc at Ch.200
107
6.22
Annual Dc at Ch.00
108
6.23
Annual Dc at Ch.-400
109
6.24
Annual Dc at Ch. -900
110
6.25
Annual Dc at Ch.-1400
110
6.26
Radar Graph - Comparison between Dl,1-yr and
measured Annual Dc
112
Variation in Dl,1-yr and measured Annual Dc along
the study area
112
5-year Dc at Ch.3100 - Comparison of SDDC and mean
of FDC between consecutive surveys at Ch.3100
114
6.29
5-year Dc at Ch.2700
115
6.30
5-year Dc at Ch.1500
116
6.31
5-year Dc at Ch.1200
117
6.32
5-year Dc at Ch.800
118
6.33
5-year Dc at Ch.400; three closure points were detected
119
6.34
5-year Dc at Ch.200
120
6.35
5-year Dc at Ch.00
121
6.36
5-year Dc at Ch.-400
122
6.27
6.28
xviii
6.37
5-year Dc at Ch.-900
123
6.38
5-year Dc at Ch.-1400
123
6.39
Comparison of 5-year Dc (effective Dc for beach-fill
design), Dco (outermost Dc) and Dl,5-yr
125
Variation in 5-year Dc (effective Dc for beach-fill design),
Dco (outermost Dc) and Dl,5-yr across the study area
126
6.41
Dc along Pantai Sabak, Kelantan
129
6.42
Dc based on different closure criteria
132
6.40
xix
LIST OF ABBREVIATIONS
CED
Coastal Engineering Division
CEM
Coastal Engineering Manual
cm
centimeter
DHI
Danish Hydraulic Institute
DID
Department of Irrigation and Drainage Malaysia
DSMM
Department of Survey and Mapping Malaysia
HAT
Highest Astronomical Tide
Kg.
Kampung; village (malay)
LAT
Lowest Astronomical Tide
LSD
Land Survey Datum
m
meter
mm
millimeter
MSL
Mean Sea Level
MHW
Mean High Water
MHHW
Mean Higher High Water
MLHW
Mean Lower High Water
MLW
Mean Low Water
MHLW
Mean Higher Low Water
MLLW
Mean Lower Low Water
Sg.
Sungai; river (malay)
SSMO
Synoptic Shipboard Meteorological Observation
UKMO
United Kingdom Meteorological Office
xx
LIST OF SYMBOLS
Dc
depth of closure
Dc,1-yr
depth of closure over 1 year
Dc,5-yr
depth of closure over 5 years
Dci
depth of closure, innershore; from profile survey
Dcm
depth of closure, middleshore; from profile survey
Dco
depth of closure, outershore; from profile survey
Dl
predicted depth of closure; water depth at the seaward limit of
significant sediment transport
Dl,t
predicted depth of closure over t years
Dl,1-yr
predicted depth of closure over 1 year
Dl,5-yr
predicted depth of closure over 5 years
d
water depth
di
lower limit of the shoal zone
dl
lower limit of the littoral zone
d50
size of material of which 50% is finer
g
acceleration due to gravity
H
predicted depth of closure (Birkemeier's equation)
hc
predicted depth of closure (Hallermeier's equation)
Hm0
energy-based wave height of the zeroth moment
Hs
significant wave height
Hs50
median annual significant wave height
Hl,t
significant wave height exceeded 12 hours over t years
H0.137
significant wave height exceeded 12 hours in a year
H0.027
significant wave height exceeded 12 hours in t = 5 years
He,t
non-breaking significant wave height that is exceeded 12 hours per t
years or (100/730t) % of the time
kN
Nikuradse's roughness parameter
xxi
s
standard deviation
t
time
T
wave period associated with a particular wave height
Te, t
wave period corresponding to He,t
Tm
mean wave period
Tp
peak wave period
Ub
maximum horizontal wave-induced near-bed velocity
xi
measurement
xm
mean of all measurements
n
number of measurements
σH
annual standard deviation of significant wave height
Φc
sediment entrainment parameter
γ’
ratio of the difference in density between sediment and fluid density
γ1
wave breaking parameter which controls wave steepness condition
γ2
wave breaking parameter which controls limiting water depth
condition
α
adjustable constant in energy dissipation equation
xxii
LIST OF APPENDICES
APPENDIX
A
TITLE
Profile Surveys from the coastline of Pantai Sabak, Kelantan
1998, 1999, 2001 and 2004
B
E
159
Summary of Grain Size Distribution from Pantai Sabak,
Kelantan Surveys 1998, 1999, 2004
D
142
Description of United Kingdom Meteorological Office
(UKMO) Dataset
C
PAGE
165
Tidal Data From Pantai Sabak, Kelantan;
2004 Survey
168
Model Wave Bathymetry
171
CHAPTER 1
INTRODUCTION
1.1
Introduction
Beach nourishment is a preferred coastal protection measure for recreational
beaches. The provision of a wider dry beach, by placing sand on the eroding shore
that extends beyond the existing beach berm, is the main component of a beach
nourishment scheme. A re-nourished beach presents a wider surface area that both
dissipates wave energy impacting on the shoreline and creates more space for
recreational activities. Sand re-nourished beaches remain as a part of the nearshore
coastal system within which sediment can be moved freely by wave and tidal action.
Inherent in the engineering design of beach nourishment is an element of
prediction and projection based on the shoreline change trend of the concerned
beach.
Typical beach nourishment schemes may require annual refill as the
nourished beach is exposed and continuously subjected to environmental forces. In
Malaysia, beach nourishment schemes are expected to last 5 years before renourishment works are initiated again. In this approach, designs are based on a
general rate of erosion for the beach and a five-year re-nourishment interval.
An
important aspect of beach nourishment design is the knowledge of the seaward limit
to which the beach-fill is expected to move. This point is called the depth of closure
and its determination involves the study of the nearshore profile over a period of
time.
2
The beach nourishment projects conducted by the Department of Irrigation
and Drainage Malaysia (DID) in the past did not have the benefit of sufficient
periodical survey data needed to determine the depths of closure.
Hence, the
predictive formula of depth of closure introduced by Hallermeier (Hallermeier,
1981) and its simplified forms (US Army Corps Of Engineers, 1984) have been
widely used. Since the completion of the beach nourishment projects, periodical
monitoring surveys have been conducted on selected re-nourished shorelines. The
situation now presents opportunities for further study and analysis of the depths of
closure with the view of improving the design of sand-fill in beach nourishment for
local conditions. This research determines and studies the depths of closure from
periodical surveys of a stretch of shoreline in Kelantan and examines the
applicability of existing predictive equations to the Kelantan shoreline.
1.2
Background of the Problem
1.2.1
Erosion Control and Beach Nourishment in Malaysia
The National Coastal Erosion Study (Unit Perancang Ekonomi, 1985)
determined that approximately 30% of Malaysia’s 4,809 km of coastline was
eroding. It proceeded to recommend immediate coastal erosion protection measures
on critical sites and led to the development of the Coastal Erosion Control Program
under the DID.
Under this program, revetment-type protection and beach
nourishment schemes were constructed along Malaysia’s eroding coasts beginning in
the late eighties. Among the major beach nourishment projects implemented by the
Government of Malaysia under this program were:
(i)
Kuala Terengganu to Kuala Ibai, Terengganu (1993);
(ii)
Taman Robina, Seberang Perai Utara, Pulau Pinang (1994);
3
(iii)
Pantai Kundur, Melaka (1995)
(iv)
Batu 4, Port Dickson, Negeri Sembilan (1996 and 2005) and;
(v)
Kg. Teritam to Kuala Sungai Pengkalan Datu, Kelantan (1997)
Since the emergence of tourism as a dominant sector of the Malaysian
economy, the need to preserve the quality and aesthetics of public beaches have
become an important agenda under the Coastal Erosion Control Program. Therefore,
the understanding of the evolution of re-nourished beaches must be enhanced so as to
improve future planning and design works.
1.2.2
Study Shoreline
The northeast coastline of Kelantan has been selected for this study due to its
long-term erosion trend. This coastline is oriented along the northwest to southeast
direction. Wind fetch lengths spanning over 1500 km across the South China Sea
influence this stretch of coast. As a result, the long fetch and the predominant
northeasterly winds during the northeast monsoon combine to generate high waves in
the adjacent offshore area (Department of Irrigation and Drainage, 1993).
Furthermore, there are no large islands off the Kelantan coast to offer any cover from
the monsoonal waves.
The study is limited to the coastline from Kg. Pantai Dasar to Kg. S.P. Besar,
Kelantan which is shown in Figure 1.1.
Locally known as Pantai Sabak, this
coastline has experienced erosion at an average rate of exceeding 5 meters per year
(Unit Perancang Ekonomi, 1985).
The situation was later exacerbated by the
construction of a breakwater at Sungai Pengkalan Datu which was completed in 1986
as part of a flood mitigation and agricultural drainage project. The breakwaters
created a terminus to the littoral transport in the area and depleted the supply of
4
sediment to the adjacent shoreline of Pantai Sabak to the northwest. An erosion of
20 meters occurred within 7 months of the completion of the northern arm of the
breakwaters and the completion of the southern arm 10 months after brought about
an additional 60 meters of erosion in the following year (Lee, 1990).
Studies by
Universiti Teknologi Malaysia indicated that minor sediment bypassing of the
Pengkalan Datu breakwaters in the northwest direction had begun within a few years
of its completion (Ahmad Khairi Bin Abdul Wahab, 1989). Nevertheless, this was
insufficient to reduce the erosion rate at Pantai Sabak.
In 1996, the DID implemented a beach nourishment project which laid 1.2
million m3 of sand along a 2.1 km stretch within the study area. The constructed
beach berms ranged from 70 m to 120 m.
Whilst the study and design of the beach
nourishment scheme took into account the reduction in sediment budget due to the
breakwater, nearly 60% of the nourished volume was lost within a single monsoon
(Jabatan Pengairan dan Saliran Malaysia, 2002).
KELANTAN
Study Area
Study area Kelantan,
MALAYSIA
Figure 1.1: Study area - 4.5 km of shoreline from Pantai Dasar Sabak to South of
Kg. K.S.P. Besar (Sungai Pengkalan Datu). (Source: Topo Maps #4068 [1985],
#3968 [1991], Jabatan Ukur dan Pemetaan Malaysia)
5
1.2.3
Beach Nourishment Design and Depths of Closure
The design of a beach nourishment scheme requires the same engineering
parameters as other coastal protection solutions. Apart from the established wave,
wind and tidal conditions, the design criteria for a typical DID beach nourishment
includes:
•
a nourished beach slope as close as possible to the existing beach
slope;
•
available funds to provide the widest beach berm possible based on a
pre-determined re-nourishment interval of 5 years;
•
the availability of suitable sand-fill of grain size d50 greater than the
native beach.
From the Shore Protection Manual (US Army Corps Of Engineers, 1984), the
design approach can be summarised as follows: (i) determination of the beach berm
elevation and width (ii) determination of nourishment volume based on native and
borrow composite material characteristics (iii) determination of post-project beach
evolution.
In practice, a pre-erosion shoreline is determined and the berm width is
‘overbuilt’ beyond the pre-erosion shoreline position based on local erosion rates and
the expected interval of re-nourishment. Hence, if the local erosion rate is 5 meters
per year and a re-nourishment is planned after every five years, the berm width will
be built 25 meters beyond the desired shoreline. Artificial beach fills are created
based on a construction cross-section. Over time and due to the action of waves and
tides, the fill material forming the nourished profile of a constructed beach will be
shaped by natural processes into a profile of generally concave upward shape called
an equilibrium profile. This equilibrium profile concept was proposed by Bruun
(1954) with further elaboration by Dean (1977) and is illustrated in Figure 1.2. In
the application of this concept, it is assumed that there is a conservation of sediment
6
Evolved
equilibrium
profile
Original nourished
profile
Original
ground
level
Dc = depth
of closure
Figure 1.2: Evolution of beach-fill based on Theory of Equilibrium Profile
volume across the profile and that a loss of sand volume from the upper profile of the
beach is associated with a similar gain in volume in the lower profile. The seaward
limit for the volume exchange process is the depth of closure.
The depth of closure is effectively, the offshore limit of the active zone
within which a nourished beach adjusts to equilibrium under the prevailing coastal
conditions. Hence, a good estimate of the depth of closure is essential to a good
estimate of the beach fill volume required. With respect to post-nourishment beach
profiles, National Research Council (1995) refers to the depth of closure as a
reference typically used by designers to estimate the limit of profile widening.
These statements further confirm the importance of the depth of closure in beach
nourishment design.
Beach nourishment schemes have been built in Malaysia since 1992 but their
evolution has not been extensively studied. Due to the lack or absence of periodical
surveys then, the depth of closure has typically been predicted from empirical
equations. With regards to this, a comparative study of the predictive and measured
7
depths of closure, in the writer’s opinion, would contribute to the understanding of
the performance of beach nourishment schemes. In the Malaysian context, such
detailed comparisons have, to date, yet to be done and this dearth of knowledge is the
impetus to this research.
1.3
Objectives of the Study
The purpose of this research is to determine the depths of closure of a 4.5 km
stretch of sandy coast extending from north of Pantai Dasar Sabak to south of the
Sungai Pengkalan Datu in the state of Kelantan. The study will analyse beach profile
surveys, determine the depths of closure and to compare them against predicted
values calculated from the Hallermeier equation.
The research will examine the
validity of this widely accepted equation for the Malaysian condition.
1.4
Benefits of the Study
In general, the study is expected to contribute towards an improved
understanding of cross-shore sediment transport and shore profile changes in the
Malaysian coastal environment. Knowledge of profile trends and depths of closure
will facilitate the design of coastal protection works primarily beach nourishment,
revetments, groynes and breakwaters. It is envisaged that from the results of this
research, engineers will be able to utilise a modified analytical method, specific to
the local conditions, to predict depths of closure with greater confidence for areas
where historical shore profile data is lacking.
8
CHAPTER 2
LITERATURE REVIEW
2.1
Introduction
Coastlines change in response to the coastal processes that prevail. Coastal
profiles develop due to the cross-shore sediment transport while the planform shapes
are a result of longshore sediment transport. Sediment transport studies are an
essential component of coastal protection works whereby its understanding
contributes towards selection of the defence strategy and ultimately engineering
design.
The contribution of sediments from sources and their transportation and
distribution alongshore is important in determining the length of shore-normal
structures.
Likewise,
cross-shore transport is equally important particularly its
seaward limit beyond which there is no significant sediment transport. This limit is
often defined as the depth of closure whose concept, methods of determination,
prediction and application will be the subject of this review.
2.2
Cross-shore Sediment Transport and Equilibrium Beach Profiles
The depth of closure has its beginnings in the studies of cross-shore sediment
transport. Cross-shore transport, the studies of which are relatively recent compared
to longshore transport, involves both onshore and offshore transport which are
associated with different modes and contrasting timescales (US Army Corps Of
Engineers, 2003). The onshore sediment transport is related to mild wave conditions
9
while offshore sediment transport is due to wave activity during storms. Offshore
sediment transport is of the greater concern to engineers due to its potential threat in
the form of erosion of beach material and undermining the foundations of coastal
structures. In applying the equilibrium beach profile concept to predict coastal
profile change, most engineering methods assume that the volume of sand is
conserved within the active profile i.e. erosion in the upper part of the profile is
compensated by a corresponding deposition in the surf zone. In beach nourishment
design, Dean (2003) described that nourished profiles are typically designed to be
steeper than the equilibrium profile and they will then equilibrate to the closure
depth.
Although longshore transport plays a role in beach morphology, where
significant longshore component exists, the movement of the profile is considered
uniform across the elevation.
The depth of closure is based on the observation that repeated nearshore
profiles tend to show a reduction in vertical variability as depth increases (Nicholls et
al, 1996). It is also a parameter which separates two distinct zones within the crossshore area with different levels of morphodynamic activity (Nicholls et al, 1998b).
2.3
Definition of Depth of Closure
The concept of the depth of closure is credited to Hallermeier (1981) and his
work in the zonation of coastal profiles. Hallermeier proposed that the coastal
profile could be divided into offshore, shoal and littoral zone as shown in Figure 2.1.
10
Mean sea level
dl
di
Variation in
beach profile
Mean sand level
littoral zone
offshore zone
Figure 2.1:
shoal zone
Zonation of seasonal beach profile (Hallermeier 1978, 1981);
extracted from Rijkswaterstaat (1987)
In proposing a zonation for seasonal beach profiles, Hallermeier (1978, 1981;
reviewed by Rijkswaterstaat, 1987) divides the beach into offshore, shoal and littoral
zones. Hallermeier defined the shallower of the two depths, dl as the lower limit of
the littoral zone while the depth di as the lower limit of the shoal zone. The littoral
zone was defined by Hallermeier as a zone where there is significant alongshore
transport and intensive onshore-offshore transport over a typical year. The shoal
zone is one that is still subject to onshore-offshore sediment transport up to depth di
while the offshore zone is where surface wave-effect on the bed is negligible. To
facilitate volume calculations in beach-fill design, it is important to estimate a
seaward limit or depth where the nourished profile is expected to develop. Yet, from
Figure 2.1, it can be seen that the actual location to set a dimension for calculation
depends on where one defines the limit of significant movement of sediment.
Nicholls et al (1996) describes the depth of closure as a “fundamental
morphodynamic boundary separating a landward active zone from a seaward less
active zone over the period defined by the profile observations used to define
closure”
and emphasizes that the time scale of data is significant to the
determination of the position of the depth of closure. Dean (2003) considers the
shallower limit Dl as the more appropriate depth for beach nourishment design.
11
In the Manual on Artificial Beach Nourishment, the Rijkswaterstaat (1987)
recommends that one assumes the active profile will develop seawards to the depth dl
due to the action of waves despite the fact that onshore-offshore transport still occurs
below this depth. Knudsen et al (2002) studied the coastal profiles in the Danish
North Sea and proved that considerable erosion occurs outside the depth of closure.
The thrust of this research however, requires the acceptance of a definition that
serves the engineering purpose of determining the depth of closure. Kraus et al
(1998) in the “Coastal Engineering Technical Note II-40 – Depth of Closure for
Beach-fill Design” considered the various descriptions for this seaward limit and
concluded that in order to apply to beach-fill design, the depth of closure should be
defined as:
“the most landward depth seaward of which there is no significant change in
bottom elevation and no significant net sediment transport between the nearshore
and the offshore”
This definition is practical from an engineering viewpoint since it implies that
bottom elevation and sediment transport can be measured.
The adjective
‘significant’ is crucial to this definition as it alludes to the fact that this is not a
terminal point in onshore-offshore sediment transport but merely one of reference.
According to Kraus et al (1998), the definition as described above is intended for the
design of fill or borrow material (also called beach-fill) in beach nourishment
projects and is purported to be applicable to the open coast where the dominant
mechanisms of sediment transport are nearshore waves and wave-induced currents.
12
2.4
Methods of Determination
2.4.1
Predictive Methods
The only analytical method of estimating the depth of closure is one put
forward by Hallermeier (1981).
Hallermeier proposed that the annual depth of
closure could be calculated as follows:
Depth of closure
hc = 2.28 H0.137 – 68.5 (H0.1372/gT2)
(2.1)
where,
H0.137 =
significant wave height exceeded 12 hours in a year
T
=
wave period corresponding to H0.137
g
=
acceleration due to gravity
Hallermeier predicted the depth of closure by associating it with the critical
value of a sediment entrainment parameter, Φc, which is in the form of a Froude
number. The threshold of sandbed agitation by wave action (Nicholls et al, 1996;
Kraus et al, 1998) is given as follows,
Φc = Ub2/(γ’gd) = 0.03
(2.2)
where,
Ub = maximum horizontal wave-induced near-bed velocity
D
= water depth
G
= acceleration due to gravity
γ’
= ratio of the difference in density between sediment and fluid density
In developing this predictive equation, Hallermeier used γ’= 1.6 for quartz
sand in seawater and applied the linear wave theory.
Validating against field
13
laboratory tests, Hallermeier found that it was insensitive to grain sizes of median
diameter 0.16 mm to 0.42 mm which are typical of the nearshore area of sandy
beaches (Kraus et al, 1998). Equation (2.1) is therefore valid only for grain sizes not
greater than 0.42 mm. Depth of closure from Equation (2.1) is referenced to MLW
to produce a conservative result acknowledging that tidal and wind-induced currents
are capable of increasing near-bed flow velocities (Nicholls et al, 1998a).
Hallermeier compared Equation (2.1) against annual predictions produced from
survey data collected at the Gold Coast (Australia) and Avondale (Florida) and
Torrey Pines (California) using a depth change criterion of 30 cm and found that the
predicted values agree to within 10% of the observed values (Nicholls et al, 1998a).
Birkemeier (1985) evaluated Equation (2.1) using the first two years of
survey data obtained at Duck, North Carolina and found that it over-predicted the
observed Dc by 25%. Specific to data from Duck, Birkemeier produced adjustments
to the coefficients in Equation (2.1) and modified it as follows:
hc = 1.75 Hs – 57.9 (H0.1372/gT2)
(2.3)
Equation (2.3), produced smaller (shallower) depths of closure than Equation
(2.1) and demonstrated that Equation (2.1) can be refined for a specific stretch of
coast if extensive survey data is available.
Discussing Hallermeier’s earlier work,
Nicholls et al (1996) reviewed and presented Equation (2.1) in a time dependent
form:–
Dl,t = 2.28 He,t – 68.5 (He,t2 / gTe,t2)
(2.4)
where,
Dl,t = is the depth of closure predicted over t years referenced to MLW;
He,t = non-breaking significant wave height that is exceeded 12 hours per t
years or (100/730t) % of the time;
Te,t = wave period corresponding to He,t ;
g
= acceleration due to gravity
14
Nicholls et al (1996) studied 12 years of repetitive beach profile data from
Duck, North Carolina and validated Equation (2.4).
This dataset comprised of
surveys extending to depths of about 8 meters and wave observations at depths of up
to 18 meters. These surveys were conducted every two weeks and also after storms.
The Dl,t calculated with Equation (2.4) was tested against two scenarios:–
i.
event-dependent depth of closure whereby the beach profile change has
occurred over a single event such as a major storm and;
ii.
time dependent depth of closure whereby the beach profile change has
occurred due to an integrated response towards a range of driving
conditions such as erosional and accretional waves and currents.
Results from the two scenarios differed: time-dependent or time-interval
depth of closure was, in general, found to be deeper than the largest event-dependent
depth of closure for the same time-period of analysis. Time-interval depth of closure
as predicted by Equation (2.4) also appeared to fail under accreting conditions as it
predicted depth of closure values that were smaller than actually observed. Nicholls
et al (1996) concluded that the application of Equation (2.4) requires an explicit
consideration of time scales.
The first term of Equations (2.1), (2.3) and (2.4) relate to the wave height
while the second term provides an adjustment for wave steepness (Kraus et al, 1998).
Hence, the selection of wave height is crucial to the prediction of the depth of
closure. Hallermeier’s initial recommendations were to use the significant wave
height exceeded 12 hours in a year which suggests extreme wave conditions. For
time interval hc, or Dl,t the significant wave height exceeded 12 hours over the time
interval is used. In any case, the offshore or deepwater wave should not be used as it
will result in very conservative depth of closure values (Kraus et al, 1998).
Kraus et al (1998) also recommends that a representative depth of closure
should be based on wave conditions averaged over a period of years and states that
the depth of closure can vary considerably with storm activity and wave conditions
from year to year. Hence, Dl,t considers both erosional and accretional processes
15
that may happen over the period of wave data obtained. On the validity of Equation
(2.1), Nicholls et al (1996, 1998b) notes that Equation (2.1) is invalid for rapidly
accreting areas.
Other derivations have been produced which simplify Hallermeier’s equation
to the form:
H = 1.57 Hs 0.137
(Birkemeier, 1985; cited in US Army Corps of
Engineers[2003])
(2.5)
where,
H
=
Hs 0.137 =
predicted depth of closure;
extreme nearshore wave height exceeded 12 hours in a year
Hallermeier also proposed a form of Equation (2.1) that did not include the
associated wave period (US Army Corps of Engineers, 2003):
hc = 2H + 11 σH
(2.6)
where,
H
=
annual mean significant wave height;
σH
=
standard deviation of wave height
2.4.2 Depth of Closure from Profile Surveys
Numerous letters or symbols have been used to represent depth of closure in
the literature. To avoid confusion, depth of closure in this study will be referred to as
Dc. The most accurate method of determining the depth of closure is from studying
profile surveys. Observed depth of closure can be empirically derived from the
16
observation of a series of profile surveys taken over a period of time.
Dc
corresponds to a pinch-out depth below which depth changes become small (Nicholls
et al, 1996). The criterion for ‘small’ is usually equivalent to the accuracy of the
survey measurements.
The accuracy of field surveys invariably influences the analysis of profiles to
determine the Dc. Topographical survey and hydrographic survey are the most
common means of obtaining profile data.
In conventional hydrographic survey
using echo-sounders and where corrective algorithms have been applied to account
for heave and other boat movements, the accepted accuracy is typically 30 cm.
Detailed profile studies at Duck (Nicholls et al, 1998a; Kraus et al, 1998) used the
Coastal Research Amphibious Buggy (CRAB) which has a survey accuracy standard
deviation of up to ±2.5 cm. Another method recommended by Kraus et al (1998) for
beach-fill projects is the sea-sled method which has an accuracy of 2.54 cm (1 inch).
2.4.3
Depth Change Criterion
There are two widely used criteria in determining the depth of closure from
profile measurements. The standard deviation of depth change (SDDC) method
involves plotting the SDDC against distance seaward of the profile origin for each
measured profile. The Dc is thus the point where the SDDC reduces to a constant,
non-zero value. The SDDC method is useful in the sense that it avoids bias from
outliers (Hinton and Nichols, 1998).
The ‘standard deviation in depth’ method has been described by Kraus et al
(1998) as one of the ways to estimate Dc from profile surveys.
The limit of
significant profile change is at the point where there is a sharp decrease of the
standard deviation of depth to a small value. Statistically, the standard deviation of a
set of measurements “is equal to the positive square root of the variance”.
formula for variance is,
The
17
s 2 = Σ ( xi – x m ) 2
(2.7)
n–1
where,
xi
measurement
xm
mean of all measurements
n
number of measurements
Therefore, the standard deviation is simply s.
By this definition, and using the elevation of the bed at the same position over
a period of surveys as the population, the standard deviation of significant depth
change at any point can be determined.
The second method is the fixed depth change (FDC) method (Nicholls et al,
1996) where the FDC is the absolute difference between the elevations of two
consecutive surveys from the same profile line. The Dc is the depth where the
variation in depth between the two profiles is equal or less than a pre-selected
criterion usually associated with the accuracy of the profile survey. Hence, if a
survey method has an accuracy of 30 cm, any absolute change exceeding 30 cm
would be considered significant. Over a collection of surveys, the limit where
significant change in depth can be estimated is the point where the mean of absolute
change in depth does not exceed 30 cm. The average absolute change in depth is
similar to SDDC but is more descriptive in deeper water (Larsen and Kraus, 1994).
When testing Equation (2.1) against data from the Gold Coast, Florida and
California, Hallermeier used a depth change criterion of 0.3 m which was the
operational accuracy of the data (Nicholls et al, 1998b).
Using profile data from
Duck, North Carolina, Nicholls et al (1996) examined the variability of Dc using a
fixed depth change (FDC) criteria of 6 cm, 10 cm and 15 cm as well as the standard
deviation of depth change (SDDC) criteria. Different definitions of Dc were found to
yield different depth estimates. Nevertheless, the SDDC method defined most of the
annual Dc.
18
Hinton and Nicholls (1998) in their analysis of depth of closure for the
Holland coast also used both methods which produced similar results. From their
analysis, they found that the phenomena of profile closing, opening and re-closing
occurs along the Dutch coast and were best depicted by the SDDC method. Hinton
and Nicholls also used an FDC criteria of 0.25 m and 0.5 m and found that since
FDC captures the largest depth variation it generally gave the more landward value
of closure. The same study also found that profile re-opening is observed only over
time-scales exceeding 10 years and at offshore distances of 1.5 km around the 12 m contour.
2.5
Application of Depth of Closure
The depth of closure plays an important role in the determination of coastal
sediment budgets and the design of erosion control solutions such as beach
nourishment and offshore breakwaters.
Considering the lifespan of such erosion
control solutions, it is necessary for depth of closure determinations to be explicitly
defined with a spatial and temporal scale. It has been stressed that the depth of
closure is not an absolute cross-shore sediment transport boundary and that it is a
morphological boundary that is highly dependent on the criteria of depth change and
the period of profile observation (Nicholls et al, 1996; Nicholls et al, 1998a and
1998b).
As described earlier, Equation (2.1) has been proven to be a robust definition
of the seaward limit of significant cross-shore sediment transport for erosion or storm
events up to the annual time-scale (Nicholls et al, 1996).
Hinton and Nicholls
(1998) studied closure depth behaviour based on the Large Scale Coastal Evolution
Concept which distinguishes time scales as follows:
ƒ
Large scale: morphodynamic length scale of 10 km and time scale of
decades;
19
ƒ
Medium scale: morphodynamic length scale of 1 km and time scale of
years;
ƒ
Small scale: morphodynamic length scale of 100 m and time scale of
storms or seasons
The large-scale analysis of data off the Dutch coast revealed that profile
closure occurs on the shoreward side at depths of 5 m to 8 m and distance of 1 km
from shore. Analysing 25 years of survey data, the profile closure then re-opens at
middle/lower shore face locations at distances further than 1.5 km offshore. This
phenomena is still being studied with possible influences being offshore sand bar
formations as well as anthropogenic structures (Hinton and Nicholls, 1998).
On the longshore variations of Dc using local wave climate, Francois et al
(2004) reviewed Hallermeier’s equation and found that it “fails to reproduce” the
longshore variations since a fixed offshore wave height is used. Francois et al (2004)
focused on the use of local waves in the analysis which is a feature incorporated in
this research.
2.6
Depth of Closure – Malaysian Context
In 1986, the Kelantan coastline from Kuala Besar to Kuala Sungai Pengkalan
Datu was the subject of a feasibility study for design of erosion control measures as
part of the National Coastal Erosion Study (Unit Perancang Ekonomi, 1986). Under
this study, an analysis of shore normal profiles was conducted based on a 1985
survey and revealed that the base of the shoreface becomes constant at a depth of 4.5
m. Referring to Hallermeier and for the case of quartz sand in seawater, the seaward
limit, referred to as Dl, was also calculated using the following equation:
Dl = 2Hs50 + 12σH
where,
(2.8)
20
Dl
water depth at the seaward limit of significant sediment transport;
Hs50
median annual significant wave height;
σH
annual standard deviation of significant wave height
The report states that the Dl is roughly twice the extreme nearshore wave
heights exceeded 12 hours per year which concurred with the existing data on
observed seaward limits of sand transport.
Using records from shipboard wave observations for the area known as Pantai
Cinta Berahi (now Pantai Cahaya Bulan), the Hs50 and σH were both found to be 0.6
m which when substituted into Equation (2.8) produced a calculated Dl of 8.4 m.
Nevertheless, due to the different results between calculated and measured Dl, the
calculated value was dropped and the measured value of 4.5 m was chosen as the
limit of significant sediment transport for the Kelantan coastline. Subsequently, it
was recommended that sand extraction be prohibited from the region of the shoreface
lesser than this depth. The report however, did not elaborate on the vertical datum
reference for the depth. It also conceded that the σH which was calculated from the
Synoptic Shipboard Meteorological Observation (SSMO) - the main source of
offshore wave data available at the time - was the probable source of error which
lead to the differences in Dl results.
A key problem in local studies is the lack of long term, periodic survey data
and concurrent measured wave data. On the other hand, it is noted that the defining
works by Hallermeier (1981) and Birkemeier (1985) and later by Nichols et al (1996,
1998a and 1998b) reviewed above appear to have the benefit of detailed, medium to
long-term survey data. Some of the profile surveys were obtained at fortnightly
intervals
and
post-storm
conditions
complete
with
corresponding
wave
measurements. Nonetheless, with the availability of four profile survey datasets
obtained in 1998, 1999, 2000 and 2004 on the Kelantan coastline, an independent
research on the depth of closure for a Malaysian coast can now be conducted.
21
2.7
Summary
This literature review has focused on the more recent work done on cross-
shore sediment transport evident in the last decade with only one reference on the
study of seaward limits of significant sediment transport done in 1986 for the
Kelantan coastline. The work of Hallermeier and Birkemeier continue to be referred
to in subsequent studies as more profile information is gathered by other researchers.
In all cases, the Hallermeier equation is accepted as the equation that determines the
seaward or upper limit of depth of closure. Of particular importance to this study are
the findings of Hinton and Nicholls (1998) and Nicholls et al (1998a and 1998b).
The former proved that the long-term behaviour of depths of closure could be
achieved with large-scale analysis using profile survey that extends both in crossshore and longshore directions.
Nicholls et al (1998b) critically examined the
predictive capability of the Hallermeier equation comparing it against the measured
depth of closure determined with several closure criterions. Several authors have
mentioned the importance of the use of local wave conditions in the Hallermeier
equation and Francois et al (2004) have focused on this in their work in studying the
alongshore variations in Dc. Francois et al (2004) reports on the use of numerical
modelling to predict the nearshore wave conditions which would be the more
appropriate wave height for calculating Dc.
The general conclusions of depth of closure studies are that Dc increases as
more profile data is accumulated.
Based on comparisons with measured profiles,
the Hallermeier equation was found to be robust; it tends to over-predict the Dc and
determines the upper boundary to the nearshore cross-shore morphological process.
An important finding presented by Nicholls et al (1998b) was that Hallermeier’s
equation is more accurate when predicting the Dc for an erosional event compared to
an accretional one.
This review also revealed that an initial study of the depth of closure has been
conducted in 1985 along the Kelantan coastline from Kuala Besar to Kuala Sungai
Pengkalan Datu albeit when the study of seaward limits of cross-shore transport was
relatively in its infancy. The results however indicated that the calculated depth of
closure was not consistent with measured profile data.
Hence, the research work
22
proposed here is obviously relevant. A detailed investigation of depth of closure for
the Kelantan coast, in the author’s opinion, would be of benefit to the local coastal
engineering community.
CHAPTER 3
RESEARCH METHODOLOGY
3.1
Introduction
The pioneering studies on the depth of closure analysed the long-term profile
measurement data obtained at the Field Research Facility operated by the Coastal
Engineering Research Center (CERC) of the US Army Engineer Waterways
Experiment Station at Duck, North Carolina (Birkemeier 1985, Nichols et al 1998a,
Hinton and Nichols 1998). This research follows closely the approach and analysis
used in those earlier works where there was a reliance on shore profile data
extending to depths up to -8 meters. It is acknowledged however that the equipment
used to obtain the profile measurements at Duck is more accurate than the
conventional method of hydrographic survey. Nonetheless, the data used in this
research would be from the conventional hydrographic survey method which is still
widely accepted for engineering purposes.
The methodology used in determining the depths of closure and investigating
the analytical methods in determination of depth of closure is presented below.
24
3.2
Scope of the Research
The depth of closure is a statistical concept hence its determination requires a
rigorous treatment of survey data where reliability depends on the volume and extent
of the series of surveys available. This research is founded on the analysis of a series
of beach profile survey data made available to the author by the Coastal Engineering
Division (CED) of the Department of Irrigation and Drainage Malaysia (DID). The
main objective of this research is (i) to determine the depth of closure from a series
of profile surveys for a certain stretch of Malaysian coastline and (ii) investigate the
applicability of the Hallermeier equation in predicting the depth of closure based on
local wave conditions.
The data for the study was from the surveys obtained on the northeastern
coastline of Kelantan where a shore monitoring programme was initiated by the DID
following a trend of steady shoreline retreat since 1997.
The research evolved along the following sequence of tasks:
(i)
Secondary Data Collection –
a. Compilation of beach profile data of the study area;
b. Compilation of meteorological and oceanographic (met-ocean)
data including wind, wave, tides and bed sediment data;
(ii)
Primary Data Collection –
Supplementation of survey and met-ocean data by hydrographic
survey and sediment sampling off the northeast Kelantan coastline;
(iii)
Determination of the seaward limits of significant changes in bed
elevation which corresponds to the depth of closure;
a. Study and selection of criteria for determination of Dc
b. Compiling, plotting and comparing survey data series;
25
(iv)
Determination
of
depths
of
closure
using
analytical
methods/predictive equations:
a. Analysis of wave data to determine input data into numerical
modelling;
b. Conduct wave modelling using numerical modelling software to
determine the nearshore wave heights and periods based on the
offshore wave input parameters;
c. Determination of Dc based on predictive equation introduced by
Hallermeier (1981) using results from (iv) b;
(v)
Synthesizing of results and establishment of trends in beach profile
and closure depths and introduction of site-specific adjustments to the
Hallermeier equation;
A model for the research is illustrated in Figure 3.1.
26
Beach
Profile
Water
Levels
Sediments
Analysis of
Profile Surveys
Waves
Bathymetry
Numerical
Modeling
Predictive/
Analytical
Equation
Depths of
Closure
Modification to
Predictive
Equation
Figure 3.3: Research model
for the
of depths of closure
Figure
3.1:determination
Research Model
27
3.3
Research Methodology
3.3.1
Data Sets
3.3.1.1 Beach Profile Survey
For the purpose of this research, beach profile surveys were reduced to a
single, common horizontal and vertical datum and this exercise would be critical to
the accuracy of depths of closure estimates.
Prior to analysis, cross-shore profiles
that best represent the study shoreline were determined, selected and subjected to a
quality check.
3.3.1.2 Wind and Wave
The UK Meteorological Office has made available to public its offshore wave
datasets that is generated by a global hindcast model.
The data set also includes
atmospheric wind data. Another source for local wind data is available with the
Meteorological Services Department where the nearest recording station to the study
site is at Pengkalan Chepa Airport, Kota Bharu, Kelantan.
3.3.1.3 Tidal Heights
Tidal information is necessary to determine the local wave regime. Predicted
tidal heights are obtainable from the Royal Malaysian Navy Tide Tables and the
Malaysian Survey and Mapping Department Tide Tables. The nearest Standard Port
to the study area is at Geting near the mouth of Sungai Golok (Malaysia-Thailand
28
border). Tidal data can also be derived from tidal measurements and can be used to
determine the tidal heights in the study area.
3.3.1.4 Sediment
The definition of depth of closure involves a study of sediment transport in
the nearshore zone. Significant changes in sediment type, grain size or colour at a
particular nearshore location over time infers that the depth of closure is further
seaward. Sediment grain size affects its fall velocity and is also an indicator of its
transportability. Hence, sediment data from borehole or grab (bed) sample records is
essential to the research and data for the study coastline will be sourced from field
surveys conducted or commissioned by the DID since 1998.
Specifically, the
required parameter is the mean particle size which can be determined through sieve
and hydrometer analysis.
3.3.2
Primary Data Collection
Additional data collection was conducted to complete the survey and beach
profile datasets in 2004.
This included nearshore bed sediment sampling and tidal
measurements that were used to run the numerical model.
New datasets were
therefore obtained for profile survey, tidal heights and nearshore waves.
29
3.3.3
Numerical Modelling
3.3.3.1 Software and its Application
Mike21-NSW is a nearshore spectral wind-wave wave model developed by
the Danish Hydraulic Institute (DHI) which was used to model the propagation of
offshore wave heights into the nearshore areas. The model is able to handle the
following phenomena:
•
Shoaling and refraction
•
Wave breaking; based on expressions by Battjes and Janssen (1978)
•
Wave-current interaction
•
Bottom friction; using a formulation based on the quadratic friction law to
represent bottom shear stress wave
•
Local wave generation or wind-forcing
•
Directional spreading
Mike21-NSW does not include diffraction, reflection and non-linear effects
such as wave-wave interaction. The model calculates the dependent variables using
the Explicit Euler method over a rectangular grid for a number of discrete directions.
The model was utilised to determine the nearshore wave climate along the study
shoreline.
The input into the model included a digitised bathymetry of the South China
Sea extending into deep waters, offshore wave heights and their corresponding wave
periods and directions.
30
3.3.3.2 Event and Scenarios for Modelling
An important element in the numerical modelling would be the selection of
the input data for the wave refraction model. In terms of modelling wave conditions,
boundary data will comprise parameters of the offshore wave condition
corresponding to an extreme event. As recommended by Hallermeier (1981), where
depths of closure is calculated for a one-year interval, this would correspond to a
wave height exceeded 12 consecutive hours of that year which is equivalent to
0.137%. This requires a statistical analysis of the offshore wave data.
Since the study area is wave dominant, only a wave refraction model is
proposed. The Mike21-NSW wave model will be utilised and the model will be run
using Mean Higher High Water as the water level in the model. This would provide
the setting for the furthest possible wave penetration into the nearshore area and the
largest incident waves to occur in the model nearshore area.
Nearshore wave heights will be extracted from the model nearshore area at
the location of the 10 m ACD depth-contour. At 10 m depth, the waves are still
considered unbroken as it is still beyond the offshore bar formations. The local wave
values will be substituted into the analytical equations to predict the depth of closure.
3.3.4
Analysis
3.3.4.1 Depths of Closure from Beach Profile Data
The study shoreline has been nourished in 1996 which created a new and
unnatural post-construction shoreline. A series of monitoring surveys was conducted
in 1998, 1999 and 2000 and will therefore be the primary dataset. The analysis of
survey data involves making certain that the various datasets represent the same
cross-shore profile locations with horizontal and vertical errors within tolerable
limits. This quality check is also necessary to remove outliers or suspect readings.
31
A graphical analysis of beach profiles will be conducted to determine profile
characteristics, envelope of changes and trends of bar migrations.
Standard
spreadsheet software will be used to tabulate profile measurement data and to
calculate variations in the depths leading to the determination of the seaward limit of
significant change in elevation. Both the standard deviation of depth change and
fixed depth change criteria shall be explored. Following this, an algorithm will be
established to facilitate the determination of closure points and the eventual Dc.
Based on the available dataset, two scenarios for investigation of Dc analysis
will be conducted on a pre and post monsoon as well as a time-dependent scenario.
The pre and post monsoon datasets are expected to reveal the effect of an erosional
event i.e. the northeast monsoon, on depths of closure.
In the time dependent
scenario, the Dc value represents an integrated effect of the various environmental
forcings on the nearshore of the study profiles over the time span of the data.
3.3.4.2 Depth of Closure from Empirical Formulae
The Hallermeier equation was used to calculate the depth of closure.
Variables used as input were the transformed offshore waves in the nearshore area
close to the seaward end of the profile dataset and their associated wave periods.
These parameters were extracted from numerical modelling results.
3.4
Summary
The research derives the depth of closure for the coastline of Kelantan. Its
findings is expected to contribute towards a better understanding of beach profile
changes in the area and its implications on the design of shoreline protection works.
The seaward limit of profile change or the depth of closure has been defined by
Kraus et al (1998) as (i) a depth seaward of which no significant change in bed
32
elevation occurs over time and (ii) a depth seaward of which no significant net
sediment transport occurs.
The research involved the analysis of surveys, beach profile and sediment
data over the study shoreline to determine the depth of closure. This was compared
with depth of closure values calculated using the Hallermeier equation. The research
was later directed at producing local adjustments to the predictive equation and
establishing a definitive depth of closure for the north-eastern shoreline of Kelantan
encompassing the rapidly eroding stretch from Pantai Dasar Sabak to Kuala Sg.
Pengkalan Datu.
CHAPTER 4
FIELD DATA ANALYSIS
4.1
Introduction
The data compiled and collected for this study on the depths of closure is
designed to fulfill two main objectives (i) to enable the study of variations in bed
elevation and (ii) the establishment of the nearshore wave conditions that feed into
the mathematical equations that will be used to calculate Dc. The required data thus
comprises hydrographic survey, meteorological and ocean wave data and sediment
properties.
This research is based on four profile survey exercises conducted in the study
area in the state of Kelantan in 1998, 1999, 2000 and 2004 (Jabatan Pengairan dan
Saliran Malaysia, 1999a, 1999b, 2000 and 2004).
All surveys were conducted by
licensed surveyors and hydrographers appointed by the Coastal Engineering
Division, Department of Irrigation and Drainage Malaysia. The purpose of the first
three surveys was essentially to capture the changes of the nearshore profile over the
northeast monsoon when erosion is expected to occur.
The fourth survey was
obtained to facilitate detailed design of coastal protection works.
This chapter describes the study area followed by each dataset as to their
form, extent, accuracy and limitations in relation to the determination of the depths
of closure. This is followed by an explanation of the processes conducted to produce
both the measured depth of closure and the calculated depth of closure.
34
4.2
Study Area
The study area lies in the state of Kelantan which is located in the northeast
of Peninsular Malaysia and south of the Thailand-Malaysia border. The study area is
the coastline of Kg. Pantai Dasar Sabak to Kg. Senok and encompasses a once
famous public beach known as Pantai Sabak. The shoreline is part of Kelantan’s
dynamic northeast coast which is generally sandy and void of headlands, rock
outcrops and offshore islands. This coastal region has developed from the alluvial
deposits originating from Sungai Kelantan to the northwest. Figures 4.1 and 4.2
show the general and specific location of the study area.
Study Area
Figure 4.1:
Location of study area
The bathymetry in the nearshore of the study area is generally parallel to the
coastline. The shore profile gradient is gentle and comprises of single or multiple
alongshore bars. The general direction of the littoral drift here is in the northwest
direction (from the Pengkalan Datu rivermouth towards Kuala Besar).
N
35
Kuala Besar
Sungai Pengkalan Datu
rivermouth breakwaters
Pantai Dasar Sabak
(CH2700 to 3100)
KELANTAN
Figure 4.2:
4.3
Kg. Kemerok
(CH1900)
Kg. S.P. Besar, Kg.
Senok (CH-400 to 1400)
Kg. Tanjung Kuala
(CH400 to 00)
Close-up of Study Area from Kg. Pantai Dasar Sabak to Kg. Senok
Environmental and Climatic Conditions
The northeast monsoon produces the strongest winds in this area with speeds
as high as 35 m/s. Nonetheless, these winds are gusty and with low duration. The
southwest monsoon produces milder wind conditions with maximum speeds of 14
m/s. The tide along the study coastline is diurnal with a maximum range of 1.77 m
based on the tidal heights at Geting from the tide tables (Royal Malaysian Navy,
2005).
Fetch lengths affecting this coastline extend up to 1480 km into the South
China Sea and 660 km into the Gulf of Siam. Based on these fetch lengths, offshore
wave heights established through wave hindcasting in the National Coastal Erosion
Study (Unit Perancang Ekonomi, 1985) range from 3.6 m to 5.3 m.
36
4.4
Data Sets
The data available for the study comprises the following:
•
profile survey data
•
bathymetric data
•
wave data
•
tidal data
•
bed sediment (from grab samples)
The profile survey data was used to establish the depth of closure by
analysing the variation in elevation change. The wave, tidal, sediment and
bathymetric data was used as input into a numerical model to establish the local
wave heights and periods that were subsequently used in the depth of closure
equations.
4.5
Beach Profile Survey
Three sets of beach profile survey data taken in 1998, 1999 and 2000 were
initially chosen for this study.
An additional set from the “Detailed Design for
Coastal Protection of Pantai Sabak” in 2004 completes the survey data required for
the analysis. These surveys were undertaken using the conventional survey
technique: profile measurements were taken using a combination of land-based
topographical survey and hydrographic survey techniques. Measurements up to
MLW were taken using total stations and staff-mounted prisms. Beyond MLW,
depth measurements were taken using boat-mounted, dual frequency echo sounders.
Echo-sounders were calibrated prior to and after each survey session. The accepted
accuracy of plotted surveys using this technique is 30 cm. A common problem with
this conventional survey method however is at and just beyond MLW where the
water is often too deep for land survey methods but still too shallow for survey boats.
37
At this location, due to turbulence caused by breaking waves, excessive vessel
movements make it difficult to survey accurately.
The dates of the surveys are listed below:
i. Survey #1: 3rd October to 14th October 1998
ii. Survey #2: 4th May to 27th May, 1999
iii. Survey #3: 20th May to 31st May 2000
iv. Survey #4: 1st June to 30th July 2004
4.5.1
Survey #1 - 1998
The first of three monitoring surveys was conducted at Pantai Sabak from 3rd
to 14th October 1998 and established the control points and baseline for subsequent
surveys in 1999 and 2000.
This survey was completed prior to the onset of the
northeast monsoon that typically produces the highest waves on the east coast of
Peninsular Malaysia.
The survey straddled the Sungai Pangkalan Datu Breakwaters
and covered a shoreline length of 5.1 km southwards and 6.1 km northwards from
the breakwaters. The cross-shore profiling survey extended seawards to a depth of
about 8 to 9 meters LSD for the northern section and 10 meters LSD for the southern
section.
4.5.2
Survey #2 - 1999
The second survey dataset was obtained from a survey conducted between 4th
and 27th May, 1999.
east coast.
This coincided with the end of the northeast monsoon in the
The bathymetric survey extended seawards to the 10 meter contour.
The shoreline length covered by this survey was similar to that covered in the permonsoon survey (survey #1).
38
4.5.3
Survey #3 - 2000
The third survey dataset was obtained from a survey conducted from 20th
May to 31st May 2000). Some difficulties were encountered with the data from this
survey since there were no x-y coordinates recorded for each point along the profile
line.
The documentation nevertheless referred the chainage to the temporary
benchmarks established by the 1998 and 1999 surveys.
4.5.4
Survey #4 – 2004
Between 2000 and 2004, serious erosion had occurred along the study
shoreline causing a shoreline retreat of at least 20 meters. The fourth survey in this
dataset conducted from 1st June to 30th July 2004 was based on an entirely new
baseline. Original profile lines produced by this survey did not coincide with those
established in the 1998 survey. Hence, the profile lines had to be re-created from the
2004 survey data points. The software Mike InfoCoast which automates profile line
creation from 3-dimensional survey data (x-y coordinates and z-elevation) was used
to extract the 2004 profile lines based on the starting and ending points of the 1998
and 1999 survey.
4.5.5
Survey Data Selection
The survey data obtained at Pantai Sabak under the DID monitoring survey
conducted in 1998, 1999 and 2000 covered a distance of 11.2 km and produced a
total of 29 profile lines. The surveys began at Ch.00 which is next to the northern
arm of the Sungai Pengkalan Datu breakwater to Ch.6100 at Pantai Cahaya Bulan.
From Ch.00 to Ch.2300, profiles were measured at intervals of 200 meters. The
shoreline stretch between Ch.3100 and Ch.00 generally experienced the worse
39
erosion. From Ch.2300 to Ch.3100, three profiles were captured at intervals of 400
meters. The surveys also extended southwards from the breakwaters to Ch. -5100 at
intervals of 400 meters. The chainages with the most data were noted and following
the starting and ending coordinates of the 1998 and 1999 dataset, new profile data
was generated from the 2004 survey.
In the final analysis,
profiles from 13
chainages as shown in Table 4.1 were selected.
Chainage basepoint
wavebuoy
Figure 4.3: Profile lines at the study area
Based on the data set, three consecutive years of profile survey data were
captured for thirteen profiles while only the baseline survey was done for 15 profiles.
Two surveys, one each in 1998 and 1999, were recorded for Ch.6100.
From the
above, annual depths of closure can be determined from the 13 profiles that had three
survey datasets. Those with less were ignored in this study.
Table 4.2 shows the
starting and ending points of the selected survey datasets and the profile lines are
illustrated in Figure 4.3. It can be seen that the seaward limits of the survey lie at
depths ranging from -8.0 m LSD to -12.0 m LSD.
40
Table 4.1: Profile Survey Data Register
No. Chainage
1 CH-400
1998
Data Availability
1999
2000
2004
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
12 CH00
√
√
√
√
13
14
15
16
17
18
CH200
CH400
CH600
CH800
CH1000
CH1200
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
19 CH1400
√
20 CH1500
21 CH1700
22 CH1900
√
√
√
√
√
√
√
√
√
23 CH2100
√
24
25
26
27
28
29
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
2
3
4
5
6
7
8
9
10
11
CH-900
CH-1400
CH-1900
CH-2400
CH-2900
CH-3400
CH-3900
CH-4400
CH-4900
CH-5100
CH2300
CH2700
CH3100
CH4100
CH5100
CH6100
√
Notes
4 years; at southern
breakwater
4 years
4 years
1 year
1 year
1 year
1 year
1 year
1 year
1 year
1 year
4 years; at northern
breakwater
4 years
4 years
1 year
4 years
1 year
4 years
1 year; Surau Insaniah,
Kg. Kemerok
4 years
1 year
4 years
1 year; bend at Sungai
Raja Gali
4 years
4 years
4 years
1 year
1 year
2 years
41
Table 4.2: Starting and ending points of selected survey dataset (13 profile lines) off
Pantai Sabak, Kelantan
Profile Start Point
No. Chainage (Cassini)
1
2
3
4
5
6
7
8
9
10
11
12
13
CH00
CH200
CH400
CH800
CH1200
CH1500
CH1900
CH2300
CH2700
CH3100
CH-400
CH-900
CH-1400
Depth at
profile end
(m)
Profile End Point
(Cassini)
Easting
Northing
Easting
Northing
18259. 93
18111. 50
17947. 90
17658. 80
17364. 62
17124. 31
16780. 26
16430. 05
16092. 04
15709. 49
18614. 95
18991. 55
19280. 08
30046. 62
30182. 11
30300. 59
30578. 63
30853. 18
31032. 77
31239. 08
31440. 15
31607. 06
31726. 16
30036. 20
29689. 44
29282. 12
20112. 40
19967. 30
19805. 10
19523. 60
19176. 70
18915. 80
18772. 40
18457. 60
16873. 10
16507. 60
21568. 30
22048. 50
22513. 70
32534. 90
32658. 20
32787. 30
33087. 50
33261. 90
33432. 30
33922. 00
34152. 30
33678. 50
33862. 90
32103. 40
31847. 90
31547. 30
-9. 75
-9. 62
-9. 71
-10. 27
-10. 14
-10. 31
-11. 65
-11. 66
-8. 27
-8. 53
-11. 04
-10. 98
-11. 54
The three survey datasets made available for this research enables a
comparison only for a single erosional event and a three-year temporal condition.
The period from October 1998 to April 1999 coincides with the northeast monsoon
in the east coast of Malaysia within which the severest wind and wave conditions
have been known to occur. Most major erosion incidents in the study area have
been associated with the northeast monsoon. The 12-month period between surveys
#2 and #3 that is from May 1999 to May 2000 covers both the typically swelldominated and accretional south west monsoon (May to September) and the wavedominated erosive northeast monsoon. The final data set obtained in 2004 allows an
examination of depths of closure over a period of six years.
presented in Appendix A.
The survey data is
42
4.5.6
Survey Data Filtering
Profile survey data from 1998, 1999 and 2000 in digital format were
compiled based on their respective survey chainage. The raw data was then checked
for abnormalities and errors. For consistency, the profile data for each chainage was
reproduced at seaward intervals of 50 meters up to approximately 3 km offshore
based on the start points and end points shown in Table 4.2.
After analysis, the
survey provided 13 cross-shore profiles for the three years of survey.
From
hydrographic sounding data, the depth elevation data were reproduced for specific
intervals by linear interpolation. Minimal smoothing was done on the 2004 dataset
using the moving average method. The 2004 coastline is at least 20 meters behind the
2000 coastline hence it must be noted that the zero position in the profile plots for the
2004 dataset does not necessarily lie on dry beach.
4.6
Sediment Data
Bed samples were successfully collected along 11 profile survey lines
corresponding to the locations of the 2 m, 5 m and 8 m to 10 m depth contours.
These samples were taken during the 1998, 1999 and 2004 survey. Grain size
analysis was conducted on these samples according to BS1377 and plotted.
Hydrometer analysis was not conducted hence, graphical plots did not capture
particle sizes of less than 0. 063 mm (the lower limit for fine sand).
From the 1998 and 1999 survey, the grain size of sediments sampled at
depths from 2 m to 10 m ranged from 0.06 mm to 1.75 mm with a mean of 0.5 mm.
Additonal samples were taken concurrent with the 2004 survey at depths of 4 m to 11
m. These provided a material d50 range of 0.07 mm to 0.7 mm and averaged at 0.3
mm. The summary of sediment data from the study area is shown in Appendix C.
Typically, beach sediments are expected to be naturally sorted with the coarser
sediments being deposited on the upper parts of the beach while finer sediments get
43
deposited further seawards. The study area data however shows that on the average,
coarser sediments are located offshore for the 1999 and 2004 data as shown in Figure
4.4.
Figures 4.5 and 4.6 illustrate the sediment distribution trends of relevant
profiles where data was available.
Sediment Distribution at Pantai Sabak
1.6
1.4
1.2
1
1998
1999
2004
0.8
0.6
0.4
0.2
0
0
2
4
6
8
10
12
Depth, m (approximate)
Figure 4.4: Distribution of sediments along Pantai Sabak 1998, 1999 and 2004 (d50
averaged across all chainages)
Distribution of Bed Sediments at Pantai
Sabak
2
1.8
1.6
Ch.1900 1998
Ch.1200 1998
Ch.00 1998
Ch.-400 1998
Ch.00 1999
Ch.1900 1999
Ch.-400 1999
Ch.1200 1999
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
2
4
6
8
Depth, m (approximate)
Figure 4.5: Distribution of bed sediments along Pantai Sabak 1998-1999. Negative
chainages are south of the breakwater
44
Sediment distribution at Pantai Sabak 2004
0.8
0.7
0.6
North of breakwater 1
North of breakwater 2
At breakwater area 1
At breakwater area 2
South of breakwater 1
South of breakwater 2
0.5
0.4
0.3
0.2
0.1
0
0
2
4
6
8
10
12
Depth, m (approximate)
Figure 4.6: Distribution of bed sediments along Pantai Sabak 2004
4.7
Wave
Earlier studies and reports on Kelantan utilised the SSMO wave data which
was the only data available at the time. Wave data used in this study was obtained
from the United Kingdom Meteorological Office (UKMO). The UKMO dataset is
produced from a Global Wave Model which analysed fields of wind and 1dimensional spectra which represents the energy within each spectral band and the
mean direction for that band.
The data is archived at 6-hour intervals in a spatial
resolution of approximately 60 km (grid spacing). The model assumes that depth is
fixed at 200 m with grid points in latitude and longitude. The model is depthdependent and includes shallow water physics, namely bottom friction, refraction
and shoaling. Output at each time-step consists of wind speed, direction and the
conventional integrated variables derived from the spectrum – the significant wave
height, period and direction for both wind-sea and swell together with the resultant
height and period.
The wind data is taken from the lowest level of the Atmospheric Model and
represent conditions approximately 20 meters above mean sea level. The UKMO
data documentation is presented in Appendix B.
45
4.7.1
UKMO Design Wave Analysis
The UKMO data procured for this study was referred to a single point
approximately 70 km offshore in the South China Sea with coordinates 6.39o N 102.
92o E as illustrated in Figure 4.7. A total of 8500 records were examined beginning
from 28th May, 1999 to 1st January 2005.
From this population, 7459 records
coincided with the temporal range of the available profile surveys which is 28th May
1999 to 31st July 2004 as can be seen in Figure 4.8. It is noted that the first wave
record is dated 28th May, 1999 which means there are no wave data available to
associate with the 1998-1999 profile change dataset. The water depth at this UKMO
data point is reported as 52 m.
Wavebuoy @ 6.2o N
102.35o E
Study Area
UKMO wave data
point @ 6.39o N
102.92o E
South China Sea
KELANTAN
Distances
TERENGGANU Wavebuoy to UKMO point = 66 km
Wavebuoy to coastline = 3.6 km
Figure 4.7: Location of wavebuoy and UKMO wavedata source relative to
Kelantan coast.
There is limited UKMO ocean wave data in the South China Sea and cost
limitations permitted only a single location dataset to be purchased. The above
location was selected since it is close to the study shoreline and is expected to
represent all waves from the northeast approach window.
46
UKMO waves 1999-2004
3.5
3
Wave height, m
2.5
2
1.5
1
0.5
0
7/24/1998 0:00
12/6/1999 0:00
4/19/2001 0:00
9/1/2002 0:00
1/14/2004 0:00
5/28/2005 0:00
Date-time
Figure 4.8: Offshore Significant Wave Heights at 6.39N 102.92E; 28/05/1999 –
30/07/2004
Although referred to a single geographical coordinate, the UKMO offshore
waves dataset represents a 60 km grid in the ocean model. The offshore waves are
probably conservative since the location is partly sheltered by Indo-China (Vietnam
and Cambodia).
47
Histogram UKMO waves 1999-2004
2500
2295
2280
Frequency
2000
1500
1058
1000
504
500
340
277
247
184
118
73
40
18
13
9
2
1
2.3
2.5
2.7
2.9
3.1
3.3
0
0.3
0.5
0.7
0.9
1.1
1.3
1.5
1.7
1.9
2.1
Wave Height, m
Figure 4.9: Histogram of UKMO waves
The maximum significant wave height from this dataset was 3.3 m
corresponding to a wave period of 6.8 seconds recorded on 22 December 1999.
From the histogram of offshore waves shown in Figure 4.9, the dominant wave
heights are in the 0.5 m to 0.7 m range. The statistics associated with the UKMO
wave dataset are shown in Table 4.3.
Table 4.3: Statistics of UKMO wave dataset
Statistical
parameter
1999-2000
1999-2004
Mean
0.81
0.76
Std. Dev.
0.45
0.4
Median
0.7
0.6
Max
3.3
3.3
Min
0.2
0.2
Figure 4.10 illustrates a plot of wave height against wave period for the
resultant wave. A regression line is then obtained where it is observed that a linear
relationship apparently exists between the two parameters and represented by the
following equation,
48
Y = 0.9526x + 3.5464
(4.1)
Applying the statistical correlation test onto the pairs of wave height and
wave period, the correlation coefficient r between the wave height and the wave
period was found to be 0.744 (R2 is 0.5537). This indicates a moderately strong
positive linear relationship between the offshore significant wave height and wave
period values. From this relationship, it is clear that the larger waves are associated
with longer periods.
Resultant Wave Height vs. Wave Period (1999-2004)
8
7
6
5
4
y = 0.9526x +
3.5464
3
R2 = 0.5537
2
1
0
0
0.5
1
1.5
2
2.5
3
3.5
Wave Height, m
Figure 4.4: Wave Height vs. Wave Period for UKMO offshore wave records 1999
to 2004
The calculation of Dc using Hallermeier’s equation required the significant
wave height exceeded 12 hours in a year equivalent to an exceedance probability of
0.137%. This wave height is determined from a plot of cumulative percentage
against significant wave height as in Figure 4.11. From this graph, the H0.137 wave
was determined to be 2.9 m with a corresponding wave period of 6.3 sec. From the
UKMO dataset, the H0.137 wave was registered on 23 December 1999 at 0600 hours.
For time-dependent Dc, the design wave height would be the significant wave height
exceeded only 12 hours over a period of t years or (100/730t)% of the time (Nichols
et al, 1996). Considering the 5-year period from May 1999 to May 2004, the
49
exceedance probability of this wave is 0.027%. From Figure 4.12, this wave, H0.027,
is 3.13 m with an associated wave period of 6.53 sec. The H0.027 wave actually
occurred on 08/03/2004 (3.13 m) and 22/12/1999 (3.3 m).
Cumulative Percentage vs Offshore Wave Heights 1999-2000
3.5
H0.137 = 2.9 m
Offshore Wave Height, m
3
2.5
2
1.5
1
0.5
0
0.01%
0.10%
1.00%
10.00%
100.00%
Cumulative Percentage
Figure 4.11: H0.137 wave from 1999-2000 UKMO wave data
It was also noted that from the UKMO dataset, the offshore waves reached
2.9 – 3.3 meters on 5 occasions between 1999 and 2004 and all occurred during the
northeast monsoon period.
50
Cumulative Percentage vs Offshore Wave Heights (1999-2004)
3.5
H0.027 = 3.13 m
Offshore Wave Heights
3
2.5
2
1.5
1
0.5
0
0.01%
0.10%
1.00%
10.00%
100.00%
Cumulative Percentage
Figure 4.12: H0.027 wave from 1999-2004 UKMO wave data
4.7.2
Measured Waves
Nearshore wave data was also obtained from a Datawell MKII Directional
Waverider Buoy from 30 June to 13 July 2004 at 30-minute intervals as part of the
2004 data collection campaign. The wave buoy was positioned at the 12 m LSD
depth-contour at coordinates N33957 E19236.3 (Kelantan Cassini) 3.6 km north of
the Sg. Pengkalan Datu breakwaters (refer to Figure 4.4). The recorded wave heights
are as shown in Figure 4.13.
Figure 4.14 is a plot of both the measured waves and the offshore waves from
the UKMO dataset. The peaks in both these wave time-series are seen to coincide
which infers that a relationship exists between the offshore UKMO dataset and the
concurrent recorded nearshore waves. Hence, both datasets could be safely used to
model the wave conditions in this study.
51
MEASURED WAVES
90
80
70
Wave ht (Hs), cm
60
50
40
30
20
10
0
7/2/2004 0:00
7/4/2004 0:00
7/6/2004 0:00
7/8/2004 0:00
7/10/2004 0:00
7/12/2004 0:00
7/14/2004 0:00
Date-time
Figure 4.13: Wave Buoy Measurements at E19236.3 N33957 (Kelantan Cassini) off
Pantai Sabak, Kelantan Coast; 30 June to 13 July 2004.
Wave Heights off Kelantan Coast
measured waves
UKMO offshore waves
0.8
0.7
Wave Height, m
0.6
0.5
0.4
0.3
0.2
0.1
0
02/07/2004
00:00
04/07/2004
00:00
06/07/2004
00:00
08/07/2004
00:00
10/07/2004
00:00
12/07/2004
00:00
14/07/2004
00:00
Date Time
Figure 4.14: Comparison of offshore (UKMO data) and nearshore waves measured
at the -12 m LSD contour
52
4.8
Tidal Heights
Tidal information is necessary to determine the vertical references of depth.
From the 2004 survey, three water level stations were set-up simultaneously at Pantai
Sabak, Sungai Pangkalan Datu and off Pantai Perupuk (see Figure 4.15). Continuous
measurements were taken from 3rd June to 14th July 2004 and the tidal constituents
were extracted.
Tidal heights were then established.
The MLW level is of
importance because it is the reference to depth of closure in the original definition
(Hallermeier, 1981). Water levels have a direct influence on wave refraction and
breaking in the nearshore zone. Larger waves typically occur during the northeast
monsoon when water levels are higher due to greater wind set-up. Department of
Irrigation and Drainage (1993) determined that MSL during the northeast monsoon
period is 0.3 m higher than during the south-west monsoon period.
Kg. Pantai Dasar
Pantai Sabak
Kg. Senok
Sg. Pengkalan Datu
breakwaters
Pantai Perupuk
WL = water level
Wavebuoy = wave station
CM = current meter
Figure 4.15: Location of water level, current and wave stations at study area.
Table 4.4, 4.5 and 4.6 shows the tidal heights established at Pantai Sabak and
Sungai Pangkalan Datu from the 2004 survey. The tidal range along this shoreline
averaged from the three stations is 0.95 m signifying a clearly micro-tidal shoreline
(tide range < 2.0 meters).
Pantai Perupuk (WL3) is located much further south of
53
the study area and considered to be of less influence. Subsequent analysis was done
using only the Pantai Sabak (WL2) and Sungai Pangkalan Datu (WL4) stations
(Appendix D). It can be observed that the MLLW level ranges from -0.56 m to -0.43
m LSD and average at 0.5 m LSD. MHHW was found to range from 0.37 m to 0.45
m LSD and average at 0.44 m. Averaging values between the two stations, MHW for
the study shoreline is calculated to be 0.18 m LSD whilst MLW is -0.36 m LSD (see
Tables 4.7 and 4.8).
Table 4.4: Tidal Levels Along Study Shoreline (meters, LSD)
Tidal Level
H.A.T.
Mean Higher-High
Water
Mean Lower-High
Water
Mean Sea Level
Mean Higher-Low
Water
Mean Lower-Low
Water
L.A.T.
Sungai
Pengkalan Datu
Pantai
Perupuk
0.88
0.87
1.06
0.37
0.45
0.51
-0.11
-0.16
0.00
-0.04
-0.01
-0.07
-0.30
-0.16
-0.20
-0.56
-0.91
-0.43
-0.80
-0.53
-0.97
Pantai
Sabak
Table 4.5: Mean Low Water (meters, LSD)
Station
Pantai
Sabak
Pengkalan
Datu
Average
MHLW
MLLW
MLW
-0.30
-0.56
-0.43
-0.16
-0.43
-0.30
-0.22
-0.51
-0.36
Table 4.6: Mean High Water (meters, LSD)
Station
Pantai
Sabak
Pengkalan
Datu
Average
MLHW
MHHW
MHW
-0.11
0.37
0.13
0.00
0.45
0.23
-0.04
0.44
0.18
54
Table 4.7: Difference between MSL and MLW at Study Coastline
Station
MSL
MLW
Pantai Sabak
-0.16
-0.43
0.27
Pengkalan Datu
-0.04
-0.30
0.26
-0.10
-0.36
0.26
Average
MSL - MLW
Table 4.8: Difference between MSL and MHW at Study Coastline
4.9
Station
MHW
MSL
MHW - MSL
Pantai Sabak
Pengkalan Datu
Average
0.13
0.23
0.2
-0.16
-0.04
-0.09
0.29
0.27
0.28
Wind
Wind data from the UKMO dataset is associated with the same point as the
wave data and is the result extracted from an atmospheric model in about the same
way as the waves (see description in Appendix B). Hence, the wind speeds actually
represent the wind speed inside the wave model at a height of 20 m above sea level.
The records indicate an average wind speed of 7 knots (3.6 m/s) with a maximum of
25 knots (12.86 m/s) with the strongest winds predominantly coming from the 45 –
120 degree sector. Based on the Beaufort scale, the strongest wind can be described
as a moderate breeze. The wind rose is shown in Figure 4.16.
55
Radial units
are in %
occurrence
Knots
Figure 4.16: Wind rose representing UKMO offshore data point (20 m above MSL)
at coordinates 6.39o N 102. 92o E
4.10
Summary
The data set obtained for this study is limited to beach and nearshore profile
surveys with an accepted accuracy of 30 cm.
The three surveys completed in
October 1998, May 1999 and May 2000 can be used to determine the variation of
depth of closure for two erosional events between October 1998 and May 1999, and
May 1999 to May 2000. When the 2004 survey is included, the depth of closure for
a temporal scale of 6 years (1998 to 2004) where changes in the depth of closure due
to an integrated effect of erosional and accretional events and can be determined.
However, to directly compare calculated Dc using Hallermeier’s equation with
56
measured Dc from survey data, the period of surveys and the wave dataset selected
must be concurrent. Therefore, the dataset from 1999 to 2004 will be used in the
analysis.
The UKMO dataset was used exclusively in this analysis. Based on a global
hind-cast model, this time-series offshore dataset provides the complete wave
parameters (wave height, period and direction) necessary for input into the wave
model to generate the nearshore wave parameters needed to predict the depth of
closure. The UKMO dataset also included wind speeds from the same point as the
waves.
From the 1998 and 1999 surveys, sediment size d50 at the study shoreline
ranged from 0.06 mm to 1.75 mm with a mean of 0.5 mm. This grain size is slightly
larger than the d50 range for valid application of Hallermeier’s equation which is
between 0.16 mm to 0.42 mm. However, the mean d50 for the 2004 samples is 0.3
mm which falls within the accepted range. The d50 for the sediments in the study
area can be summarised as being marginally higher than the accepted range. How
they affect the results of this study will eventually become evident.
The analysis also determined MLW at -0.36 m LSD which will be significant
in the subsequent calculations of Dc.
Since Hallermeier’s equation refers the
calculated Dc to MLW and all surveys were referred to LSD, this difference must
therefore be adjusted before comparisons are made between the two.
CHAPTER 5
NUMERICAL MODELLING
5.1
Introduction
One of the terms in the Hallermeier equation represents the wave condition at
the depth of closure.
To establish the nearshore wave climate, the UKMO offshore
wave data for the periods 1999-2004 has been transformed to 13 points along the 10m depth contour nearest to the offshore endpoints of the 13 cross-sections analysed
in this study. The significant wave height Hs exceeded 12 hours in a year or H0.137
has been determined as the minimum wave height that causes significant movement
in bed sediments. This wave and its corresponding wave period, is required to
compute the annual Dc using the empirical equations by Hallermeier. For the 5-year
Dc, the 12-hour exceedence Hs over the 5 years or H0.027 is used.
This chapter explains the wave refraction modelling that was conducted to
produce the nearshore wave parameters.
5.2
Model Description
A wave refraction model is a static wind-wave model which calculates the
wave height and direction at each grid point within the model grid lay-out based on a
set of input wave parameters entered at one end of the grid. The software Mike21NSW was used to model the wave refraction in this study. The Mike21 NSW is a
58
stationary spectral wave model that handles wave-breaking phenomena including
shoaling, refraction and energy dissipation due to bottom friction. It however, does
not simulate diffraction, reflection or wave-wave interaction effects. Since there are
no large islands off the Kelantan coast, there is no risk of the model diffracting
waves around islands.
Mike21 NSW requires that the offshore wave parameters be entered at the
left water boundary of the model. Wave directions are referred to in degrees from
north. Initially working with the offshore waves from N330o to N120o, it was
necessary to create up to 6 model layouts in order to transform offshore waves into
the nearshore area and produce the required wave heights and periods to calculate the
depth of closure. The overall description of the modelling is shown in Figure 5.1
Figure 5.1: Orientation of rectangle model layout for the input (offshore) wave
approach conditions N330o, N0o, N30o, N60o, N90o and N120o.
59
Subsequently, only the waves approaching from N0o to N120o were
modelled. Due to the orientation of the study shoreline, it is assumed that N330o
waves would not be critical since it would have been refracted at least 90o to reach
the study area. The model study therefore focuses on the waves approaching from
the northeast sector.
5.3
Numerical Modelling
The numerical modelling work is described below.
5.3.1
Model Area and Orientation
The Mike21-NSW module uses a calculation grid where the spacing along
the x-axis is 4 times that of the y-axis. The offshore wave parameters are entered at
the left (open) boundary. The module’s numerical scheme also requires that the
maximum deviation between the propagating waves and the x-axis to be around 4060 degrees. Hence, five wave approach windows were created for N0o, N30o, N60o,
N90o and N120o approach directions (see Appendix E). Offshore bathymetries were
found to be fairly parallel to the coastline and no islands are present offshore of
Kelantan.
5.3.2
Wave Breaking Conditions
Mike21-NSW applies wave breaking based on the formulation by Battjes and
Janssen (1978) whereby the rate of energy dissipation is expressed by:
60
dE
=
dt
- α_ . Qb . ω . Hm2
8π
and,
1 - Qb
=
- Hrms 2
ln (Qb)
Hm
where,
E
total energy
ω
frequency
Hrms
root-mean square of Hm
Hm
maximum allowable wave height
Qb
fraction of breaking waves
α
adjustable constant
Hm
=
γ1 . k -1 . tanh (γ2 . kd/ γ1)
where,
k
wave number
d
water depth
γ1
wave breaking parameter that controls steepness condition
γ2
wave breaking parameter that controls limiting water depth
The user is able to directly control the parameters γ1, γ2 and α. The model
also includes bottom dissipation which is controlled by the Nikuradse’s roughness
parameter.
61
5.3.3
Calibration
Numerical wave models need to be calibrated against actual wave
measurements whenever data is available. In this study, the only measured wave
data available was captured by a solitary wave buoy installed at a depth of -12 m
LSD. This wave measurement was conducted over a period of 14 days in July 2004
(see 4.7.2). It is important to note that this measurement period does not coincide
with the north-east monsoon within which the H0.137 and H0.027 waves occur. It is
therefore not appropriate to calibrate the wave model using this dataset. Nonetheless,
the following exercise was carried out in order to demonstrate how wave Mike21
NSW transforms the offshore waves.
For this purpose, offshore wave heights from the UKMO data point
corresponding to the period 3/7/2004 to 13/7/2004 were separated into their
respective directions and averaged.
The approach between N345o and N15o
therefore represents N0o (north) and similar grouping was carried out for the rest of
the dataset.
Upon analysis, it was found that the selected wave dataset contained
waves from N0o, N90o, N120o and N150o only. Since wave measurements were
obtained during the southwest monsoon in July 2004, the northeasters were low in
height. The sea was dominated by waves from the N120o and N150o.
Input data was determined from an analysis of offshore waves corresponding
in time with the available wave buoy measurements. The mean wave height or Hm0
and corresponding wave period for N0o, N90o and N120o were calculated from the
UKMO offshore data.
The N150o
waves were not considered in the analysis
because these waves are essentially propagating parallel and away from the Kelantan
coast.
Typically, Mike21NSW can be calibrated using a single parameter which is
the Nikuradse’s roughness parameter that controls bottom dissipation. Other values
such as wave breaking parameters are usually kept at model default values.
62
The input parameters for Mike21-NSW module as used in the attempted
calibration process were as follows:
•
Model water level: the water level records along the length of the
study shoreline indicate that the mean water level during the period of
calibration was calculated at -0.07 m LSD (see Figure 5.3). A model
water level of 0 m LSD was used during the calibration of the model;
•
Bottom dissipation:
this
is
represented
by
the
Nikuradse’s
roughness parameter kN. DHI recommends that a kN value equal to
2.5 times d50 (of the bed sediments) is used for bottom dissipation.
Based on a mean d50 of 0.7 mm at depths greater than -10 m ACD
(see Appendix C), the kN value is calculated to be 0.002 m. The effect
of bottom dissipation on mean wave period is included;
•
Wave breaking parameters were kept at constant (default) values: γ1 =
1.0, γ2 = 0.8 and α = 1.0. The effect of wave breaking on mean wave
period was excluded since the area of concern is before the surf zone.
N90-K02
N90-K0002
Bathymetry
15
0.55
0.5
10
0.45
0.35
0
0.3
-5
0.25
-10
0.2
0.15
Bathymetry [m]
5
0.4
-15
0.1
-20
0.05
0
-25
0
25
50
75
100
125
150
175
200
225
250
275
300
Grid Spacing [40 meter]
Figure 5.2: Sensitivity of kN parameter and location of breaking wave based
on waves in July
63
A sensitivity analysis was done on the kN value by comparing the wave
heights produced by kN = 0.002 m and kN = 0.2 m. From Figure 5.2, the following
was observed for the waves in July (south-west monsoon):
•
Offshore waves decrease significantly at a depth immediately after
-10 m ACD indicating that this is the start of the surf zone;
•
there is no significant change to the wave heights prior to -10 m ACD
when different kN values are used.
The results of the model runs based on kN of 0.002 m are shown in Table 5.1,
Figure 5.4 and Figure 5.5. Based on the analysis above, the nearshore wave
extraction point from the wave model was located at the -10 m ACD contour to
capture the non-breaking condition.
Table 5.1: Results of wave model calibration
Direction
Model input
(Offshore)
Model output
(nearshore)
Measured
(nearshore)
Significant
Wave Height
& Mean Wave Period
Hm0 (m)
Tm (sec)
Hm0 (m)
Tm (sec)
Direction
Hs (m) mean
Tz (sec) mean
Direction
N0o
N90o
N120o
0.4
4.1
0.39
4.1
0.37
0.31
4.54
358.6
0.50
4
0.48
4
87.9
0.42
6.55
90.5
0.45
4.1
0.36
4.1
110
0.28
3.36
197.25
64
Tidal Heights at Pantai Sabak
1.2
1
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1
6/30/04 0:00
7/2/04 0:00
7/4/04 0:00
7/6/04 0:00
7/8/04 0:00
7/10/04 0:00
7/12/04 0:00
7/14/04 0:00
Date-time
Figure 5.3: Water level measurements at Pantai Sabak during calibration period
Predicted Wave Height, m
Wave Model Calibration:
Measured vs. Model-predicted Wave heights
0.60
0.50
0.40
y = 1.1798x + 0.0098
2
R = 0.992
0.30
0.20
0.10
0.00
0.00
0.10
0.20
0.30
0.40
0.50
Measured Wave Height, m
Figure 5.4: Wave Model Calibration – Wave Heights (for offshore waves from 0 to
120 degrees)
65
Predicted Wave Direction,
degrees
Wave Model Calibration: Measured vs. Model-predicted
Wave Directions
400
350
300
250
200
150
100
50
0
y = 1.001x + 2.5823
2
R = 0.9984
0
50
100
150
200
250
300
350
400
Measured Wave Direction, degrees
Figure 5.5: Wave Model Calibration – Wave Directions (for offshore waves from 0
to 120 degrees)
From the graph plotted in Figure 5.4, the wave heights from the model were
found to be slightly higher than the measured wave data for the corresponding
period.
There were no waves from the N30o and N60o directions during the
particular period of calibration therefore the analysis were based on results using the
N0o, N90o and N120o offshore wave approach angles. The model was found to be
generally over-predicting the measured wave heights at the calibration point by about
20%. It is noted that the measured waves are given as Hs which is assumed to be
equivalent to H1/3 and by definition smaller than H0.137. According to US Army Corps
of Engineers (2003): (i) Hm0 is a good estimate of Hs in deep water (ii) near breaking,
Hs is 1.1 Hm0 and (iii) Hs can be 10% lower than Hm0 after breaking. Since, the
measured wave heights from the wave recorder in section 4.7.2 are given in Hs, and
the model-predicted Hm0 values are larger than Hs, the model predicted waves would
actually be closer to H0.137. Hence, it is assumed that the wave heights at -10 m ACD
predicted by the model, following this calibration, would be a reasonable
approximation of the transformed offshore H0.137 and H0.027 waves.
It is also observed that the predominant wind direction is blowing from the
110 degrees to 157 degrees sector during the calibration period. Including the wind
forcings would therefore not contribute to a more accurate model of the wave
66
propagating towards the Kelantan coast.
Furthermore, the runs without wind
forcings have already overpredicted the Hs.
5.3.4
Prediction of Nearshore Waves from Wave Model
5.3.4.1 Input Data
In order to predict the nearshore wave, the input wave at the offshore
boundary must correspond to the accepted wave definitions for calculation of the Dc .
For the annual Dc , the wave height exceeded for only 12 hours in a year or H0.137
(Hallermeier, 1981; Nichols et al, 1998a) was determined using statistical analysis.
For the temporal depth of closure or Dl , the wave height exceedence percentage
equivalent to 100/730t where t equals the period of data in years was used. From the
analysis of UKMO wave data (see 4.7.1) the H0.137 wave (for the purpose of annual
depth of closure calculations) was determined to be 2.9 m with a corresponding
period (Tm) of 6.3 seconds. For the 5-year wave record from 1999-2004 (100/730t,
where t = 5), the H0.027 wave was calculated to be 3.13 m with a wave period of 6.54
seconds. A matrix of offshore wave data was prepared for the model for approaches
from N0o, N30o, N60o, N90o and N120o. Model water level was set at 0.4 m to
account for storm surges during the monsoon. Following completion of the model
runs for the parameter sets in the matrix, wave heights were extracted from the model
nearshore area at 13 locations along the 10 m ACD depth contour nearest to the
offshore limit of each profile line. The coordinates of these offshore points are
shown in Table 5.2.
67
Table 5.2: Location of Offshore Points in Model Grid for Extraction of Wave
Parameters
Profile End Point (Geographical Coordinates)
o
6
6o
6o
6o
6o
6o
6o
6o
6o
6o
6o
6o
6o
11’
11’
11’
11’
11’
11’
12’
12’
11’
12’
11’
10’
10’
Latitude
17.1742”
21.1898”
25.3945”
35.1705”
40.8520”
46.4016”
2.3454”
9.8459”
54.4382”
0.4449”
3.11”
54.7863”
44.9948”
o
102
102o
102o
102o
102o
102o
102o
102o
102o
102o
102o
102o
102o
21’
21’
21’
21’
21’
20’
20’
20’
19’
19’
22’
22’
22’
Longitude
32.5251”
27.8063”
22.5314”
1 3.3778”
2.0953”
53.61”
48.9503”
38.7123”
47.1632”
35.2752”
19.8794”
35.4967”
50.6253”
Figure 5.6: Location of extraction points in wave model
68
5.3.4.2 Wave Modelling Results
The results of the wave modelling are given in Tables 5.3 and 5.4 based on
the respective offshore extreme wave conditions H0.137 and H0.027.
Figures 5.7
through 5.16 illustrate the refraction patterns from the wave model using the H0.137
and H0.027. The series of dots represent points where nearshore wave parameters
were extracted which are near the 10 m ACD-depth contour (see Figure 5.6). The
transformed wave heights predicted at nearshore were found to be generally smaller
than the offshore waves. Another significant finding is that the offshore waves close
to the seaward limits of profiles CH.00 to CH.3100 were slightly higher than those at
CH.-400 to CH.-900 which are to the southeast of CH.00. For the H0.137 condition,
predicted near shore wave heights range from 1.61 m to 2.61 m.
The model
predicted higher waves for the H0.027 condition and these range from 1.77 m to 2.81
m.
In terms of maximum wave heights, the model indicated that these were
produced by offshore waves from the N30o.
Study Area
Kilometers
Figure 5.7: Wave Refraction Diagram; H0.137 = 2.9, Tm = 6.3 sec; North approach.
69
Study Area
Figure 5.8: Wave Refraction Diagram; H0.137 = 2.9, Tm = 6.3 secs; N30o approach.
Study Area
Figure 5.9: Wave Refraction Diagram; H0.137 = 2.9 m, Tm = 6.3 secs; N60o
approach.
70
Study Area
Figure 5.10: Wave Refraction Diagram; H0.137 = 2.9 m, Tm = 6.3 secs; N90o
approach.
Study Area
Figure 5.11: Wave Refraction Diagram; H0.137 = 2.9 m, Tm = 6.3 secs; N120o
approach.
71
Study Area
Kilometers
Figure 5.12: Wave Refraction Diagram; H0.027 = 3.13 m, Tm = 6.54 secs; North
approach.
Study Area
Figure 5.13: Wave Refraction Diagram; H0.027 = 3.13 m, Tm = 6.54 secs; N30o
approach.
72
Study Area
Figure 5.14: Wave Refraction Diagram; H0.027 = 3.13 m, Tm = 6.54 secs; N60o
approach.
Study Area
Figure 5.15: Wave Refraction Diagram; H0.027 = 3.13 m, Tm = 6.54 secs; N90o
approach.
73
Study Area
Figure 5.16: Wave Refraction Diagram; H0.027 = 3.13 m, Tm = 6.54 secs; N120o
approach.
Table 5.3: Predicted wave heights at 10 m depth based on offshore wave of H0.137 = 2.9 m and Tm = 6.3 secs
WAVE
DIRECTION
CH2700
2.55
6.09
4.05
CH2300
2.52
6.08
4.59
CH1900
2.52
6.07
5.10
CH1500
2.52
6.07
4.56
CH1200
2.52
6.07
4.15
CH800
2.53
6.06
4.20
CH400
2.53
6.06
3.52
CH200
2.54
6.05
3.48
CH00
2.56
6.06
3.38
CH
-400
2.53
6.04
4.26
CH
-900
2.54
6.03
4.44
CH
-1400
2.53
6.03
4.46
North
Hm0 (m)
Tm (s)
MWD (deg)
CH3100
2.58
6.10
3.87
N30
Hm0 (m)
Tm (s)
MWD (deg)
2.58
6.09
28.37
2.58
6.08
28.47
2.59
6.07
28.60
2.61
6.06
29.10
2.58
6.06
28.39
2.58
6.06
28.12
2.59
6.05
28.20
2.60
6.05
27.84
2.60
6.05
27.90
2.61
6.05
28.11
2.59
6.06
28.74
2.55
6.03
28.64
2.53
6.02
28.44
N60
Hm0 (m)
Tm (s)
MWD (deg)
2.50
6.03
52.21
2.53
6.03
52.54
2.52
6.02
52.72
2.50
6.01
52.99
2.48
6.01
52.25
2.50
6.01
52.32
2.49
6.00
52.49
2.54
6.00
52.70
2.54
5.99
52.62
2.55
6.00
53.10
2.55
5.99
52.87
2.52
5.99
53.17
2.53
5.98
53.16
N90
Hm0 (m)
Tm (s)
MWD (deg)
2.16
5.93
73.65
2.17
5.93
73.96
2.18
5.92
74.07
2.15
5.91
73.53
2.19
5.91
72.70
2.20
5.91
73.16
2.22
5.90
73.14
2.21
5.90
73.40
2.19
5.90
73.00
2.19
5.90
73.55
2.23
5.89
74.57
2.23
5.89
74.94
2.28
5.88
75.32
N120
Hm0 (m)
Tm (s)
MWD (deg)
1.61
5.72
90.15
1.62
5.71
90.68
1.64
5.70
91.34
1.62
5.68
90.54
1.66
5.67
90.15
1.68
5.67
91.00
1.70
5.66
91.35
1.74
5.65
92.66
1.75
5.64
92.51
1.78
5.65
93.04
1.92
5.63
95.06
1.97
5.63
95.75
2.02
5.62
96.48
2.29
5.97
2.58
2.29
5.97
2.58
2.29
5.96
2.59
2.28
5.94
2.61
2.29
5.94
2.58
2.30
5.94
2.58
2.31
5.94
2.59
2.32
5.93
2.60
2.32
5.93
2.60
2.34
5.93
2.61
2.36
5.92
2.59
2.36
5.91
2.55
2.38
5.90
2.53
6.09
6.08
6.07
6.06
6.06
6.06
6.05
6.05
6.05
6.05
6.06
6.03
6.03
Mean Wave Ht.
Mean Wave Period
Max Hm0
Corresponding
Tm
74
Table 5.4 Predicted Wave Heights at 10 m depth based on offshore wave of H0.027 = 3.13 m and Tm = 6.54 secs
WAVE
DIRECTION
North
Hm0 (m)
Tm (s)
MWD (deg)
CH3100
2.78
6.28
4.09
CH2700
2.74
6.28
4.27
CH2300
2.72
6.26
4.83
CH1900
2.71
6.25
5.35
CH1500
2.71
6.25
4.79
CH1200
2.71
6.25
4.36
CH800
2.72
6.24
4.39
CH400
2.73
6.24
3.69
CH200
2.73
6.24
3.64
CH00
2.75
6.24
3.55
CH 400
2.72
6.22
4.49
CH900
2.73
6.21
4.67
CH1400
2.72
6.20
4.69
N30
Hm0 (m)
Tm (s)
MWD (deg)
2.78
6.27
28.17
2.78
6.26
28.27
2.79
6.25
28.40
2.81
6.24
28.93
2.78
6.24
28.20
2.78
6.24
27.92
2.79
6.23
28.00
2.80
6.23
27.62
2.80
6.22
27.69
2.81
6.23
27.91
2.79
6.25
28.57
2.75
6.21
28.49
2.72
6.20
28.28
N60
Hm0 (m)
Tm (s)
MWD (deg)
2.69
6.21
51.62
2.72
6.20
51.98
2.71
6.19
52.16
2.69
6.18
52.45
2.67
6.18
51.69
2.69
6.18
51.76
2.68
6.17
51.92
2.73
6.17
52.16
2.74
6.16
52.10
2.74
6.17
52.61
2.75
6.16
52.37
2.71
6.16
52.67
2.73
6.14
52.64
N90
Hm0 (m)
Tm (s)
MWD (deg)
2.31
6.09
72.81
2.32
6.09
73.12
2.34
6.08
73.22
2.30
6.07
72.69
2.34
6.06
71.80
2.36
6.07
72.27
2.38
6.06
72.26
2.37
6.06
72.49
2.34
6.06
72.06
2.34
6.06
72.62
2.38
6.05
73.64
2.38
6.05
74.01
2.44
6.04
74.41
N120
Hm0 (m)
Tm (s)
MWD (deg)
1.79
5.89
87.69
1.80
5.88
88.24
1.81
5.86
88.98
1.77
5.84
88.33
1.82
5.84
87.94
1.84
5.83
88.80
1.85
5.82
89.17
1.88
5.81
90.54
1.89
5.80
90.44
1.92
5.80
91.00
2.06
5.78
93.17
2.11
5.78
93.92
2.15
5.77
94.66
Mean Hm0
Mean Tm
Max Hm0
2.47
6.15
2.78
2.47
6.14
2.78
2.47
6.13
2.79
2.46
6.11
2.81
2.46
6.11
2.78
2.47
6.11
2.78
2.49
6.11
2.79
2.50
6.10
2.80
2.50
6.10
2.80
2.51
6.10
2.81
2.54
6.09
2.79
2.54
6.08
2.75
2.55
6.07
2.73
Corresponding
Tm
6.27
6.26
6.25
6.24
6.24
6.24
6.23
6.23
6.22
6.23
6.25
6.21
6.14
75
Figure 5.17 illustrates the maximum wave conditions that were produced by
the offshore wave from N30o. It can be observed that there is very slight alongshore
variation in the transformed wave heights. Nonetheless, lower waves are noted at
Ch.-900 and Ch.-1400.
MODEL-PREDICTED MAXIMUM WAVE HEIGHT AT -10 M ACD
H0.137 Wave (1999-2000)
H0.027 Wave (1999-2004)
2.85
2.80
2.75
2.70
2.65
2.60
2.55
2.50
2.45
2.40
2.35
CH3100
CH2700
CH2300
CH1900
CH1500
CH1200
CH800
CH400
CH200
CH00
CH-400
CH-900
CH-1400
Chainage
Figure 5.17: Predicted Maximum Wave Heights at 10-m depth ACD contour along
Pantai Sabak, Kelantan.
In the case of mean wave heights, a more definite pattern has developed as
illustrated in Figure 5.18. The local wave heights decrease as one moves from Ch.1400 to Ch.1200 however the percentage changes are insignificant.
77
MODEL-PREDICTED MEAN WAVE HEIGHTS AT -10M ACD
H0.137 Wave (1999-2000)
H0.027 Wave (1999-2004)
2.60
2.55
2.50
2.45
2.40
2.35
2.30
2.25
2.20
2.15
2.10
CH3100
CH2700
CH2300
CH1900
CH1500
CH1200
CH800
CH400
CH200
CH00
CH-400
CH-900
CH-1400
Chainage
Figure 5.18: Predicted Wave Heights at 10-m depth (ACD) contour along Pantai
Sabak, Kelantan averaged over all directions
5.4
Summary
The purpose of wave modelling is to transform the offshore wave heights to
their nearshore equivalents which will be subsequently applied in the equation to
predict Dc.
The software Mike21-NSW is used for this purpose.
Two major
assumptions at this point in this study are that (i) model-predicted Hm0 is greater than
Hs at the -10 m ACD depth contour and is a good approximation of H0.137 and H0.027
(ii) the kN value of 0.002 m applied for the model which used data from the calmer
conditions and swell-dominated wave climate of the south-west monsoon, is valid for
predicting nearshore wave conditions for the more severe north-east monsoon.
Though not preferred, in the absence of measurements during the northeast monsoon,
this dataset offers the only means of calibrating the wave model. Fundamentally, the
laws applying to shoaling, refraction and breaking incorporated in the model hold for
all meteorological conditions. With the benefit of only a single and limited set of
field data, the attempted calibration conducted in this study succeeded only to
describe that the model overpredicts the inshore wave height by 20% during the
south-west monsoon (July). Refining the calibration using the July dataset would
78
therefore not be beneficial if the runs are to be done for the north-east monsoon. A
validated model using north-east monsoon data would add confidence to the
predicted results.
The UKMO wave data set obtained for this study for the years 1999-2004
corresponds to the periods of surveys available for the analysis of Dc. The 12-hour
per t year exceedence waves essential to the predicted Dc calculations were derived
from the 1999-2000 dataset for the annual condition (H0.137), and the 1999-2004
dataset for the ‘t = 5 years’ case (or H0.027), respectively.
The highest waves were observed to be from N30o.
Two scenarios of
resultant waves were produced from the numerical model – the mean and maximum
transformed wave heights for the H0.137 and H0.027 offshore wave conditions. The
results from the wave modelling indicate that maximum wave heights at -10 m ACD
for the annual or H0.137 condition is 2.61 meters while for the 5 year or H0.027
condition is 2.81 meters.
CHAPTER 6
DETERMINATION OF DEPTHS OF CLOSURE
6.1
Introduction
The depth of closure is a morphological limit of sediment transport which can
be determined in the field from a series of profile data.
In designing beach
nourishment schemes, the depth of closure is an important parameter which signifies
the seaward limit where the beach-fill will move. In the following, the depth of
closure is determined for the purpose of beach-fill design. Determination of the
depth of closure always requires an association with a criteria and time frame. When
considering the depth of closure in relation to beach nourishment projects, it is
important to be able to differentiate between offshore sand transport processes and
the nearshore processes which are most likely to affect the shoreline position or the
beach-fill.
This chapter describes the Dc analysis done on the selected chainages of
periodical survey data based on a chosen criteria and time frames.
The known
methods of analysis, the standard deviation of depth change (SDDC) and fixed depth
change (FDC) method, are both applied for determination of an effective Dc on the
study area and examined against Hallermeier’s predictive formula for selected cases.
6.2
Depth of Closure – Scope and Criteria
6.2.1
Definition
There are two definitions of depth of closure being addressed in the following
discussion. Firstly, Dc is regarded as the seaward limit of foreshore morphological
changes.
Hence, this would be the furthest point from the shoreline where
significant bed elevation changes occur which in turn is linked to the highest prebreaking wave conditions. Secondly, considering that this analysis is to improve
beach-fill design, the definition by Kraus et al (1998) whereby the Dc is the most
landward depth seawards of which, there is no significant change in bottom elevation
and no significant net sediment transport between the nearshore and the offshore,
also applies. This infers a closure point nearest to the shoreline that will serve as a
limit for beach-fill placement.
6.2.1.1 Event-dependent Dc
Event-dependent Dc
in this analysis attempts at determining an event-
dependent Dc (Nicholls et al, 1998) where the event is the northeast monsoon.
Generally, shoreline erosion occurs along the east coast of Peninsular Malaysia
during the northeast monsoon which is from November to April (Unit Perancang
Ekonomi, 1985). A monsoon Dc can be determined from the changes between the
October 1998 and May 1999 surveys which exactly envelopes the northeast monsoon
period.
6.2.1.2 Depth of Closure from Empirical Formulae (Dl,t )
The predicted depth of closure has been presented by Nicholls et al (1998) as
Dl,t to indicate its association to the selected period of analysis.
The 12-hour
exceeded wave height for the annual (H0.137) and 5-year (H0.027) cases have been
81
transformed to their nearshore equivalents using the software Mike21 NSW. Dl,t is
referred to MLW following Hallermeier’s original definition.
6.2.1.3 Time-interval Dc
Time-interval Dc is determined from surveys taken from 1999 to 2004. It
encompasses the erosion events over the northeast monsoon and the accretion phase
that happens over the southwest monsoon (May through September). Two timeinterval Dc scenarios are investigated:1.
Annual Dc – determined from the changes between two post-monsoon
surveys i.e. the May 1999 and May 2000 surveys which are exactly 12
months apart;
2.
5-year Dc – determined from the May 1999, October 2000 and July
2004 surveys.
6.2.2
Algorithm for Determination of Dc from Profile Surveys
Depths of closure from surveys are determined from the SDDC or FDC
method. For SDDC, where the plot of the standard deviation of the selected series of
surveys down-crosses below 0.3 m and tails off, a limit to the nearshore profile
change i.e. the depth of closure, has been reached. Similarly, when the FDC plot
down-crosses and remains below 0.3 m, the first point after the down-cross is
deemed as the depth of closure. The algorithm is as follows:
1.
Determine and plot envelope of bed elevations over series of surveys
(distance shorewards as x-axis; bed elevation as y-axis); alternatively,
and to clearly show profile changes over two consecutive surveys,
each profile survey may be plotted;
82
2.
Plot SDDC/FDC criteria line of 0.3 m (plotted on secondary y-axis);
3.
Determine:•
standard deviation of depth change between a series of surveys
and;
4.
•
fixed depth change between consecutive surveys;
•
Determine opening and closing points along each profile:
Beginning from shoreline where the shoreline is 0 m LSD, assuming
that SDDC /FDC plot starts above the criteria line, the first point
where the SDDC/FDC graph down-crosses the criteria line is deemed
a closure point. If the SDDC/FDC line at the shoreline starts below
the criteria line, the first up-crossing point is recorded as an opening
point and the analysis proceeds from there;
5.
From a closure point and continuing seawards, the point when
SDDC/FDC graph next up-crosses the criteria line is recorded as a reopening point;
6.
Identify morphological zones:•
Closure zones – profile regions where the SDDC/FDC graph
down-crosses and remains below the criteria line for a series of
profile points. For this research, a zone is decided if the SDDC/
FDC line remains below the criteria line for at least 300 m ;
•
Reopening zones – when the SDDC/FDC graph up-crosses and
remains above the criteria line;
83
•
Multiple closure points are thus expected across a profile and
these would be designated as:
•
Dci - for the starting point of the first closure zone that occurs
(expected at innershore locations);
•
Dcm - for the starting point of a subsequent closure point that
occurs seawards of Dci (expected at middleshore locations);
•
Dco – for the starting of a closure zone occurring in the
outershore and seawards of Dcm .
•
Reopening zones are zones of significant cross-shore sediment
transport. When the SDDC/FDC graph up-crosses and downcrosses the criteria line alternately along the profile, the length of
this recurring phenomena is considered an area of significant
sediment transport activity.
7.
Determine effective Dc for beach fill design – the depth of closure is
the depth where there is a clear tailing-off of the SDDC/FDC graph
below the criteria line which is related to a change in the shoreline
and foreshore but unrelated with offshore sediment transport
phenomena. A tailing-off zone (closure zone) occurring between two
zones of significant bed elevation change indicates that their
processes differ from one another.
In multi-barred profiles, there is a tendency for double or triple contours to
occur. If a closure depth occurs twice along the same profile, the outermost point is
chosen.
84
6.3
Predicted Depth of Closure, Dl,t
The predicted depth of closure or Dl,t was determined for the annual and 5-
year period (hence, Dl,1-yr and Dl,5-yr) . The application of Hallermeier’s equation
requires the determination of the 12-hour exceeded significant wave height over the
period of study resulting in a design wave exceedance of 0.137% (H0.137 ) for the
annual case and 0.027% (H0.027) for the 5-year case. These wave conditions and their
associated periods have been determined in Chapter 5.
6.4
Monsoon Dc (1998-1999 surveys)
6.4.1
Profile Descriptions and Application of Algorithm
The criteria line for both SDDC and FDC methods applied herein is 0.3 m
which corresponds to the accuracy of hydrographic surveys.
Figures of
representative profiles are presented for better appreciation of the analysis. The
discussion is presented beginning from the updrift to downdrift locations (starting
from Ch.3100 and ending at Ch.-1400). It is useful to note that a breakwater situated
between Ch.-400 and Ch.00 interrupts the littoral drift.
6.4.2
Monsoon Dc at Ch.3100 and Ch.2700
Ch.3100 and Ch.2700 are 3-bar profiles with the bar systems occurring
between 300 m and 800 m from the baseline. These profiles appear to be part of a
stable region of the study coastline where the shoreline was essentially unchanged
over the monsoon period.
85
6.4.2.1 Monsoon Dc Ch.3100
Bed elevation changes are insignificant at Ch.3100 especially in the
innershore area. The SDDC method does not produce a closure. The FDC method
however shows a Dcm of -3.64 m LSD and a Dco of -7.1 m LSD at 400 m and 1750 m
from the baseline (Figure 6.1). The FDC method shows no change in shoreline
position but an inshore reopening zone is noted at the inshore bar between 250 m
and 350 m from the baseline before closing at 400 m. Significant bed elevation
changes also occur at the outershore bar at 1300 m from the baseline. The effective
Dc is -3.64 m LSD.
Depth of Closure: Ch 3100; 1998-1999
Min envelope
SDDC
Max envelope
Criteria line
MLW
FDC
Mean depth
3
1
FDC Dcm = Dc = -3.64 m @ 400 m
2
1
0.9
0
FDC Dco = -7.1 m @ 1450 m
-2
-3
0.7
0.6
-4
0.5
-5
-6
0.4
-7
0.3
-8
-9
0.2
-10
0.1
-11
-12
0
0
500
1000
1500
Distance Offshore, m
Figure 6.1: Monsoon Dc at Ch.3100
2000
FDC/SDDC, m
0.8
-1
86
6.4.2.2 Monsoon Dc Ch.2700
At Ch.2700, the SDDC plot exceeds the 0.3 m-criteria line above MLW and
closes 150 m from the baseline. The effective SDDC Dc for Ch.2700 is thus the first
closure point -1.82 m LSD and 150 m from the baseline. Using the FDC method,
Ch.2700 registered slight profile changes above MLW, and an innershore closure
point coinciding with a bar location at -1.82 m LSD from the baseline (Figure 6.2).
In the outershore, a reopening zone exists beyond the outershore bar between 1350 m
and 1700 m from the baseline before closing again at -7.46 m LSD (1750 m from the
baseline) near the offshore limit of the survey.
The FDC Dc of Ch.2700 is
determined to be -1.82 m LSD as the innershore bar does not contribute to the
shoreline changes.
Depth of Closure: Ch. 2700; 1998-1999
Mean bed elevation
SDDC
Min envelope
Criteria line
Max envelope
FDC
MLW
2.4
4
SDDC, FDC Dci = Dc = -1.82 m @ 150 m
2
2.1
1.5
-2
FDC Dco = -7.46 m @ 1750 m
1.2
-4
0.9
-6
Change criteria, m
1.8
0
0.6
-8
0.3
-10
0
0
500
1000
1500
2000
Distance offshore, m
Figure 6.2: Monsoon Dc at Ch.2700
6.4.3
Monsoon Dc at Ch.2300 and Ch.1900
Ch.2300 and Ch.1900 are 2-bar profiles with the outer bars located
significantly further offshore at 1300 m and 1700 m respectively. The comparison of
the 1998 and 1999 plots show a growth and shoreward movement of the innershore
87
bar but with a flat middleshore. At Ch.1900, the shoreline is seen to have eroded
over this monsoon corresponding to a growth in the innershore bar.
6.4.3.1 Monsoon Dc at Ch.2300
Applying the SDDC method, a closure zone is observed at Ch.2300 from 100
m to 400 m until the first reopening point appeared at the innershore bar 450 m from
the baseline (Figure 6.3). The FDC Dc for Ch.2300 is found to be the same as the
SDDC case. The effective Dc for Ch.2300 is -2.17 m LSD which lies 100 m from the
shoreline.
Depth of Closure: Ch.2300; 1998-1999
Mean bed elevation
MLW
FDC
Profile 1998
SDDC
Profile 1999
Criteria line
1
4
3
2
1
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-10
-11
-12
0.9
SDDC, FDC Dc = -2.17 m @ 100 m
0.8
0.6
0.5
0.4
0.3
0.2
0.1
0
0
500
1000
1500
2000
2500
Distance offshore, m
Figure 6.3: Monsoon Dc at Ch.2300
3000
SDDC/FDC, m
0.7
88
6.4.3.2 Monsoon Dc at Ch.1900
No significant bed change occurred between 100 m to 750 m from the
baseline at Ch.1900 (Figure 6.4). SDDC Dc for Ch.1900 is -1.8 m LSD and located at
100 m from the baseline. From the FDC analysis, triple contours occur for the depth
corresponding to the innershore closure point of -2.75 m LSD at 250 m from the
baseline.
Depth of Closure: Ch.1900; 1998-1999
Mean bed elevation
SDDC
Min envelope
Criteria line
Max envelope
FDC
MLW
2.1
4
SDDC Dc = -1.80 m @ 100 m
3
2
1.8
1
FDC Dc = -2.75 m @ 250 m
1.5
-2
1.2
-3
-4
-5
0.9
-6
-7
SDDC/FDC, m
0
-1
0.6
-8
-9
0.3
-10
-11
-12
0
0
500
1000
1500
2000
2500
3000
3500
Distance Offshore, m
Figure 6.4: Monsoon Dc at Ch.1900
6.4.4
Monsoon Dc at Ch.1500, Ch.1200 and Ch.800
The 1999 profile shows that a 3-bar profile has developed at Ch.1500,
Ch.1200 and Ch.800 with outer bars at 1250 m to 1400 m from the baseline and
inner-shore bars at 200 m to 400 m from the baseline. The Ch.1500 and Ch.1200
shoreline positions do not appear to change over this monsoon however a distinct
lowering of the middleshore and seawards migration of the offshore bar can be
89
observed. Due to the proximity of the two innershore bars, they are both affected by
erosion of the shoreline and by each other.
6.4.4.1 Monsoon Dc at Ch.1500
The SDDC Dc for Ch.1500 (Figure 6.5) is at -1.86 m LSD (250 m from
baseline). Using the FDC method, a Dci for Ch.1500 is determined at -3.51 m LSD.
The profile envelope separates at the outershore bar and Dco of -2.49 m LSD appears
at 950 m offshore. The shallower Dco is due to the bar formation. The FDC Dc is
therefore -3.51 m LSD at 550 m away from the shoreline.
Depth of Closure: Ch. 1500; 1998-1999
Mean
SDDC
Min envelope
criteria line
Max envelope
FDC
MLW
3
1.2
SDDC Dci = Dc =
-1.86 m @ 250 m
2
1
FDC Dci = Dc = -3.51 m @ 550 m
0
SDDC, FDC Dco = -2.49
m @ 950 m
-2
-3
-4
0.6
-5
-6
-7
0.3
-8
-9
-10
0
-11
0
500
1000
1500
2000
Distance offshore, m
Figure 6.5: Monsoon Dc at Ch.1500
2500
3000
SDDC/FDC, m
0.9
-1
90
6.4.4.2 Monsoon Dc at Ch.1200
At Ch.1200 (Figure 6.6), both the SDDC and FDC Dc coincide at -3.0 m (500
m from baseline). A reopening zone appears between 1200 m and 1450 m from the
baseline. The effective Dc for Ch.1200 is therefore -3.0 m LSD.
Depth of Closure: Ch.1200; 1998-1999
Min envelope
Max envelope
MWL
SDDC
Criteria line
FDC
mean
4
SDDC, FDC Dci = Dc = -3.0 m @ 500 m
2
0
0.9
-2
0.6
-4
Closure zone
-6
0.3
-8
-10
-12
0
0
500
1000
1500
2000
Distance offshore, m
Figure 6.6: Monsoon Dc at Ch.1200
2500
3000
SDDC/FDC, m
FDC Dco = -3.53 m @ 1500 m
91
6.4.4.3 Monsoon Dc at Ch.800
SDDC Dc for Ch.800 (Figure 6.7) is located at -1.3 m LSD (100 m from
baseline). A reopening zone appears at 1300 m to 1500 m from the baseline.
Applying the FDC method on Ch.800, the reopening is at 1250 m and 1550 m from
the baseline. The FDC Dc for Ch.800 is -2.77 m LSD.
Depth of Closure: Ch.800; 1998-1999
5
Min envelope
Max envelope
MLW
SDDC
Criteria line
FDC
SDDC Dci = Dc = -1.30
m @ 100 m
3
Mean
2.1
FDC Dci = Dc = -2.77 m @
550 m
1.8
1
SDDC, FDC Dco = -4.1 m
@ 1550 m
-3
1.2
-5
0.9
-7
Closure zone
-9
SDDC/FDC, m
1.5
-1
0.6
-11
0.3
-13
-15
0
0
500
1000
1500
2000
2500
3000
Distance offshore, m
Figure 6.7: Monsoon Dc at Ch.800
6.4.5
Monsoon Dc at Ch.400, Ch.200 and Ch.00
At these chainages, the innershore bars are located furthest from the baseline
at 450 to 600 m. The outershore bars are at distances of 1300 m to 1500 m. Ch.00 is
located next to the northern arm of the Sungai Pengkalan Datu breakwaters. The
Ch.00 innershore bars experienced 1.0 m change in elevation over the monsoon
making it a very active section of this coastline.
92
6.4.5.1 Monsoon Dc at Ch.400
Both Ch.400 (Figure 6.8) and Ch.200 (Figure 6.9) show their SDDC graph
spiking over the criteria line at the innershore bars but further offshore the SDDC
plots do not up-cross the criteria line. There was some doubt whether closure within
50 m of the baseline is accurate since this is the region where gaps in survey data
often exist. Hence, the Dci for Ch.400 is placed at -2.59 m LSD located 550 m from
the baseline.
The FDC analysis reveals more significant changes at the bar.
However, the Dc location is the same at -2.59 m LSD.
Depth of Closure: Ch. 400, 1998-1999
Min envelope
MLW
SDDC
Criteria line
FDC
4
3
2
1
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-10
-11
Mean depth
SDDC, FDC Dc = -2.59 m @ 550 m
0.9
0.6
0.3
0
0
500
1000
1500
2000
2500
Distance offshore, m
Figure 6.8: Monsoon Dc at Ch.400
3000
SDDC/FDC, m
Max envelope
93
6.4.5.2 Monsoon Dc at Ch.200
Ch.200 (Figure 6.9) has a very uniform slope with 4 visible bars at nearly
regular intervals. Following the same arguments as in Ch.400, the SDDC Dc for
Ch.200 is at
-1.05 m LSD at 100 m from the baseline where a closure zone of 300
m wide begins. By the FDC method, the Dci is also -1.05 m LSD at Ch.200. Both
the SDDC and FDC method produce the same Dco at -2.89 m.
Depth of Closure: Ch.200; 1998-1999
Min envelope
Max envelope
MWL
SDDC
Criteria line
FDC
Mean depth
6
1.8
SDDC, FDC Dci = Dc = -1.05 m LSD @ 100 m
2
1.6
SDDC, FDC Dco = -2.89 m LSD @ 650 m
0
1.4
1.2
-2
1
-4
0.8
-6
0.6
-8
0.4
-10
0.2
-12
0
0
500
1000
1500
2000
2500
Distance Offshore, m
Figure 6.9: Monsoon Dc at Ch.200
3000
SDDC/FDC, m
4
94
6.4.5.3 Monsoon Dc at Ch.00
At Ch.00 (Figure 6.10), no significant bed elevation changes occured
between the shoreline and the innershore bar. However, distinct zones of reopening
are noted at 600 m to 850 m and 1300 m to 1650 m. Hence, the Dci and Dco are
determined to be at depths of -2.07 m and -5.44 m LSD respectively.
By the FDC method, the Ch.00 profile is essentially unchanged until a
reopening occurs at 300 m from the baseline. The profile envelope later converges at
900 m from the shore just beyond the innershore bars where the depth is -3.04 m
LSD and qualifies as the Dc.
Depth of Closure: Ch.00; 1998-1999
Mean bed elevation
MWL
FDC
4.0
SDDC Dci = Dc =
-2.07 m @ 850 m
3.0
2.0
Min envelope
SDDC
Max envelope
Criteria line
FDC Dci = Dc =
-3.04 m @ 900 m
2.4
SDDC Dco = -5.44
m @ 1700 m
2.1
1.0
FDC Dco = -6.21 m @
2000 m
-2.0
-3.0
-4.0
-5.0
1.5
1.2
0.9
-6.0
-7.0
0.6
-8.0
-9.0
0.3
-10.0
-11.0
0
500
1000
1500
2000
Distance offshore, m
Figure 6.10: Monsoon Dc at Ch.00
2500
0
3000
SDDC/FDC, m
1.8
0.0
-1.0
95
Monsoon Dc at Ch.-400, Ch.-900 and Ch.-1400
6.4.6
Ch.-400, Ch.-900 and Ch.-1400 represent the shoreline updrift of the Sungai
Pengkalan Datu breakwaters and characterised by a smooth nearshore gradient. This
section of the shoreline is observed to be accreting as a result of the interruption of
the northwest bound littoral supply by the breakwaters.
6.4.6.1 Monsoon Dc at Ch.-400
Referring to Figure 6.11, up-crossing of the SDDC graph occurred only at
Ch.-400 at the location of the innershore bar 500 m from the baseline and closed at
550 m. The effective Dc is placed at -3.07 m LSD. The FDC method when applied
to Ch.-400 establishes a zone of high sediment transport up to 500 m from the
baseline. The Dc is registered at -3.07 m LSD.
Depth of Closure: Ch. -400; 1998-1999
Min envelope
Max envelope
MLW
SDDC
Criteria line
FDC
Mean depth
1.5
4
SDDC, FDC Dc = -3.07 m @ 550 m
2
1.2
-2
0.9
-4
0.6
-6
-8
0.3
-10
-12
0
500
1000
1500
2000
2500
Distance Offshore, m
Figure 6.11: Monsoon Dc at Ch.-400
3000
0
3500
SDDC/FDC, m
0
96
6.4.6.2 Monsoon Dc at Ch.-900
From Figure 6.12, the SDDC Dc is not defined For Ch.-900 but the FDC Dci
which defines Dc is located at -3.3 m LSD (300 m from the shoreline). Dco is
located at -4.04 m LSD which is 850 m from the baseline and just seawards of the
innershore bar.
Depth of Closure: Ch. -900; 1998-1999
4
Min envelope
Max envelope
MLW
SDDC
criteria line
FDC
Mean
1.5
FDC Dci = Dc = -3.3 m @ 300 m
3
2
1
1.2
-1
-2
0.9
-3
-4
-5
0.6
-6
-7
-8
0.3
-9
-10
-11
-12
0
500
1000
1500
2000
2500
3000
Distance Offshore, m
Figure 6.12: Monsoon Dc at Ch.-900 (slope 1:400)
0
3500
SDDC/FDC, m
FDC Dco = -4.04 m @ 850 m
0
97
6.4.6.3 Monsoon Dc at Ch.-1400
SDDC Dc is also not defined in Ch-1400 but FDC Dci is -4.18 m LSD and Dco
is -7.59 m. The effective Dc is therefore -4.18 m LSD which is 600 m from the
baseline (Figure 6.13).
Depth of Closure: Ch.-1400; 1998-1999
Min envelope
Max envelope
MLW
SDDC
Criteria line
FDC
Mean depth
6
1.8
4
1.5
FDC Dc = -4.18 m @
600 m
0
1.2
-2
0.9
-4
-6
0.6
SDDC/FDC, m
2
-8
0.3
-10
-12
0
0
500
1000
1500
2000
2500
3000
3500
Distance Offshore, m
Figure 6.13: Monsoon Dc at Ch.-1400; closure is not defined with SDDC method at
Ch.-1400
6.4.7
Summary for Monsoon Dc
6.4.7.1 Profile Evolution and Dc over a Monsoon
The Dc from the October 1998 and May 1999 surveys define the monsoon Dc
typically associated with an erosional event in the east coast of peninsular Malaysia.
By the interpretion that a distance of about 300 m of insignificant bed change
constitutes a closure zone, zones can be differentiated from points of significant bed
elevation change and simplifies the analysis. Dc could be determined at all 13
profiles using the FDC method but was observed in 10 out of 13 profiles analysed
98
using the SDDC method. FDC being based on absolute change between elevations
may however suffer from survey errors.
The results from both methods indicate that profile envelopes typically
separate over the bars. Closures occur at least at two locations across the profiles
separated by closure and reopening zones.
Over the 1998-1999 monsoon, bar
movement was very active and there is a tendency for the innershore bars to move
shorewards while the outershore bars shift seawards. The offshore migration of the
outershore bars proves that the monsoon is an erosive event.
6.4.7.2 Monsoon Dc for Beach-fill Design
The effective Dc for beach-fill design will indicate the location of where the
toe of a beach-fill should be situated. Hence, the most landward closure which is
separated from the offshore bar processes is assumed to be the effective Dc. From
Table 6.1 and 6.2, it is observed that the effective SDDC Dc ranges from -1.05 m
LSD to -3.07 m LSD and the effective FDC Dc is from -1.05 m LSD to -4.24 m
LSD. These depths are located very close to the innershore bars and the FDC
generally produces more seaward Dc values. Figure 6.14 presents a comparison of
the Monsoon Dc for the two methods. It can be seen that in clearly eroding areas of
Ch.200, Ch.400 and Ch.800, the SDDC and FDC method both concur on Dc.
The FDC method to determine Dc would be recommended for beach-fill
design since it captures more significant changes and regularly produces deeper Dc
than the SDDC method. Another observation is that Dci occurs at distances of 600 m
or less from the shoreline which encompasses the inner bars. Dco on the other hand
was detected between 650 m and 2300 m offshore towards the limit of the survey
data. Since this occurs over a single monsoon, the results are indicative of a highly
active shoreface.
99
Table 6.1: Depths of Closure (SDDC) for Monsoon Event 1998-1999
Chainage
Hm0
CH00
CH200
CH400
CH800
CH1200
CH1500
CH1900
CH2300
CH2700
CH3100
CH-400
CH-900
CH-1400
Average
2.61
2.60
2.60
2.59
2.58
2.58
2.61
2.59
2.58
2.58
2.59
2.55
2.53
2.58
Mean
Profile
Gradient
0.0030
0.0028
0.0027
0.0027
0.0025
0.0024
0.0029
0.0031
0.0038
0.0035
0.0031
0.0028
0.0026
0.0029
SDDC Dc (1998-1999)
Dci ,
m
LSD
Dco m,
LSD
Dc m,
LSD
Dc, m
MLW
Distance
offshore,
m
-2.07
-1.05
-2.59
-1.3
-3.00
-1.86
-1.80
-2.17
-1.82
na
-3.07
na
na
-2.28
-5.44
-2.89
-2.59
-4.09
na
-2.49
na
na
na
na
na
na
na
-3.75
-2.07
-1.05
-2.59
-2.77
-3.00
-2.49
-1.80
-2.17
-1.82
na
-3.07
na
na
-2.28
-1.71
-0.69
-2.23
-2.41
-2.64
-2.13
-1.44
-1.81
-1.46
na
-2.71
na
na
-1.92
850
100
550
550
500
950
100
100
150
na
550
na
na
440
Dci = innershore closure; Dcm = middleshore closure; Dco = outershore closure;
Dc = effective closure
Table 6.2: Depths of Closure (FDC) for Monsoon Event 1998-1999
Mean
Profile
Gradient
FDC Dc (1998-1999)
Dci,
Distance
Dco,
Dc, m Dc , m
offshore,
m
m
LSD MLW
m
LSD LSD
CH00
2.61
0.003 -3.04 -6.21 -3.04 -2.68
900
CH200
2.60
0.0028 -1.05 -2.89 -1.05 -0.69
650
CH400
2.60
0.0027 -2.59
na
-2.59 -2.23
550
CH800
2.59
0.0027 -2.77 -4.09 -2.77 -2.41
550
CH1200
2.58
0.0025 -3.00 -3.53 -3.00 -2.64
1500
CH1500
2.58
0.0024 -3.51 -2.49 -3.51 -3.15
550
CH1900
2.61
0.0029 -2.75
na
-2.75 -2.39
250
CH2300
2.59
0.0031 -2.17
na
-2.17 -1.81
100
CH2700
2.58
0.0038 -1.82 -7.46 -1.82 -1.46
150
CH3100
2.58
0.0035 -3.64
-7.1
-3.64 -3.28
400
CH-400
2.59
0.0031 -3.07
na
-3.07 -2.71
550
CH-900
2.55
0.0028 -3.3
-4.04
-3.3
-2.94
300
CH-1400
2.53
0.0026 -4.18
na
-4.18 -3.82
600
Average
2.58
0.0029 -2.84 -4.73 -2.84 -2.48
542
Dci = innershore closure; Dcm = middleshore closure; Dco = outershore closure;
Dc = effective closure; MLW = -0.36 m LSD
Chainage
Hm0
100
Monsoon Dc (1998-1999) from MLW (LSD - 0.36 m)
CH3100
4.0
CH-1400
3.5
CH2700
3.0
2.5
CH-900
CH2300
2.0
1.5
1.0
CH-400
CH1900
0.5
0.0
CH00
CH1500
CH200
CH1200
CH400
FDC Dc
CH800
SDDC Dc
Figure 6.14: Comparison of SDDC and FDC methods in determining Monsoon Dc
6.5
Annual Dc (1999-2000)
6.5.1
Profile Description and Application of Algorithm
Applying the same algorithm to the 1999-2000 surveys, the depth of closure
for exactly one-year interval between surveys was determined for the study area and
presented in the following sections. The similarity in results using both the SDDC
and FDC method is illustrated for Ch.3100. For subsequent chainages, the FDC
method is used and the absolute bed change along the same profile over the two
surveys is plotted. The application of the algorithm is described below for selected
profiles which represent the study shoreline. Ch.2300 and Ch.1900 were excluded
due to irregularities in the profile dataset.
101
Annual Dc at Ch.3100
6.5.2
A shoreward migration of the innershore bars can be seen at Ch.3100 (Figure
6.15). The SDDC and FDC methods produce similar Dc of -3.70 m LSD at Ch.3100
but at slightly different locations.
Depth of Closure (FDC): Ch.3100; 1999-2000
Profile 1999
FDC
4
Profile 2000
FDC criteria (0.3m)
MLW
SDDC
Mean depth
1.6
SDDC Dc = -3.70 m @ 300 m
3
1.4
2
1
FDC Dc = -3.70 m @ 550 m
0
1.2
-1
0.8
-3
-4
0.6
-5
-6
0.4
-7
-8
0.2
-9
-10
0
500
1000
1500
Distance Offshore, m
Figure 6.15: Annual Dc at Ch.3100
2000
0
2500
FDC,
1
-2
102
Annual Dc at Ch.2700
6.5.3
A shoreline retreat of almost 40 m has occurred at the baseline with closure
achieved before the nearshore bars. Dc is -2.0 m at 150 m from the baseline with no
signs of offshore reopening (Figure 6.16).
Depth of Closure (FDC): Ch.2700; 1999-2000
Profile 1999
Profile 2000
MLW
Mean Depth
FDC
FDC criteria (0.3m)
4
3
Dc = -2.0 m @ 150 m
2
3
1
0
2.4
-1
-3
1.8
-4
-5
-6
1.2
-7
-8
-9
0.6
-10
-11
-12
0
500
1000
1500
Distance offshore, m
Figure 6.16: Annual Dc at Ch.2700
2000
0
2500
FDC, m
-2
103
Annual Dc at Ch.1500
6.5.4
Significant bed elevation changes can be seen at the shoreline, and across the
nearshore and offshore bars. Dci is -2.48 m LSD and located at 300 m from the
baseline for Ch.1500 just seawards of the innershore bar. The profile envelope
closes again at the depth of -3.32 m LSD at 1300 m offshore. The Dci is the effective
annual Dc since it is separated from the outer bar by a closure zone (Figure 6.17).
Depth of Closure: Ch. 1500; 1999-2000
Profile 1999
Profile 2000
MLW
Mean Depth
FDC
FDC criteria (0.3m)
3
1.4
2
Dci = Dc = -2.48 m @ 300 m
0
-1
1.2
Dco = -3.32 m @ 1300 m
-2
-3
1
0.8
-4
-5
0.6
-6
-7
0.4
-8
-9
0.2
-10
-11
0
500
1000
1500
2000
Distance offshore, m
Figure 6.17: Annual Dc at Ch.1500
2500
0
3000
FDC, m
1
104
Annual Dc at Ch.1200
6.5.5
At Ch.1200, the outershore bar has migrated seawards while the innershore
bar has reduced in height and moved shorewards indicating that they are influenced
by different factors. The Dc is therefore the Dci at -2.02 m LSD and located 400 m
offshore (Figure 6.18).
Depth of Closure (FDC): Ch.1200; 1999-2000
Profile 2000
Profile 1999
Mean depth
MLW
FDC
FDC criteria (0.3m)
3
2.4
Dci = Dc = -2.02 m @ 400 m
2
1
Dco = -3.07 m @ 1450 m
0
2.1
1.8
-1
-2
-4
1.2
-5
0.9
-6
-7
0.6
-8
-9
0.3
-10
-11
0
0
500
1000
1500
2000
2500
Distance offshore, m
Figure 6.18: Annual Dc at Ch.1200
3000
FDC, m
1.5
-3
105
Annual Dc at Ch.800
6.5.6
The 1999 and 2000 profile envelope first closes at -0.61 m LSD merely 50 m
from the baseline but immediately separates at the innershore bar (Figure 6.19).
Another closure, point is detected at -2.39 m LSD at 350 m from the shoreline
marking the beginning of a long closure zone before the offshore bar is reached. The
profile envelope separates at the offshore bar but closes again at -4.13 m LSD. The
most landward closure is -0.61 m LSD yet it is maintained that closures within 50 m
of the shoreline should be disregarded due to possible survey inaccuracies and also
because there is significant bed activity at the innershore bar. Dc is hence the
location of Dcm where the depth is -2.39 m LSD.
Depth of Closure (FDC): Ch.800; 1999-2000
Profile 1999
Mean
Profile 2000
FDC
MLW
FDC criteria (0.3m)
1.8
5
Dcm = Dc = -2.39 m @ 350 m
3
1.5
1
-1
Dco = -4.13 m @ 1550 m
1.2
-5
0.9
-7
0.6
-9
-11
0.3
-13
-15
0
0
500
1000
1500
2000
Distance offshore, m
Figure 6.19: Annual Dc at Ch.800
2500
3000
FDC, m
-3
106
Annual Dc at Ch.400
6.5.7
A 500 m zone of insignificant bed elevation change exists at the shoreline
hence, the Dc is established at a depth of -2.56 m LSD (Figure 6.20). From a beach
nourishment aspect, the toe of the beach-fill may be placed in this zone.
Depth of Closure (FDC): Ch.400; 1999-2000
Profile 1999
4
Profile 2000
Mean depth
MLW
FDC
FDC criteria line
1.6
Dci = Dc = -2.56 m @ 550 m
2
1.4
1.2
Dco = -3.83 @ 1550 m
-2
1
-4
0.8
-6
0.6
-8
0.4
-10
0.2
-12
0
0
500
1000
1500
2000
2500
Distance offshore, m
Figure 6.20: Annual Dc at Ch.400
3000
FDC, m
0
107
Annual Dc at Ch.200
6.5.8
Significant sediment transport occurs at the bar of this profile as shown in
Figure 6.21. A 500 m zone of insignificant bed elevation change exists at the
shoreline hence, the Dc is established at a depth of -3.42 m LSD.
Depth of Closure (FDC): Ch.200; 1999-2000
Min envelope
MLW
Max envelope
FDC
Mean depth
FDC Criteria (0.3m)
4
1.8
2
Dc = -3.42 m @ 1150 m
0
1.2
FDC, m
-2
-4
-6
0.6
-8
-10
-12
0
-14
0
500
1000
1500
2000
2500
Distance offshore, m
Figure 6.21: Annual Dc at Ch.200
3000
108
Annual Dc at Ch.00
6.5.9
Based on the FDC criteria of 0.3 m, the Ch.00 profile appears as very active
over the annual period (Figure 6.22). The plots indicate a seaward movement of the
outershore bar but accreting innershore bars. Three closure points are found along
the profile: Dci at -2.24 m LSD, Dcm at -3.81 m LSD and Dco at -6.19 m LSD which
is situated 1900 m from the shoreline. The significant cross-shore sediment transport
occurring offshore can be attributed to the discharge at the mouth of the breakwaters.
Hence, this makes the Dci the selected Dc.
Depth of Closure (FDC): Ch. 00; 1999-2000
FDC criteria (0.5m)
MLW
FDC Criteria (0.3m)
Profile 1999
Mean depth
Profile 2000
FDC
4
1.8
Dci = Dc = -2.24 m @ 850 m
2
Dcm = -3.8 m @ 1100 m
0
1.2
Dco = -6.19 m @ 1900 m
FDC, m
-2
-4
-6
0.6
-8
-10
0
-12
0
500
1000
1500
2000
Distance offshore, m
Figure 6.22: Annual Dc at Ch.00.
2500
3000
109
6.5.10 Annual Dc at Ch-400, Ch.-900 and Ch.-1400
These three chainages updrift of the breakwaters have similar characteristics
of gentle sloping nearshore and the absence of offshore bars (Figure 6.23, 6.24 and
6.25 respectively). The annual Dc at Ch.-400, Ch.-900 and Ch.-1400 are -4.37 m
LSD, -3.35 m LSD and -4.59 m LSD respectively.
Depth of Closure (FDC): Ch. - 400; 1999-2000
Profile 1999
Profile 2000
MLW
Mean depth
FDC
FDC criteria (0.3m)
3
2
2
1.8
1
0
1.6
-1
1.4
Dc = -4.37 m @ 950 m
-3
1.2
-4
1
-5
-6
0.8
-7
0.6
-8
-9
0.4
-10
0.2
-11
-12
0
500
1000
1500
2000
2500
Distance Offshore, m
Figure 6.23: Annual Dc at Ch.-400
3000
0
3500
FDC, m
-2
110
Depth of Closure (FDC): Ch.- 900; 1999-2000
Profile 1999
Profile 2000
Mean
MLW
FDC
FDC criteria (0.3m)
6
1.4
Dc = -3.35 m @ 650 m
4
1.2
2
0
-2
0.8
-4
FDC, m
1
0.6
-6
0.4
-8
0.2
-10
-12
0
0
500
1000
1500
2000
2500
3000
3500
Distance Offshore, m
Figure 6.24: Annual Dc at Ch. -900
Depth of Closure (FDC): Ch. - 1400; 1999-2000
Profile 1999
Profile 2000
MLW
Mean Depth
FDC
FDC criteria (0.3m)
6
3
Dc = -4.59 m @ 700 m
4
2
2.4
1.8
-2
-4
1.2
-6
-8
0.6
-10
-12
0
0
500
1000
1500
2000
2500
Distance Offshore, m
Figure 6.25: Annual Dc at Ch.-1400
3000
3500
FDC, m
0
111
6.6
Summary for Annual Dc (1999-2000)
The analysis for annual Dc revealed that multiple closure and reopening
zones develop across the profile producing two or three closure points (see Table
6.3). The Dco was consistently situated just beyond the outershore bars while Dc
varied between 150 m to 900 m. To enable comparison with calculated Dl,t from
Hallermeier’s equation, the measured values were reduced to MLW which has been
established to be -0.36 m below LSD. The comparison between Dl,1-year and the
effective Dc is illustrated using both a radar chart in Figure 6.26 and a line graph as
in Figure 6.27. Dl,1-year is found to be greater than the measured Dc. The selection of
local wave height from the model could be the reason for this overprediction. The
outer bars alter both the wave height and direction in its lee creating a different wave
condition. The examination of the effect of using waves from various parts of the
crossshore on Dl,t is however outside the scope of this study.
Table 6.3: Annual Dc (May 1999 – May 2000)
FDC, m LSD
FDC, m MLW
Chainage
Dci
Dcm
Dco
Dci
Dcm
Dco
Dc
Dl, 1-year
CH00
-2.24
-3.80 -6.19 -1.88 -3.44 -5.83
-1.88
-4.65
CH200*
na
na
-3.42
na
na
-3.06
-3.06
-4.64
CH400
-2.56
na
-3.83 -2.20
na
-3.47
-2.20
-4.64
CH800
na
-2.39 -4.13
na
-2.03 -3.77
-2.03
-4.62
CH1200
-2.02
na
-3.07 -1.66
na
-2.71
-1.66
-4.62
CH1500
-2.48
na
-3.32 -2.12
na
-2.96
-2.12
-4.61
CH2700
-2.00
na
na
-1.64
na
na
-1.64
-4.61
CH3100*
na
-3.70
na
na
-3.34
na
-3.34
-4.63
CH-400*
na
na
-4.37
na
na
-4.01
-4.01
-4.63
CH-900*
na
-3.35
na
na
-2.99
na
-2.99
-4.56
CH-1400*
na
na
-4.59
na
na
-4.23
-4.23
-4.53
Average
-2.05
-3.10 -4.00 -1.74 -2.74 -3.64
-3.01
-4.61
Dci = innershore closure; Dcm = middleshore closure; Dco = outershore closure; Dc =
effective closure
na = not applicable; * the location designation (Dci, Dcm or Dco) is estimated
112
FDC Annual Depth of Closure (1999-2000), m LSD
CH3100
5.00
CH-1400
CH2700
4.00
3.00
CH-900
CH1500
2.00
1.00
0.00
CH-400
CH1200
CH00
CH800
CH200
CH400
Calculated Dc Annual
FDC Dc
Figure 6.26: Radar Graph - Comparison between Dl, 1-yr and measured Annual Dc
Annual FDC Dc (1999-2000) in meters below ML
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
3100
2700
1500
1200
800
400
200
0
-400
-900
-1400
Chainage
Annual Dc
Calculated Dc
Figure 6.27: Variation in Dl, 1-yr and measured Annual Dc along the study area
113
6.7
Time-interval Dc (1999-2004)
6.7.1
Profile Description and Application of Algorithm
The profiles off Pantai Sabak over the period 1999 to 2004 have undergone
erosion.
Offshore bars can be seen to have eroded and some have totally
disappeared. Zones of closure are identified as areas where the FDC line dips below
the criteria line and remains for at least 200 m.
The time-interval Dc for the period 1999-2004 was determined based on the
1999, 2000 and 2004 surveys using the mean absolute FDC method. The FDC
method applied in this case is by finding the mean of the FDC in bed elevation
between the 1999-2000 and 2000-2004 surveys. Due to the gaps in annual surveys
from 2001 to 2003, the profile envelope established from three surveys representing
5 years may not necessarily mean that the actual maximum bed elevation change has
been captured.
It would be desirable to have such surveys in order for better
understanding of the profile changes over annual periods.
114
Five-year Dc at Ch.3100
6.7.2
The application of different methods or criteria for determination of Dc may
produce different results. In this section, this variability in Dc is demonstrated by
using both the SDDC and FDC method for Ch.3100 (Figure 6.28). Both the SDDC
and mean FDC method produce nearly identical results in the case of Ch.3100. Dc is
placed at -3.48 m LSD. The FDC method has been reported by Larsen and Kraus
(1994a) to be more descriptive in deeper water. This is demonstrated at Ch.3100
where the mean FDC method detects a change in bed elevation at 2000 m offshore
not registered by the SDDC method.
Depth of Closure: Ch. 3100; 1999-200
Min envelope
FDC criteria (0.3m)
Max envelope
Mean FDC
MLW
SDDC
Mean depth
3
2
2.4
Dc = -3.48 m @ 550 m
1
-1
1.8
-2
-3
-4
1.2
-5
-6
-7
0.6
-8
-9
-10
0
0
500
1000
1500
2000
2500
Distance Offshore, m
Figure 6.28: 5-year Dc at Ch.3100 - Comparison of SDDC and mean of FDC
between consecutive surveys at Ch.3100
SDDC/FDC, m
0
115
6.7.3
Five-year Dc at Ch.2700
From Figure 6.29, a closure zone appears to exist between 150 m to 350 m
from the baseline but it is also part of the innershore bar system. To place a closure
point here would be judgemental. A less controversial location would be at -4.14 m
LSD where a tailing off of the FDC line occurs.
Depth of Closure (FDC): Ch.2700; 1999-2004
Min envelope
Mean depth
Max envelope
FDC criteria (0.3m)
MLW
Mean FDC
4
6
3
5.4
2
4.8
Dc = -4.14 m @ 700 m
0
4.2
-1
3.6
-2
3
-3
-4
2.4
-5
1.8
-6
1.2
-7
0.6
-8
-9
0
0
500
1000
1500
Distance offshore, m
Figure 6.29: 5-year Dc at Ch.2700
2000
FDC, m
1
116
Five-year Dc at Ch.1500
6.7.4
Ch.1500 is addressed in Figure 6.30. A distinct closure zone can be seen
between 350 m and 900 m offshore separating the shoreline changes from the outer
bar evolution. Therefore the Dci of -2.92 m LSD is selected as the Dc.
Depth of Closure (FDC): Ch. 1500; 1999-2004
Min envelope
Max envelope
MLW
Mean depth
FDC criteria (0.3m)
Mean FDC
2.4
4
3
Dc = Dci = -2.92 m @ 350 m
2
1
2.1
Dco = -3.99 m @ 1450 m
0
1.8
1.5
-2
-3
1.2
-4
-5
0.9
-6
-7
0.6
-8
-9
-10
0.3
-11
-12
0
0
500
1000
1500
2000
Distance offshore, m
Figure 6.30: 5-year Dc at Ch.1500
2500
3000
FDC, m
-1
117
6.7.5
Five-year Dc at Ch.1200
From Figure 6.31, there are similarities between Ch.1200 and Ch.1500 in
terms of the closure zone in the nearshore area. The Dci at -2.06 m LSD is selected as
the Dc.
Depth of Closure (FDC): Ch.1200; 1999-2004
3
Min envelope
Max envelope
Mean depth
MLW
Mean FDC
FDC criteria (0.3m)
2.4
Dc = Dci = -2.06 m @ 400 m
2
2.1
1
0
Dco = -3.9 m @ 1600 m
-1
1.8
-2
-4
1.2
-5
-6
0.9
-7
-8
0.6
-9
-10
0.3
-11
0
-12
0
500
1000
1500
2000
2500
Distance offshore, m
Figure 6.31: 5-year Dc at Ch.1200
3000
FDC, m
1.5
-3
118
Five-year Dc at Ch.800
6.7.6
Ch.800 is described in Figure 6.32. The innershore bar processes are clearly
separated from the outershore bar processes at Ch.800 and a Dc of -2.56 m LSD is
chosen. The offshore deepens quite suddenly immediately after the outershore bar.
Depth of Closure (FDC): Ch.800; 1999-2004
Max envelope
Min envelope
MLW
Mean Depth
FDC criteria (0.3m)
Mean FDC
3.6
4
3
3.3
Dc = Dci = -2.56 m @ 500 m
2
3
1
2.7
-1
2.4
-2
2.1
-3
1.8
-4
-5
1.5
-6
1.2
-7
0.9
-8
0.6
-9
0.3
-10
-11
0
0
500
1000
1500
2000
Distance offshore, m
Figure 6.32: 5-year Dc at Ch.800
2500
3000
FDC, m
Dco = -4.75 m @ 1700 m
0
119
Five-year Dc at Ch.400
6.7.7
Ch.400 (Figure 6.33) presents an overall active profile but spikes and dips of
the FDC graph pose uncertainties in determining the closure points. By strictly
following the algorithm and assuming that a closure zone exists if the graph remains
below the criteria line for more than 300 m, three closure points can be isolated. The
Dcm of -3.65 m LSD is selected as the effective Dc as a conservative measure.
Depth of Closure (FDC): Ch.400; 1999-2004
Max envelope
Mean depth
Min envelope
FDC Criteria line (0.3m)
MLW
Mean FDC
4
2.4
Dci = -1.86 m @ 150 m
2
Dc = Dcm = -3.65 m @ 800 m
1.8
Dco = -4.65 m @ 1650 m
-2
1.5
-4
1.2
-6
0.9
-8
0.6
-10
0.3
-12
0
0
500
1000
1500
2000
2500
3000
Distance offshore, m
Figure 6.33: 5-year Dc at Ch.400; three closure points were detected
FDC, m
0
2.1
120
6.7.8
Five-year Dc at Ch.200
Ch.200 (Figure 6.34) presents a similar situation as Ch.400 and again using
the same argument, the Dco is selected as the Dc. The FDC line indicates a very
active profile at this chainage and following the criteria, innershore closures could
not be defined.
Depth of Closure (FDC): Ch.200; 1999-2004
Min envelope
MLW
Max envelope
FDC criteria (0.3m)
Mean depth
FDC
6
3
Dc = Dco = -6.13 m @
2000 m
4
2
2.7
2.4
1.8
-2
1.5
-4
1.2
-6
0.9
-8
0.6
-10
0.3
-12
0
0
500
1000
1500
2000
2500
Distance Offshore, m
Figure 6.34: 5-year Dc at Ch.200
3000
FDC, m
2.1
0
121
Five-year Dc at Ch.00
6.7.9
At Ch.00 (Figure 6.35), a closure zone extends seawards of the offshore bar
but caution has been applied here due to the presence of the breakwater. The
discharge from the mouth of the breakwater would influence the bar formation but
this phenomena is outside the scope of this study. The Dcm of -3.74 m LSD which is
the beginning of a 300 m closure zone in the middleshore area is selected as the Dc.
Depth of Closure (FDC): Ch.00; 1999-2004
Min envelope
Max envelope
MLW
Mean depth
FDC Criteria line (0.3m)
Mean FDC
4
Dci = -1.50 m @ 300 m
2
Dc = Dcm = -3.74 m @ 1050 m
3.6
3
-2
Dco = -6.33 m @ 2000 m
2.4
-4
1.8
-6
1.2
-8
0.6
-10
-12
0
0
500
1000
1500
2000
Distance Offshore, m
Figure 6.35: 5-year Dc at Ch.00
2500
3000
FDC, m
0
122
6.7.10 Five-year Dc at Ch.-400, Ch.-900 and Ch.-1400
The 5-year Dc at these chainages were easily determined due to their smooth
and regular offshore gradients. As shown in Figures 6.36 to 6.38, this accreting
portion of the Pengkalan Datu shoreline have Dc located at less than 1 km from the
shoreline. The Dc for Ch.-400, ch.-900 and Ch.-1400 are thus -3.63 m LSD, 4.19 m
LSD and -4.65 m LSD respectively.
Depth of Closure (FDC): Ch. - 400; 1999-2004
Min envelope
Max envelope
Mean profile
MLW
FDC criteria (0.3m)
Mean FDC
2.4
4
3
2
1
0
1.8
Dc = -3.63 m @ 750 m
-1
-3
1.2
-4
-5
-6
-7
0.6
-8
-9
-10
-11
0
-12
0
500
1000
1500
2000
2500
Distance Offshore, m
Figure 6.36: 5-year Dc at Ch.-400
3000
3500
FDC, m
-2
123
Depth of Closure (FDC): Ch.- 900; 1999-2004
Min envelope
MLW
Max envelope
FDC
Mean depth
FDC criteria (0.3m)
6
2.4
4
2.2
Dc = Dci = -4.19 m @ 900 m
2
2
1.8
0
1.4
-2
Dco = -8.59 m @ 2700 m
-4
1.2
FDC, m
1.6
1
-6
0.8
-8
0.6
0.4
-10
0.2
-12
0
500
1000
1500
2000
2500
3000
3500
0
4000
Distance Offshore, m
Figure 6.37: 5-year Dc at Ch.-900
Depth of Closure (FDC): Ch. - 1400; 1999-2004
Max envelope
Min envelope
Mean depth
MLW
Mean FDC
FDC criteria (0.3m)
6
3
4
2.4
2
1.8
-2
-4
1.2
-6
-8
0.6
-10
-12
0
0
500
1000
1500
2000
2500
Distance Offshore, m
Figure 6.38: 5-year Dc at Ch.-1400
3000
3500
FDC, m
Dc = -4.65m @ 700 m
0
124
6.8
Summary of 5-year Dc (1999, 2000 and 2004)
The detailed results from the 5-year Dc analysis describing the prominent
closure points along each profile is as shown in Table 6.4. The effective Dc for
beach-fill design at the study shoreline of Pantai Sabak is in the range of -1.70 m to
-4.29 m MLW and average at -3.36 m MLW. It follows that the Dl,5-yr predicted the
upper boundary of the depths of closure as displayed in Figure 6.39 hence affirming
earlier studies that:
Dl,t > Dc
In the foregoing analysis, the Dc has been selected from two or three closure
points following the algorithm explained earlier. The Dc is hence subjective and a
change in criteria or interpretation can shift the position of Dc. In most instances, the
outer closure point Dco is not the selected Dc since it is often located at the outershore
bars therefore far removed from innershore processes that effect the shoreline
position. However, the Dco being a significant point of bed elevation change would
be closely related to the pre-breaking wave and its relationship will also be discussed
vis-à-vis Dl,t .
Studying Figure 6.39, Ch.-900, Ch.00 and Ch.200 are exceptions to the norm
whereby their Dco is greater than Dl,5-yr which may be explained by:
•
Ch.00 and Ch.200 are immediately downdrift of the breakwaters and
the mouth of the breakwaters discharges at a location 500 m from the
baseline of both the profiles and;
•
Ch.-900 is updrift of the breakwater and the profile is accreting. In
such cases Hallermeier’s equation has been known to fail (Nicholls et
al, 1996).
125
Table 6.4: Five-year Dc (1999, 2000, 2004 surveys) for beach-fill design
FDC, m LSD
Chainage
Dcm
Dci
FDC, m MLW (-0.36 m LSD)
Dco
Dci
Dcm
Dco
Dc
Dl, 5-yr
CH00
-1.50
-3.74
-6.33
-1.14 -3.38 -5.97 -3.38
CH200
na
-6.13
na
na
-5.77 -5.77
na
CH400
-1.86
-3.65
-4.65
-1.50 -3.29 -4.29 -3.29
CH800
-2.56
na
-4.75
-2.20
na
-4.39 -2.20
CH1200
-2.06
na
-3.90
-1.70
na
-3.54 -1.70
CH1500
-2.92
na
-3.99
-2.56
na
-3.63 -2.56
CH2700
-2.03
na
-4.14
-1.67
na
-3.78 -3.78
CH3100
na
na
-3.68
na
na
-3.32 -3.32
CH-400
na
na
-3.63
na
na
-3.27 -3.27
CH-900
-4.19
na
-8.59
-3.83
na
-8.23 -3.83
CH-1400
na
na
-4.65
na
na
-4.29 -4.29
Average
-2.98
-3.81
-5.48
-2.62 -3.45 -5.12 -3.36
Dci = innershore closure; Dcm = middleshore closure; Dco = outershore closure;
Dc = effective closure; Dl,5-yr = predicted Dc for period of analysis
-4.97
-4.96
-4.96
-4.95
-4.94
-4.94
-4.95
-4.96
-4.96
-4.89
-4.85
-4.94
5-year Depth of Closure (1999-2004), m below MWL
Dc, 5-yr (measured)
Dl, 5-yr (predicted)
Dco, 5-yr (measured)
CH3100
CH-1400
CH-900
9
8
7
6
5
4
3
2
1
0
CH2700
CH1500
CH-400
CH1200
CH00
CH800
CH200
CH400
Figure 6.39: Comparison of 5-year Dc (effective Dc for beach-fill design), Dco
(outermost Dc) and Dl,5-yr
126
5-year Depth of Closure (1999-2004), m below MWL
Dc, 5-yr (measured)
Dl, 5-yr (predicted)
Dco, 5-yr (measured)
9
8
7
6
5
4
3
2
1
0
3100
2700
1500
1200
800
400
200
0
-400
-900
-1400
Chainage
Figure 6.40: Variation in 5-year Dc (effective Dc for beach-fill design), Dco
(outermost Dc) and Dl,5-yr across the study area
6.9
Comparison of Event and Time-Interval Dc
The summary of Dco and Dc over the monsoon, annual and 5 year period is
shown in Table 6.5 and 6.6. From the 1-year and 5-year results, it can be seen that
with increasing years, the outer closure depth Dco generally increases. Exceptions to
this trend occurred only at Ch.200 downdrift of the breakwater and in the accreting
shoreline south of the breakwater. The same trend is noted in the effective Dc for
beach-fill design. The monsoon Dc is presented here for completeness but should be
excluded from the analysis because it has a base year of 1998 while the annual and 5year Dc analysis used a base year of 1999. Notwithstanding the above, Dco for the
1998-1999 monsoon event (6 months) was found to be deeper than Dl,5-yr at only 2
out of the 13 profiles examined (Table 6.5).
127
Table 6.5: Outer Closure Depths Dco (MLW) from Profile Plots
Chainage
Measured Outer Closure
Points, Dco
Dco 6
Predicted Dl,t
Dco 1 yr
Dco 5 yr
Dl, 1-yr
Dl, 5-yr
-4.65
-4.64
-4.64
-4.62
-4.62
-4.61
-4.61
-4.63
-4.63
-4.56
-4.53
-4.61
-4.97
-4.96
-4.96
-4.95
-4.94
-4.94
-4.95
-4.96
-4.96
-4.89
-4.85
-4.94
mths
CH00
-5.85
-5.83
-5.97
CH200
-2.53
-3.06
-5.77
CH400
na
-3.47
-4.29
CH800
-3.73
-3.77
-4.39
CH1200
-3.17
-2.71
-3.54
CH1500
-2.13
-2.96
-3.63
na
na
-3.78
na
na
-3.32
-3.27
CH2700
CH3100
CH-400
-7.1
-4.01
CH-900
-6.74
na
-8.23
CH-1400
na
-4.23
-4.29
Average
-4.46
-3.64
-4.59
6.10
% Diff. % Diff.
Dco and Dco and
Dl,t for
Dl,t for
1-yr
5-yr
-ve indicates
overprediction
25.38%
20.12%
-34.05%
16.33%
-25.22%
-13.51%
-18.40%
-11.31%
-41.34%
-28.34%
-35.79%
-26.52%
na
-23.64%
na
-33.06%
-13.39%
-34.07%
na
68.30%
-6.62%
-11.55%
-21.04%
-7.02%
Measured Dc vs. Hallermeier’s Equation
Hallermeier’s equation has been applied using local wave conditions to
produce the predicted annual and the time-interval depths of closure Dl,1-yr and Dl,5-yr.
Alongshore variability of both Dl,1-yr and Dl,5-yr is not discernible from these results
since the bathymetry is essentially parallel to the coastline.
The results have proven that Hallermeier’s equation remains valid and
typically produces the upper limit to Dc. It overpredicts the measured effective Dc
values by an average 42.5% for the 1-year case and 34.8% for the 5-year case. In
comparison, for the outermost depths of closure Dco, Hallermeier’s
equation
overpredicts Dco by 21% for the annual case and 7% for the 5-year case. The
distribution along the coastline is shown in Figure 6.41. These findings reveal a
trend of increasing accuracy of Dl,t in estimating actual Dc with an increase in
number of surveys and time. The case of predicting the 5-year Dco is encouraging
128
since the accuracy improved by 10% with a singular addition of the 2004 survey to
the earlier 1999 and 2000 survey data.
The study area was a re-nourished area and it has been mentioned earlier that
based on 1998-1999 bed samples, the mean d50 for the bed material in the study area
is 0.5 mm thereby exceeding the suggested range of material d50 valid for
Hallermeier’s equation which is 0.16 mm to 0.42 mm. The results however do not
invalidate Hallermeier’s equation as providing the upper limit to Dc on micro-tidal
coasts. This is perhaps mitigated by the fact that the 2004 samples have produced a
mean d50 of 0.3 mm thereby falling within the permissable range.
Table 6.6: Effective Dc and Predicted depth of closure, Dl,t , MLW
Predicted Dl,t
Chainage
CH00
(Measured) Dc
5-yr
Monsoon
1-yr Dc
Dc
-Dc
-2.68
-1.88
-3.38
%
% Diff.
Diff. 15-yr
yr
-ve indicates
overprediction
Dl, 1-yr
Dl, 5-yr
-4.65
-4.97
-59.6%
-32.0%
CH200
-0.69
-3.06
-3.42
-4.64
-4.96
-34.1%
-31.0%
CH400
-2.23
-2.20
-3.29
-4.64
-4.96
-52.6%
-33.7%
CH800
-2.41
-2.03
-2.2
-4.62
-4.95
-56.1%
-55.6%
CH1200
-2.64
-1.66
-1.7
-4.62
-4.94
-64.1%
-65.6%
CH1500
-3.15
-2.12
-2.92
-4.61
-4.94
-54.0%
-40.9%
CH2700
-1.46
-1.64
-3.78
-4.61
-4.95
-64.4%
-23.6%
CH3100
-3.28
-3.34
-3.32
-4.63
-4.96
-27.9%
-33.1%
CH-400
-2.71
-4.01
-3.27
-4.63
-4.96
-13.4%
-34.1%
CH-900
-2.94
-2.99
-3.83
-4.56
-4.89
-34.4%
-21.7%
CH-1400
-3.88
-4.23
-4.29
-4.53
-4.85
-6.6%
-11.5%
Average
-2.55
-2.65
-3.36
-4.61
-4.94
-42.5%
-34.8%
129
Depths of Closure at Pantai Sabak, Kelantan
1-yr Dc
5-yr Dc
Dl, 1-yr
Dl, 5-yr
Baseline elev. MLW
-8
-6
-4
-2
breakwater
0
2
4
3000
2500
2000
1500
1000
500
0
-500
-1000
-1500
Chainage, m
Figure 6.41: Dc along Pantai Sabak, Kelantan
6.11
Simplified Dc Equations
The simplified forms of the Hallermeier equation as described in Section
2.4.1 do not carry the wave period term within them and are therefore convenient in
providing quick estimates of Dc. Equations 2.5, 2.6 and 2.8 are of such nature and
are reproduced below:
H = 1.57 Hs 0.137
(2.5)
hc = 2H + 11 σH
(2.6)
Dl = 2Hs50 + 12σH
(2.8)
Where,
130
H, hc and Dl =
depth of closure
H, Hs
=
mean annual significant wave height
Hs 0.137
=
significant wave height exceeded 12-hours a year
Hs50
=
median significant wave height
σH
=
standard deviation of mean Hs
The following have been determined from the UKMO dataset (in meters
MLW) and comparing against Ch.1500 which is eroding and far away from the
influence of the breakwater (see Tables 6.7 and 6.8):
Table 6.7: Dc from simplified equations compared with effective Dc
H
Predicted
Dc
Ch.
1500
Dc -1 yr
Hs50
σH
-
-
-
4.55
2.12
114.6%
-
0.812
-
0.446
6.53
2.12
208.0%
-
-
0.7
0.446
6.75
2.12
218.4%
Equation
Hs 0.137
1.57 Hs 0.137
2.9
2H + 11σH
2Hs50 + 12σH
% diff.
Table 6.8: Dc from simplified equation compared to Dco
Equation
Hs 0.137
1.57 Hs 0.137
2.9
2H + 11σH
2Hs50 + 12σH
H
-
-
0.812
-
Hs50
σH
-
-
4.55
Ch.
1500
Dco -1 yr
2.96
-
0.446
6.53
2.96
120.6%
0.7
0.446
6.75
2.96
128.0%
Predicted
Dc
% diff.
53.7%
131
Tables 6.7 and 6.8 above reveal that Dc from simplified equations also
overpredict the effective Dc values. Equation 2.8 was tested by Unit Perancang
Ekonomi (1986) on the Kelantan coast and produced wave heights of 8.4 m. Within
the limits of the Pantai Sabak data, the lowest measured annual Dc or Dl,1-yr based
on the algorithm used above was found to be -4.23 m MLW at Ch.-1400. A simple
relationship can thus be formed between this and the UKMO offshore wave, H0.137:
Dc,1-yr / H0.137
=
4.23 / 2.9
=
1.45
therefore, equating the above to Dl.1-yr
say,
6.12
Dl.1-yr
=
1.45 H0.137
Dl.1-yr
=
1.5 H0.137
(6.1)
Observation
The annual Dc analysis has revealed that when the pre-breaking wave
condition is applied, Hallermeier’s equation tends to predict the outer closure depths
(Dco) which are associated with the outer bar changes and not the beach-shoreline
area. A cursory view of the wave heights in the middleshore area (Figures 5.7 to
5.16) landwards of the offshore bar indicates that they are smaller than the prebreaking waves at the -10 m depth contour which were the basis of the predictive
equation and could produce shallower Dc values. Francois et al (2004) commented
that Hallermeier did not specify at what depth of ‘local’ wave heights should be used
in the Hallermeier equation.
The results of the depth for closure analysis above has shown that predicted
Dc or Dl,t based on waves at -10 m depth consistently overpredicts the measured
values over the annual period and 5-year period. Predicted values from simplified
equations overpredict Dc since these are essentially calculated using offshore waves.
132
Comparatively, the Hallermeier equation is a better choice as the percentage
difference averages around 42% and improves with more data avalaibility.
The use of an algorithm to estimate Dc is designed to produce consistency.
The selection of a criteria value, in this case 0.3 m, is based on commonly acccepted
accuracy of survey. It is noted that if a lower criteria of 0.2 m is used, the area of
‘significant’ bed elevation could possibly encompass the entire foreshore from MLW
to the innershore bar as shown in Figure 6.42. Consequently, a different Dc could
result.
Depth of Closure (FDC): Ch.400; 1999-2000
Profile 1999
Profile 2000
Mean depth
MLW
FDC
FDC criteria line
criteria-2
4
1.6
Dc = -2.56 m based on
0.3 m criteria
2
Dc = -3.7 m based on
0.2 m criteria
1.4
1.2
-2
1
-4
0.8
-6
0.6
-8
0.4
-10
0.2
-12
0
0
500
1000
1500
2000
2500
Distance offshore, m
Figure 6.42: Dc based on different closure criteria
3000
FDC, m
0
133
CHAPTER 7
CONCLUSIONS AND RECOMMENDATIONS
7.1
General Conclusions
The determination of the depths of closure requires a definition of the depth
of closure and the determination of a criteria to pinpoint the depth of closure. Hence,
depth of closure studies include an element of the subjective. Nevertheless, Dc is an
important parameter in cross-shore transport studies as it separates the nearshore into
the respective zones of shoreline and offshore morphology. Knowing the depth and
location of Dc facilitates the design of beach-fill in beach nourishment projects.
Determining the position of depth of closure requires an analysis of a series of
overlapping profile surveys. Such data is not always available hence, predictive
equations based primarily on nearshore wave height conditions are often used.
In this study, the depths of closure for the shoreline of Pantai Sabak, Kelantan
were determined by analysing 4 sets of profile surveys. The depths of closure were
also calculated using the Hallermeier equation and both results were compared. The
findings have re-affirmed that Hallermeier’s equation is robust in predicting the
upper boundary of depth of closure and its applicability to wave-dominated microtidal coasts. In the case of Pantai Sabak, the prediction exceeds the measured value
of effective annual Dc by 42.5%. Exceptions to this general conclusion nonetheless
have manifested in profiles that were (i) close to coastal structures specifically, a
rivermouth breakwater in the study area and (ii) accreting stretches of the studied
134
shoreline. To summarise, the following relationships hold true in the case of the
Kelantan shoreline:
Dl,t > Dc (for beach fill design)
Dl,t > Dco
Dl,5-yr > Dl,1-yr
Referring to the results in Chapter 6, the following relationship for the Pantai
Sabak coast has been observed:
Dl,1-yr = 1.5 H0.137
The commonly used methods of standard deviation of depth change (SDDC)
and the Fixed Depth Change (FDC) were both utilised in the analysis and both
yielded results consistent with each other.
This research has determined that in the
multi-barred profiles of the Kelantan coast, cross-shore profiles typically close
around the innershore bars, re-open before the outershore bars and close again
beyond the outershore bars revealing zones of closure and reopening as wide as 500
meters. This phenomenon can be observed from pre and post-monsoon surveys
(northeast monsoon).
Due to this, it was necessary to add new definitions such as
Dci, Dcm and Dco to the terminology to describe the innershore, middleshore and
outershore closure points. From these points, an effective depth of closure for the
purpose of beach-fill design, Dc, was chosen. Outer closure points Dco are often
unrelated to the inshore and shoreline processes that produce Dci and in some
instances Dcm. Hence, the Dci and Dcm would be the best representative Dc for beachfill design purposes.
135
7.2
Suggestions for Future Research
This study has benefited from a periodical survey program initiated in 1998.
Similar type of programs will add more avenues for research in the field of crossshore transport and beach-fill design.
Some suggestions are added below for
consideration as future research areas.
7.2.1
Dc Criteria and Survey Techniques
The analysis above has used only a 30 cm closure criterion associated with
hydrographic survey accuracy.
Other criteria can be applied if more improved
measurement techniques are used. This will allow for a redefinition of the term
‘significant’ when applied to Dc studies.
7.2.2
Wave Data
One of the key limitations of this study was the absence of wave data over the
erosional northeast monsoon period. As a result, the calibration of the wave model
was done based on the wave data recorded over the weaker southwest monsoon
which is dominated by low swells.
Wave data collection over the northeast
monsoon period would provide the more appropriate dataset for verification of the
wave model. Such collection has been attempted by many parties with little success.
There is generally very little measured wave data available throughout the country
which hinders the progress of coastal research.
136
7.2.3
Profile Surveys and Bar Migration Phenomena
The profile surveys in this analysis extended over 3000 m from the study
shoreline and provided sufficient hydrographic information. In some profiles, when
using the FDC method, there were indications of re-opening well beyond the
outershore bars suggesting further cross-shore transport activities.
Though
prohibitive cost-wise, detailed surveys should be attempted beyond 3500 meters
from the shoreline to ascertain if the profiles do re-open in deeper waters.
A key observation in this research was that the innershore and offshore bars
migrated in opposite direction over the same monsoon period. This suggests that
different processes take place at different locations along the same profile. One way
to study this further is by establishing a periodical survey program supplemented
with post-storm surveys.
The results of this research have also pointed that the Pengkalan Datu
breakwaters have a distinct effect on the Dc results on the adjacent profiles. It is
inferred that with both Ch.00 and Ch.200 being immediately on the downdrift side of
the breakwater, the alongshore drift would have been eliminated and that the profile
formations at both these locations would be predominantly driven by cross-shore
process. However, other hitherto uninvestigated factors such as wave reflection off
the northern breakwater begs further study.
7.2.4
Determining a predictive formula for local Dc
This research has established the major profile trends and the results have
pointed to an over-estimation of the Dc by the Hallermeier equation. It is therefore
possible to follow the footsteps of Birkemeier and produce a local equation for
predicting Dc provided long-term nearshore wave measurements are available to
validate the wave numerical model.
A simplified relationship between H0.137 and
Dl,1-yr (Equation 6.1) has been proposed which establishes an upper limit to the
137
Pantai Sabak Dc based on the criteria applied. It however, cannot be claimed to be
applicable to other Malaysian coasts as yet.
138
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142
APPENDIX A
PROFILE SURVEYS FROM COASTLINE OF PANTAI
SABAK, KELANTAN 1998, 1999, 2000 AND 2004
CH-1400
Distance
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
2050
2100
2150
2200
2250
2300
Profile
1998
3.76
2.74
-0.26
-1.28
-1.96
-2.64
-3.18
-3.46
-3.71
-3.6
-3.99
-4.19
-4.24
-4.26
-4.49
-4.6
-4.66
-4.67
-4.77
-5
-4.42
-4.3
-4.66
-4.81
-4.81
-5.02
-5.08
-5.31
-5.34
-5.63
-5.64
-5.69
-5.86
-5.94
-6.14
-6.1
-6.12
-6.41
-6.29
-6.5
-6.5
-6.56
-6.79
-7.14
-7.25
-7.31
-7.54
All levels in m LSD
Profile
Profile
1999
2000
3.76
3.99
2.78
3.26
0.1
-0.46
-1.14
-1.19
-2.14
-2.23
-2.79
-3.05
-3.06
-3.38
-3.25
-3.49
-3.36
-3.8
-3.92
-4.13
-3.93
-4.3
-3.86
-4
-4.11
-3.8
-4.5
-4.06
-4.66
-4.52
-4.72
-4.92
-4.91
-4.8
-4.91
-4.84
-4.98
-4.73
-4.82
-4.55
-4.48
-4.54
-4.49
-4.73
-4.81
-4.81
-4.88
-4.85
-4.98
-4.95
-5.18
-5.02
-5.33
-5.24
-5.56
-5.36
-5.6
-5.5
-5.73
-5.65
-5.89
-5.76
-5.97
-5.88
-5.98
-6.01
-6.23
-6.15
-6.23
-6.32
-6.41
-6.21
-6.21
-6.16
-6.43
-6.34
-6.47
-6.36
-6.61
-6.44
-6.8
-6.76
-6.96
-6.97
-7.17
-7.11
-7.31
-7.3
-7.46
-7.51
-7.63
-7.57
-7.64
-7.67
Profile
2004
3.67
3
1.85
-0.17
-2.19
-2.95
-4.03
-4.22
-4.24
-4.31
-4.34
-4.56
-4.86
-4.68
-4.78
-5.18
-4.97
-4.7
-4.44
-4.4
-4.56
-4.85
-4.99
-4.16
-4.64
-5.17
-5.31
-5.31
-5.32
-5.67
-5.89
-6
-5.95
-6.03
-6.26
-6.27
-6.24
-6.31
-6.36
-6.42
-6.6
-6.66
-6.65
-6.75
-6.92
-7.02
-7.14
143
CH-1400
Distance
2350
2400
2450
2500
2550
2600
2650
2700
2750
2800
2850
2900
2950
3000
3050
3100
3150
3200
3250
3300
3350
3400
3450
3500
3550
3600
3650
3700
3750
3800
3850
3900
3950
Profile
1998
-7.63
-7.63
-7.79
-7.83
-7.89
-8.03
-8.2
-8.22
-8.44
-8.5
-8.73
-8.92
-9.01
-9.09
-9.15
-9.49
-9.45
-9.72
-9.81
-10.04
-10.13
-10.32
-10.46
-10.55
-10.72
-10.76
-10.86
-10.88
-11.08
-11.18
-11.39
-11.39
0
CH.-900
Distance
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
Profile 1998
3.19
2.57
2.85
-0.27
-1.21
-2.66
-3.44
-3.58
-3.05
-3.35
-3.72
-3.63
-3.28
-3.44
-3.5
All levels in m LSD
Profile
Profile
1999
2000
-7.74
-7.69
-7.92
-7.83
-7.95
-7.83
-7.97
-7.97
-8.08
-8.08
-8.15
-8.24
-8.36
-8.34
-8.38
-8.48
-8.44
-8.53
-8.6
-8.69
-8.71
-8.82
-8.99
-8.95
-9.13
-9.09
-9.19
-9.23
-9.36
-9.35
-9.55
-9.48
-9.81
-9.56
-9.88
-9.66
-9.98
-9.79
-10.07
-9.83
-10.26
-9.95
-10.2
-10.06
-10.42
-10.21
-10.54
-10.33
0
-10.51
0
-10.59
0
-10.72
0
-10.87
0
-10.93
0
-11.06
0
-11.12
0
-11.23
0
-11.22
All levels in m LSD
Profile 1999 Profile 2000
3.19
3.39
2.83
2.74
3.19
3.09
-0.1
-0.94
-1.62
-1.87
-2.33
-2.75
-3.15
-3.34
-3.59
-3.4
-2.82
-2.6
-3.22
-2.75
-3.89
-3.66
-3.94
-3.61
-3.71
-3.27
-3.3
-3.41
-3.16
-3.45
Profile
2004
-7.24
-7.37
-7.47
-7.48
-7.56
-7.83
-7.93
-7.94
-8.19
-8.26
-8.47
-8.53
-8.7
-8.87
-9.03
-9.08
-9.24
-9.31
-9.53
-9.43
-9.72
-10.02
-9.99
-10.1
-10.23
-10.46
-10.5
-10.7
-10.74
-10.89
-11.03
-11.19
0
Profile 2004
0
2.58
2.93
0.58
-0.69
-2.11
-2.97
-3.69
-3.93
-3.75
-4.05
-4.05
-4.03
-3.51
-3.79
144
CH.-900
Distance
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
2550
2600
2650
2700
2750
2800
2850
2900
2950
3000
3050
3100
3150
3200
3250
3300
3350
3400
Profile 1998
-3.46
-3.63
-3.92
-4.04
-4.31
-4.48
-4.71
-4.85
-4.97
-5.05
-5.2
-5.34
-5.57
-5.54
-5.63
-5.73
-5.76
-5.9
-6.07
-6.17
-6.3
-6.4
-6.54
-6.33
-6.69
-6.87
-7.24
-7.29
-7.5
-7.51
-7.39
-7.5
-7.6
-7.74
-7.9
-8.03
-8.28
-8.38
-8.52
-8.61
-8.75
-8.86
-9.01
-9.05
-9.26
-9.43
-9.5
-9.63
-9.72
-9.99
-10.11
-10.13
-10.37
-10.51
All levels in m LSD
Profile 1999 Profile 2000
-3.75
-3.63
-3.97
-3.73
-4.15
-3.84
-4.22
-4.14
-4.31
-4.33
-4.5
-4.49
-4.75
-4.61
-4.91
-4.81
-4.99
-4.98
-5.2
-5.21
-5.27
-5.33
-5.43
-5.4
-5.54
-5.47
-5.58
-5.58
-5.69
-5.66
-5.8
-5.69
-5.93
-5.81
-6.09
-5.9
-6.11
-5.94
-6.1
-6.11
-6.36
-6.38
-6.48
-6.55
-6.53
-6.71
-6.68
-6.8
-6.82
-6.8
-7.07
-7.05
-7.15
-7.21
-7.28
-7.24
-7.39
-7.34
-7.46
-7.43
-7.56
-7.56
-7.68
-7.67
-7.78
-7.73
-7.95
-7.84
-8
-7.99
-8.13
-8.06
-8.24
-8.28
-8.35
-8.33
-8.56
-8.46
-8.72
-8.59
-8.79
-8.72
-8.93
-8.89
-9.14
-9.03
-9.22
-9.11
-9.41
-9.28
-9.47
-9.4
-9.73
-9.54
-9.69
-9.62
-9.85
-9.77
-9.98
-9.9
-10.06
-10.01
-10.14
-10.08
-10.33
-10.18
-10.41
-10.31
Profile 2004
-4.34
-3.46
-3.73
-4.21
-4.57
-4.79
-4.96
-5.07
-5.27
-5.21
-5.37
-5.58
-5.49
-5.63
-5.76
-5.92
-5.99
-6.01
-6.04
-6.23
-6.1
-6.27
-6.36
-6.57
-6.58
-6.76
-6.77
-6.76
-6.82
-7.01
-7.07
-7.42
-7.34
-7.44
-7.51
-7.68
-7.55
-8.24
-8.23
-8.45
-8.79
-8.75
-9
-9
-9.17
-9.24
-9.53
-9.88
-9.83
-9.96
-9.73
-10.26
-10.45
-10.53
145
CH.-900
Distance
3450
3500
3550
3600
3650
3700
3750
Profile 1998
-10.66
-10.75
-10.74
-10.94
-10.99
-11.18
0
CH.-400
Distance
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
Profile
1998
2.39
2.4
2.23
1.71
-0.97
-1.93
-2.86
-3.16
-2.78
-2.82
-2.48
-3.05
-3.27
-3.41
-3.66
-3.57
-3.58
-3.81
-3.95
-4.24
-4.36
-4.36
-4.57
-4.7
-5.02
-5.04
-5.07
-5.28
-5.47
-5.53
-5.9
-6.03
-6.07
-6.13
-6.26
-6.43
-6.65
-6.63
-6.87
-6.78
-6.96
All levels in m LSD
Profile 1999 Profile 2000
-10.54
-10.47
-10.66
-10.57
-10.66
-10.7
-10.8
-10.84
0
-10.99
0
-11.08
0
-11.21
All levels ini m LSD
Profile
Profile
1999
2000
2.4
2.36
2.38
2.79
2.19
2.42
1.38
1.62
-1.09
-1.21
-2.29
-2.61
-3.21
-3.16
-3.61
-3.1
-2.91
-2.19
-2.45
-2.51
-3.01
-3.29
-3.08
-3.48
-3.19
-3.17
-3.48
-2.88
-3.79
-3.09
-3.8
-3.46
-3.75
-3.85
-3.82
-4.11
-3.97
-4.3
-4.25
-4.49
-4.65
-4.61
-4.65
-4.61
-4.84
-4.71
-4.97
-4.91
-5.2
-5.12
-5.33
-5.2
-5.4
-5.27
-5.49
-5.39
-5.68
-5.53
-5.72
-5.66
-5.96
-5.9
-6.18
-6.02
-6.14
-6.14
-6.31
-6.24
-6.41
-6.35
-6.49
-6.5
-6.58
-6.58
-6.71
-6.73
-6.78
-6.78
-6.86
-6.89
-7.11
-7.03
Profile 2004
-10.53
-10.65
-10.84
-10.86
-11.06
-11.35
-11.03
Profile
2004
-0.71
-1.31
1.42
2.51
0.55
-1.44
-2.68
-3.34
-3.68
-3.05
-2.5
-2.54
-3.11
-3.38
-3.5
-3.62
-3.75
-3.95
-4.16
-4.43
-4.67
-4.84
-5.06
-5.2
-5.29
-5.29
-5.39
-5.46
-5.57
-5.7
-5.79
-5.89
-5.97
-6.04
-6.1
-6.23
-6.3
-6.47
-6.57
-6.66
-6.78
146
CH.-400
Distance
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
2550
2600
2650
2700
2750
2800
2850
2900
2950
3000
3050
3100
3150
3200
3250
3300
3350
3400
3450
Profile
1998
-7.05
-7.19
-7.26
-7.49
-7.5
-7.84
-7.78
-8.04
-8.07
-8.2
-8.47
-8.66
-8.76
-8.84
-8.97
-9.13
-9.33
-9.37
-9.61
-9.62
-9.93
-9.96
-10.12
-10.31
-10.52
-10.66
-10.81
-11.01
-11.07
All levels ini m LSD
Profile
Profile
1999
2000
-7.26
-7.14
-7.4
-7.24
-7.57
-7.38
-7.61
-7.58
-7.63
-7.66
-7.94
-7.84
-7.98
-7.88
-8.17
-8.13
-8.35
-8.23
-8.56
-8.3
-8.59
-8.43
-8.75
-8.63
-8.88
-8.73
-8.94
-9.03
-9.1
-9.21
-9.2
-9.3
-9.26
-9.46
-9.54
-9.62
-9.61
-9.77
-9.78
-9.94
-9.99
-10.14
-10.05
-10.28
-10.29
-10.43
-10.35
-10.53
-10.51
-10.56
-10.56
-10.56
-10.86
-10.7
-10.98
-10.86
-11.01
-10.99
CH.00
Distance
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
Profile1998
2.35
3.04
-1.06
-1.09
-1.31
-1.56
-1.76
-1.53
-1.88
-2.4
-2.66
-2.17
-2.35
-1.84
-2.81
-3.23
-2.91
-2.7
-3.02
All levels in m LSD
Profile 1999
Profile 2000
2.56
2.6
3.09
2.91
-0.99
-1.1
-0.89
-1.11
-1.4
-1.6
-1.79
-1.87
-1.42
-1.53
-1.91
-1.93
-2.22
-2.26
-2.64
-2.83
-2.67
-2.88
-1.89
-1.92
-1.87
-1.45
-3.04
-2.72
-3.56
-3.74
-3.85
-4.1
-3.62
-3.14
-2.34
-2.15
-3.06
-2.93
Profile
2004
-6.93
-7.09
-7.2
-7.36
-7.54
-7.69
-7.88
-8.08
-8.33
-8.45
-8.6
-8.77
-8.9
-9.09
-9.25
-9.37
-9.5
-9.62
-9.78
-9.88
-10.05
-10.22
-10.28
-10.51
-10.66
-10.8
-10.89
-11.11
-11.24
Profile 2004
2.45
1.37
0.98
-0.82
-0.8
0.36
-1.56
-1.99
-2.33
-2.92
-3.13
-1.95
-1.93
-2.52
-3.71
-3.73
-2.98
-3
-3.06
147
CH.00
Distance
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
2550
2600
2650
2700
2750
2800
2850
2900
2950
3000
CH.200
Distance
0
50
100
150
200
250
300
Profile1998
-3.53
-3.82
-3.93
-3.79
-4.01
-4.22
-4.08
-3.22
-3.12
-3.85
-4.49
-4.7
-4.72
-4.76
-5.04
-5.39
-5.47
-5.54
-5.69
-5.69
-5.88
-6.07
-6.42
-6.52
-6.62
-6.77
-6.85
-6.85
-6.94
-7.1
-7.31
-7.61
-7.85
-7.97
-8.17
-8.42
-8.52
-8.7
-9.08
-9.4
-9.66
Profile 1998
1.25
-0.86
-1.01
-1.39
-1.59
-1.78
-1.86
All levels in m LSD
Profile 1999
Profile 2000
-3.6
-3.82
-3.87
-4.14
-4
-3.63
-3.79
-3.81
-3.97
-4.03
-4.2
-4.28
-4.44
-4.52
-4.17
-4.47
-4
-4.3
-3.55
-4.1
-3.63
-4
-4.27
-4.12
-4.98
-4.63
-5.27
-5.51
-5.46
-5.77
-5.49
-5.9
-5.55
-6
-5.67
-6.09
-5.86
-6.25
-6.1
-6.28
-6.22
-6.47
-6.35
-6.48
-6.52
-6.52
-6.53
-6.6
-6.64
-6.68
-6.74
-6.76
-6.84
-6.96
-6.99
-7.03
-7.08
-7.07
-7.14
-7.26
-7.32
-7.64
-7.72
-7.84
-7.88
-7.94
-8.04
-8.25
-8.24
-8.37
-8.35
-8.48
-8.5
-8.66
-8.81
-8.87
-9.08
-9.28
-9.47
-9.53
-9.64
-9.72
-9.84
-9.94
All levels in m LSD
Profile 1999 Profile 2000
0.95
1.28
-1.35
-1.21
-1.09
-1.3
-1.38
-1.61
-1.64
-1.77
-1.74
-1.86
-1.87
-2.07
Profile 2004
-3.08
-3.44
-3.6
-3.77
-3.96
-4.19
-4.14
-4.5
-4.41
-4.81
-4.79
-4.88
-5.15
-5.25
-5.54
-5.47
-5.63
-5.71
-5.97
-5.9
-6.05
-6.16
-6.21
-6.42
-6.49
-6.75
-6.64
-6.85
-7
-7.45
-7.72
-7.82
-8.21
-8.12
-8.12
-8.32
-8.92
-9.08
-9.49
-9.47
-9.7
-10.22
Profile 2004
-1.44
-1.49
-1.55
-1.7
-1.83
-1.98
-2.02
148
CH.200
Distance
350
400
450
500
550
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
2550
2600
2650
2700
2750
2800
2850
2900
2950
3000
Profile 1998
-2.16
-2.42
-2.43
-2.26
-1.46
-1.75
-2.91
-3.31
-3.22
-2.57
-2.86
-3.37
-3.67
-3.67
-3.06
-2.99
-3.66
-4.01
-4.22
-4.5
-4.42
-3.75
-3.75
-3.99
-4.37
-4.92
-5.09
-5.05
-5.09
-5.25
-5.37
-5.58
-5.86
-6.05
-6.16
-6.29
-6.39
-6.44
-6.63
-6.82
-6.91
-7.11
-7.48
-7.73
-7.84
-7.98
-8.19
-8.36
-8.38
-8.57
-8.95
-9.34
-9.5
-9.56
All levels in m LSD
Profile 1999 Profile 2000
-2.06
-2.33
-2.65
-2.7
-2.79
-2.68
-1.95
-2.14
-1.73
-1.62
-2.48
-1.97
-2.87
-2.72
-3.38
-3.63
-3.35
-3.8
-2.49
-3.18
-3.06
-2.19
-3.44
-3.43
-3.81
-4.11
-3.95
-4.08
-3.29
-3.29
-2.65
-3.13
-3.37
-3.48
-3.97
-3.98
-4.24
-4.21
-4.49
-4.42
-4.64
-4.49
-4.14
-4.28
-4
-4.28
-3.86
-4.1
-4.24
-4.37
-4.7
-4.77
-5.02
-5.04
-5.25
-5.17
-5.22
-5.23
-5.35
-5.31
-5.36
-5.29
-5.44
-5.28
-5.89
-5.66
-6.05
-6.06
-6.22
-6.24
-6.44
-6.31
-6.51
-6.48
-6.69
-6.63
-6.78
-6.75
-6.92
-6.85
-7.05
-7.2
-7.37
-7.43
-7.65
-7.7
-7.9
-7.83
-7.89
-7.92
-8.14
-8.06
-8.23
-8.14
-8.36
-8.36
-8.36
-8.46
-8.56
-8.73
-9.1
-9.13
-9.4
-9.38
-9.53
-9.59
-9.63
-9.74
Profile 2004
-2.14
-2.51
-1.96
-1.82
-1.7
-2.6
-3.26
-3.78
-2.99
-2.16
-2.46
-3.18
-3.61
-3.65
-3.62
-4
-4.12
-4.13
-4.25
-4.49
-4.42
-4
-3.95
-4.28
-4.65
-5.14
-5.42
-5.55
-5.7
-5.79
-5.92
-6.02
-6.14
-6.27
-6.39
-6.45
-6.56
-6.84
-6.91
-7.04
-7.1
-7.41
-7.55
-7.71
-7.88
-8.03
-8.33
-8.65
-8.9
-9.19
-9.39
-9.57
-9.63
-9.83
149
CH.400
Distance
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
2550
Profile 1998
2.14
-0.96
-1.24
-1.59
-1.89
-2.17
-2.41
-2.49
-2.28
-1.89
-2.02
-2.56
-2.79
-2.99
-3.3
-3.48
-3.47
-3.39
-3.38
-3.83
-3.7
-3.15
-3.07
-3.61
-4.05
-4.2
-4.07
-4.23
-4.05
-3.77
-3.67
-3.81
-4.13
-4.69
-5.06
-5.37
-5.47
-5.63
-5.81
-5.87
-6.1
-6.1
-6.23
-6.36
-6.55
-6.67
-6.77
-6.92
-7.15
-7.37
-7.58
-7.7
All levels in m LSD
Profile 1999
Profile 2000
2.65
2.39
-1.02
-1.15
-1.5
-1.65
-1.8
-1.93
-1.91
-2.17
-2.06
-2.32
-2.47
-2.45
-2.8
-2.65
-2.57
-2.42
-1.79
-1.66
-2.54
-1.77
-2.61
-2.51
-2.76
-2.76
-2.94
-3.21
-3.27
-3.42
-3.49
-3.76
-3.65
-3.78
-3.35
-3.22
-3.63
-3.62
-3.92
-3.98
-3.78
-3.8
-3.24
-3.12
-3.32
-3.46
-3.72
-3.58
-3.98
-3.7
-4.21
-4.14
-4.45
-4.59
-4.26
-4.61
-3.87
-3.51
-3.82
-3.39
-3.58
-3.93
-3.71
-3.94
-4.1
-3.92
-4.74
-4.6
-5.11
-4.81
-5.01
-5.28
-5.44
-5.22
-5.51
-5.56
-5.67
-5.52
-5.76
-5.63
-5.91
-5.85
-6.02
-5.99
-6.26
-6.18
-6.42
-6.36
-6.58
-6.47
-6.59
-6.62
-6.81
-6.82
-6.95
-6.87
-7.14
-7.18
-7.43
-7.29
-7.55
-7.56
-7.69
-7.72
Profile 2004
-0.54
-0.65
-0.75
-1.84
-2
-2.01
-2.22
-2.42
-2.6
-2.61
-1.57
-1.4
-2.56
-3.06
-2.93
-2.95
-3.54
-3.64
-3.47
-3.78
-3.97
-3.68
-3.19
-3.16
-3.46
-3.86
-4.1
-4.32
-4.54
-4.59
-4.2
-4.21
-4.46
-4.61
-4.82
-4.84
-4.86
-5.28
-5.61
-5.74
-5.98
-6.14
-6.28
-6.39
-6.48
-6.75
-6.98
-7.18
-7.36
-7.45
-7.59
-7.79
150
CH.400
Distance
2600
2650
2700
2750
2800
2850
2900
2950
3000
CH.800
Distance
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
Profile 1998
-7.89
-8.02
-8.24
-8.45
-8.65
-8.78
-9.1
-9.33
-9.68
All levels in m LSD
Profile 1999
Profile 2000
-7.95
-7.92
-8.06
-8.1
-8.27
-8.25
-8.48
-8.43
-8.65
-8.6
-8.64
-8.76
-8.99
-8.9
-9.29
-9.3
-9.57
-9.59
Profile 2004
-8.02
-8.18
-8.38
-8.47
-8.68
-8.96
-9.14
-9.37
-9.69
Profile 1998
1.82
0.05
-1.12
-1.93
-2.19
-1.89
-1.35
-2.17
-2.77
-2.99
-2.13
-2.67
-3.02
-3.25
-3.37
-3.5
-3.62
-3.8
-3.54
-3.46
-3.4
-3.62
-3.72
-3.68
-3.57
-3.43
-3.45
-2.94
-2.76
-3.41
-3.94
-4.08
-4.32
-4.57
-4.85
-4.95
-5.18
-5.34
-5.46
-5.61
-5.74
All levels in m LSD
Profile 1999
Profile 2000
1.82
2.41
-0.61
-0.57
-1.47
-1.38
-2.23
-1.95
-2.43
-2.34
-2.33
-1.85
-1.55
-2.14
-2.44
-2.33
-2.81
-2.51
-2.8
-2.59
-2.75
-2.68
-2.86
-2.77
-3.04
-3.01
-3.25
-3.26
-3.39
-3.51
-3.61
-3.61
-3.67
-3.76
-3.9
-3.78
-3.74
-3.81
-3.57
-3.71
-3.7
-3.78
-3.73
-3.86
-3.77
-3.57
-3.51
-3.43
-3.59
-3.48
-3.71
-3.83
-4.05
-4.68
-3.8
-3.83
-3.15
-2.39
-2.76
-2.86
-3.43
-3.75
-4.1
-4.16
-4.43
-4.44
-4.76
-4.68
-4.93
-4.93
-5.1
-5.14
-5.29
-5.29
-5.53
-5.37
-5.54
-5.58
-5.77
-5.75
-6.05
-5.72
Profile 2004
0.47
0.26
-1.22
-2.04
-2.29
-2.47
-2.68
-2.82
-1.98
-1.73
-2.26
-2.47
-2.78
-3.13
-3.37
-3.7
-3.88
-4.02
-3.9
-3.82
-4.1
-4.04
-3.19
-2.94
-3.62
-3.93
-4.15
-4.25
-4.17
-3.91
-3.33
-3.74
-3.72
-3.96
-4.4
-4.95
-5.44
-5.69
-5.73
-5.78
-5.95
151
CH.800
Distance
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
2550
2600
2650
2700
2750
2800
2850
2900
2950
3000
CH.1200
Distance
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
Profile 1998
-5.9
-6.01
-6.17
-6.38
-6.52
-6.66
-6.86
-6.98
-7.29
-7.6
-7.95
-8.17
-8.4
-8.5
-8.72
-8.94
-9.08
-9.32
-9.71
-10.13
Profile 1998
1.35
1.86
-0.82
-1.53
-1.2
-2.02
-2.46
-2.51
-1.61
-2.08
-3.04
-3.26
-3.23
-3.4
-3.66
-3.77
-3.68
-3.67
-3.7
-3.34
-3.3
-3.48
-3.35
-2.95
-2.23
-2.02
-3.05
-3.6
-3.46
All levels in m LSD
Profile 1999
Profile 2000
-6.06
-5.88
-6.18
-6.09
-6.26
-6.18
-6.48
-6.38
-6.61
-6.4
-6.86
-6.46
-7.06
-6.97
-7.31
-7.25
-7.47
-7.38
-7.75
-7.78
-8.13
-8
-8.29
-8.16
-8.5
-8.32
-8.66
-8.57
-8.9
-8.73
-9.04
-8.94
-9.2
-9.15
-9.47
-9.43
-9.79
-9.62
-9.95
-9.87
All levels in m LSD
Profile 1999
Profile 2000
1.35
1.53
1.98
2.25
-0.9
-1.23
-1.46
-1.56
-1.43
-1.73
-1.98
-2.14
-2.57
-2.6
-2.77
-2.13
-1.88
-2.17
-2.53
-2.65
-2.87
-2.89
-3.17
-3.07
-3.31
-3.21
-3.44
-3.42
-3.61
-3.54
-3.7
-3.6
-3.76
-3.67
-3.72
-3.66
-3.81
-3.78
-3.56
-3.52
-3.4
-3.2
-3.24
-3.29
-3.42
-3.47
-3.04
-3.21
-2.58
-2.78
-2.36
-3.28
-2.82
-2.96
-3.19
-2.35
-3.17
-2.49
Profile 2004
-6.15
-6.26
-6.33
-6.5
-6.65
-6.95
-7.17
-7.49
-7.7
-7.94
-8.25
-8.42
-8.67
-8.73
-8.95
-9.17
-9.55
-9.8
-9.91
-10.11
Profile 2004
1.61
0.52
-1.47
-2.66
-2.77
-2.3
-1.69
-1.53
-2.12
-2.49
-2.98
-3.19
-3.34
-3.53
-3.7
-3.77
-3.78
-3.82
-3.75
-3.43
-3.18
-3.36
-3.58
-3.63
-3.59
-3.46
-3.51
-3.51
-2.96
152
CH.1200
Distance
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
2550
2600
2650
2700
2750
2800
2850
2900
2950
3000
CH.1500
Distance
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
Profile 1998
-3.47
-3.62
-3.8
-4.04
-4.26
-4.27
-4.28
-4.20
-4.28
-4.37
-4.49
-4.65
-4.85
-5.01
-5.08
-5.21
-5.36
-5.45
-5.57
-5.82
-6.12
-6.49
-7.03
-7.49
-7.74
-8.09
-8.49
-8.91
-9.4
-9.87
-10.08
-10.13
Profile 1998
1.32
1.88
-1.27
-2.03
-1.95
-1.98
-2.48
-2.64
-2.79
-3.08
-3.18
-3.5
-3.65
-3.76
-3.84
-3.86
-3.45
All levels in m LSD
Profile 1999
Profile 2000
-3.13
-3.01
-3.43
-3.39
-3.82
-3.66
-4.13
-3.83
-4.21
-4
-4.29
-4.03
-4.41
-4.02
-4.27
-4.1
-4.33
-4.15
-4.39
-4.24
-4.6
-4.35
-4.67
-4.53
-4.84
-4.71
-4.99
-4.86
-5.15
-5
-5.3
-5.11
-5.48
-5.2
-5.52
-5.29
-5.65
-5.44
-5.87
-5.67
-6.14
-5.96
-6.62
-6.45
-7.13
-6.95
-7.5
-7.41
-7.85
-7.69
-8.18
-8
-8.57
-8.44
-8.93
-8.86
-9.38
-9.39
-9.82
-9.85
-9.94
-10
-10.03
-10.19
All levels in m LSD
Profile 1999 Profile 2000
1.32
1.61
1.87
0.54
-1.33
-1.28
-2.21
-2.27
-2.51
-2.1
-1.74
-2.37
-2.34
-2.61
-2.98
-2.99
-3.15
-3.12
-3.43
-3.37
-3.6
-3.49
-3.51
-3.61
-3.76
-3.66
-3.76
-3.83
-3.88
-3.9
-3.88
-3.84
-3.74
-3.87
Profile 2004
-2.14
-2.12
-3.2
-3.73
-3.72
-3.77
-3.94
-3.97
-4.01
-4.11
-4.4
-4.69
-4.73
-4.8
-4.94
-5.21
-5.3
-5.24
-5.49
-5.79
-6.05
-6.55
-6.98
-7.41
-7.79
-8.26
-8.6
-9.08
-9.52
-10.09
-10.32
-10.54
Profile 2004
3.39
-0.23
-2.42
-2.46
-2.37
-2.16
-2.23
-2.8
-3.19
-3.53
-3.68
-3.83
-3.81
-3.87
-3.88
-4.05
-4.03
153
CH.1500
Distance
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
2550
2600
2650
2700
2750
2800
2850
2900
2950
3000
CH.1900
Distance
0
50
100
150
200
Profile 1998
-2.93
-2.58
-2.38
-2.8
-3.08
-3.42
-3.85
-3.85
-3.54
-3.37
-3.58
-3.77
-3.97
-4.04
-4.04
-4.08
-4.06
-4.15
-4.15
-4.18
-4.28
-4.28
-4.28
-4.34
-4.4
-4.56
-4.63
-4.82
-4.94
-5.07
-5.38
-5.63
-5.99
-6.42
-7.06
-7.76
-8.33
-8.67
-9.12
-9.69
-9.88
-9.98
-10.18
All levels in m LSD
Profile 1999 Profile 2000
-3.48
-3.89
-3.18
-3.46
-2.59
-2.43
-2.52
-2.78
-3.2
-3.31
-3.61
-3.24
-3.89
-3.78
-4.03
-4.2
-3.84
-3.42
-3.46
-3.18
-3.51
-3.64
-3.74
-3.97
-3.99
-4.13
-4.11
-4.16
-4.23
-4.15
-4.11
-4.19
-4.02
-4.11
-4.07
-4.05
-4.16
-4.08
-4.19
-4.05
-4.21
-4.15
-4.24
-4.15
-4.32
-4.27
-4.42
-4.34
-4.49
-4.48
-4.55
-4.62
-4.77
-4.72
-4.75
-4.8
-4.92
-5
-5.17
-5.2
-5.42
-5.35
-5.69
-5.61
-6.1
-6.05
-6.49
-6.46
-7.12
-7.09
-7.85
-7.74
-8.32
-8.4
-8.69
-8.79
-9.26
-9.33
-9.82
-9.82
-9.93
-10.04
-10.09
-10.2
-10.5
Profile 1998
2.42
-0.17
-1.64
-2
-2.22
All levels in m LSD
Profile 1999 Profile 2004
2.42
-2.42
-1.29
-2.86
-2.01
-3.02
-2.2
-3.16
-2.54
-3.1
Profile 2004
-3.86
-3.83
-3.61
-3.33
-3.54
-4.05
-4.24
-4.31
-3.61
-2.57
-2.48
-3.11
-3.84
-4.2
-4.25
-4.26
-4.25
-4.22
-4.18
-4.19
-4.17
-4.16
-4.22
-4.43
-4.48
-4.67
-4.95
-4.97
-5.12
-5.27
-5.52
-5.75
-6.06
-6.47
-7.12
-7.69
-8.15
-8.67
-9.39
-9.97
-10.3
-10.5
-10.62
-10.79
154
CH.1900
Distance
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
2550
2600
2650
2700
2750
2800
2850
2900
Profile 1998
-2.74
-3.07
-3.29
-3.5
-3.68
-3.57
-3.66
-3.96
-4.04
-4.18
-3.14
-2.8
-3.28
-3.75
-3.93
-4.05
-4.11
-4.25
-4.17
-4.29
-4.49
-4.53
-4.52
-4.45
-4.21
-3.96
-3.86
-3.47
-3.23
-2.74
-3.05
-3.25
-3.66
-4.07
-4.21
-4.45
-4.86
-5.26
-5.53
-6.04
-6.44
-6.86
-7.19
-7.81
-8.15
-8.62
-8.92
-9.24
-9.61
-9.69
-9.9
-9.96
-10.15
-10.25
All levels in m LSD
Profile 1999 Profile 2004
-2.76
-2.84
-3.09
-3.03
-3.31
-3.33
-3.53
-3.62
-3.69
-3.84
-3.82
-4.02
-3.82
-4.15
-3.92
-4.27
-4.07
-4.22
-4.3
-4.3
-2.73
-4.07
-2.34
-3.17
-2.87
-3.12
-3.63
-3.67
-3.9
-4.29
-4.11
-4.64
-4.08
-4.32
-4.11
-3.45
-4.34
-3.33
-4.41
-3.62
-4.61
-4.03
-4.76
-4.4
-4.48
-4.5
-4.4
-4.59
-4.27
-4.69
-4.1
-4.58
-3.82
-4.22
-3.38
-3.9
-3.14
-3.54
-3.01
-3.45
-2.93
-3.45
-3.18
-3.57
-3.59
-3.69
-3.88
-3.91
-4.23
-4.17
-4.46
-4.48
-4.78
-4.84
-5.27
-5.18
-5.57
-5.48
-5.98
-5.94
-6.38
-6.37
-6.88
-6.77
-7.17
-7.21
-7.75
-7.71
-8.11
-8.14
-8.58
-8.51
-8.86
-8.92
-9.24
-9.44
-9.59
-9.77
-9.74
-9.94
-9.86
-10.08
-10.12
-10.24
-10.24
-10.43
-10.42
-10.53
155
CH.1900
Distance
2950
3000
3050
3100
3150
3200
3250
3300
3350
Profile 1998
-10.41
-10.64
-10.64
-10.87
-11.03
-11.23
-11.31
-11.41
CH.2300
Distance
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
Profile 1998
2.71
-1.33
-2.23
-2.58
-2.97
-3.17
-3.32
-3.44
-3.67
-3.4
-3.05
-3.63
-3.89
-3.94
-3.99
-3.88
-3.96
-3.82
-3.84
-3.76
-3.79
-3.99
-4.21
-4.43
-3.86
-3.31
-2.98
-3.15
-3.46
-3.72
-4.03
-4.2
-4.63
-5.01
-5.38
-6
-6.59
-6.91
-7.07
-7.24
-7.41
All levels in m LSD
Profile 1999 Profile 2004
-10.55
-10.7
-10.58
-10.81
-10.58
-10.91
-10.78
-11.08
-10.97
-11.19
-10.96
-11.36
-11.29
-11.5
-11.65
-11.84
All levels in m LSD
Profile
1999
Profile 2004
1.96
-2.61
-1.6
-2.63
-2.11
-2.14
-2.36
-2.34
-2.82
-2.88
-3.07
-3.05
-3.29
-3.29
-3.44
-3.48
-3.59
-3.62
-2.88
-3.74
-3.03
-3.89
-3.51
-4.1
-3.68
-3.54
-3.79
-2.58
-3.88
-2.92
-3.9
-3.65
-4.01
-4.09
-3.8
-4.09
-3.9
-3.6
-3.87
-3.29
-3.78
-3.6
-3.98
-3.82
-4.28
-4.09
-4.35
-4.21
-3.92
-4.04
-3.37
-3.4
-3.06
-3.13
-3.15
-3.28
-3.35
-3.52
-3.61
-3.67
-4.03
-3.87
-4.3
-4.08
-4.6
-4.43
-5.03
-5.26
-5.49
-5.96
-6.13
-6.44
-6.81
-6.67
-7.07
-6.84
-7.19
-7.09
-7.32
-7.24
-7.51
-7.49
156
CH.2300
Distance
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
2550
2600
2650
2700
2750
2800
2850
2900
2950
3000
3050
3100
3150
3200
3250
3300
3350
3400
Profile 1998
-7.5
-7.75
-7.99
-8.19
-8.43
-8.56
-8.71
-8.79
-9.06
-9.09
-9.25
-9.43
-9.69
-9.85
-10.14
-10.3
-10.37
-10.51
-10.58
-10.77
-10.84
-11.15
-11.46
-11.44
-11.46
0
CH.2700
Distance
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
All levels in m LSD
Profile
1999
Profile 2004
-7.62
-7.64
-7.77
-7.83
-8.04
-7.97
-8.23
-8.12
-8.24
-8.33
-8.44
-8.43
-8.7
-8.57
-8.89
-8.71
-8.98
-8.85
-9.06
-9
-9.23
-9.13
-9.5
-9.38
-9.85
-9.5
-9.95
-9.65
-10.09
-9.81
-10.17
-9.96
-10.3
-10.14
-10.45
-10.33
-10.52
-10.57
-10.73
-10.75
-10.89
-10.92
-10.99
-11.11
-11.26
-11.43
-11.59
-11.78
-11.88
All levels in m LSD
Profile
1998
2.09
2.72
-0.8
-1.72
-2.36
-2.79
-3.27
-2.81
-2.41
-3.1
-3.71
-3.93
-3.35
-3.56
-4.16
-3.71
-3.18
-3.34
Profile
1999
2.09
1.82
-1.4
-1.92
-2.12
-2.68
-3.1
-2.54
-2.07
-3.28
-3.57
-3.72
-3.51
-3.68
-4.24
-3.52
-3.12
-3.41
Profile
2000
2.53
-1.37
-2.14
-2.07
-2.17
-2.63
-3.1
-2.71
-2.23
-3.09
-3.46
-3.54
-3.55
-3.98
-3.99
-3.34
-3.4
-3.6
Profile
2004
-0.01
-1.29
-2.45
-2.1
-2.34
-2.91
-3.21
-3.09
-3.34
-3.58
-3.47
-2.76
-3.55
-4.42
-4.18
-3.35
-3.29
-3.56
157
CH.2700
Distance
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
2050
2100
2150
2200
2250
All levels in m LSD
Profile
1998
-3.64
-4.05
-4.37
-4.8
-5.19
-5.62
-5.94
-6.14
-6.33
-6.47
-6.64
-6.72
-6.83
-6.89
-7.07
-7.21
-7.22
-7.33
-7.48
-7.56
-7.69
-7.8
-7.87
-8.01
-8.13
-8.21
Profile
1999
-3.69
-4.11
-4.52
-4.84
-5.17
-5.65
-6.06
-6.42
-6.62
-6.79
-6.98
-7.11
-7.19
-7.31
-7.31
-7.51
-7.57
-7.6
-7.74
-7.77
-7.84
-7.92
-8.01
-8.01
-8.01
-8.12
-8.18
-8.25
CH.3100
Distance
0
50
100
150
200
250
300
350
400
450
500
550
600
650
700
750
800
850
Profile
2000
-3.65
-4.25
-4.6
-4.96
-5.24
-5.87
-6.33
-6.44
-6.61
-6.75
-6.88
-6.97
-7.08
-7.18
-7.27
-7.32
-7.43
-7.49
-7.6
-7.72
-7.78
-7.84
-7.94
-8.05
-8.16
-8.3
-8.39
Profile
2004
-3.91
-4.18
-4.51
-4.92
-5.36
-5.76
-5.97
-6.11
-6.3
-6.39
-6.49
-6.64
-6.72
-6.83
-6.95
-6.99
-7.09
-7.22
-7.28
-7.34
-7.51
-7.59
-7.7
-7.7
-7.8
-7.89
-8
-8.07
All levels in m LSD
Profile 1998
1.71
-1.56
-1.87
-2.36
-3.04
-3.09
-2.19
-2.8
-3.6
-3.35
-2.89
-3.75
-4.02
-4.28
-4.21
-3.3
-3.16
-3.54
Profile 1999
1.9
-1.58
-1.82
-2.45
-3.08
-2.77
-2.5
-3.22
-3.69
-3.07
-2.92
-3.71
-3.88
-4.06
-4.12
-3.13
-3.33
-3.71
Profile 2000
0.53
-1.71
-1.93
-2.46
-2.98
-2.24
-3.02
-3.67
-3.44
-2.71
-3.27
-3.68
-3.94
-4.23
-3.81
-3.26
-3.28
-3.69
Profile 2004
-0.22
-0.5
-2.11
-2.65
-2.91
-3.35
-3.65
-3.56
-3.29
-2.77
-2.66
-3.64
-4.29
-4.58
-3.71
-3.3
-3.49
-3.81
158
CH.3100
Distance
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
All levels in m LSD
Profile 1998
-4.02
-4.47
-4.96
-5.42
-5.91
-6.13
-6.28
-6.5
-6.58
-6.79
-6.84
-7.03
-7.08
-7.25
-7.3
-7.43
-7.5
-7.65
-7.75
-7.9
-7.9
-8.01
-8.04
-8.23
-8.19
-8.33
-8.44
0
0
0
0
0
0
Profile 1999
-4.14
-4.53
-5.08
-5.51
-5.93
-6.39
-6.6
-6.75
-6.97
-7.05
-7.14
-7.2
-7.3
-7.4
-7.46
-7.51
-7.62
-7.66
-7.83
-7.81
-7.89
-7.9
-8.05
-8.05
-8.18
-8.31
-8.37
-8.54
-8.63
0
0
0
0
Profile 2000
-4.09
-4.52
-5.01
-5.43
-5.85
-6.3
-6.53
-6.65
-6.75
-6.95
-6.99
-7.04
-7.18
-7.24
-7.33
-7.37
-7.49
-7.56
-7.62
-7.75
-7.84
-8.03
-8.12
-8.23
-8.35
-8.37
-8.45
-8.57
-8.68
-8.75
-8.89
-9.01
-9.2
Profile 2004
-4.1
-4.51
-5.14
-5.58
-5.88
-6.04
-6.19
-6.27
-6.4
-6.57
-6.63
-6.72
-6.84
-7.01
-7.04
-7.11
-7.25
-7.36
-7.46
-7.57
-7.63
-7.75
-7.82
-7.96
-8.02
-8.12
-8.23
-8.35
-8.47
-8.55
-8.61
-8.78
0
159
APPENDIX B
DESCRIPTION OF UNITED KINGDOM
METEOROLOGICAL OFFICE (UKMO) DATASET
160
APPENDIX B.1
QUALITY STATEMENT: UK Met Office Wave Model archive
The Met Office Wave Model Archive consists of the hindcast fields of winds and waves
produced during the operation of the atmospheric and wave model forecast suite. To
produce the best possible analysis of surface wind, all available reports of surface
pressure, wind speed and direction (from ships, buoys, platforms and land stations) are
subjected to a range of consistency checks before being assimilated into the model's
analysis. The resulting wind field is then used to modify the wave field derived from
earlier timesteps. For each of the 16 directional and 13 frequency bands, the changes
in wave energy are computed at each gridpoint, using the local wind as energy input,
and allowing for propagation, dissipation and transfer between spectral bands. The
model is a so-called ‘Second Generation' model, where the spectral shape is empirically
defined, rather than being calculated at run time; this latter process is too expensive of
computing time for an operational model of this resolution. For further details see
Golding (1983) and Francis (1985). There are two versions of the wave model, both in
operation since 1986 - one covers the Global oceans and the other European waters.
The Global Wave Model The analysed fields of wind and 1-dimensional spectra (i.e.
energy within each spectral band, plus a mean direction for that band) have been
archived, initially at 12-hour intervals and subsequently (since June 1988) at 6-hour
intervals. The spatial resolution was initially 150km (approx.) (13.8k gridpoints), this
was improved in June 1991, to a resolution of 85km (approx.) (37.3k gridpoints). Both
versions of the model operated with an assumed fixed depth (200m) on a lat/long grid.
In May 1999, a higher resolution Global Model was brought into operational use with
60km (approx.) grid spacing. The model is depth-dependent and includes shallow water
physics, namely bottom friction, refraction and shoaling.
Nested within the Global Wave Model, and taking boundary conditions from it, is a
European Waters Wave Model. This is a depth-dependent second-generation model
operating on a lat/long grid with spacing approx. 25km (8.5k gridpoints). The model
covers West European waters to 14degW between 30.5N and 66.7N and also covers
the Mediterranean and Baltic Seas; the Black Sea was added in 1993. Wind and wave
hindcast values were archived initially at 6-hour intervals and since June 1988 at 3-hour
intervals.
Output at each timestep consists of wind speed and direction, plus either:
1-dimensional spectrum (energy and mean direction in each of the 13 spectral bands)
or the conventional integrated variables derived from the spectrum (i.e. significant wave
height, period and direction for both windsea and swell, together with resultant height
and period).
Since the winds are taken from the lowest level of the Atmospheric Model, they
represent conditions approx. 20m above mean sea level.
As with any operational model, there have been many small-scale improvements
incorporated over the years. Most of these are introduced for computational reasons, to
improve the efficiency of the calculations, but some are more fundamental, including the
assimilation of wave height data from the ERS-1 (from June 1993) and ERS-2 satellites
into the Global Wave model analysis (see Foreman et al, 1994). Further detail (and
dates) of the more significant changes to the model's operation are available on
request. Over the years, there have been occasional interruptions to the operational
routine due to mainframe malfunction. Consequently, there are some periods of
missing data in the archive, most of them of 12 hours duration or less.
161
References
Foreman, SJ, Holt, MW
& Kelsall, S
Francis, P E
(1994)
(1985)
Golding, B
(1983)
Holt, M W
(1993)
Preliminary assessment and use of ERS-1 altimeter
wave data
J Atmos & Ocean Tech 11 pp1370-1380
Sea surface wave and storm surge models
Meteorol Mag 114 pp 234-241
A wave prediction system for real-time sea state
forecasting
Q J R Meteorol Soc 109 pp393-416
Modelling Ocean Waves
Meteorol Mag 122 pp238-247
March 2002
162
APPENDIX B.2
Changes to UK Met Office Wave Models since 1986
Any operational model is subject to small-scale modifications over time, to deal with minor
problems which are detected in day-to-day usage of the model products. It should also be
recognised that changes in the formulation of the atmospheric models' winds will have some
effect on the wave model results. Many of these changes are minor, and will have little impact
on the wave model output for most practical applications. Listed below are the more significant
changes which have been made to the formulation of either Atmospheric or Wave model since
1986. Because of the inherent month-to-month variability in winds and waves over many parts
of the globe, it is difficult in most cases to detect and quantify changes in the archived data as a
result of these modifications.
Jul 1986
Global and European lat/long grids introduced on CYBER mainframe computer.
Global:1.5deg lat x 1.875deg long
European:
0.25deg lat x 0.4deg long
Oct 1986
Archiving begins of wave model hindcasts from Global (12-hour intervals) and
European (6-hour
intervals) models.
Apr 1987
Revised physics introduced for Global Wave Model, including improved GreatCircle turning for swell.
Feb 1988
Ice edge now updated (approx weekly) for Global Model.
Jun 1988
Global Model now archived at 6-hourly intervals and European Model at 3-hour
intervals.
Nov 1988
Analysis-correction (AC) scheme introduced to assimilate data into Atmospheric
Model.
Apr 1990
Coastal point depths in European model amended to correct erroneous swell
directions near coasts.
Jun 1991
Unified (Atmospheric) Model introduced on CRAY computer. Global Wave Model
resolution changed to match Atmospheric Model's grid (now 0.833deg lat x
1.25deg long – approx 90km)
European Wave Model grid unchanged.
Oct 1992
Wave Model physics revised to improve retention of swell.
Apr 1993
European Wave Model extended to cover Black Sea.
Jun 1993
Wave height data derived from ERS-1 altimeter assimilated into Global model
analysis.
Aug 1993
ERS-1 scatterometer winds assimilated into Global Atmospheric Model analysis.
Nov 1993
Bottom friction increased in European wave model.
Nov 1994
Wave Model revised to improve waves at low windspeeds and reduce swell
dissipation.
Jan 1995
New version of Gravity Wave Drag implemented in atmospheric models,
resulting in improved
surface pressure fields and directions of low-level winds.
Jan 1996
Change of orographic roughness, giving improvement to low-level winds.
Apr 1996
Improved assimilation of temperature profiles from satellite soundings, giving
lower wind field errors, especially in the tropics. Also, ERS-1 altimeter data
superseded by data from ERS-2,further reducing bias against wave
measurements.
Nov 1996
Improvements to Convective Momentum Transport, Gravity wave Drag and
satellite humidity assimilation, resulting in lower RMS errors in winds and
pressures.
Jan 1998
Global atmospheric model resolution increased from 90km to approx 60km.
(26 Feb 1999-21 July 1999: Global wave model assimilation of ERS-2 wave data switched off.)
May 1999
Global wave model spatial resolution increased to 60km and depth-dependency
introduced.
163
Oct 1999
April 2000
New surface wind data from Special Sensor Microwave Imager (SSMI) on
board the DMSP F13 satellite and further data from F15 from early 2000,
resulted in further improvements to wind fields.
Operational implementation of new Mesoscale (UK Waters) wave model,
covering coast of Denmark to approx 15deg W, 47.5N to 61N (on same grid as
surge model). Includes wave-current interactions, and uses Mesoscale
atmosphere model winds. Resolution is approx 12km, giving better treatment of
coastlines. Currently running in parallel with the (unchanged) European wave
model.
March 2002
164
APPENDIX B.3
MET OFFICE WAVE MODEL GRIDPOINT DATA
INTEGRATED FORMAT (FROM OCTOBER 1986)
Layout of data record
Byte No.
Parameter
1-2
4-5
7-8
10-13
16-20
21-21
23-28
29-29
31-31
33-35
37-37
39-42
HOUR (GMT/UTC)
DAY
MONTH
YEAR
LATITUDE
LATITUDE (N OR S)
LONGITUDE
LONGITUDE (E OR W)
WIND INDICATOR
WATER DEPTH
SEA INDICATOR
WIND SPEED
44-46
48-51
53-56
58-60
62-65
67-70
72-74
76-79
81-84
86-88
WIND DIRECTION
RESULTANT WAVE HEIGHT
RESULTANT WAVE PERIOD
RESULTANT WAVE DIRECTION
WIND-SEA HEIGHT
WIND-SEA PERIOD
WIND-SEA DIRECTION
SWELL HEIGHT
SWELL PERIOD
SWELL DIRECTION
Units
degrees
degrees
metres
knots
ms-1
degrees true
metres
seconds
degrees true
metres
seconds
degrees true
metres
seconds
degrees true
Data Type
I2
I2
I2
I4
F5.2
A1
F6.2
A1
I1
I3
I1
I4
F4.1
I3
F4.1
F4.1
I3
F4.1
F4.1
I3
F4.1
F4.1
I3
Notes:
WIND INDICATOR: 1 - Wind speed in ms-1
2 - Wind speed in knots
SEA INDICATOR:
1 - Open Sea Point
2 - Coastal Point
(N.B. Coastal points should be treated with caution. Please contact Met Office for further details).
For each gridpoint, there is one record per timestep.
March 2002
165
APPENDIX C
SUMMARY OF SEDIMENT GRAIN SIZE
DISTRIBUTION FROM PANTAI SABAK,
KELANTAN SURVEYS 1998, 1999, 2004
Depth
Depth
APPENDIX C.1: SUMMARY OF GRAIN SIZE DISTRIBUTION FROM 1998, 1999 AND 2004 SURVEYS
1998
2m
5m
> 7m
CH
3100
Na
0.35
Na
CH
2700
0.44
0.36
na
CH
2300
0.12
0.7
na
CH
1900
0.12
0.38
na
CH
1500
0.35
na
na
CH
1200
0.18
0.62
0.43
CH
800
0.6
Na
0.35
CH
400
0.07
na
0.3
CH
200
na
na
na
CH
00
0.15
0.62
0.28
CH
-400
0.68
na
0.38
CH900
na
na
na
CH1400
0.16
na
na
MIN
0.07
0.35
0.28
MAX
0.68
0.7
0.43
MEAN
0.287
0.505
0.348
1999
2m
5m
> 7m
CH
3100
Na
0.56
Na
CH
2700
na
0.34
na
CH
2300
na
0.62
na
CH
1900
0.06
0.43
na
CH
1500
0.21
0.58
0.3
CH
1200
na
0.47
1.75
CH
800
Na
Na
Na
CH
400
na
na
1.6
CH
200
na
na
na
CH
00
0.26
na
1.6
CH400
0.2
na
1.6
CH900
na
na
na
CH1400
0.26
na
na
MIN
0.06
0.34
0.3
MAX
0.26
0.62
1.75
MEAN
0.198
0.5
1.37
SUMMARY FOR 2004 SURVEYS
DEPTH
2-5 m depth
>5 - 7 m depth
>= 10 m depth
MEAN
MAX
MIN
0.19
0.35
0.70
0.30
2.46
0.70
0.09
0.07
0.7
166
APPENDIX C.2
Area A
Date
6/9/04
Area B
BED SEDIMENT SAMPLES AND GRAIN N SIZE DISTRIBUTION FROM 2004 SURVEY
NORTH OF BREAKWATERS
Time
11:58
11:49
Line
17
17
12:23
41
11:20
41
BREAKWATER AREA
Tide
1.0m
0.95m
Water
Depth
4.0m
7.0m
Samples
No.
AA17D
A17E
Fix No.
12
11
1.0m
0.85m
4.4m
6.9m
AA41D
A41E
13
10
Coordinates Samples
N 34704.5m
E 9071.8m
N 35309.9m
E 9470.6m
Remarks
Find Sand (Black)
Soft Mud Brown
D50
0.12
0.32
N 32985.4m
N 33653.4m
Sand
Soft Mud Brown
0.3
0.55
E 13605.4m
E 13917.4m
Date
Time
Line
Tide
Water
Depth
Samples
No.
Fix No.
6/9/04
12:40
10:58
23
23
1.1m
0.8m
4.3m
6.9m
BB23D
BB23E
14
9
N 32073.9m
N 32982.5m
E 15790.8m
E 16643.1m
Remarks
Muddy & Fine
Sand
Soft Sand
12:56
10:27
10:39
89
89
89
1.1m
0.7m
0.8m
4.4m
7.1m
10.9m
BB89D
BB89E
BB89F
15
7
8
N 31424.5m
N 32915.3m
N 33390.7m
E 17372.4m
E 18883.2m
E 19057.7m
Muddy & Fine
Sand
Coarse Sand
Muddy & Shell
0.6m
0.7m
3.6m
6.8m
BB177D
BB177E
1
6
N 30380.1m
N 31267.4m
E 19401.4m
E 20206.9m
Sandy Black
Muddy
Area C
Date
6/9/04
8:49
177
10:14
177
SOUTH OF BREAKWATERS
Time
9:05
9:50
Line
12
12
Tide
0.6m
0.7m
Water
Depth
3.8m
6.7m
Samples
No.
CC12D
C12E
Fix No.
2
5
9:20
9:30
25
25
0.65m
0.65m
3.9m
6.8m
CC25D
C25E
3
4
Coordinates Samples
D50
0.3
0.09
0.12
0.65
0.7
0.07
Coordinates Samples
N 27755.0m
E 20821.2m
N 28831.6m
E 22337.6m
Remarks
Muddy Soft
Muddy & Sand
D50
0.09
0.7
N 25652.4m
N 26278.6m
Muddy & Fine
Sand
Muddy Black
0.2
0.08
E 22308.5m
E 23209.3m
167
168
APPENDIX D
TIDAL DATA FROM PANTAI SABAK,
KELANTAN; 2004 SURVEY
APPENDIX D.1: Time Series Plot of Tidal Heights at WL2,Pantai Sabak
1.20
WL2 - Pantai Sabak
Tide(m)LSD
1.00
0.80
0.60
0.40
0.20
0.00
-0.20
-0.40
-0.60
-0.80
-1.00
7/3/04
14:00
7/4/04
0:00
7/4/04
10:00
7/4/04
20:00
7/5/04
6:00
7/5/04
16:00
7/6/04
2:00
7/6/04
12:00
7/6/04
22:00
7/7/04
8:00
7/7/04
18:00
7/8/04
4:00
7/8/04
14:00
7/9/04
0:00
7/9/04
10:00
7/9/04 7/10/04 7/10/04 7/11/04 7/11/04 7/11/04 7/12/04 7/12/04 7/13/04
20:00
6:00
16:00
2:00
12:00
22:00
8:00
18:00
4:00
169
APPENDIX D.2: Time series Plot of tidal heights at WL4 Sg. Pengkalan Datu
WL4 - Sg Pgkl Datu
Tide(m) LSD
1.00
0.80
0.60
0.40
0.20
0.00
-0.20
-0.40
-0.60
-0.80
7/3/04
13:30
7/4/04
1:30
7/4/04
13:30
7/5/04
1:30
7/5/04
13:30
7/6/04
1:30
7/6/04
13:30
7/7/04
1:30
7/7/04
13:30
7/8/04
1:30
7/8/04
13:30
7/9/04
1:30
7/9/04
13:30
7/10/04
1:30
7/10/04
13:30
7/11/04
1:30
7/11/04
13:30
7/12/04
1:30
7/12/04
13:30
7/13/04
1:30
170
171
APPENDIX E
WAVE MODEL BATHYMETRY
172
WAVE MODEL BATHYMETRY
Model orientation for waves from North
Model orientation for waves from N30
173
Model orientation for waves from N60
Model orientation for waves from N90
174
Model orientation for waves from N120o