niomr industrial attachment report 2006
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FEDERAL UNIVERSITY OF TECHNOLOGY OWERRI, IMO STATE
STUDENTS INDUSTRIAL WORK EXPERIENCE SCHEME (SIWES)
A REPORT ON SIWES 400 LEVEL HELD BETWEEN 19TH JUNE 2006 TO 9THDECEMBER 2006 AT THE NIGERIAN INSTITUTE OF OCEANOGRAPHY AND
MARINE RESEARCH 1 WILMOT POINT ROAD BAR BEARCH VICTORIAISLAND LAGOS
BY
NWOSU VICTOR OBINNAYA CHIKEZIEREGISTRATION NO: 20021189285
DEPARTMENT OF GEOSCIENCESSCHOOL OF SCIENCE
SIWES 400 LEVEL (JUNE – DECEMBER 2006) NWOSU VICTOR O.C 20021189285
DEDICATION
I dedicate this industrial training report to Almighty God for His grace and Goodness which
have been greatly bestowed on me.
SIWES 400 LEVEL (JUNE – DECEMBER 2006) NWOSU VICTOR O.C 20021189285
ACKNOWLEDGEMENT
My Profound gratitude goes to God for his guidance and protection on me for having
successfully completed this Program.
Also, I wish to express my sincere appreciation to my Supervisor for his gentle, precise,
constructive criticism and assistance given to me during my industrial training. My gratitude
goes to Dr Green, Dr Adesina Adebiyi, Chief Uko, Mr Abdul, Mr James and my Geology
Lecturers in FUTO(Federal University of Technology Owerri.)
I also give thanks to my sponsor; Nigerian Institute for Oceanography and Marine Research,
the director general, Dr B.N Ezenwa and the rest staff of the institute for being there for me.
These acknowledgments will not be completed without my utmost gratitude my parents. I
shall not leave out my other I.T colleagues for their support, cooperation and companionship
during the training period.
SIWES 400 LEVEL (JUNE – DECEMBER 2006) NWOSU VICTOR O.C 20021189285
TABLE OF CONTENTS
TITLE
PAGE...................................................................................................................................1
DEDICATION.....................................................................................................................2
ACKNOWLEDGEMENT...................................................................................................3
TABLE OF
CONTENTS.........................................................................................................................4
CHAPTER 1.........................................................INTRODUCTION TO TIDAL
OBSERVATION
CHAPTER 2.........................................................SEDIMENTOLOGY STUDY OF THE
VICTORIA BEACH
CHAPTER 3..........................................................OCEANOGRAPHY AND ITS
TECHNIQUES FOR MEASUREMENT
CHAPTER 4..........................................................COASTAL PROCESS AND EROSION
EXPERIENCED GAINED
SUMMARY
SIWES 400 LEVEL (JUNE – DECEMBER 2006) NWOSU VICTOR O.C 20021189285
COMPANY PROFILE
The Nigerian Institute For Oceanography and Marine Research(NIOMR) was created from
The Marine Research Division of the Federal Department of fisheries by The Research
Institute establishment order with effect from 1st November 1975 by this order, the assets,
properties and rights held in respect of the oceanographic and marine research functions of
The Federal Department of Fisheries was invested in The Institute.
NIOMR is charged with the responsibility to conduct research into the resources and physical
characteristics of the Nigerian territorial waters and the high seas beyond. Specifics of the
mandate are as follows:
1. Genetic Improvement of marine water fisheries in the marine waters.
2. Abundance and other biological characteristics of fisheries and other aquatic
resources
3. Improvement of brackish water aquaculture.
4. Preservation and utilization of fishes and other aquatic products.
5. Physical characteristics of The Nigerian Territorial Waters, topography of the seabed
and deposits.
6. Effects of pollution on Nigerian coastal waters and its prevention.
7. Extension research and liaison services in areas of mandate.
Also, NIOMR is organized into six divisions, four research, one administrative, finance and
technical services. The six divisions are given as follows:
SIWES 400 LEVEL (JUNE – DECEMBER 2006) NWOSU VICTOR O.C 20021189285
1. Administrative and Finance.
2. Technical Services.
3. Fisheries Resources.
4. Marine Geology and Geophysics.
5. Fish Technology, Statistics and Economics.
6. The African Regional Aquaculture Centre.
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CHAPTER ONE
INTRODUCTION TO TIDAL OBSERVATION
1.1 TIDES
The term “tide” describes the periodic and regular variations in sea level which have a
coherent amplitude and phase relationship to some periodic geophysical forces; the moon,
and to a lesser extent, the sun creates ocean tides by gravitational forces. These forces of
attraction and the fact that the sun, the moon and the earth are in motion in relation to each
other, cause water masses to be set in motion. These tidal motions of water masses are a form
of a very long period wave motion, resulting in a rise and fall of the water surface giving rise
to episodes of high tide and low tide. The change in level occurs twice each day in case of
diurnal tides such that there are two high water and two low water in each lunar day (about
24.8hrs) where there is a long bay or a river mouth, the rise in water level is accompanied by
an inward flow of water termed the “flood” while the subsequent outward flow is termed the
“ebb”. The state where the sea water is at the lowest level is termed “low water” while the
state where the sea water is at its maximum level is termed “high water”. The difference
between the low and high tide is termed the “tidal range”.
Tides of the highest magnitude occur at new moon and again during full moon when the
positions of the moon, sun and earth are aligned. This means that the gravitational forces of
the sun and moon come into phase and the range of the tides increases to a maximum. These
are known as “ spring tides”. Minimal tides occur during the first and third lunar quarters
when the sun and moon are acting in opposition to each other or are aligned at right angles.
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These are known as neap tides successive spring and neap tides occur at intervals of about 15
days. In localities subjected to semi-diurnal tides. There are to highs and two lows waters in
each lunar day. For semi-diurnal tides in some regions, two successive high waters will have
nearly the same height and two successive low water will have nearly the same (lower)
height. In other regions, successive high and low waters will have nearly the same (lower)
height will each have different height in some areas a per-dominantly semi-diurnal tide
becomes diurnal for a short time each month during for a short time each month during neap
tides. The tidal oscillation generate currents termed “tidal currents”. Tidal currents are
generally in phase with tidal direction and are stronger during ebb tides than during flood
tides
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1.1.1 TIDAL PREDICTION AND INFORMATION
The tidal prediction gives the times and heights of high and low waters at the Lagos Bar
Beach .The 24-hour system of time keeping is used, 0000 being midnight, 0600,1200noon
and 2300pm which are expressed in zone- 1time. The heights are referred to the datum of the
sounding of the largest scale chart of the place and should be added to the depth given the
chart. The heights are expressed in metres. The tidal predictions take account of astronomical
variation plus average meteorological condition
1.1.2 THE TIDAL TABLE
The tidal table contains the name of the area which is given, the position of area in longitude
and latitude, time zone, the year, the times and the heights of the stations in each month at
each day.
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1.1.3 CALCULATION OF THE HEIGHT OF TIME AT A SPECIFIED TIME
From a prediction table, the time and height of high or low water proceeding the time at
which the height is required and the time of the low or height water succeeding that time;
determine the duration of rise or fall from the difference between the height of these two
tides, and the interval from the time required to the time required for the time of low water.
Enter the left or right hand column of the upper part of the table with the duration of rise or
fall and follow the horizontal line or figures until the appropriate interval is met. Follow the
column in which this interval is found; down into the lower part of the table until the
horizontal line for the range is reached. The figure at their intersection is the figure to be
added to be subtracted from the height of the low water from which the interval was
calculated to give the height of the tide at the time; it may be necessary to interpolate which
the figures on the tables to be apply your data from the tidal predication so as to determine
the correction to be applied to the predictions to give you the exact height of tide at a
specified time. For example, to find the height of tide at Lagos at 1200 on Tuesday 18th July
2006:
From Lagos prediction: low water 1031hrs=0.1m high water 1645hrs=0.8m
Preceding tide= 1031 hrs-0.1m
Succeeding tide= 1645 hrs-0.8m
Duration and Range-0614=0.7m
Time for which height is required-1200 hr
Time for nearest height(low water)= 1031 hrs -1645 hrs interval 0129 hrs
Interpolating for duration, range and interval, the corrections to be applied to the height
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of low (high) water at 0.1(0.6 metres).
Height of low (high) water=0.1(0.8m)
Correction =+0.1(-0.6m)
Height of the tide at 1200 hrs 0.2(0.2m)
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1.1.4 IMPORTANCE OF TIDES
Humans have found ways to use the tides. Ships sail to sea and return to port with the tides.
Intentional grounding of a ship with the fall of tide can provide a convenient, temporarily dry
dock. To these traditional uses has been added a potential alternative to our growing
dependence on fossil fuels by taking advantage of trapped high tide water to generate
electricity. The daily ebb and flood sweep pollutants from the shallows; movement of the
juvenile stage of animals from inter-tidal nurseries to the deeper ocean, and generates current
that distribute sediments.
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CHAPTER TWO
SEDIMENTOLOGICAL STUDY OF THE VICTORIA BEACH SAND IN LAGOS
2.1 INTRODUCTION
The sediment on the beach originates from either terrigenesis or pelagic environment. The
terrigeneous inorganic sources are generally coarser silicate, quartz and feldspar mineral. The
pelagic organic source are coral calcareous and siliceous. Between the mangrove swamps and
the open sea along the coast of Nigeria is a series of about 20 major beaches with ridge
barrier island separated from one another by deep tidal ebb channels leading from the sea to
the swamps. In the western part of the coastline around Lagos, the barrier bar define the
marginal lagoon but are generally absent between 100km east of Lagos . Each of the barrier
bar island consist of active beach and a succession of generally co-parallel sand ridge
developed in relation to older strand lines. This chapter is aimed at studying the
sedimentological aspect of the beach sand, and it is limited to the Victoria beach mainly due
to its position as the direct area of interaction between the sea and the land. It will also sere as
a guide to the understanding of the coastal erosion processes with a view to provide a long
term management practice. The sedimentology of beach sand is also of interest to the
petroleum industry; sand being a reservoir rock of oil and gas.
2.2 METHOD OF STUDY
The study will be categorized into four aspect these include: (1) Field method. (2) Laboratory
method. (3) Presentation of Result. (4) Discussion of Result.
SIWES 400 LEVEL (JUNE – DECEMBER 2006) NWOSU VICTOR O.C 20021189285
2.3 FIELD METHOD
This includes material and method of sample collection. Samples are collected along
shoreline which is taken at the foreshore, The berm crest and from the back shore at various
beach profiles sedimentary structures will also be observed and recorded.
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2.4 LABORATORY ANALYSIS
(a) PETROGRAPHY: Samples collected are thin sectioned and mounted on slide of a
petrographic microscope for textural parameters and mineral composition
(b) GRANULOMETRIC ANALYSIS: Samples are subjected to a sieving to determine their
grain size distribution for silt and clay particles; pipette analysis or a sedigraph is used. The
method of folk is normally used to calculate the granulometric characteristics of sediment
samples statistical parameters of importance in this regard are mean grain size, standard
deviation, skewness and kurtosis; but before that, the weight values obtained will converted
to weight and cumulative weight percentages. There are two methods for obtaining statistical
parameters. The most commonly used, is to plot the cumulative curve of sample and read the
diameter represented by various cumulative percentages. Much more accurate results can be
achieved if one plots the cumulative curve on probability paper the equations for deriving
these parameters from the sieve data are shown below:
The mean grin size(Mz ) show the overall average size of the sediments which is given:
(O16+O50+O84)/(3).
The inclusive standard deviation (Oi) is the measure of sorting of sediments which is given:
Oi=(O84-O16)/(4)+(O95-O5)/(6.6).
The Graphic Skewness (SK1) is the measure of the asymmetry of the graphs which is given
below:
SK1=(O16+O84-2O50)/2(O84-O16)+(O5+O95-2O50)/2(O95-O5).
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The Kurtosis (KG) is the measure of the sharpness or pointedness of graph which is given:
KG= (O95-O5)/2.44(O75-O25).
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2.5 GRAIN SIZE ANALYSIS
Grain size analysis is one which is very important in determination of sedimentary processes,
transport and geological sensitivity of sediments to erosion and oil spills also the study of the
analysis is also determined by depositional environment of sediments encountered in oil
exploration wells. In order to tabulate data for this analysis, the grain size analysis data sheet
and graph sheet. The data sheet consists of sieve sizes from 2.00-0.063mm and phi(O) of
-1.00-4.00 with sample title consisting of the frequency, cumulative frequency, percentage of
cumulative frequency and individual percentage for each sample and the formulas used.
The frequency is gotten after the sieving process which is the amount of times a given weight
occurs in the table. The cumulative frequency is gotten by the adding of the frequency
progressively one value to the other. The percentage of cumulative frequency is given as the
ratio of frequency of one sample in the sieve size to the total cumulative frequency expressed
in percentage. The individual percentage is the same as the cumulative frequency but it is use
to check whether the total cumulative value is right or wrong.
2.5 EQUIPMENT USED IN GRAIN SIZE ANALYSIS
The equipment used are stated below:
(a) Set of Sieves.
(b) Oven.
(c) Sieve Shaker.
(d) Digital weigh balance (max.200g).
(e) Crucibles.
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(f) Standard sample quantity of 70g at least.
2.6 PRACTICAL PROCEDURES IN GRANULOMETRIC ANALYSIS
In the beach, lateral sampling is done in three places as stated (a) Back shore (b) Waterline (c)
Berm mark which are 100 metres apart from each. The other sampling is done randomly by
picking in different places 100 metres apart in the same vicinity. After that, we collect
samples and label wet samples with the area they were collected from; they are placed in
oven which heats up pulling the moisture from them and placed in a set of sieves. These
sieves are calibrated from 2.00-pan and placed in a sieve shaker for a period of 15 minutes
which after that; the sample sieved are collected according to the sizes of sieves and were
weighed on digital weigh balance and the weight is recorded on the data sheet. Also, the
standard quantity weigh for each samples is 70g while the maximum weight for an analytical
or digital weigh balance is 200g. The sieve sizes are from 2.00-0.063 which the 0.063 is the
most important because it contains the smallest particles use for the analysis
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2.7 GRAIN SIZE SCALES FOR SEDIMENT SAMPLES
(I) MEAN
Coarse sand-(0.00,0.25,0.50,0.75,1.00), Medium sand-(1.25,1.50,1.75,2.00), Fine Sand-
(2.25,2.50.2.75,3.00) and Very fine sand-(3.25,3.50,3.75,4.00).
(II) INC.GRAPHIC STANDARD DEVIATION
Under 0.35- very well sorted.
0.35-0.50-well sorted.
0.50-0.71-moderately well sorted.
0.71-1.00-moderately sorted.
1.00-2.00-poorly sorted.
2.00-4.00-very poorly sorted.
Over 4.00-Extremely poorly sorted.
(II) SKEWNESS
1.00-0.30-strongly fine skewed.
0.30-0.10-fine skewed.
0.10-(-0.10)-near symmetrical.
(-0.10)-(-0.30)-coarse skewed.
(-0.30)-(-1.00)-strongly coarse skewed.
(IV) KURTOSIS
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Under 0.67-very platy kurtic
0.67-0.90-platy kurtic
0.90-1.11-mesokurtic
1.11-1.50-leptokurtic
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2.9 PRIMARY SEDIMENTARY STRUCTURES
Primary sedimentary structures, been the most likely to preserve the imprint of depositional
environment in which the sediments are formed and constitute about the most important
descriptive attributes of sedimentary sequences from laboratory flume studies; it has been
demonstrated that a sediment bed could be made to pass through the following sequence of
bed form with increasing flow conditions or flow strength. Flat bed ripples-dunes-washed out
dunes. Observations of primary sedimentary structures on Nigerian beaches show a striking
variation of bed forms of spanning the entire flow regime sequence. In the inter-tidal zone,
however; bed forms of transitional to upper flow regime are dominant. Anti-dunes are among
the commonest types of bed forms occurring on the beaches. Measurements of sets of anti-
dunes reveal laterally persistent and even lamination having low inclinations and range from
1 to 4mm thickness. They are delineated either as concentrations of heavy minerals or as
barely perceptible contrast in grain size.
2.9.1 SEDIMENTOLOGY OF OCEAN FLOOR AT THE LAGOS BEACH
Deep-water cameras have allowed researchers to photograph bottom sediments. The first of
these camera was simply lowered on a cable and triggered by the trip wire. Other more
elaborate cameras have been taken to the seafloor on towed sled or deep submersibles.
Actual samples usually provide more information than photographs do; scientists use
weighted wax-tipped poles and other tools attached to long lines to obtain samples, but
today's oceanographers have more sophisticated equipment. Shallow samples maybe taken
using a clam shell sampler; so named because of its method of operation, but not its target.
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Deeper samples are taken by a piston corer, a device capable of punching through as much as
25 metres (82 feet) of sediments and returning an intact plug of material using a rotary
drilling technique which is also similar.
Powerful new continuous seismic profilers have also been used to determine the thickness
and structure of layers of sediment on the continental shelf and slope and assist n the beach
for oil and natural gas. Recent improvements in computerized image processing of the echoes
returning from the sea bed now permit detailed analysis of these deeper layers when these
samples are taken from the sea, they are sent to the laboratory for analysis.
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CHAPTER 3
OCEANOGRAPHY AND ITS TECHNIQUE FOR MEASUREMENT
3.1 THE OCEAN
Over 97% of the water on or near the earth's surface is contained in the ocean, only 3% is
held in the land ice, groundwater, and all the fresh water lakes and rivers. The ocean may be
defined as the vast body of saline water that occupies the depressions of the earth's surface.
Traditionally, we have divided the oceans into artificial compartment called “oceans and
seas” using the boundaries of continents and imaginary lines such as equator. In fact, there
are few dependable natural divisions, only one great mass of water. The pacific and Atlantic
oceans, the Mediterranean and Baltic seas, so named for our convenience; are in reality only
temporary features of a single-world ocean. Looking at the ocean as a single world ocean
unit brings a philosophical advantages. Such a view emphasizes the interdependence of ocean
and land, life and water; atmosphere and liquids, and natural and human-made environment
before that, we talk about waves.
3.2 WAVES
Waves involve water motions which are largely confined to the surface and may be described
as the surface disturbance of a fluid medium. There are also waves that form below the
surface. Waves are typified by an up and down bobbing periodic motion which is particularly
apparent at the surface. The observed alternate elevations and depressions of the surface
above and below its mean position is merely indicate of the passage of energy. In wave
motion, the medium through which the wave passes does; not move along with the wave. If a
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cork was left on the surface, the cork bobs up and down but does not travel horizontally even
through the ripples are propagated horizontally across the surface. The horizontal movement
of the wave results from the vertical oscillations of the water column with the same frequency
but with a progressively increasing phase lag; the further the waves are from the source.
Wave parameters of importance and which may need to be recorded during survey include:
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1. Wave height: The wave height (h) is the vertical distance between a crest and an adjacent
trough.
2. Amplitude: The is a measure of the intensity of oscillation. It is defined as h/3.
3. Wavelength: The wavelength (L) is the horizontal distance between neighboring crests or
troughs in the direction of wave travel.
4. Wave period: The wave period (T) is the time interval between the occurrence of
successive troughs or crests at a fixed position.
5. Wave frequency: This is the number of crests passing a given point per second; i.e,
oscillation per second. It is the reciprocal of the wave period i.e V/T
6 Wave velocity: The distance a given crest appears to travel in a second.
Intervals waves can be caused by a wide variety of phenomena including storms,
tidal action, traveling ships or a combination of factors. They usually occur at density
interfaces in the ocean. The water masses of differing densities may be set in motion in a
similar manner to that previously described for the ocean surface. Below the density
interface, there is orbital motion in the direction of propagation while above it; there is a
movement in the opposite direction. In comparison with surface waves; internal waves
are slow moving and are generally sinusoidal in shape. This result largely from the fact
that the density interface is easily distorted from the difference in density across this
interface which is small. Wind generated wave can be categorized into three types.
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(a) SEA: refers to most wing generated waves and include waves under the direct
influence of the wind, the wave pattern are complex and the shape is trochoidal (I.e peaked
crest and rounded trough). The type of “ sea “ can be used as an estimate of wind speed and
corresponding sea characteristics. This is the basis of the Beaufort scale.
(b) SWELL: This term describes waves which, at the time of observation; are not under
the direct influence of wind. This may arise because the wind causing the waves has ceased
or the waves may have moved away from the sea of active wind. The pattern are simpler
than those of “sea” and they approach the ideal sinusoidal pattern. They are characterized by
a smooth undulating surface and may occur simultaneously with a sea-type wave pattern.
(c) SURF: Unlike the first two categorizes, surf is restricted to shallow waters. It marks
the steepening and eventual breaking of the wave form.
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There are various ways in which the breaking of the wave forms can be described. In
a “spilling breaker”, the break is gradual over some distance and the water appears to be
spilling over some distance and the water appears to be spilling over the side of a container-
hence the nomenclature. In a “ plunging breaker”, the wave form steepens; curls over and
eventually breaks with a crash of water. In a surging breaker, the wave form also steepens.
However, rather than spilling or plunging; it rushes up the beach face. The three categories
just described belong to the category of so-called running waves because the wave term is
moving across the water surface hence distinguishing them from standing waves. The break
point of a wave is the position along the beach profile where the wave height is at its
maximum associated breaking point parameters include the following: 1. The breaker height
(Hb) 2. The breaker depth (Db), which is related to the still water level. Alternative definition
is (Hb); the breaker depth is related to mean water level. 3. The breaker distance(Bb) which is
the distance fro the shoreline to the breaking point measured perpendicular to the coast, along
the X-axis.
3.3 CURRENTS
Also in oceanography, we talk about currents which are classified into main types responsible
for transport in the ocean which are tidal currents; wave generated long shore currents and rip
currents.
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1. TIDAL CURRENTS
The rise and fall in sea level generate currents which are called tidal currents; when currents
and tides are both semi-diurnal, there is a definite relationship between times of current and
times of high and low water in the locality. Tidal currents that attain maximum velocity
during the time from low water to high water are called flood currents and those that attain
their maximum velocity during the time from high water to low water are called ebb currents.
The variation in the speed of the tidal current from place to place is not necessarily consistent
with the range of the tide.
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2. WAVE GENERATED CURRENTS
When waves break obliquely to the shoreline, they generate currents in the direction of the
wave opening. These currents are called long shore currents which move parallel to the
general orientation of the shoreline. Long shore currents are mainly responsible for moving
sediments as well as other suspended matter along the shore. Long shore movement takes
place in two zones which are the drifting zone and the surf zone.
3. RIP CURRENTS
Rip currents flow seaward perpendicular to the shoreline when wave breaks; rip currents are
responsible for transporting sediments out to sea particularly in the surf zone
3.4 OCEAN MEASUREMENTS
1. MEASUREMENT OF WATER LEVEL VARIATION
They are two types of gauges used for measuring water level variation (1) Non-registering
gauge (2) Self-registering gauge. The Non-registering gauge include the staff or a board
about 2-5cm thick and 5-15cm wide and graduated. The staff is secured in a vertical position
by fastening it to a pile or other suitable support the height of water variation level can be
read from the graduations on the staff while self-registering water level variation gauge
include floating gauges with direct mechanical registration of the water level.
2. MEASUREMENT OF OCEAN SURFACE WAVES
Float gauges and electrical measuring devices are suited for measurement from the sea
surface . They are deployed from fixed platforms, like bridges at the coast or pole research
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towers. Float gauges are similar to those used for the measurement of tides with electrical
devices, variations of water level are converted into changes in electrical resistance
capacitance. In the capacitance method, an insulated wire is stretched in a vertical position
with cylindrical capacitor in the range where it is wet clinger; or the variation in size of the
capacitor respectively correspond to the variation in water level.
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3. MEASUREMENT OF CURRENTS
Two quantities must be determined by sensors for current measurements. These are the
absolute value and the direction of the velocity or its components in right angle coordinate
system. The absolute value is usually obtained by measuring the rotation rate of mechanical
sensors such as propellers, rotors, paddle wheels or turnstiles with hemispherical bowls. The
direction is determined by means of a current vane relative to the north direction.
The acoustic current metre, which makes use of the fact that sound is carried
along with moving sea water, consists of two sonar path for each consists of two
sonar path for each coordinate direction through which sound propagates in
opposite directions. The difference in the travel times is a measure of the carrier
velocity. Current measurement are ideally made at the three depth level i.e near the
surface within 1.0m from the surface mud-depth and near the bottom (within 1.0m
from bottom). Such measurement provide a good current profile of the bottom
column of water.
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4. MEASUREMENT OF DENSITY
In coastal waters with strong differences in hydrographic stratification, density is determined
indirectly through salinity, temperature and pressure. Direct measurement of the specific
weight however are required for fundamental determination and also in cases when it is not
certain that the content of sea water is constant. Method s that might be applied for this
determination include the weighing by a pycnometer, the hydrostatic weight of a float or the
frequency determination weight of a float or the frequency determination of the
characteristics oscillation of a body that is dependent upon the density of sea water.
5.MEASUREMENT OF SALINITY
Salinity can be calculated on the basis of well known functional relationships determining
physical properties such as density, optical refractive index, electrical conductivity or sound
velocity and in addition, temperature and pressure. Chemical methods; based on chlorine
(C.I) content can be also used to calculate the salinity of water samples. This involves
chlorine titration using silver nitrate. Also, salinometer almost replacing most other methods
of determine salinity permitting the simultaneous measurement of electrical conductivity
(salinity), temperature and pressure.
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CHAPTER 4
4.1 COASTAL PROCESSES AND EROSION
Before we talk about the coast, its processes and erosional activities we will start with
elaborating more about the beach.
4.2 BEACH
The most familiar feature of a depositional or an erosional coast is the beach which is a zone
of unconsolidated (loose) particles that covers part or all of the shore. The land ward limit of
a each maybe vegetation; a sea cliff relatively permanent sand dunes, or construction such as
seawall. The seaward limit occurs where sediments movement on and offshore ceases- a
depth of about 10 metres (33 feet) at low tide. Beaches result when sediments, usually sand is
transported to places suitable for deposition. Such place include the calm spots between the
headlands, shore sheltered by off shore islands and region with usually quiet surf. Sometimes,
the sediments is transported to place suitable for deposition. Such places include area which
sediments have moved for a long distances to its present location. Whenever they are found ;
beaches are in constant state of change . They may be thought of as rivers of sand-zones of
continuous sediment transport.
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4.3 COMPOSITION OF BEACH
The material of beaches can range from boulders, cobbles, pebbles and gravel to very fine
silt. The rare sand beach of Lagos are made of finely fragmented rock. Some beaches consist
of shells and debris or fragments of coral; unfortunately, some include large quantities of
human junk; glass or metal or plastic beaches are not unknown. Cobbles beaches can be very
steep, but wide beaches of fine sand are sometimes flatter than parking lots. In general, the
flatter the beach, the finer the material from which it is made. The relation between particle
size and beach slope depends on wave energy, particle shape and the porosity of the packed
sediments. Water from waves washing onto a beach-The swash carries particles onshore;
increasing the beach's slope; if water returning to the ocean-The back wash carries back the
same amount of material as it is delivered; the beach slope will be in equilibrium and the
beach will not become larger or steeper.
TYPE OF BEACH SIZE(mm) AVERAGE SLOPE
Very Fine Sand 0.0625-0.125 10
Fine Sand 0.125-0.25 30
Medium Sand 0.25-0.50 50
Coarse Sand 0.50-1.0 70
Very Coarse Sand 1.0-2.0 90
Granules 2.0-0.4 110
Pebbles 6.0-64 170
Cobbles 64-256 240
Table 1.0: Relationship between The Particle size and Average slope of Beach materials
SIWES 400 LEVEL (JUNE – DECEMBER 2006) NWOSU VICTOR O.C 20021189285
4.4 BEACH EROSION AND ITS CAUSES
Beach erosion can be caused by both natural and human activities. These causes however,
very form area to area and in intensity. Some of the natural causes include: low lying
topography, intensive wave climate, vulnerable soils characteristics, nature of shelf width and
topography and the occurrence of offshore canyons. Anthropogenic activities causing beach
erosion include: damming of rivers which reduces the sediment reaching the shoreline;
construction of harbor; protection structures and jetties, beach sand mining, removal of
coastal vegetation and dredging activities. Subsidence which may be induced by natural
compaction of sediment or by human activities such as oil and ground water extraction can
be exacerbated by predicted sea level rise.
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4.5 BEACH MONITORING AND PROFILING
Monitoring of beach involves the sedimentary analysis of beach sediment using
granulometric characteristics; sample for analysis is taken at the foreshore, the berm crest and
the back shore. Also, profiling of beach can be done or it involves leveling or by sighting;
using a surveyor's graduated staff . Leveling involves establishing transect lines paced at
specific intervals to cover the stretch of shore. Each transect line is referenced by two or more
permanent markers placed above high water mark whose position and heights are accurately
surveyed; each transect line is then leveled from the shore as far into the water as possible at
low tide. The distance between each profile station will depend on the general morphology of
the beach as well as the severity of erosion problem. The interval of profiling could also
range from weekly to monthly, however profiling should be done immediately after any big
storm. The equipment needed to conduct this type of beach profiling comprises an engineer's
level with tripod, a leveling staff and 100m steel measuring tape. The profile line which
should be perpendicular to the general orientation of the beach should start as far back as the
beach mark installed far behind the beach . The leveling procedure is as follows below:
SIWES 400 LEVEL (JUNE – DECEMBER 2006) NWOSU VICTOR O.C 20021189285
(1) Place the level approximately half-way between the back sight staff (which is on the
benchmark whose height is known) and the foresight staff (ahead of the level).
(2) Level the instrument using the appropriate adjustments.
(3) Read off the back sight staff.
(4) Transit to foresight and read off the staff .it
(5) Measure the distance between A and B using steel tape.
(6) Keeping the foresight staff in the same position, move the instrument ahead of it so that
position B now becomes the back sight while a new foresight position is established. Repeat
steps 2 and 4. This procedure is continued along the same straight line until the last point is
reached which is usually some safe distance into the water. The following precautions must
be taken in order to minimize errors:
(A) To eliminate cumulative errors, the level should preferable be at an equal distance from
the forward staff and the back staff.
(B) The instrument should always be leveled along the profile line before any reading is
taken.
© Features along the profile line should be noted e.g berm, higher water line, low water line;
any beach structure as well as the time. Reading and computing of the leveling data are made
by reference to the rise and fall or sighting. Parameters for the rise and fall method are as
follows:
STATION BACKSIGHT FORESIGHT ALTITUDE REMARK
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A a Ha bench
B c b Ha+(a-b) berm
C e d Hb+(c-d) rock
Where “Ha” is the known altitude (i.e fixed bench mark) which is the control point of the
profile to determine altitude of B,C,etc; Subtract the foresight reading from the back sight
reading and add the results to the altitude of the station at back sight. For example, the
altitude of B=(Ha+{a-b}) where Ha is altitude of A, a= back sight reading of staff on station
A, b=fore sight reading of staff on station B.
The above procedure is followed for subsequent points whose altitudes are to determined.
When a level and other topographic equipment are not available profile seen still be easily
done by a simple method of sighting with the aid of a 1.5m surveyor's staff which replaces
the leveling instrument. It is placed vertically on the bench mark (BR) with other observer
sighting the horizon from behind the staff .The line of sight intercepts a height H on a
graduated staff which is displaced along the profile of the beach; as in classical leveling. The
distance from the stake to the observer is measured by means of a graduated tape . This
simple method is relatively accurate when measuring distances and the slope of the beach do
not force the observer to change position several times along a single profile.
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4.6 COASTAL PROCESSES THAT AFFECT THE COASTAL ZONE OF THE BEACH
Before we start talking about the processes that affect the coastal zone; lets talk about the
coastal zone. The coastal zone is a long narrow features of mainland , island and seas,
generally forming the outer boundary of coastal domain. Coastal zones, which in our
definition include the entire continental shelf , occupy about 18% of the surface of the globe,
supplying about 90% of the global fish catch and accounting for some 25% of global primary
productivity . They are also the most endangered area; pollution, eutrophication, changing
sediment load, urbanization, land reclamation, over fishing, mining and tourism continuously
threaten the future of coastal management and ecosystems. The major challenge facing us
today is managing the human use of the area , so that future generation can also enjoy the
fantastic visual,cultural and edible products that it provides. From the point of view of ocean
science, many advancement has been made in recent decades in our understanding of the
processes that affect the continental shelves and their boundaries with land in the coastal
zone.
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Coastal marine ecosystems are not in steady state, but exhibit continuous changes in
production and species composition. The question we have to answer is to what extent these
changes the question we have to answer is to what extent which is due to natural variation or
to the impact of human activities. Our awareness and scientific understanding of this
variability has increased during the past decades. Foe example, long-term data sets on phyto-
plankton, zooplankton, macrobeths, fishes and birds. Until recently, these data sets were
mainly used to demonstrate the effects on the ecosystem of human use. However, when the
various data sets are combined; as striking picture emerges. Certain changes are sudden rather
than gradual, as one would have expected from a progressively increasing human impact.
Also, the coastal processes are those processes that affect the morphology of beaches
including coastal areas and shallow near shore waters. Such processes are usually the result
of interactions between marine and fluvial processes and meteorological conditions. Such
land/sea at atmosphere interaction can be modified by human activities and can lead to
significant changes in coastal morphology can be modified by human activities and can lead
to significant changes in coastal morphology.
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4.7 THE LAGOS BEACH AS AN EROSIONAL COAST
The Lagos beach undergoes both land erosion and marine erosion both work to modify the
nature of the coast. Erosional coast such as the lagos beach are shaped and attacked from the
land by stream erosion, the abrasion of wind -driven drift, the alternative thawing of water
cracks; the probing of plant roots, glacial activity, rainfall, dissolution by acid from soils and
slumping. The crashing waves pushes air and water into tiny rock crevices. The repeated
build up and release of pressure within these crevices can weaken and fracture the rock. But
it is not the hydraulic pressure of moving water alone that abrades the coasts. Tiny pieces of
sand bits of gravel or stones hurled by waves towards the shore are even more effective at
eroding coast. Dissolution, the dissolving of minerals in the rocks by water, contributes to the
erosion of easily soluble coastal rocks.
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4.8 IMPACT OF EROSION AND COASTAL STRUCTURES IN THE NIGERIAN
VICTORIA BAR BEACH
It is evident from the foregoing account that erosion is a dominant phenomenon
along the Nigerian Coastline and that the rate of shoreline retreats up to 30 metres per year
among the fastest anywhere in the world. A number of factors are responsible for the trends:
(1) Rising sea level.
(2) A high intensity of wave action.
(3) The diurnal tides when approaching the coast.
(4) The beach composition and grain sizes.
(5) The nearly flat coastal terrain for breaking waves.
Also, beaches are constantly changing formations. Sea defense result in beach accretion or
erosion. Sometimes, the changes maybe seen just months after the structures is built, three
groups of structures which protect land and beaches built parallel and at right angles to the
store which are given as follows; (I) Retaining wall. (II) Bulk head.
Structures built parallel to the shore are made of steel concrete, rock or wood and are
designed to protect land and buildings from erosion by the sea or sea accretion (beach
accretion) stronger structures may then be required to withstand the increased wave impact,
making cost higher. A retaining wall is built adjacent to the beach to define property
boundaries and to provide privacy for the hotel and property which is undergoing
construction by HITECH CONSTRUCTION COMPANY. When beach erosion takes place,
they come under them and may collapse; they are designed to retain land and soil but not to
withstand wave impact. A bulk head protects only land and buildings, immediately behind it.
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Erosion will continue in front of the unprotected land on either side of the structure and the
waves will eventually cut in behind it. Also, beach nourishment can be used to check coastal
erosion of a beach which consist of adding large volumes of sand to the beach. The sand may
be obtained from an inland or offshore source. Since land sources of sand are limited in the
beach; the sand is usually obtained from the offshore zone,the sand is pumped up often using
a suction dredge. The sand and water mixture is the pumped via a floating pipeline onto
shore. This operation should not be viewed as a once only operation, since periodic re-
nourishment will be required at intervals of between two and eight years depending on the
dynamics of a particular beach several factors should be considered in determining the
feasibility and design of a beach nourishment operation are as follows:
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(I) SAND SOURCE: Offshore sand is the main source in the lagos beach in order to be cost
effective, the dredge site should be as near the beach to be replenished as possible. Sand in
shallow water close to the beach is part of the natural reserve and may eventually replace
eroded sand through natural beach processes. It should therefore not be disturbed; sand found
at depths of 15-40 metres is generally the best source since it lies beyond the natural beach
sand replacement system and is relatively easy to dredge.
(II) QUANTITY OF SAND TO BE USED AS FILL:During the sand replacement process,
it is necessary to place above 50% more sand than is actually needed, since much of the sand
will be lost overtime as the waves form a natural slope over the beach and offshore zone.
(III) QUANTITY OF THE SAND: The size of the sand grains used for replenishment
should be the same as the original beach sand or slightly coarser.
4.9 THE VICTORIA ISLAND BEACH-HISTORY
The beach is located at lat.60 25 minutes and long.30 25 minutes extending from east to
illaro beach. It is inline with the light house beach to the west; both forming a contemporary
barrier beach and having a consistent west-east transport of sand along the coast forming an
underwater sand bar. However, with the dredging of a deep channel across the bar to permit
entry of ships into the Lagos Harbour and the construction of stone moles to perfect the
channel, sand subsequently piled against the west mole and Victoria beach. Meantime, the
angle at which the moles were constructed did nothing to mitigate the effect of waves on the
coast. Infact, the eastern mole; by promoting eddying accentuated the destructive impact of
the waves which has continued to move sand eastward s from the Victoria Beach thereby
precepitating the continuing erosion problem. From the old chart of this area, it is estimated
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that about 2.5km of the shoreline has been lost between 1912 till date. There is a graphical
representation of the shoreline changes, littoral environment observations within the same
period yielded the result.
4.10 MEAN LITTORIAL ENVIRONMENT OBSERVATION AT VICTORIA BEACH
STATION TWO YEARS BACK
PARAMETERS 2004 2005
Breaker Type Spilling(50-60%) Plunging(80%)
Wave Period(sec) 8.1_10.3 09_11
Wave Height (cm) 64-107 95-104
Wave Inclination (X0) 3_50 5_80
Wind Speed (mph) 9.5 9.5
Wind Direction Variable (190-254)o
Long Shore Current Velocity
(m/s)
0.24-0.28 0.4-0.67
EXPERIENCE GAINED
During the period of my training, I gained experience in the following areas:
(1) I was opportune to learn how to calculate and tabulate tidal observation of The
Victoria Bar Beach and the terms involved on the computer using Microsoft Excel.
(2) I gained experience in the area of granulometric analysis of sediments of the beach
and within the ocean floor which the practical aspect was done in the laboratory
(3) I also learn about coastal and beach processes; the beach, the coast, profiling, littoral
observation of the sea ; studying erosion of the beach and ways to check it.
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SUMMARY
The importance of students industrial work experience scheme to students in tertiary
institutions especially in the field of management, engineering, science and agriculture cannot
be over emphasized. As such, This laudable program should be encouraged and given the
necessary assistance and attention by all and sundry- The students, the school and industries
and the nation at large.
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