Alexandria city in Egypt is one of important cities in the Mediterranean coast.
Alexandria suffers from many erosion problems along its coastline. The shore line of
Alexandria beach was studied using remote senescing and field data. A case study of a
submerged breakwater, which was constructed at Alexandria beach to stabilize the
eroded beach of Miami - Montaza areas in years 2000 to 2016, is presented. The data
of Alexandria beach were provided by Landsat7 satalite and proccseed by software
program ERDAS IMAGINE 2013 which gives high resolution of the studied area. Then
the shorelines were digitized by using software ARC GIS 10.1. This study introduce the
shoreline response due to the construction of the submerged breakwater using the
Digital Shoreline Analysis System (DSAS). The analysis shows shoreline accretion
along most areas of Miamy - Asafra - Mandara - Montaza beach with range from 1 to
20 meter per year. The shoreline erosion exist at eastern part of Asafra beach and
western part of Mandara beach with range from -1.5 to -10 meter per year. A beach
width varied from 30 to 55 m compared to 0.0 to 25 m before the submerged
breakwater. Shoreline change prediction model for coastal zone at Mimi to Montaza
beach in years 2020, 2030, and 2050 is estimated according to DSAS settings and
Linear regression rate. It was observed that during 2016-2050 the accretion distance
along the coastline of Miami to montaza beach was varied between (5- 60) m. Also the
predicted shoreline indicates that the erosion will take place in the Montaza beach with
distance varied between (20) m.
2. Elbagory, I. A, Heikal, E. M and Koraim, A. S
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KEY WORDS: ARC GIS; Shoreline; submerged breakwaters; sediment transport.
Alexandria
Cite this Article: Elbagory, I. A, Heikal, E. M and Koraim, A. S, Shoreline Changes
Using Digitizing of Landsat Images at Miami to Montaza Beach, Alexandria, Egypt.
International Journal of Civil Engineering and Technology, 10(05), 2019, pp. 75-91
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=05
1. INTRODUCTION
The total length of the Mediterranean sea coastline is about 995 km. the Egyptian northern
coast faces a serious problems such as erosion and accretion. The interaction between waves
and currents causes the main problem of erosion and accretion [Frihy,1991]. Submerged
breakwaters are suggested to control and protect this coastal zone. Miami to Montaza brach in
Alexandria city is an example for case study in this research. Change detection is the process
of identifying differences in the state of an object as a shoreline by observing it at different
periods. Remote sensing has widely been used in environmental change detection
studies.ERDAS Imagine software was used to perform image processing of satellite image. In
addition image digitizing was applied for delineating the shoreline 46 trend at the study area
using the ArcGIS V. 10.1 Software Package.
2. LITERATURE REVIEW
2.1. Description of Alexandria beach
Alexandria's beaches are the main summer resort of the country and are considered one of the
most notable summer resorts in the Middle East. Alexandria beaches stretch for 140 km along
the Mediterranean Sea, from Abu Qir, in the east to Al-Alamein and Sidi Abdul Rahman, in
the west as shown in Figure (1). These attributes make Alexandria a favorite tourist spot; more
than one million local summer visitors together with about 4.5 million residents enjoy the
summer season at Alexandria every year [Frihy et al. , 1996].
Figure: (1). Alexandria map
3. Shoreline Changes Using Digitizing of Landsat Images at Miami to Montaza Beach, Alexandria,
Egypt
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2.2. Wave run-up over Alexandria coastline:
Soliman and Reeve 2007 studied the phenomenon of wave run-up at Alexandria numerically
using the 2-D BWNM to estimate the wave run-up due to wave attack. The section has been
chosen as shown in Figure (2). Table (1) presents the estimated horizontal displacement of
shoreline due to wave run-up using the numerical simulation. The expected beach width which
will be attacked by wave run-up ranges from 9.56 m to 13.83 m and 11.69 m on average.
Figure (2): Section in Miami beach, including water depths, beach width and road details, Soliman
and Reeve 2007
Table (1) Average estimated displacement due to wave run-up, Soliman and Reeve 2007
2.3. Miami to Montaza beach
This zone is about 3500 meters long from Miami to Montaza beach. This area has suffered
severe erosion in 2003 storm. With time, the beach width decreased and vanished in some
locations. The waves attacked the road itself after washing all the sand as can be notice from
Figure (3). Sub-aerial parallel rubble mound breakwater (4.0 meter above water level) was
effective at controlling erosion in Mandara area (from Miamy beach to Montaza palace).
However, it had a quite severe adverse impact on beach amenity and aesthetics. El-Sharnouby,
B., & Soliman, A. 2011
4. Elbagory, I. A, Heikal, E. M and Koraim, A. S
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Figure (3) :. Example of flooding at the Alexandrian coastline. [El-Sharnouby, B., & Soliman, A.
2011].
The installation of the emerged breakwater in 2005 led to a rapid deterioration in water
quality as can see from Figure (4). [El-Sharnouby, B., & Soliman, A. 2011].
Figure (4): Contamination of water at the leeside of emerged breakwater, Miamy area. [El-
Sharnouby, B., & Soliman, A. 2011]
2.4. ALEXANDRIA SUBMERGED BREAKWATER
The 2520 meters rubble mound submerged breakwater in Alexandria is considered one of the
longest,deepest, and widest submerged breakwaters all over the world (Allsop et al., 2009). A
submerged breakwater system was installed to protect the seashore of Miamy - Asafra -
Mandara -Montaza areas in Alexandria, Egypt in years 2006 to 2008. The submerged
breakwater consists of three segments with two overlaps as shown in Figure (5), [A. Soliman
et al, 2014]
5. Shoreline Changes Using Digitizing of Landsat Images at Miami to Montaza Beach, Alexandria,
Egypt
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Figure (5): Plan of the submerged breakwater system for Miamy, Asafra, Mandara and Montaza area,
[A. Soliman et al, 2014].
El-Sharnouby et al. (2007) gave details of the design procedures, environmental analysis,
predicted wave and shoreline response of Alexandria submerged breakwater. The findings of
El-Sharnouby et al. (2007) can be summarized as follows:
1. The shoreline is well protected from wave attack providing a width of beach sand not
less than 30 meters.
2. Continuous submerged breakwater provides better shoreline stability with a 60%
decrease of the total eroded volume.
3. Accretion will take place within 12 months after installation. The depth of water at the
breakwater varies from 2.5 to 8.5 meters. Five cross sections at different locations are
considered for design according to the depth and wave height. Details of the submerged
breakwater cross section at water depths from 3 to 5 meters are shown in Figure (6).
Figure (6): Cross section 1-1 of submerged breakwater at depth 3 to 5 m, [El-Sharnouby et al.
(2007)].
6. Elbagory, I. A, Heikal, E. M and Koraim, A. S
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3. SHORELINE ANALYSIS
3.1. Shoreline digitizing
Befor constuction of the submerged breakwaters at maimi to montaza beach the shoreline was
illustterated as shown in figure (7). The figure shows the photos of digitized shoreline for years
from 2000 to 2006 before constuction of the submerged breakwaters. Thos photos taked by
Landsat7 satalite and proccseed by software program ERDAS IMAGINE 2013 which gives
high resolution of the studied area. Then the shorelines were digitized by using software ARC
GIS 10.1. Change in shoreline position were determined by establishing 65 transects along
coastline that are oriented perpendicular to the baseline at 50 m spacing alongshore by using
DSAS model. The rates of erosion and accretion along the study area are calculated from three
statistical approaches of DSAS (End point rate, Linear regression rate, Least median of square).
7. Shoreline Changes Using Digitizing of Landsat Images at Miami to Montaza Beach, Alexandria,
Egypt
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Figure (7): the digitized shoreline for years from 2000 to 2006.
After constuction of the submerged breakwaters by using proccessing of landsat images as
illusteruted before. The shorelines from year 2010 to year 2016 for Miami to Montaza beach
were digitizied as shown in figures (8).
8. Elbagory, I. A, Heikal, E. M and Koraim, A. S
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Figure (8): the digitized shoreline for years from 2010 to 2016.
3.2. Analysis of shoreline changes
Digital Shoreline Analysis System (DSAS) softwar used to calulate the rate of changes in
shoreline using 3 models: a- LRR Model; b- EPR Model ; c- LMS Model. The DSAS
application is setup in ARC GIS software backages. The base line and transectes lines are draw
to can calculate the rate of changes in shoreline as shown in figure (9) and figure (10). The
distances between transects is 50 meter and it cover all distances of shorline and it pripindcular
to the base line.
9. Shoreline Changes Using Digitizing of Landsat Images at Miami to Montaza Beach, Alexandria,
Egypt
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a- Linear Regression Rate (LRR):
A linear regression rate-of-change statistic can be determined by fitting a least-squares
regression line to all shoreline points for a particular transect (figure 11).
b- End Point Rate (EPR) :
The end point rate is calculated by dividing the distance of shoreline movement by the time
elapsed between the oldest and the most recent shoreline.
c- Least Median of Squares (LMS) :
In ordinary and weighted least-squares regression, the best-fit line is placed through the
points in such a way as to minimize the sum of the squared residuals. In the least median of
squares method the median value of the squared residuals is used instead of the mean to
determine the best-fit equation for the line (figure 11); Rousseeuw and Leroy (1987).
Figure (9): digitizing of shorelines from year 2000 to year 2006 fo Maimi to Montaza beach
10. Elbagory, I. A, Heikal, E. M and Koraim, A. S
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Figure (10): digitizing of shorelines from year 2010 to year 2016 fo Maimi to Montaza beach
11. Shoreline Changes Using Digitizing of Landsat Images at Miami to Montaza Beach, Alexandria,
Egypt
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Figure (11): comparison between the least median of squares rate and the linear regression rate
4. RESULTS AND DISCUSSION
4.1. Shoreline change along Miami to Montaza beach
The rate of changes of the shoreline before construction of the breakwater (from year 2000 to
year 2006) is shown in figures (12). The figure shows that the accretion in Miami zone was up
to 20 m/year from the base line and about 15 m/year in Mandara area. But in Montaza area the
erosin was about 10 m/year.
Figure (12) the rate of changes of shoreline form year 2000 to 2006.
12. Elbagory, I. A, Heikal, E. M and Koraim, A. S
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After construction of the submerged breakwater, the shoreline changed from year 2010 to
year 2016 is shown in figures (13). Also the table 2 describes the rate of changes of the
shorelines from year 2010 to 2016. The positive sign means accretion and the negative sign
means erosion. The figure shows that the accretion in Miami zone was up to 10 m/year from
the base line and about 20 m/year in Asafra to Mandara zone. But in Montaza area the erosin
was about 40 meter/year.
Figure (13) the rate of changes of shoreline form year 2010 to 2016.
4.2. Comparison between current study and other studies:
Figure (14) and table (3) presents a comparison between the present study and A.Soliman et al.
,(2014), for the same study area. The figure shows a reasonable agreement between the present
study and A.Soliman et al ,(2014) results. Additionally, the figure shows that the present
introduced higher values of value of accretion particularly in Mandara zone than other author
for the same studied case.
13. Shoreline Changes Using Digitizing of Landsat Images at Miami to Montaza Beach, Alexandria,
Egypt
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Table 2: the rate of changes of shoreline form year 2010 to 2016.
Figure (14): Comparison between current study and A.Soliman et al. ,(2014)
14. Elbagory, I. A, Heikal, E. M and Koraim, A. S
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Table 3: Comparison between current study and A.Soliman et al. ,(2014)
4.3. Prediction Model for Miami to Montaza Beach:
The prediction accuracy of shoreline position depends on the pervious data (assumed to be
captured by Landsat imagery data). In coastline analysis research, extrapolation of a constant
rate of change is the most commonly used method to predict the shoreline. Several methods
have been used for prediction of shoreline position as a function of time, rate of erosion and
deposition. The most simple and useful ones are the End Point Rate (EPR) and the Linear
Regression Rate (LRR) models. In the present study, the LRR model has been adopted to
predict the future shoreline. The model is based on the assumption that the observed periodical
rate of change of shoreline position is the best estimate for prediction of the future shoreline.
The position of the future shoreline for a given data is estimated using the rate of shoreline
movement (slope), time interval between observed and predicted shoreline. In that method the
regression equation is used to get a relation between the time and distance from the baseline.
The regression equation is given by the formula (y = mx + b) where (y) is the distance from
the baseline in meters, (x) is the shoreline date, (m) is the rate of change given from DSAS for
15. Shoreline Changes Using Digitizing of Landsat Images at Miami to Montaza Beach, Alexandria,
Egypt
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each transect, (b) is y-intercept (the value of y when x=0) is calculated by the equation [y-
intercept (b) = (mean of y) - (mean of x) * m]. Examples of the estimate of the future scenarios
that are obtained using the prediction model for all transects lines with continuous accretion
and erosion are shown in Table (4) . Also, the estimated position of years 2030and 2050
shorelines presented in figure (15). It was observed that during 2016-2050 the accretion
distance along the coastline of Miami to montaza beach was varied between (5- 10) m. Also
the predicted shoreline indicates that the erosion will take place in the Asafra beach with very
small distance varied between (5) m.
Figure (15): Predicted shorelines 2020, 2030, and 2050
16. Elbagory, I. A, Heikal, E. M and Koraim, A. S
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Table (4): Examples on the future estimates for shoreline retreat.
5. CONCLUSIONS
Alexandria beach is one of the most important beaches along the Mediterranean coast, Egypt,
Mimi to Montaza beach is a part of Alexandria beach and it faces many erosion and accretion
17. Shoreline Changes Using Digitizing of Landsat Images at Miami to Montaza Beach, Alexandria,
Egypt
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problems. Alexandria submerged breakwater was installed to protect the sea shore of Miamy -
Asafra -Mandara - Montaza areas in Alexandria, Egypt in years 2006 to 2008. Digitizing of
landsat Images for shoreline from year 2000 to year 2016 were processed by the layer stacking
function using ERDAS Imagine, 2013 and Geographic Information System (GIS) model.
Change in shoreline position were determined by establishing 65 transects along coastline that
are oriented perpendicular to the baseline at 50 m spacing alongshore by using DSAS model.
The rates of erosion and accretion along the study area are calculated from three statistical
approaches of DSAS (End point rate, Linear regression rate, Least median of square). Results
showed that that the accretion in Miami zone was up to 10 m/year from the base line and about
5 m/year in Asafra to Mandara zone. But in Montaza area the erosin was about 40 meter/year
for period. . Also the predicted shoreline indicates that the erosion will take place in the
Montaza beach with distance varied between (10 -20) m/year.
ABBREVIATIONS
GIS: Geographic Information System
DSAS: Digital Shoreline Analysis System
LRR: Linear regression rate
EPR :End point rate
LMS: Least median of square
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