Journal of Coastal Research
1109-1118
Royal Palm Beach, Florida
Summer 1998
Natural and Human Impact on the Northeastern Nile
Delta Coast of Egypt
Omran E. Frihy, Khalid M. Dewidar, and Mahmod M. EI Banna
Coastal Research Institute
15 EI Pharaana Street
21514 EI Shallalat
Alexandria, Egypt
ABSTRACT
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FRIHY, a.E.; DEWIDAR, K.M., and EL BANNA, M.M., 1998. Natural and human impact on the northeastern Nile
delta coast of Egypt. Journal 0/ Coastal Research, 14(3), 1109-1118. Royal Palm Beach (Florida), ISSN 0749-0208.
Beach profile data along the northeastern Nile delta, measured during the years 1971 to 1993, identify long-terrn seafloor and shoreline changes and sediment transport patterns. Two major zones of pronounced erosion occur in the
vicinity of the Damietta Harbor and along the tip of the Damietta promontory. The erosion along the Damietta
promontory is largely the result of cut off sediment supply to the coast. In the absence of sediment supply from the
Nile river, waves and currents have strongly eroded the delta promontory close to the river mouth. Accretion continued
further west in sediment sinks at the Gamasa emabyment, east of the river mouth, and locally along Manzala lagoon
barrier. Based on results of profile analyses the inferred directions of transport indicate that there has been a crossshore component to the sediment movement, with erosion of the beach face and inner surf zone and the transport of
the eroded sand toward the offshore as well as in the longshore direction. The spatial distributions of shoreline and
bottom changes reflect the natural effect of interrupted sediment supply, sediment transport processes, shoreline
configuration, seafloor gradient as well as impacts of the construction of protective structures.
ADDITIONAL INDEX WORDS:
Nile delta, Egypt, beach erosion, bottom changes, sediment transport, profile analysis.
INTRODUCTION
Beach profile survey has been widely used to determine
changes in coastline and sea bottom as well as sediment
transport. In this study analyses of beach profile data were
conducted in order to interpret the response of seabed and
shoreline response to natural processes, such as waves, and
currents. In addition, to determine the effects of coastal manmade structures placed in the path of the longshore movement in the area, both at the Damietta Harbor and at the
entrance of the Damietta river mouth.
The study area (Figure 1) is located at the northeastern
Nile delta coast, extending approximately 15 km east and
west of the Nile mouth of the Damietta promontory. The
Damietta branch is one of the two major distributaries of the
Nile River. These branches have been the only source of sediments to form the delta promontories. The Damietta branch
has developed the Damietta promontory. The most conspicuous features of the study area and the recent coastal
changes are depicted on the aerial photograph (Figure 2). In
this figure the shorelines of 1955 and 1983 are superimposed
revealing a maximum shoreline retreat of about one kilometer over the last 28 years. The extensive erosion has modified
the outer margin of the promontory and threatens developments within the resort community of Ras EI Bar as well as
the narrow sand barrier that separate the Mediterranean Sea
from Manzala Lagoon. To the west of Ras EI Bar is the new
Damietta Harbor, Figure 1, which was developed in 1975-80
96042 received 6 May 1996; accepted in revision 5 October 1997.
by excavation into the delta and the construction of jetties to
control the navigation channel leading into the Mediterranean Sea. The navigation channel extends to a depth of 15m,
so periodic dredging is required and the dredged sand is
placed on the beach to the east of the harbor jetties. A number of structures have been constructed along the shores of
the Damietta promontory to protect the coast from erosion,
and also to reduce shoaling in navigation channels. These
structures are described in detail by FANOS et al. (1995).
Little information is published on sea floor changes along
the Nile delta beaches. To date, however, information on bottom changes obtained from beach profile analysis has not
been used systematically in the Nile delta region. The investigations by TOMA and SALAMA, 1980 and FRIHY et al., 1991
were limited to determine bottom changes using historical
hydrographic maps. However, several reports have been published on erosion of the delta coast (MANOHAR, 1976; UNDP/
UNESCO, 1978; KLEMAS and ABDEL KADER, 1982; SMITH
and ABDEL KADER, 1988; BLODGET et al., 1991). Sediment
transport patterns (QUELENNEC and MANOHAR, 1977; CoLEMAN et al., 1981; FANOS, 1986; STANLEY, 1989; FRIHY et
al., 1991; INMAN et al., 1992).
Earlier studies on coastal changes at the northeastern
coast of the Nile delta using historical maps reveal that the
promontory advanced seaward by about 2.8 km between 1800
to 1900 (Figure 4 in FRIHY and NIAFAGY 1991). The reversal
from general accretion to erosion began about 1900, with a
subsequent shoreline retreat rate of 18 to 28 m/yr (FRIHY and
KHAFAGY~ 1991). The extensive erosion has modified the out-
1] ]0
Frihy, Dewidar and EI Banna
A. NILE DELTA
NILE DELTA
Idku Laguun
JIO 00'
13. STUDY AREA
Mediterranean Sea
Manzala Lagoon
o
2
4
6
II
kilt
Figure I (AI Nile Delta coast of Egypt, showing the active Rosetta and Darnietta branches of the Nile and the two sub-cells mapped from FRIHYet al.
11991 I. The wave-rose diagram is from NAFAA et al. (1991) and shows the expected dominance of waves from the northwest. (B) Study area showing the
pos itions of the 40 beach profiles analyzed, and the coastal protection structures including offshore breakwaters and groins west of the Damietla branch
mouth .
er margin of the promontory and threatens the resort community of Ras El Bar. In addition, the channels of the Nile
branch and the Damietta harbor are suffering from serious
siltation problems resulting from human intervention and a
reduction in the river flow. This problem has progressed so
that shoaling of their entrances has created navigation hazards for fishing boats entering the Damietta branch and for
the commercial shipping activities within the Darniet.ta Harbor. As a result, these entrances are being dredged periodically to remove sediments accumulated in the navigation
channel. The dredged materials are ordinarily placed in the
nearshore area east of the harbor.
Previous studies of the northeastern Nile delta have concentrated on shoreline and bathymetric changes using his-
torical hydrographic maps. Our study differs from these approaches in that we used direct profile measurements. The
objective is to determine the long-term bottom and shoreline
changes and thereby to determine sediment dispersal in the
longshore and cross-shore directions in response to natural
processes and the existence of coastal engineering structures.
This information is needed to better plan and implement
coastal protection structures along this important sector of
the Nile delta.
MEASUREMENT OF SHORE AND
SEA FLOOR CHANGES
This study is a part of a current program at the Egyptian
Coastal Research Institute to document coastal changes
J ou rn a l of Coas tal Research, Vol. 14, No.3, 1998
S hore line Change in Egy pt
1111
Figu re 2. Aeria l pho tog rap h of th e Da miett a promon tory tak en in May 1983, with t he May 1955 ae rial ph otogr aph ic sho re line posi ti on s upe r im posed
(blac k line l. The as teri s k indica te s pos iti ons of nodal point s, i .e points of cha nge from er os ion to accretio n.
along t he north ern Nile delta . More th an 100 beach pr ofiles
have been surv eyed si nce 1971 to mon itor coas tl ine cha nges.
From th ese extens ive sur vey 40 pr ofiles have been selecte d
to cover th e northeastern coast of the Nile delta (F igu re 1B).
, MSL
-,
h = Waler depth
:1 = Diatance between proflles
dy = Change In shor elin e posltlon
dh = ChJU1gc in bottom posltion
MSL = Mean sea level
0.2
0.4
0.6
-,
<,
-,
1988
<,
<,
1993 .....
<,
0.8
1.0
1.2
OFF SHORE DISTANCE FROM BASELINE (km)
Figure 3 . S ke tch of two hypoth et ical beach profiles s how ing hor izon tal
shi ft in shore line posi ti on (d y) a nd ver t ica l change in sea floor (dh ), be ·
tween th e yea rs 1988 and 1993 a s an exa mple.
Th e profile lin es are perpend icular to the coas tli ne , a nd exte nd sea wa rd to about 6 m wa te r de pt h or about 1,000 m from
th e fixed baseli ne. Distanc e between profiles ranges from 0.1
to 4.2 k m. A hi gh den sity of profile lines exists a round a reas
of unsta ble bea ches. Field surveys h ave been carried out a nnu all y or bi-ann ually usin g a rubber boat associa ted with a
Stand ard Fathomet er System during t he calm condi tio ns of
September a nd October. When collecting profile data, onsho re level ing a nd un derwater soundings a re adj us ted to
mean sea level (MSLl , using fixed local ben ch marks of
kn own elevation. Along th e seawa rd seg me nt of th ese profiles , sta tion soundings we re tak en a t 100 m inter val s, i.e. 9
to 10 sta tions for eac h profile lin e. In th e presen t stu dy, da ta
for 40 pr ofile lines have been selected for a na lysis, ex te nding
from a bout 15 km east a nd wes t from th e Dam iet ta mou th
(F igu re I B ). Th e profile s urvey wer e ca rried out during the
yea rs 1971 to 1993. Th e time spa n of these data ran ge from
a minimum of 9 yea rs to a maximum of 22 ye a rs . The shorttime sp an profiles were surve yed later a dja cent to th e e nt ran ce of th e Damie tta ha rbo r . Th e spa tial distri butions of
the selected profil es compr ise a gr id map of 388 offsh ore stations. The profil e a na lyses provide a dat a bas e to calc ula te
four pa rameters (F igu re 3).
J ou rn al of Coasta l Resea rch, Vol. 14. No. :3, 1998
Frihv, Dcwidar and 10:1 Hanna
1112
(1) Change in the measured distance (y) between the baseline point fixed at the backshore and the shoreline position
t dy r.
(2) Change in the measured depth (h) between the seabed
and the sea surface at each station relative to mean sea level
t dh i. This variable provides data on the bottom changes over
the time of profile survey. The data for each profile are arranged in a three-dimensional array, where (h) is the water
depth relative to mean sea level, (y) is the shoreline position
relative to a bench mark, and (t) is the date of profile survey.
These data permit the determination of the mean annual
rates of bottom changes (cm/yr) and shoreline changes (m/yr).
The data set was subjected to least squares regression analysis, the slope of the Ih) or (y) versus (t ) plot, to determine
the mean annual shoreline retreat (dy/dt l and the rate of bottom changes (dh/dt.l, respectively.
(3) The average water depth for each station was also computed through the survey time (t), so as to provide a generalized bathymetric map for the littoral zone of the study area.
(4) The results of shoreline change rates (dy/dt) were used
to calculate the local sediment, transport (dQ/dx) after FRIHY
et al. (1991),
DISCUSSION
Rates of Shoreline Change
Time series of shoreline positions for 4 representative sites
are graphically presented in Figure 4A. The curves show
marked variations in long-term mean rate of retreat and advance. A downward sloping line represents erosion while upward trends indicate bottom accretion. Most of the examined
time series reveals linear and cyclic trends. Cycles of erosion
and accretion peaks are repeated every 3 to 5 years. The alternating pattern of erosion and accretion may indicate cyclic
change in waves and currents. Previous research has revealed that cyclic change in the position of shoreline and bottom level are common on sandy beaches and are associated
with episodic events such as storms or water level rise. Such
cycles of erosion and accretion have been documented by INMAN et al, (1992) for various parts of the Nile delta.
The long-term average rates of shoreline erosion or accretion, determined from the analysis of the examined profiles,
are plotted in Figure 5B. The alongshore distribution shows
a considerable variability in shoreline changes. Starting from
the west along the western flank of the promontory, it can be
seen that west of the Damietta Harbor the rate of accretion
(12.1 rn/yr: profile no.Z) declines toward the jetties, while erosion appears to the east of the jetties where it increases to a
maximum at profile No.10 1-39 m/yr), further evidence that
the construction has affected longshore sediment movement.
Accretion to the west is part of the much larger-scale shoreline deposition that is naturally continuing along the Gamasa
embayment between the Burullus and the Darnietta promontories. Local accretion occurring at a rate of 6.8 m/yr at
profile no.5 at the updrift side of the west harbor jetty and
is caused by interrupting the transport of sand to the east.
The erosion to the east up to Ras El Bar is part of the
overall erosion of the Darnietta promontory. Part of this erosion, at profile No.13 about 3.3 krn west of the Nile entrance,
where erosion of - 10.3 m/yr might result from the construction of the five detached breakwaters. In 1993/94, five detached offshore breakwaters were constructed at about 3.3
krn west of the Nile mouth to reduce the erosion impact at
Ras El Bar beach. The breakwaters are oriented approximately parallel to the shore and extend over a distance of
about 2 km. They serve as a littoral-sediment trap and thus
provide protection by reducing wave energy across the nearshore area off Ras EI Bar. The local beach erosion at the
western terminal of these breakwaters that averaging -10.3
mlyr is resulted from the interruption of the westward longshore transport by these structures, during seasonal reversal
in wave climate, and thereby the amount of sediments is reduced in this locality. On contrary, significant beach sand has
accumulated in the shadow zone in the form of tornbolo in
front of these structures.
Significant rates of erosion, ranging from -0.22 to -10
m/yr prevail along most of the area east of the harbor starting
at profile No.10 to the entrance of the Nile adjacent to Ras
El Bar beach (Figure 5B). Beach erosion rates along this
stretch progressively decreased from -10 m/yr east of the
harbor to less than 1 m/yr west of the river mouth. Beach
erosion in this area is least along Ras El Bar resort beach,
just west of the Nile mouth, largely due to the presence of
coastal protection structures such as seawall and groins.
Along the resort of Ras El Bar beach, approximately 2 km
long, 3 short groins were built during 1970. Subsequently basalt embankment was placed between these groins in 1982
(inset of Figure 1 B). To protect the Nile entrance from waves
and currents, two jetties were built on both sides of the river
mouth, the western jetty was constructed in 1941, and the
eastern jetty was completed in 1979. However, shoaling of
the Nile channel has caused navigation problem for the fishing boats entering the Damietta branch which is being used
as a fishing harbor. Periodic dredging is undertaken to keep
the channel safe for fishing fleet activities with a dredged
sand being placed on the beach east of the river.
Erosion continues east of the Nile mouth along the promontory tip at a higher rate of -9.8 m/yr. This eroding sector
suddenly reverts to accretion at a nodal point at 7 km from
the mouth at profile 38, beyond which significant accretion
continued and then reverted to erosion again at profile 40.
The pronounced accretion on the flank of the Damietta promontory forms the sand spit that has extended seaward from
the promontory (Figure 5B). The local accretion (1 m/yr) at
profile 30 is produced by the blockage of the westward longshore sediment transport by the eastern jetty of the Nile
mouth. The problem of beach erosion along the promontory
tip was largely in response to a combination of cutoff River
Nile sediment discharge from the construction of two dams
at upper Egypt, prevailing coastal processes, and also by construction of jetties and groins. First the Aswan Low Dam in
1902, and in particular the Aswan High Dam in 1964, that
cutoff all water discharge from the river and the delivery of
sediment to the coast.
RATES OF BOTTOM CHANGES
Of the 40 profile lines, 6 have been selected as representative of sites in the study area. Time series of bottom
Journal uf Coastal Research. Vol. 14, Nu. 3. 1998
Shoreline Change in Egypt
A. TRENDS OF SHORELINE CHANGES
120
120
Profile No.3
100
0
~
6
0
80
80
0
Z
0
0 60
~ 0
0
R=9.8 m/yr
87
0
0
0
0
0
40
0
0
00°
0
~
rJ:J
Profile No.36
0
91
89
70
93
78
76
74
72
80
c,
~
Z 150
~
150
Profile No.9
~ 100
0
100
0
0
0
=
r:n 50
Profile No.39
0
0
0
0
R=-15 m1yr
0
0
50
00
0
0
0
0
R=2.4 m1yr
0
87
89
93
91
70
72
76
74
80
78
YEAR
YEAR
B. TRENDS OF BOTTOM CHANGES
Profile No.31 (300m offshore)
.
Profile No.2 (400m offshore)
-2
• • • • • •
-3
-4
R=4.0 cmlyr
-1 [ .
-3
•
••• •
-5
•
•
R=-6.5 cm/yr
.
•
-5
88
89
91
90
70
93
92
80
15
90
85
~
g
Profile No.13 (300m offshore)
Z;
-2
0
.....
-3
00
-4
~
-5
~
0
~
•• •
•
•
R=-9.9 cmlyr
80
0
••••• • •
•
84
~
88
Profile No.35 (600m offshore)
-4
-5
• •
-6
92
70
0
=
Profile No.23 (100m offshore)
-1
•
-2
87
88
• •
'89
90
• • •
R=17.4 cm/yr
91
92
93
YEAR
•• •
•
•
74
72
R=-2" 8 cm/yr
•
80
78
76
.- .
Profile No.38 (lOOOm offshore)
-5
•• • • •
•
-6
-7
-8
R=16 cmlyr
68
70
11
74
76
78
80
82
YEAR
Figure 4. A. Time series of changing shoreline positions for representative profile lines Nos. :3, 9, 36 and 39. B. Time series of changing positions of sea
bottom for representative profile lines Nos. 2, 1:3,23,31,35 and :38. Locations of the profile lines are shown in Figure 1B. The annual rates of shoreline
change (dy/dt.l and bottom change (dh/dt.), R, indicated in each graph, are derived from least-square regression analysis of the profile data set.
changes along each selected profile are graphically shown in
Figure 4B, each being a plot of the bottom position relative
to the mean sea level through successive profiling years. As
in the time series of shoreline changes, they show a downward trend (erosion or deepening) and upward trend of accretion (bottom shoaling). Also, most of them show marked
variation of erosional and accretionary cycles superimposed
on the average trend. This variation shows that there is a
strong cyclicity in the bottom changes, with periods on the
order of 3 to 8 years. This cyclicity could be related to the
longshore and cross-shore movement of "sand blankets" as
suggested by INMAN et al. (1992), at various locations along
the delta shoreline.
Linear regressions have been undertaken for the 40 profile
series at 388 stations, and the resulting long-term average
seafloor variation (dh/dt) have been graphed in Figure 613.
The computer-generated spatial interpolation of these values
across the nearshore zone shows considerable variations. The
rates of mean erosion versus accretion vary substantially
from site to site. Zones of erosion represent areas of sediment
source, while zones of accretion act as sediment sinks. A maximum rate of bottom erosion of -45 cm/yr exists in two main
.Iournal of Coastal Research, Vol. 14, No. :3, 199H
Fr ihy, Dewidar and 1'1 Banna
1114
A.
PROFiLE POSITIONS
....
5
I I JII
II
15
10
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B. ANNUAL RATE OF
20 25
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30.
35
40
JII
1
I
SHORELINE CHANGES
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10
5
0
5
10
15
ALONGSHORE DISTANCE FROM RiVER MOUTH (km)
C. LONGSHORE SEDiMENT TRANSPORT RATES
9.5
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10
15
ALONGSHORE DISTANCE FROM RIVER MOlJIli (km)
Vigure fi. A. l.ocat.ion or beach profile>; along the nor-theastern Nile. relative to the mouth or the Damictt.a river mouth. The two heavy arrows denote
til(' positions or the Damietla harbor jetties and the river mouth. B. Alongshore variations in the rates or shoreline change (dy/dt ) with the scale for the
inferred gr"di('nt or the longshore sand transport rate (dQ 'dx I. C. Alongshore variations in the transport rates (Q) determined by the longshore integratIOn or
~Udx.
regions. The first zone is situated in the nearshore area just
east of the Darnictta Harbor, whereas the second zone is located as a narrow zone off the promontory tip close to the
river mouth including Ras EI Bar (Figure 68). These two
zones are surrounded from the sea side by broad areas with
small erosion rates «- 15 cm/yr),
On the other hand, three zones of accretional sinks exist
across the nearshore zone, consider as major sinks in the
study area. One is located west of the study area within the
Gamasa embayment, while the others are formed east of the
river, positioned about 5 and 15 km from the Nile mouth,
respectively. ln comparison, the general distribution of bottom changes is in agreement with the erosion and accretion
pattern along the shore as we observed it during this study
(Figure 4 and 5), The accumulation of sediment off Gamasa
embayment is a result of sand transported from material
eroded from the central bulge of the Burullus promontory.
Likewise, the accretion area in the vicinity of the Damietta
spit is derived from sand eroded from the Damietta promontory east of the river. Further to the east, the offshore sand
accumulation east of this promontory, 11 to 15 km from the
mouth, is produced from the erosion of spit and beaches close
to the river.
Sediment Transport
Sediment paths can be delineated if sediment sinks and
sources are considered, and thereby the erosion/accretion patterns. In this study, the sediment transport regime can be
inferred from the established erosion and accretion patterns
Journal or Coastal Research. Vol. 14, No.3. 199H
Shoreline Change in Egypt
A
IlLS
PH.()FILE P()SlTIONS
5
15
10
II!!
II
20 25
30
IIII! "!I!I!III! "
III
35
40
I
I
EROSION (cmlyr)
B. ANNUAL RATE OF BOTTOM CIIANGRS
.>
ACCRETION (cm/yr)
E8l
~ -15 to -45
~
0 to -15
o
0 to 15
15 t035
A
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I
5
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----Burullus Sub-cell
I
c. WATER DEPTll (In) AND
SEDIMEN1~
~
I
I
5
10
15
5
10
15
TRANSPORT
1
0
....,
10
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E
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ALONGSIIORE DISTANCE FH.OM RlVEH. MOLTTlI (km)
...,
L.
~
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~
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~
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=
0
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Figure 6. A. Location of beach profiles along the northeastern Nile. B. The spatial variations of annual long-term average rate of bottom changes,
showing areas of erosion (sources) and areas of accretion (sinks), The two sub-cells identified by FRIHY et al. (1991) are positioned on the bottom margin
of this figure. C. The average bathymetry of the nearshore region, and the schematic sediment transport model generalizing sediment transport paths
interpreted from the identified patterns of erosion and accretion in Figures 5B and 6B. The arrows depict the paths of longshore and cross-shore sediment
transport. Seasonal reversal in sediment transport is shown by a dashed arrow.
in the alongshore and offshore direction and also from their
corresponding sediment sources and sinks (Figures 5 and 6),
The spatial patterns of erosion versus accretion in the study
area indicate that sand is transported in two directions: an
alongshore path with erosion of beach face and transport of
sand by littoral current to the east; and a cross-shore component with erosion of the beach face and inner surf zone and
the transport of the eroded sand toward the offshore. This
-Iournal of Coastal l{esparch, Vol. 14, No. ;), 199H
u is
Frihy. Dowidar and 1':1 Hanna
pattern of' sediment movement is depicted by arrows in the
generalized map in Figure 6C. The onshore-offshore movement only exists in the vicinity of the Damietta spit, in which
sand movement follows more or less the down slope contours
as well as the spit curvature. Across the nearshore zone, the
local accretion areas that is surrounded by areas of erosion
evidenced the inferred onshore-offshore transport.
Three main zones of accretion were recognized in the study
area; Gamasa embayment in the west, and Darnietta spit and
Munzala barrier in the east. The entire quantity of the accumulated sand at Ga masa embayment is derived from the
eroded remnant Burullus headland midway between the two
Ni!o promontories. This embayment corresponds to the end
part of the Burullus sub-cell identified by FRIHY 1'1 al. (1991)
who identified four discrete sedimentation compartment
called "littoral sub-cells". Each sub-cell contains a complete
cyc!« of' littoral transportation and sedimentation, including
sources and sinks of sediment and transport paths. Along the
coast of the Nile delta coast, the principal sources ofsediment
for each littoral sub-cell are the eroded promontories which
supply large quantities of sand to the coast (Figure 6Bl. The
eroded sand is transported along the coast by waves and currents until it is intercepted and terminated in the downcoast
direction by adjacent sinks including promontory saddles,
«mbaymcnts and long jetties (Figure lAJ. According to their
analysis, the Burullus sub-cell contains the arcuate bulge of
the central-delta region to the Damietta Harbor. In this subcell, sand eroded from the relict Burullus promontory and
coastal dunes is transported downcoast to the east and southwest, resulting in shoreline and bottom accretion along Gamasa embayment (Figures 58 and 68). This sand is wavedrive-n by eastward littoral currents and currents generated
by the cast Mediterranean gyre which sweep across the inner
shelf' (INMAN and JJ<:NKINS 1984l. This general pattern appears to be consistent with net easterly littoral transport.
As previously noted, the western jetty of the Darnietta Harhor has interrupted the easterly littoral currents causing
sand accumulation on its updrift side, west of the harbor (Figures GB and 6B). Substantial amounts of this sand bypass
the jetty and settle in the harbor entrance causing siltation.
In fact, the potential siltation induces by the interruption of
prevailing eastward coastal currents by the dredged navigation canal. This means that the canal act as a long jetty, it
has lfi-k m long and 15 to 16 meters water depth. This is
evidenced from the maximum siltation that taking place
along the offshore terminal of this canal along 3 to 5 km
length offshore (personal communications with the harbor
authority). This confirms the idea that coastal currents in the
nearshore zone of the Damietta harbor is responsible for the
creating the siltation problems and not the cross-shore ones.
'I'hr- coast between the Damietta Harbor and Ras EI Bar is
subjected to sediment bypassing to the west during seasonal
reversal in wave climate that come from the NE direction.
This can be interpreted from 1983 aerial photographs which
show a small local accretion on the eastern sides of three
groins placed at Has El Bar beach. Fluorescent-tracer experimcnts by Milill 119691 also suggest a net eastward drift
with seasonal reversal to the west along Ras EI Bar beach.
Accordinglv, on occasions sediments erode from the outer
margin or the promontory and move to the west and deposit
as a tornbo!o in the wave shadow of the five offshore breakwaters built west of the Nile mouth (Figure IB, inset),
East of the river, the massive erosion along the outer margin of the promontory represents an area of divergence transport, directing transport to the east and locally to the west,
and to some extent in the cross-shore direction in the vicinity
ofthe spit area (Figures 5 and 6C). The accumulation of sand
downcoast along the eastern flank of the Damietta promontory results in both sand spit formation and additions to the
lagoon barrier. Offshore of the lagoon barrier the sediment
comes from the erosion or the promontory tip and partly from
the adjacent formed spit in this area. The spacial erosion!
accretion pattern in this area suggests an offshore transport
direction (Figure 6C). The offshore accretion zones indicate
sediment bypassing to the north as evidenced from the erosion measured landward of these zones. This transport pattern is confirmed by study of COLE:\1AN et al. (1981) in which
they suggested that there may be an offshore movement of
sediment to the east producing sand shoals in this region.
According to their suggestion, these shoals may be an important element in accounting for the extensive shoreline erosion
that has occurred on the promontory. The dynamic pattern
along the eastern flank of the Damietta promontory corresponds to the Damietta sub-cell defined by FRIHY et al.
(}9911. This sub-cell includes the entire length of Manzala
lagoon barrier starting from the river mouth and ending at
the 7.7 krn jetty or Port Said (Figure l ).
In Figure 5B, the long-term average rate of shoreline
changes (dy/dt.) is related to the longshore gradient of sand
transport rate (dQjdx), rather than to the absolute quantities
of that transport. If (y) is the shoreline position so that dy/dt
is its time-rate of change (dy/dt negative signifies erosion,
and dy/dt positive represents accretion l. Therefore, there is a
simple proportionality between dy/dt and dQjdx, so that both
scales can be given in Figure 5B. Note that negative dy/dt
corresponds to the dQjdx, i.e. an increasing transport rate in
the longshore direction. The Q, values are plotted along the
shore in Figure 5C. It has been assumed that Q, = 0 at the
river mouth, that is, there is presently no exchange of sand
with the area close to the river mouth. It is seen that Q,
progressively increases with longshore distance to the east
and west from the river as sand is deposited in the areas of
accretion. The Q, reaches a maximum of approximately 9.5
X 10" mvyear at. Camasa embayment. Areas of small Q" being less than 1 X 10'; m'/year are noted close to the river
mouth and also close to the protective structures at Ras El
Bar and the Damietta Harbor. This is appeared from the examined aerial photograph (Figure 2) and also from our field
observations that the three groins placed at Ras EI Bar show
little accretion on both sides.
The alongshore variations in the shoreline changes indicate
a transport reversal lrom erosion to accretion or vis versa
exists at several points along the coast creating a set of divergent longshore sediment transport "nodal points" (Figure
58). These points of change from erosion to accretion resulted
from orientational changes of the shoreline along the Damietta promontory and due to jetty construction.
The interpreted transport paths in the alongshore and
-Journal olCoastul I{('sear('h. Vol. 14. No. :l. 19(1H
1117
Shoreline Change in Egypt
cross-shore directions are confirmed by studies of wave refraction and sediment transport (QUELENNEC and MANOHAR, 1977), and current measurements (COLEMAN et al.,
1981; FANOS, 1986; INMAN et al., 1992). The established pattern of longshore transport shown in Figure 6C corresponds
to the predominant wave direction from NW and NNW (NAFAA et al., 1991). The predominant wave approach is responsible for the eastward-flowing longshore current. A smaller
component of winds from the NNE produces the seasonal
longshore currents toward the southwest (inset in Figure 1B).
SlJMMARY AND CONCLUSIONS
Analyses of intensive beach profiling spanning 9 to 22
years (1971 to 1993) along the northeastern Nile Delta coast
have contributed to the interpretations of shoreline and bottom erosional and accretionary changes in response to sediment transport processes. The profile analysis reveals that
there is a strong cyclicity in the shoreline and bottom
changes, with periods on the order of 3 to 8 years. This cyclicity is due to the longshore movement of "sand blankets"
as noted by INMAN et al. (1992) at various locations along the
delta shoreline. Mapping of the annual rates of shoreline
changes along the coast, together with the spatial distribution of changes in the seafloor, reveals distinct erosion and
accretion patterns that result from, sediment input, shoreline
orientation, transport processes, and coastal structures. The
overall pattern of sediment transport paths is largely wavedriven, controlled by shoreline orientation relative to the
dominant NW waves and the construction of protective structures. The pronounced changes in downcoast orientation
along the outer margin of the promontory, produce erosion
on both sides. The areas of highest rates of beach erosion and
nearshore seabed deepening occur at the tip of the Damietta
promontory and east of the Damietta Harbor that indicates
sediment movement, as waves and currents transport sand
away from these zones to adjacent accretion sinks. Areas of
accretion exist within the sinks of Gamasa embayments,
Damietta spit and off Manzala lagoon barrier.
The sediment sink at Gamasa embayment is derived from
sand eroded from the central part of the delta that is mostly
transported toward the east forming a littoral cell. East of
the mouth, the divergence of current downcoast from eroding
the promontory tip (resulting in an accretionary sand spit)
together with sand accumulation off the Manzala lagoon barrier, form another littoral cell. This general pattern has been
locally affected by the existence of jetties at the Damietta
Harbor and protectional structures close to the river mouth.
The regional patterns of erosion versus accretion along the
study area reflect the existence of sub-cells along the delta
coast, as identified by ORLOVA and ZENKOVICH (1974) and
FRIHY et al. (1991). The analyses of shoreline and bottom
change rates provide a framework for discussing sediment
dynamics relating to the entrances of the harbor as well as
to the mouth of the Nile branch. The defined accretion/erosion patterns indicate an alongshore and to some extent
cross-shore sediment transport. The inferred directions of
transport, shown by arrows in Figure 6C, suggest that the
coastal sand transport is the main factor causing siltation
problem in the navigation channel of the Damietta harbor.
This siltation is resulted from the interruption of coastal currents by the artificially dredged navigation canal of the harbor.
The coastal instability in the study area is due to the combined effects of interrupted sediment supply from the river,
natural coastal processes and construction of coastal protective structures. The erosion at the Damietta mouth is induced
by darn construction along the Nile which has eliminated
sand delivery to the coast, and the prevailing longshore sand
transport. On the other hand, the erosion east of the Damietta Harbor is mainly due to human intervention in constructing harbor jetties that blocked the longshore transport
of sand resulting in erosion east of the harbor. Shoreline configuration and coastal sedimentation have been modified by
artificial structures close to the inlet of Damietta river mouth
and the two jetties placed at the Damietta Harbor. This study
provides useful information for preparation and implementation of effective plans to help protect and rernediate the
northeastern Nile delta region by decision makers dealing
with coastal zone management and planning.
ACKNOWLEDGEMENT
The authors wish to thank Dr. Alfy Fanos, director of the
Coastal Research Institute of Egypt, for providing data and
general help in completing this study, and Dr. Shaleh M. EI
Kafay, Alexandria University, for assistance in developing a
computer program for processing profile data used in this
study.
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