Geomorphology 53 (2003) 263 – 279
www.elsevier.com/locate/geomorph
Processes reshaping the Nile delta promontories of Egypt:
pre- and post-protection
Omran E. Frihy *, Essam A. Debes, Waleed R. El Sayed
Coastal Research Institute, 15 El Pharaana St., El Shallalat, 21514 Alexandria, Egypt
Received 19 November 2001; received in revised form 20 September 2002; accepted 5 October 2002
Abstract
Shoreline positions established from beach profile surveys combined with wave data are jointly analyzed, as a function of
their contribution to coastal processes, to investigate the interaction between waves, shoreline orientation and coastal structures
along the Nile delta promontories, Rosetta, Burullus and Damietta. Repeated beach profile surveys along the promontory
sectors (64 km long in total) have been analyzed to determine rates of shoreline changes prior to construction (1971 – 1990) and
after construction of protective structures (1990 – 2000). The behavior of coastline pre- and post-construction indicates that
coastal erosion fronting protective structures has declined in the case of the seawalls at the tips of the Rosetta and Damietta
promontories, or has been partially replaced by sand accumulation in the case of detached breakwaters at Baltim (east of
Burullus promontory) and at Ras El Bar (west of the Damietta promontory). As a consequence, downdrift erosion has been
initiated in local areas adjacent to these structures in the direction of longshore sediment transport. The 5-km-long seawall
protecting the Rosetta promontory has stopped the dramatic erosion of this highly eroded area (formerly shoreward retreated
f 88 m/year), with adverse local erosion at its west and east ends, being 3 and 13 m/year, respectively. Similarly, the 6-km-long
seawall built on the eastern tip of the Damietta Promontory, still under construction, has nearly stopped the severe erosion,
which was formerly f 10 m/year. The detached breakwaters at both Baltim and at Ras El Bar have accumulated sand at
accretion rates of 37 and 14 m/year, respectively. This sand accumulation is associated with downdrift erosion of 25 and 13 m/
year at Baltim and Ras El Bar, respectively. Results reaffirm that the original erosion/accretion patterns along the Nile delta
promontories have been reshaped due to the massive protective structures built during the last decade. This reshaping along the
examined promontories is generally controlled by the temporal variability in the intensity and reversibility of wave directions
and associated longshore currents, coastline orientation and by the existing coastal protection structures.
D 2002 Elsevier Science B.V. All rights reserved.
Keywords: Nile delta; Wave; Pre- and post-construction
1. Introduction
The Nile delta is located on the Egyptian Mediterranean coast and extends along approximately 240
* Corresponding author. Fax: +20-2-4285792.
E-mail address: [email protected] (O.E. Frihy).
km from east of Alexandria to Port Said (Fig. 1). The
most conspicuous topographical features along the
delta are the large present-day Rosetta and Damietta
promontories. Between them lies a broad headland
that forms the remnant Damietta promontory that was
formed by the sediment discharged from the former
Sebennitic branch of the Nile about 6500 years ago
0169-555X/02/$ - see front matter D 2002 Elsevier Science B.V. All rights reserved.
doi:10.1016/S0169-555X(02)00318-5
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Fig. 1. Map of the Nile delta coast showing the positions of the Nile delta promontories (Rosetta, Burullus and Damietta) and main
geomorphologic units. Positions of wave gauges are also denoted.
(Orlova and Zenkovitch, 1974; UNESCO/UNDP,
1978). During the Holocene, the delta was built by
seven distributaries that have subsequently silted up
and been replaced by the present-day Rosetta and
Damietta channels (Toussoun, 1934; Stanley and
Warne, 1993, 1998). These distributary channels were
then the only source of sediments for the present-day
delta promontories. Following the development of the
former distributary channels about 6500 years BP,
longshore currents induced from an oblique wave
approach formed the delta beach (Stanley and Warne,
1998). From f 4000 years ago to the latter part of the
19th century, the delta beach is backed by coastal flat,
dunes, or by lagoon barriers. Three lagoons (Idku,
Burullus and Manzala) are separated from the sea by
narrow elongated sand barriers.
Similar to other deltas worldwide, the Nile delta is
presently subjected to significant coastal changes due
to a combination of several factors. The main factor is
the reduction in the Nile discharge and sediment load
to the Nile promontory mouths due to the construction
of water control structures and dams along the Nile
(UNESCO/UNDP, 1978). In the meantime, and since
building of the High Aswan Dam in 1964, sediment
discharge at the Nile promontories has reduced to near
zero. In the absence of sediment supply to the coast,
the continued action of waves and currents acts to
induce beach erosion. This erosion is mitigated by the
construction of a series of coastal engineering structures at the rapidly eroding promontories. Protective
measures, which started during the last decade, are in
progress and others are planned for the future. These
measures include jetties, groins, seawalls and breakwaters. Some of these measures have been built to
reduce shoaling processes in the lagoon inlets and the
navigation channels of the Nile estuaries and delta
ports.
Previous studies on the Nile delta coast have
documented the extensive erosion that had occurred
along the delta shorelines. Reports concentrated on
O.E. Frihy et al. / Geomorphology 53 (2003) 263–279
beach erosion (Manohar, 1976; UNESCO/UNDP,
1978; Klemas and Abdel Kader, 1982; Frihy, 1988;
Smith and Abdel Kader, 1988; Fanos et al., 1991;
Frihy and Khafagy, 1991; Blodget et al., 1991; Frihy
et al., 1991; Chen et al., 1992; Frihy and Komar,
1993) and on bathymetric changes (Misdorp and
Sestini, 1976; Toma and Salama, 1980; Frihy et al.,
1991). Other studies in this area deal with alongshore
sediment transport (Inman et al., 1976; Quelennec and
Manohar, 1977; Manohar, 1981; Frihy et al., 1991)
and shelf sediment transport (Tebelius, 1977; Coleman et al., 1981; Stanley, 1989).
The objective of this study was to analyze the
morphodynamic behavior of the coastline of the Nile
delta promontories prior to and after protection by
engineering works implemented in the last decade,
and so to determine whether the general erosion/
accretion pattern along the delta has been reshaped.
Beach profile measurements between 1971 and 1990
(pre-construction) and between 1990 and 2000 (postconstruction) supplemented by wave data are used to
interpret processes reshaping the coastline of these
dynamically active promontories.
2. General erosion/accretion patterns along the
Nile delta coast
The Nile delta is a typical wave-dominated or
perhaps more accurately termed wave- and currentdominated (Coleman et al., 1981; Manohar, 1976,
1981; Naffaa, 1995). Earlier analyses of wave refraction and longshore sediment transport rates along the
Nile delta have been documented by Inman et al.
(1976), Quelennec and Manohar (1977) and Inman
and Jenkins (1984). Each of these studies reports
remarkable zones of wave convergence and divergence that result in strong longshore gradients of wave
heights and breaker angles, and therefore of sand
transport rates. The results of Quelennec and Manohar
(1977) for the refraction of waves arriving from the
NNW are shown in Fig 2A, with the computed littoral
drift, for those waves as well as those from the NNW
and NNE given in Fig. 2B. The predominant wave
approach from the NNW and WNW is responsible for
generating the eastward-flowing longshore current.
Rates of shoreline changes have been determined
from successive beach surveys along the Nile delta
265
(Frihy and Komar, 1993). Their study revealed greatest retreat along the Rosetta promontory (106 m/year)
with a significant erosion at Damietta promontory (10
m/year) and at the central Burullus promontory (7 m/
year) (Fig. 2C). Conversely, areas of accretion exist
within the saddles or embayments between the promontories, with the maximum shoreline advance averaging about 13 m/year.
Studies of the shoreline positions and sediment
budget along the coastline of the Nile delta show that
the coastal areas can be divided into a series of
discrete sedimentation compartments or ‘‘littoral
cells’’ (Frihy et al., 1991; Frihy and Lotfy, 1997).
These subcells are part of the regional Nile littoral
cells extending from Alexandria to Akko on the
northern part of Haifa Bay, Israel (Inman and Jenkins,
1984). Each cell contains a coherent trend of littoral
transportation and sedimentation, including sources
and sinks of sediment and transport paths (Fig. 2D).
The principal sources of sediment for each littoral
subcell are the eroded promontories that supply large
quantities of sand to the coast. The eroded sand is
transported along the coast by wave and longshore
currents until it is intercepted and terminated in the
downcoast direction by adjacent sinks including
promontory saddles, embayments, breakwaters and
jetties. These littoral subcells are Abu Quir subcell,
Rosetta subcell, Burullus subcell, Damietta subcell
and Port Said subcell (Fig. 2D).
3. Methodology
3.1. Wave measurements
In order to analyze beach changes, the relationships
between incoming waves and shoreline orientation are
incorporated to interpret sediment transport directions.
In this study, wave regime was statistically analyzed
based on wave records at Abu Quir Bay (west of
Rosetta promontory) and at Damietta harbour (west of
Damietta promontory) (Fig. 1). At Abu Quir bay,
waves were measured using a Cassette Acquisition
System (CAS) directional wave recorder over 13
months between 1988 and 1990. The system is a
portable, self-contained remote recording system for
sensing waves and wave-induced currents (Boyd and
Lowe, 1985). The wave gauge was installed about 18
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Fig. 2. (A) Wave refraction diagram from Quelennec and Manohar (1977) for waves from the NNW. (B) Alongshore sand transport rate calculated by
Quelennec and Manohar (1977) from their refraction diagrams for the three most important deep-water wave directions. (C) Delta-wide alongshore
shoreline change rates calculated by Frihy and Komar (1993). (D) The position of the four littoral subcells along the delta identified by Frihy et al.
(1991) and Frihy and Lotfy, 1997: I = Abu Quir subcell; II = Rosetta subcell; III = Burullus subcell; IV = Damietta subcell and V = Port Said subcell.
O.E. Frihy et al. / Geomorphology 53 (2003) 263–279
267
km offshore and in 16-m water depth (Fig. 1). The
gauge was mounted about 5 m below the mean sea
level, and 10 m above the seabed. Wave data are
recorded for 34 min every 6 h per day.
Another pressure S4DW wave gauge was installed
approximately 1200 m from the western side of the
navigation channel of the Damietta harbour in about
12-m water depth (Fig. 1). The wave gauge recorded
the directional wave and current spectrum for 20 min
every 4 h. Wave measurements were recorded over 16
months between 1997 and 1999. In the laboratory,
data obtained from the two wave gauges were transferred to the PC computer and statistically analyzed to
determine wave height, wave period and wave direction using dedicated software.
The longshore sediment transport rate at 200-m
intervals along the shoreline of the study promontories
was estimated using the RCPWAVE model (Ebersole
et al., 1986). The input data include wave characteristics [height (H), period (T), angle (a)] and seabed
bathymetry including the shoreline surveyed in 2000.
The wave data measured at Abu Quir bay were used
in calculating the sediment transport rate along the
Rosetta while wave data recorded at Damietta harbour
were used in estimating the sediment transport rate
along Damietta promontory. Unfortunately, there are
no available data measured at the Burullus promontory, therefore waves of the Rosetta were first backrefracted to deep water and then shoreward using the
principle of optical Snell’s Law (CERC, 1984).
(POWER Set 3010). Auto-Cad 14 software was used
to construct maps used in this study. Owing to the
difficulty in accessing the most eastern part of the
Damietta promontory, the spit and its adjacent downcoast areas were digitized as vectors from rectified
TM remote sensing images acquired in 1990 and
2000.
A total of 24, 45, and 39 profiles that cover,
respectively, the entire coastlines of Rosetta, Burullus
and Damietta promontories have been chosen for the
analysis of shoreline position. Profile surveys relate to
prior to (1971 –1990) and after protection of the study
promontories (1990 –2000). The measured shoreline
displacement from the fixed baseline ( Y) provides a
database for monitoring the shoreline changes over
the time of profile collection. The data from each
profile are arranged in a 2-D graph, where Y is the
shoreline position relative to the fixed baseline, and X
is the date of survey. This permits the determination of
the mean annual rate of shoreline displacement
(meters per year) employing a least squares technique.
In addition, data obtained from beach surveys taken in
1990 and 2000 were utilized to detect changes in
planform configuration resulting from protection of
the study promontories.
3.2. Beach profile survey
Wave regime was analyzed based on records measured at Abu Quir Bay and at Damietta harbour (Fig.
1). Owing to the arcuate nature of the delta coastline,
one of the best ways to characterize wave action
versus morphodynamic changes is to analyze wave
ability to induce longshore transport. The first significant parameter to be analyzed regarding longshore
current is that of wave direction since it controls the
intensity of longshore transport. In this study, wave
data recorded west of Rosetta promontory and at
Damietta harbour have been statistically analyzed in
terms of directional and wave height distributions
(Figs. 3 and 4). It can be seen that main wave
components exist within two quadrants, the N – W
and N –E. The N – W waves are of greater importance
for morphological processes because of their long
duration, particularly in winter, and are responsible
The Coastal Research Institute of Egypt initiated a
beach profile survey program early in 1971. The
program covers the entire Nile delta coast from Abu
Quir headland at Alexandria on the west to Port Said
at the east. The profile lines are perpendicular to the
coastline, and extend to about 6-m water depth or up
to about 1200-m distance from the fixed baseline. The
beach leveling and water soundings are adjusted to the
mean sea level (MSL) datum using local fixed benchmarks of known elevation. The survey was carried out
during the calm conditions of September and October.
The beach survey including the positions of the coastline and protective structures was done using a Differential Global Positioning System (DGPS) type GBXPro, Theodolite and an Electronic Total Station
4. Results and discussion
4.1. Wave characteristics
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Fig. 3. (A) Directional distributions of monthly average waves recorded during 1988 and 1990 at Rosetta promontory showing dominant N and
N – W frequency distribution associated with minor NNE, NE and WSW reversals. (B) Wave height – direction distribution of total average for
the 13 months examined.
for generating the net longshore sediment transport
scheme along the Nile delta. The N – E components
occasionally prevail over 4 – 6 months during the
examined wave periods obtained at the Rosetta and
Damietta promontories. A very small component
rarely blown from S –W quadrants occurs over 1 to
3 months during the examined wave data recorded at
the Damietta and Rosetta promontories.
The monthly directional wave distributions in Figs.
3 and 4 demonstrate that waves blown from two main
O.E. Frihy et al. / Geomorphology 53 (2003) 263–279
269
Fig. 4. (A) Directional distributions of monthly average waves recorded during 1997, 1998 and 1999 off the Damietta harbour showing
dominant north and N and N – W frequency distribution associated with minor NNE, NE and WSW reversals. (B) Wave height – direction
distribution of total average for the 16 months examined.
quadrants; the N – W (NNW, NW and WNW) and N –
E (NNE, NE and ENE). Measurements at Abu Quir
revealed that waves dominate from the N –W sector
(81%) with small components from the N – E quadrant
(14%) and from the S – W (5%) (Fig. 3A). Of the 13
months examined, 9 reveal N –W waves (February
1988, March 1988, May 1988, October 1988, November 1988, December 1988, September 1990, October
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1990, November 1990 and December 1990) and 4
record a N –E wave component (April 1988, October
1988, January 1990 and August 1990). Only 3 months
(February 1988, December 1988 and August 1990)
show waves from S – W quadrant. Maximum significant wave height recorded west of the Rosetta promontory is 5.4 m approaching from the WNW direction
in December 1988. On average, wave height and
period are 1.2 m and 5.6 s, respectively.
Similarly, wave data recorded west of the Damietta
promontory show predominant wave directions mainly
from the N – W (78%), N –E (21%) and S – W (1%)
quadrants (Fig. 4). Of the 16 months recorded, 9 show
N –W waves (December 1997, May 1998, June 1998,
August 1998, September 1998, October 1998, April
1999, May 1999 and June 1999) and 7 reveal N – E
components (October 1997, November 1997, January
1998, November 1998, January 1999, February 1999
and March 1999). Only 1 month (December 1997)
shows waves from WWS direction (Fig. 4A). Maximum significant wave height recorded is 4.2 m
approaching from the North at the Damietta harbour,
which occurred in January 1998. On the whole, the
average wave height and period are 0.5 m and 6.3 s,
respectively. Generally, the average wave direction –
height distributions for the Rosetta and Damietta
promontories reveal that frequency distributions of
wave height between 0.5 and 1.0 m are more dominant
than others between >1 and 2 m height (Figs. 3B and
4B).
4.2. Effects of waves on reshaping delta promontories
This section focuses on discussing the relationships
between effective angle of incident waves responsible
for sediment movement, littoral drift and rate of
shoreline changes along the Nile delta promontories.
The relationships between the effective angle of
incident waves and average shoreline orientation are
constructed along the examined coastal sectors of
Rosetta, Burullus and Damietta. The angle of incident
waves is measured graphically with respect to the
2000 coastline.
4.2.1. Rosetta promontory
The Rosetta promontory on the western coast of
the Nile delta has been subjected to the most severe
erosion of the delta coastline (UNESCO/UNDP, 1978;
Frihy et al., 1991; Fanos et al., 1991; Chen et al.,
1992). Superposition of the 1990 and 2000 shorelines
shows pronounced erosion along the tip of this
promontory (Fig. 5A). Analysis of incident waves
versus shoreline orientation revealed that the N,
NNW, NW, WNW and NNE (totaling 90j) waves
are jointly acting to transport sediment toward the
southwest and east along the western and eastern
flanks of the Rosetta promontory, respectively (Fig.
5A). Conversely, small wave components approaching from W (20j) and NE (30j) move sediment to the
NNE and west directions, respectively, along these
coastal stretches.
The variations of longshore sediment transport
along the length of the Rosetta promontory show
wide variability in the intensity and directions due
to the pronounced angle between shoreline orientation
and incident waves. As expected, increasing gradient
of sediment transport rates corresponds with areas of
shoreline erosion while decreasing gradient alongshore corresponds with areas where there has been
shoreline accretion (Fig. 5B). The net longshore sediment transport (heading southwest) along the west
coast is relatively higher than that along the east coast
(heading east), being 1292 103 and 549 103 m3
year, respectively (Fig. 5B). These higher rates result
from the higher obliquity of the wave approach
compared with that experienced along the east side.
The decrease in longshore sediment transport along
the western and eastern downdrifts of the promontory
coast indicates an accretionary pattern. A major transport reversal occurs in front of the Rosetta mouth
creating a divergence of longshore sediment transport
nodal points, i.e. a place where sand moves alongshore to both the east and southwest away from the
mouth (Fig. 5A,B).
The annual rates of shoreline change prior to 1990
demonstrate that higher erosion centered on both sides
of the promontory tip, but with accretion to either side
Fig. 5. (A) The Rosetta promontory showing the positions of 1990 and 2000 shorelines, location of the examined 24 beach profiles. Waveinduced littoral currents are schematically denoted. (B) Alongshore pattern of estimated littoral transport rate. (C) The effect of protection
system on the behavior of the coastline based on comparison between shoreline change rates before (1971 – 1990) and after protection (1990 –
2000). R1 to R24 denote Rosetta beach profile numbers.
O.E. Frihy et al. / Geomorphology 53 (2003) 263–279
271
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O.E. Frihy et al. / Geomorphology 53 (2003) 263–279
along the promontory flanks (Fig. 5C). Maximum
erosion revealed on the east and west sides adjacent
to the River mouth are 52 and 88 m/year, respectively.
This erosion decreases systematically alongshore both
to the west and the east, then reverses to accretion at
nodal points. Nodal points denote the change of areas
of sediment transport from erosion to deposition or
vice versa that result from the orientation changes of
the shoreline. These points are located 6.2 km southwest of Abu Quir Bay and 7 km of the Rosetta saddle
of Abu Khashaba., both measured from the Rosetta
mouth. This presents a simple pattern of erosion from
the tip of the promontory near the mouth of the river,
with eroded sand moving alongshore as it is transported by longshore currents to the southwest along
the shoreline of Abu Quir Bay and to the east along
the eastern flank of the promontory. The western and
eastern parts adjacent to the Rosetta mouth are parts of
the Abu Quir and Rosetta subcells, respectively,
identified by Frihy et al. (1991) (Fig. 2D).
To reduce the erosion impacts at the Rosetta
promontory, two dolos seawalls (4 and 7 tons) were
constructed between 1989 and 1991 on both sides of
the Rosetta Nile branch mouth (Figs. 5A and 6A). The
western and eastern seawalls were constructed inland
and extend alongshore to a length of 1.5 and 3.35 km,
respectively. The seawalls stand 6.75 m above MSL,
and vary in width from 48 to 70 m (Fig. 6A and B).
The rate of shoreline changes after protection reveals
that the two seawalls have succeeded in stopping the
shoreline erosion along the tip of the promontory.
However, they have shifted the erosion at the promontory tip to downdrift areas at the east and west wall
ends, being 3 and 13 m/year, respectively (Figs. 5C
and 6A). The post-construction erosion rates are lower
than those that were being experienced prior to
building the seawalls (originally 88 m/year). Consequently, five groins were built to combat the local
erosion that resulted at the eastern end of the seawall
(Fig. 5A). The length of these groins varies between
400 to 500 m seaward and they are spaced 800 –900
m apart.
4.2.2. Burullus promontory
The Burullus bulge-headland is located midway
between the Rosetta and Damietta promontories (Fig.
1). The coast forms a broad, arcuate headland and is
located on a very active littoral zone which has
experienced widespread erosion. The east barrier is
covered by an 8-km-long barchan dune system (Fig.
7A). These dunes are suffering from sea cutoff erosion
that represents a particularly significant source of sand
to the beach of the Burullus subcell (Fig. 6C and D).
This promontory represents a part of the Burullus
subcell, which extends from Abu Khashaba east of
Rosetta promontory to a point between Damietta
harbour and Damietta river mouth (Fig. 2D). With
regard to protective measures, three jetties were built
successively to control the navigation activities in the
inlet of the Burullus lagoon (Fig. 6C). A concrete
seawall and basalt revetment were built to protect the
beach downdrift of these jetties (Fig. 7A). Further to
the east, at about 11km from the Burullus inlet, an
intensive erosion control project that consisted of nine
emerged detached breakwaters was built in the active
surf zone in a water depth between 3 and 4 m (Fig.
7A). These breakwaters were constructed in an
attempt to mitigate coastal erosion and were built in
stages between 1993 and 2001 and fronting about 4.5
km long (Fig. 6E). Each breakwater extended between
250 and 350 m parallel to the beach, and they are
spaced 320 – 400 m apart. Other breakwaters are
expected to be built to cover an additional 5-km
alongshore east from the implemented breakwaters.
The predominant wave approaches from the NNW,
NW, WNW, W and WWS are responsible for generating the eastward-flowing longshore currents along
the entire Burullus coastline (Fig. 7A). The opposing
westerly longshore current is relatively small and is
induced by waves approaching occasionally from
NNW, N, NNE and NE sectors. This directional
distribution of waves is reflected in the net longshore
transport rate, which seems to be unidirectional all
year long, being a maximum of 300 103 m3 year.
The rate of sediment transport has increased systematically along the lagoon barrier from 95 103 m3
year near the inlet to a maximum of 338 103 m3
year just west of the detached breakwaters and has
decreased beyond to 300 103 m3 year in the shadow
zone of the breakwaters where accretion prevails (Fig.
7B).
Further to the west, the gradual decreasing of the
sediment transport gradient from 200 10 3 to
100 103 m3 year along the coast west of the inlet
indicates sand deposition produced by the interruption
of the eastward longshore sediment transport by the
O.E. Frihy et al. / Geomorphology 53 (2003) 263–279
273
Fig. 6. Selected photographs showing main features along the Nile delta coast. (A) Spot image (1997) showing the 6-km-long seawall
constructed on both sides of the Nile estuary of the Rosetta promontory to protect the promontory tip from erosion and the impacts on downdrift
beaches; (B) portion of the Rosetta dolos seawall on the western promontory flank; (C) aerial photograph (1983) of the Burullus inlet showing
the lagoon inlet and portion of the sand dune lagoon barrier; (D) barchan dunes directly exposed to the sea along the Burullus lagoon barrier; (E)
detached breakwaters and tombolo formation at Baltim resort beach; (F) portion of the 6-km-long dolos seawall built along the eastern tip of the
Damietta promontory, also showing the long jetties constructed at the Damietta River estuary to mitigate sedimentation; (G) detached
breakwaters at Ras El Bar resort beach; and (H) TM satellite image of the Damietta promontory (2000) showing the active sand spit at the
eastern flank and the W – E dolos seawall built on the outer margin of the promontory.
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Fig. 7. (A) The Burullus – Baltim coastal sector showing the positions of 1990 and 2000 shorelines, the location of 45 beach profile lines
examined and protective structures. Wave-induced littoral currents are schematically denoted. (B) Alongshore pattern of estimated littoral
transport rate. (C) The effect of the detached breakwaters on reshaping the coastline along the Burullus promontory based on comparison
between shoreline change rates before (1971 – 1990) and after protection (1990 – 2000). B1 to B45 denote Baltim beach profile numbers.
O.E. Frihy et al. / Geomorphology 53 (2003) 263–279
jetties that have been constructed at the inlet to the
Burullus lagoon (Fig. 7B). The westerly net longshore
transport component along the whole Burullus coast is
insignificantly small, being 16 103 m3 year at its
maximum.
Patterns of shoreline change rates along the Burullus promontory coast show local accretion (5 m/
year) along the 3-km section to the west of the barrier
which resulted in sand accumulation on the updrift
side of the western inlet jetty that is because the
predominant littoral drift is toward the east (Fig.
7C). Prior to constructing the detached breakwaters
at Baltim resort, erosion dominated farther along the
most eastern barrier, attaining a maximum of 6 m/
year. Following construction of these breakwaters,
accretion in the form of tombolos that have been
formed in the leeward side of these structures has
occurred at a maximum rate of 37 m/year (Fig. 6C).
This accretion has filled the shadow area between the
coastline and the breakwaters. As expected, local
erosion is observed farther downcoast of these breakwaters at approximately 25 m/year. This erosion is
higher than that which occurred previously in 1990,
which originally was 6 m/year. This erosion has
resulted from interruption of the prevailing eastward
sediment transport by the tombolo formation, thus
increasing sand starvation of downcoast beaches.
4.2.3. Damietta promontory
The Damietta promontory is located in the eastern
half of the Nile delta, and its shoreline extends about
35 km (Fig. 1). At the western coast of the Damietta
promontory, the N, NNW, NW (totaling 90j) and
WWN (40j) waves are responsible for the generation
of longshore current toward the southwest and northeast, respectively (Fig. 8A). As with the Rosetta
promontory, the western coast is partially sheltered
from N to E waves. On the east coast, waves coming
from the N, NNW, NE (ranging 65 – 90j) generate a
unidirectional longshore current towards the southeast
with no westward current reversals. The prevailing
southeastward longshore current along this sector is
responsible for creating the sandy spit located down
coast of this promontory (cf. Klemas and Abdel
Kader, 1982; Frihy, 1988). The outer margin of this
promontory is subjected to eastward sediment transport with significant westward reversal (Fig. 8A).
Similar to the Rosetta promontory, the longshore
275
transport pattern along the Damietta coast fluctuates
in intensity and direction due to shoreline orientation
and coastal structures. This distribution mirrors the
pattern of shoreline erosion versus accretion as reaffirmed here below. The gradient of longshore transport rates (net and eastward littoral drift) fluctuate
between upward ‘‘increasing’’ and downward ‘‘decreasing’’ values (Fig. 8B). Upward increasing rates
indicate eroded areas such as the area between Damietta harbour and Ras El Bar detached breakwaters
(449 103 m3 year maximum) and the updrift eroded
coast of the Damietta spit (200 103 m3 year maximum), while decreasing rates denote accreting
beaches behind the Ras El Bar breakwaters and at
Damietta spit ( f 100 103 m3 year maximum). The
longshore transport rate along the east coast of the
Damietta promontory is southeasterly all year long,
while it fluctuates between northeasterly and southwesterly along the west coast (Fig. 8B).
The general erosion/accretion pattern along the
Damietta promontory before protection is similar to
that at Rosetta (Fig. 8C). Maximum erosion is occurring at the tip of the promontory (10 m/year) with
accretion taking place to the east along its flank at the
neck of the sand spit. One difference from the Rosetta
promontory is that the accretion has taken the form of
a sand spit growing in a southeasterly direction. The
spit acts as a buffer for sand transport farther southeast, further increasing sand starvation of down-spit
coasts (Fig. 6H). On the west coast, significant erosion (4 m/year) appears along Ras El Bar resort beach
and decreases westward where it is changed to accretion (14 m/year) at the updrift of the Damietta harbour
breakwaters (Fig. 8C).
The first protection structure was built along the
Damietta promontory sector in 1941 with the construction of a jetty at the western side of the Damietta
mouth (Fig. 6F). In 1971, additional groins were
constructed with basalt and dolos walls in between to
protect the resort beach of Ras El Bar from erosion.
As a response, erosion occurred downdrift of these
groins. Other structures built in this area include the
breakwaters of the Damietta harbour, which was
constructed in 1982 and is located at about 9.7 km
to the west of the mouth of the Damietta branch (Fig.
8A). The western and eastern breakwaters extend
1500 and 500 m seaward, respectively (Fig. 6H).
Recently, a series of detached breakwaters, eight so
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O.E. Frihy et al. / Geomorphology 53 (2003) 263–279
O.E. Frihy et al. / Geomorphology 53 (2003) 263–279
far, have been built in stages since 1991 (Fig. 6G). As
with Baltim, these breakwaters are parallel to the
coastline leaving an offshore distance of about 350
m at a water depth of 4 m. The breakwater length and
gap distance are 250 m with a crest level of 1.5 m
above mean sea level. They are armored by 4 ton
dolos units. They are effective in trapping sand in the
form of salients on the leeward side. However, erosion
continued westward downcoast of the first breakwater
(Fig. 8C). The sedimentary pattern along the west
coast has been disrupted following construction of the
detached breakwaters. The accretionary salient formation (primitive tombolo) has blocked the sediment
transport flow causing areas of local erosion. At the
eastern flank of the Damietta promontory, a 6-kmlong seawall similar in design to the Rosetta seawall,
trending W – E along the promontory tip, is being
completed. It is expected that this seawall would
diminish sand nourishment to the spit that may disturb
the processes of spit growth.
5. Summary and conclusions
Analyses of extensive beach profiles spanning 29
years (1971 –2000) along the Nile delta promontories
supplemented by wave measurements has contributed
to a better understanding of shoreline changes and
sediment dynamics. These data have been analyzed
separately to determine shoreline changes before protection (1971 – 1990) and after protection of these
promontories (1990 – 2000). Before protection, the
general patterns of erosion and accretion on the littoral
zone of the Nile delta appear to follow a conceptually
simple coastal straightening model, with erosion of
promontory tips and deposition in sinks of saddles and
embayments on both sides of these promontories. The
promontory beaches and the adjacent coastal dune
fields along the central coast of the delta are the main
sediment sources for longshore and cross-shore transport. The general sedimentation pattern of the Rosetta
and Damietta promontories is governed by the deflec-
277
tion of their shoreline orientation which enhances the
angle of wave attack and favors a unidirectional
easterly sediment transport accompanied with a westerly reversals. The regional patterns of shoreline
changes prior to 1990 is consistent with the subcells
identified by Frihy et al. (1991) and Frihy and Lotfy
(1997). This regional pattern has been disrupted during the last decade in response to the construction of
protective structures along the three promontory sectors. The two seawalls built at Rosetta promontory
and the detached breakwaters at both Baltim (east of
the Burullus remnant promontory) and at Ras El Bar
west of the Damietta promontory have modified the
littoral subcells fronting these coastal sectors. As
expected, the rate of shoreline erosion over the last
10 years (1990 – 2000) has declined along the outer
margin of these promontories, accompanied by local
downdrift erosion and updrift accretion as a result of
these structures. These changes are also associated
with local accretionary areas such as the tombolo and
salient sand formations fronting the Baltim and Ras El
Bar beaches, which result in shoreline accretion of 37
and 14 m/year, respectively.
The pattern of erosion versus accretion reflects the
natural processes of wave-induced longshore currents
and sediment transport. The longshore transport rates
estimated along the delta promontories indicate a
predominantly easterly sand transport during most of
the year, and occasionally to the west. The easterly
longshore sediment transport is generated by the
prevailing N and N – W waves due to the acute angle
of wave attack versus shoreline orientation. This
situation is different in the case of the Rosetta and
Damietta promontories due to the contrasting deflection of their shoreline orientation. Generally, the
shores east of the Nile promontories are influenced
by southeasterly longshore current generated from the
prevailing N, NNW, NW, WNW, NNE and NE waves.
These currents are responsible for transporting sediments from the eroded zones along the Rosetta
promontory tips to the east saddles, and as a sand
spit east of the Damietta promontory. The opposite
Fig. 8. (A) The Damietta promontory showing the positions of 1990 and 2000 shorelines, the location of the 39 examined beach profiles. Waveinduced littoral currents are schematically denoted. (B) Alongshore pattern of estimated littoral transport rate. (C) The effect of protection works
on the behavior of the coastline along the Damietta promontory based on comparison between shoreline change rates before (1971 – 1990) and
after protection (1990 – 2000). D1 to D39 denote Damietta beach profile numbers.
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O.E. Frihy et al. / Geomorphology 53 (2003) 263–279
shores west of these promontories are partially sheltered from the N – E waves and directly affected by the
westerly longshore currents during the prevailing
waves from the N and N –W. These longshore currents are largely responsible for transporting sediments from the eroded zones west of the Rosetta
promontory tip along Abu Quir Bay and from Ras
El Bar beaches toward Gamasa sink at Damietta
promontory. As a consequence, divergence areas of
opposing sediment transport have been generated in
front of the Rosetta and Damietta promontories as an
interaction between wave activities and shoreline
orientation. This study provides vital information for
preparation and implementation of future plans to help
protect and remediate the rest of the delta region, and
also useful for decision-makers dealing with coastal
zone management. Moreover, interactions between
the natural forcing and human influences in terms of
protective structures have altered the original sedimentation pattern of these promontories.
Acknowledgements
The present investigation was undertaken as part of
the program of the Coastal Research Institute, Egypt,
to monitor morphodynamic changes along the Nile
delta. The authors appreciate the assistance of the staff
of the Coastal Research Institute who contributed to
the field and laboratory activities of this study.
Appreciation is also given to Mrs. Mona Kaiser, the
University of Reading, UK, for providing the TM
image 2000 of the Damietta promontory. The critical
comments by the editorial reviewers were appreciated
and contributed appreciably to the quality of this
paper, including Dr. Zhongyuan Chen, East China
Normal University, Shanghai, China, and Dr. Andrew
Plater, University of Liverpool, UK.
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