DOI : 10.4197/Mar. 23-2.9
165
The Impact of the Unplanned Structural Adjustment of Breakwaters on the Marine Environment of Port of
Alexandria, Egypt:
A Lesson Learnt for Future Concern.
Ahmed E. Rifaat* and Mona Kh. Khalil**
National Institute of Oceanography and Fisheries, Al’Anfushi 21556, Alexandria, Egypt
*[email protected] **[email protected]
Abstract. Port of Alexandria (POA) is the main trade port in Egypt. It handles more than 75% of Egypt’s external trade and plays a major role in the national economy. Due to the excessive shipping activities in the port and the industrial-agricultural-municipal effluents, the port is subjected to a pollution problem. Human intervention to protect the port against the wave and current actions by erecting improperly designed breakwaters and changing the natural coastal forms all often led to increased pollution. This study evaluates the structural adjustment carried out on the breakwaters in POA pertaining to their negative impacts on the marine environment and assesses the present quality of the marine environment in the port. A set of maps are used to delineate the development of the breakwaters in POA since 1857.
The heavy metal concentrations for bottom sediment samples that are collected in 1980 and 2010 are used for comparing the marine environmental quality in the respective years. The adjustment carried out on the breakwaters led to the stagnation of POA water.
Consequently, the pollutants are trapped in the port basin and the environmental quality is decreased. The increase in ratios of heavy metals’ concentrations, between 1980 and 2010, are 1.4 for iron, 1.5 for zinc, 2.4 for copper and 2.6 for cadmium. To remedy the POA deteriorated environment the study proposes a tunneling project that would enhance the water exchange between the port and the Mediterranean Sea and consequently improve the water quality by continuously washing out the polluted water masses.
Keywords: Alexandria port – structural adjustment – breakwaters – marine environment.
Introduction
The importance of maritime transportation in global freight trade is unmistakable, as it handles about 90% of the global trade (Rodrigue et al., 2009). Ports are, therefore, important for the economy of nations as they play the principal role in the international trade. Most of the ports’
marine environments, if not all, are undergoing great stress and suffer more or less from the deterioration of their quality. The sustainability of harbour management from an environmental standpoint is a prime concern for port authorities and it includes dealing with problems that may seriously affect the quality of harbour waters (Mestres et al., 2007).
In fact, ports are very complex systems in which almost all elements that can be associated with anthropogenic pollution can be found (Darbra et al., 2004). Noise, dredging, waste production, waste waters, emissions of particles into the atmosphere or the water, accidental releases of hazardous substances, are likely to be present in one way or another.
Moreover, pollution sources may include activities or facilities that do not belong strictly to the port, but are closely linked to it, such as neighbouring industrial installations (Darbra et al., 2004; and Ruggieri et al., 2011). Human intervention to protect the ports against the wave and current actions by erecting improperly designed breakwaters and changing the natural coastal forms often led to increased pollution. One of these ports is Port of Alexandria (POA), sometimes called Alexandria western harbour, which is the main trade port in Egypt. It handles more than 75% of Egypt’s external trade and plays a major role in the national economy. Once, the port was a naturally sheltered basin with a remarkable wide connection with the Mediterranean Sea. Since 1869 it has undergone several stages of development. Man-made breakwaters were erected to protect the port from the action of the waves and new berths were added to keep pace with the increasing shipment activities.
This study evaluates the structural adjustment carried out on the breakwaters in POA pertaining to their negative impacts on the marine environment and assesses the present quality of the marine environment in the port.
Area of Study
The Port of Alexandria (Fig. 1) is a main harbour on the northwest coast of Egypt (at 31° 10' 56.15" N, 29° 51' 48.64" E). It is the oldest port
in the Mediterranean Sea, with a wide range of different activities. Its basin is oval having a length of 4.8 km and a maximum breadth of 2.3 km and is sheltered by two connected, arrow-like breakwaters known as the Outer- and Inner breakwaters. The port is divided into two parts, separated by the line running across the Coal Quays and the break between the inner and outer breakwaters. The eastern part is known as the Inner Harbour while the western is the Outer Harbour. The port basin is characterized by shallow depths near the breakwaters (5-9 m.), increasing gradually towards the center and the navigational channels (13-16 m.). Noubariya navigational channel is opening into the port.
Mahmoudiya channel was once opening into the harbour but it ceased to flow in several years ago. The port has a narrow connection (el Boughaz), at its western extremity, with the Mediterranean Sea. It was naturally sheltered by growths of coral reef and accumulations of off- shore sand bars that were reinforced into man-made breakwaters (Alexandria Port Authority publication, 1978). Physiographically, POA is a coastal lagoon which is enclosed by a series of barrier chains.
Tectonically, the port was formed by submergence of the coast with the subsequent transgression of the Mediterranean waters during Pre- Holocene time (Butzer, 1960). In fact, POA basin represents a bar and lagoon sequence among a series of eight offshore bars and lagoons running, in a nearly straight line, parallel to the coast (Rifaat, 1982). The current pattern at the port’s entrance composed of an inflowing bottom current (velocity range 15-20 cm/sec and general direction N to NE) and an outflowing surface current (velocity range 20-50 cm/sec and general direction S to SW); the periodic tidal flow has a little but remarkable effect on the circulation inside the port (Farag, 1982).
POA receives mixed industrial, agricultural and domestic pollutants that are trapped in due to the semi-enclosed nature of the harbour area.
The major sources of pollutants are, the tanneries and slaughterhouse (sulphide, ammonia and chromium); Misr Chemical Industries (calcium- chloride,-carbonate and - sulphate, chlorine, mercury, ammonia and sludge); Portland Cement Factories (heavy metals mainly cadmium);
Noubariya channel (municipal and agricultural effluents); el Mex Pumping Station (industrial, agricultural and domestic liquid wastes);
Cement packing units (cement dust); Marine vessels and containers (domestic wastes and litter); Fall outs from the unloading/loading processes of the exported/imported raw materials (native sulphur,
ammonia-, nitrate-, and phosphate- fertilizers, coal, petroleum, and others) (Rifaat, 1982; and Barakat et al., 2002).
Fig. 1. An outline map of Port of Alexandria showing the port’s features at present. The map was digitized from Google Earth Map 2011 (see text for details). Sediment samples locations are shown by black dots.
Materials and Methods
A set of maps were used to delineate the development of the breakwaters in POA since 1857. These are:
1.Port of Alexandria Chart No. 243 (1857), (Hydrographic Office), 2.Port of Alexandria Chart No. 243 (1962), (Hydrographic Office), 3.Port of Alexandria from GoogleTM Earth 2011.
First the POA map 2011 from Google Earth is calibrated using several reference points to minimize the root mean square error. The scanned POA Charts No 243 (1857 and 1962) are rectified (image to image technique) using the calibrated Google Earth map as a reference map and WGS84 as the map datum. The maps are then scaled to
1:100000 to obtain a set of matched charts. The POA outline maps for 1857, 1962 and 2011 are digitized using Didger software and the maps are created using Surfer software from Golden Software Incorporation.
Since the bottom sediments act as sinks for the pollutants of the water column, the measurements of pollutant concentrations in the sediment are efficient indicators for the assessment of the pollution.
Heavy metals are considered as one of the most serious pollutants for their high toxicity, persistence in marine environment and bioaccumulation (Papaefthymiou et al., 2010).
Data on the concentrations of heavy metals in bottom sediments from POA and its vicinity during 1980 (Rifaat, 1982) and the concentration of the same heavy metals in sediments determined in this study are used for comparing the marine environmental quality in the respective years. Rifaat (1982) used the distributions of 1) iron to assess the environmental impact of the tanneries and slaughterhouse activities;
2) zinc to assess the environmental impact of the municipal effluents, 3) copper to assess the environmental impact of the shipyard activities and 4) cadmium to assess the environmental impact of the industrial effluent from the surrounding factories. To ensure accurate comparison of the obtained results in 1980 and that of 2010, the same methods for bottom sediment sampling, extraction and determination of metals were applied.
Twenty two VanVeen grab bottom sediment samples were collected in 2010 from the study area. The extraction of iron, zinc, copper and cadmium from the sediment samples was carried out following the methods mentioned by Piper (1971). The metal determinations were carried out using the Atomic Absorption Spectrophotomer (Perkin Elmer Analyst 800, equipped with Zeman background correction).
Results
The outline maps of POA are presented in Fig. 1-3. In 1857 the port was a naturally sheltered area with a remarkable wide connection with the Mediterranean Sea (Fig. 2). The port basin is a bar and lagoon sequence among a series of eight offshore bars and lagoons running, in a nearly straight line, parallel to the coast. This bar and lagoon structure is indicated by the chain of reefs and islets extending off Pharos island (now called Kayet Bey Headland) across the ruins of Fort Abbassia to the
longitude of El Hammam. An almost unbroken chain of near surface reefs and rocks extends for some 4 km. between Kayet Bey and Ras el Tin, separated from the shore by al Anfushi Bay, and then continues over El Aramil rocks as a chain of shoals and reefs at 2-6 m below the mean sea level. These include El Ikhwan, El Hut, El Kelb, E1 Kot, El-Fara, North Shoal, Hydrographer Shoal, El Medjul, Hommy Shoal, Etram Reef, Mazula Reef and the islets of El Agrash and El Agami.
Fig. 2. An outline map of Port of Alexandria in 1857 showing the expected prevailing current regime. The map was digitized from Admiralty Chart No. 243, Scale 1:18,200 Port of Alexandria 1857 produced by the Hydrographic Office (see text for details).
The outline map of POA 1962 (Fig. 3) shows that two breakwaters were erected to protect the port from waves and storms. Many quays and berths have been added to keep pace with the increasing shipping activities. At Ras el Tin Head, an opening was left unblocked to allow the flowing out of the currents that enter the port from the western entrance (el Boughaz).
Fig. 3. An outline map of Port of Alexandria in 1962 showing the prevailing current regime.
The map was digitized from Admiralty Chart No. 243, Scale 1:25,000 Port of Alexandria 1926 produced by the Hydrographic Office (see text for details).
Since 1962 and after, the Egyptian Navy constructed a concrete barrier over the inner breakwater and added more berths for the warships.
The opening at Ras el Tin head was blocked for reasons of security.
Alexandria Port Authority also added more quays to the port.
In 1980 the average concentrations (n=27) of iron, zinc, copper and cadmium in bottom sediments from POA were 13500, 232, 99 and 25 µg g-1, respectively (Rifaat, 1982). In the present study, the average concentrations of the same metals in bottom sediments are 18739, 339, 241 and 65 µg g-1, respectively (Table 1 and Fig. 4).
Table 1. Summary of the concentrations of Fe, Zn, Cu and Cd in Port of Alexandria sediment in 2010 and 1980.
Sediment of 2010 (This study)
n=22 Fe Zn Cu Cd
Mean 18739 ± 9461 339 ± 134 241 ± 172 65 ± 7
Minimum 4120 59 32 52
Maximum 33060 464 492 74
Sediment of 1980 (Rifaat 1980)
n=27 Fe Zn Cu Cd
Mean 13500 ± 6500 232 ± 127 99 ± 48 25 ± 20
Minimum 2800 23 30 3
Maximum 29300 474 230 82
Fig. 4. The concentrations of iron, zinc, copper and cadmium and their increase ratios (Conc.2010/Conc. 1980) in bottom sediments from Port of Alexandria in 1980 and 2010.
Discussion
The current system dominating in the Egyptian Mediterranean coast is S-SE (Sabra, 1979). This current approaches the nearshore zone and transforms into an easterly longshore current running parallel to the shore and follows the coastal morphology. Before 1869, it is expected that, the longshore current was entering the old POA basin forming an anti-clockwise gyre circulating the basin and went out in a NW direction at Ras el Tin Head. This current pattern was rejuvenating the port’s water and washes out all types of pollutants (Fig. 2).
In 1869 the offshore sand bars and reefs were reinforced and an arrow-like breakwater was constructed to enhance the shelter of the port.
The breakwater was extending parallel to the shore over a series of shoals and reefs and an opening, between the eastern end of the breakwater and Ras el Tin Head, was left unblocked. Although the result of shielding of
the port by the breakwater has limited the movement of currents in the port and decreased the rejuvenation rate of the port’s water, the current entering the port from the western entrance was strong enough to wash the pollutants out through Ras el Tin opening. The easterly longshore current that was entering the port from the western entrance was circulating both the outer and inner parts of the port then went out through the north opening at Ras el Tin Head (Fig. 3).
This current pattern persisted until 1968 when the Egyptian Navy blocked Ras el Tin opening for reasons of security. The blocking of Ras el Tin opening dramatically changed the situation inside POA. The current pattern dominating the port’s basin has been changed and the marine environmental quality has been decreased apparently.
In 1980 Alexandria Port Authority appealed for a research investigation to find out the cause behind the strong bad odour emanating from the port’s seawater and the accumulation of the floating litter inside the port and around the quays. The bad odour problem appeared lately and was more pronounced in the inner harbour. Farag (1982) studied the current pattern in POA and found out that the current regime at the western entrance consists of an outflow in the upper 5 m layer and an inflow at a depth of 10 m. The water exchange between the port and the sea was found to be very slow and led to stagnation conditions inside the port’s basin (El-Gindy, 1986; and Hassan & Saad, 1996). Inside the port the circulation was varying greatly and no distinct pattern could be identified. It is obvious that the circulation pattern in POA has changed from the open pattern in the period before 1869 to the restricted pattern after that date due to the erection of the breakwaters. In the 1968 the circulation pattern took another trend and the inflow and outflow currents became occurring at the western entrance of the port. Accompanied by the increase of pollutant discharges and the semi-enclosed nature of the area, the deterioration of the marine environment quality has started due to the trapping of the disposed municipal/industrial wastes and the discharged litter and wastes from the transient vessels. In 1980 the levels of iron, zinc, copper and cadmium in bottom sediments were high (averages 13500, 232, 99 and 25 µg g-1, respectively) and the amounts of floating litter were enormous (Rifaat, 1982). The recommended remedies were:
1) Unblocking and widening the northern opening at Ras el Tin Head to enhance the circulation and the washing out of the port’s water and thus the water quality would be improved,
2) prohibiting the ships and vessels from dumping their litter in the area, and
3) preventing dumping the municipal, industrial and agricultural discharges into and around the port area.
In spite of that, the Egyptian Navy reinforced the northern breakwater and added more berths for the military warships.
Consequently, the marine environment quality in POA has been worsening remarkably. In 2010 the levels of iron, zinc, copper and cadmium in marine sediment (averages 18739, 339, 241 and 65 µg g-1, respectively) became higher than those in 1980. The amounts of increase, between 1980 and 2010, are 1.4 for iron, 1.5 for zinc, 2.4 for copper and 2.6 for cadmium (Fig. 4). Moreover, the dissolved and particulate lead concentrations in POA water were higher than the corresponding values reported in the Egyptian and other coastal waters worldwide (Saad et al., 2003). The low average concentration of dissolved oxygen in the port’s water (3.5 mg l-1 for surface layer and 2 mg l-1 for bottom layer) (Dorgham et al., 2004) compared with that in the Mediterranean water just outside the port (11 mg l-1) (Farag, 1982) indicates that the seawater exchange rate through el Boughaz is very limited.
A mitigation plan is required to remedy the POA low environmental quality. One or more tunnels should be dug to promote the water exchange between the port’s basin and the Mediterranean Sea. An extensive study inside the port and its vicinity is required to identify the current circulation pattern and to determine the present bottom topography. CAD-simulation models should be designed, considering the field observations, and used to decide upon the best specification(s) and location(s) of the tunnel(s). An environmental impact assessment (EIA) is also required to assess the sustainability of the proposed tunnel(s).
It is expected that the proposed tunneling project would enhance the water exchange between the port and the Mediterranean Sea and consequently improve the water quality by continuously washing out the polluted water masses.
Conclusions
Knowledge on the marine processes and the behavior of the coastal ecosystem are essential to the successful implementation of coastal development plans. If such data are not included in the project plan, significant impacts are likely to arise. The unplanned modification of the breakwaters in POA has led to the alteration of the current pattern from the open circulation to the stagnant state and consequently, to the trapping of the pollutants and the deterioration of the environmental quality. Ignoring the recommendations proposed by field studies under the pretext of economic gains or security precautions leads to serious environmental consequences. The main lesson learnt from this study is that the remedy of the implications resulted from the malpractices in POA is undoubtedly very costly and takes a lot of time.
The case of POA highlights the necessity for carrying out an environmental impact assessment (EIA) study before implementing any coastal development or modification plan. As a general lesson learnt, understanding of the future impacts requires field data and model development which quantitatively describe the predicted impacts.
Mathematical and simulation modeling are prerequisite for identifying future impacts of coastal construction works.
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