Vulnerability risk assessment and adaptation to climate change induced sea level rise along the Mediterranean coast of Egypt

Consequence of the sea level rise (SLR) on the Mediterranean coastal areas in Egypt, particularly the Nile River Delta, has become an issue of major concern to Egypt’s population and the government. Previous publications disregard the entire Mediterranean coast of Egypt as an integral unit subject to the impacts of the SLR. This study aims to analyzing the risks, ranking the vulnerability and suggesting adaptation measures to mitigate the impact of the SLR along the Mediterranean coast of Egypt. Although the prominent features of Egypt’s Mediterranean coastal zone are the low lying coast of the Nile Delta, associated with land subsidence, tectonic activities and erosion; the contiguous coastal sectors are backed by shore-parallel carbonate ridges and Plateau (the western coast) and sand dune belts (Sinai coast). The coastal zone is ranked as high, moderate, and low vulnerable to the SLR. The social and biophysical vulnerabilities demonstrate the asymmetrical impacts of the SLR on the Mediterranean coast of Egypt. Areas at risk in the Alexandria region are Mandara and El Tarh whereas in the Nile Delta region, they are the Manzala Lagoon barrier, east and west of the Rosetta City, Gamil, and the Tineh plain. Risk associated with these impacts may be reduced provided the consideration of immediate and adequate adaptation measures.     

Vulnerability Assessment of Sea Level Rise Over Port Said Governorate, Egypt

An assessment of the impact of sea level rise on the city of Port Said, Egypt has been carried out using remote sensing and GIS techniques. Bruun's is used to estimate horizontal retreat, due to three scenarios of sea level rise, taking into account local subsidence rates. Overlaying horizontal retreat on land use obtained by remote sensing enabled us to estimate possible losses and socio-economic impacts. Results indicate serious physical and socio-economic impacts. It is suggested that protection measures must be carried out with emphasis on building breakwaters along the most vulnerable shoreline area.     

Pre- and post-beach response to engineering hard structures using Landsat time-series at the northwestern part of the Nile delta,Egypt

Analyses have been undertaken to examine shoreline positions established from remote sensing data along the northwestern part of the Nile delta from the Abu Qir Bay to Gamasa embayment (∼143 km length). The image data used (MSS, TM and ETM+ sensors) are acquired at unequal intervals between 1972 and 2006, i.e., covering a time span of 34 years. Automated waterline positions extracted from Landsat satellite images during this period of time were computer generated. A digital shoreline analysis software was used to calculate the annual rate of beach changes at 1,432 cross-shore transects prior to (1972–1990) and after protection (1993–2006). On comparison, rates estimated from three statistical approaches (the end point rate, the Jackknife and a weighted linear regression) at corresponding positions are successfully validated with those measured from ground survey. Before protection, results reveal longshore patterns wherein erosion along a coastal stretch gives way to accretion in an adjacent stretch, refining the sub-cells previously identified within the littoral system of the delta. Maximum shoreline retreat occurs along the Rosetta promontory (−138.52 m/year) and along the central bulge of the delta at Burullus headland (−6.07 m/year). In contrast areas of shoreline accretion exist within saddles or embayments between the promontories at west Abu Qir Bay (20.04 m/year), Abu Khashaba saddle (16.17 m/year) and Gamasa embayment (20.68 m/year). These rates of changes have been significantly altered by the construction of intensive shoreline protective structures built from 1990 to combat areas of rapid erosion at both the Rosetta promontory and Burullus–Baltim headland, ∼15-km length in total.     

The Nile delta-Alexandria coast: vulnerability to sea-level rise,consequences and adaptation

Like many delta systems, the coastal zoneof the Nile delta has been designated as avulnerable zone to a rising sea level as aconsequence of expected climate changescombined with geological and human factors.In view of the understanding of thesefactors, a degree of vulnerabilityanalysis has been carried out to betterlocate which sectors need to be assessedand adapted to possible sea level rise(SLR) for the Nile delta-Alexandria region of Egypt.Results reveal that not all of the coastalzones of the Nile delta are vulnerable toaccelerated sea-level rise at the samelevel. Based on multiple criteria the Niledelta-Alexandria coast can be categorizedinto vulnerable (30%), invulnerable (55%)and artificially protected coastalstretches (15%). These criteria include:local subsidence or uplifting, relativesea-level rise (RSLR), land topography,width of lagoon barriers, beach-face slope,high-elevated features such as dunes andridges, eroding and accreting coastlinesand protection works.Moreover, this study evaluates thelong-term relative sea-level rise andsubsidence rates along the Nile delta andAlexandria coasts. Statistical analysis oflong-term tide gauge data recorded atAlexandria, Burullus and Port Said yieldsvalues of 1.6, 1.0 and 2.2 mm/yr,respectively. These values of relativesea-level rise and long-term subsidencerate obtained from age-dated sediment coresections are inconsistent: long-termsubsidence appears to be larger (maximum of7 mm/ yr). This discrepancy might beexplained if the subsidence is episodic,and occurs rather abruptly during majorearthquakes that occur every few hundredyears associated with fault trend lines.Rising sea levels could have significantlongterm impacts on the Nile delta,including the distribution of ground watersalinity and erosion of the narrow andlow-lying barriers of the Burullus andManzala lagoons. Adaptive measures alongthe study area particularly those relatedto coastal protective structures are alsoevaluated.     

Beach impacts of shore-parallel breakwaters backing offshore submerged ridges, Western Mediterranean Coast of Egypt

Seven breakwaters were constructed behind offshore submerged ridges to create a safe area for swimming and recreational activities west of Alexandria on the Mediterranean coast of Egypt. Morphodynamic evaluation was based on the modified Perlin and Dean numerical model (ImSedTran-2D) combined with successive shoreline and beach profile surveys conducted periodically between April 2001 and May 2005. Results reveal insignificant morphologic changes behind the detached breakwaters with slight coastline changes at the down and up-drift beaches of the examined breakwaters (+/-10 m). These changes are associated with salient accretion (20-7 0m) in the low-energy leeside of such structures. Concurrent with this sand accretion is the accumulation of a large amount of benthic algae (Sargassum) in the coastal water of the shadow area of these structures, which in turn have adverse effects on swimmers. Practical measures proposed in this study have successfully helped in mitigating such accumulation of algae in the recreation leeside of the breakwaters. The accumulation of Sargassum, together with the virtual insignificant changes in the up-drift and down-drifts of these structures, is a direct response to both coastal processes and the submerged carbonate ridges. Coastal processes encompass reversal of the directions of long-shore sand transport versus shoreline orientation, the small littoral drift rate and sand deficiency of the littoral zone. The beach response to the breakwaters together with the submerged ridges has also been confirmed by applying the ImSedTran-2D model. Results indicate that submerged ridges play a principal role in the evolution of beach morphology along the west coast of Alexandria. Although the study area is exposed to more than 70% wave exposures, the morphodynamic behavior of the beaches indicates that the submerged ridges act in a similar way as an additional natural barrier together with the artificial detached structures.