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Coastal Erosion
FIGURE 5.5
Major Factors Affecting Coastal Morphology, Including Coastal Erosion
Source: Giardino et al. 2018. Available under Creative Commons Attribution license (CC BY-NC-ND).
stabilize areas through sediment buildup in one location, but they starve the sediment and intensify the erosion rate at other locations; in extreme instances, poorly informed adaptation measures may cause more damage than doing nothing (Hoggart et al. 2014).
Coastal and inland development can exacerbate coastal erosion locally and at other sites, as shown by examples in the Middle East and North Africa. Because of the blocking of sediment transport, structures further upstream can cause or accelerate erosion of downstream coastlines. Although the 2010 expansion of the commercial port Tanger-Med in northern Morocco included an environmental impact assessment (EIA) with a desk-based assessment of known archeological sites, the port’s presence has affected the coastline at the nearby archeological site of Ksar es-Seghir (Trakadas 2020). In addition, there is a lack of environmental and social impact assessment (ESIA) regarding coastal erosion in the region. These circumstances highlight potential insufficiencies in the understanding of erosion processes and their proper incorporation into EIAs and ESIAs.
As illustrated in figure 5.5, the construction of a dam inland can have negative effects on sediment transport by the river on which it is built. While this alone has adverse effects on coastal regions at the mouth, coastal protection measures along the coast can also trap sediments that would otherwise feed the coastline. River deltas can be starved of replenishment by upstream construction; combined with coastal construction, the impacts on coastlines can be severe. An example is at the Rosetta promontory in the Nile delta, where the construction of 15 groins has exacerbated the erosive forces caused by the building of the Aswan High Dam. These groins have led to a reversal from accretion to fast erosion along the leeside of the promontory, with some segments exhibiting erosion rates as high as 30.8 meters per year (Ghoneim et al. 2015).
The following brief discussion of key drivers of coastal erosion in the Middle East and North Africa provides a concise view of the issues the region faces. It includes drivers stemming from both anthropogenic sources and natural forces that have been, and will be, exacerbated by climate change.
Dam Construction
Many rivers in the region have been dammed to provide water supplies, control flooding, and produce hydroelectric power, with the unintended consequences of reducing flows of sediment to the coast (Syvitski et al. 2005). Diminishing sediment flows can be important drivers of coastal erosion, reducing beach areas and eroding shorelines, as seen with Egypt’s Aswan High Dam (Masria et al. 2015b) and with the Moulouya River in Morocco, where dams capture over 90 percent of the sediment supply (Snoussi, Haïda, and Imassi 2002). Such sediment-flow issues also threaten the dam’s functions because as sediment is trapped, the dam’s capacity decreases. Thus, it is crucial to use various techniques proven internationally to manage sediment flows for dams (Kondolf et al. 2014).
Subsidence
Ground deformation is a severe geological hazard in the Middle East and North Africa. It results mainly from anthropogenic activities such as fluid extraction or injection, underground excavations, and construction expansion. The Islamic Republic of Iran is one of the most-affected countries in the Middle East because of groundwater overexploitation and 30 years of drought affecting large cities such as Mashhad, Neyshabour, Rafsanjan, and Tehran (Fattahi 2019; Khorrami et al. 2020). Coastal subsidence over time negatively affects farmland, urban areas, and wastewater infrastructure, and it can cause cracks in roads and water and natural-gas pipes.
The United Arab Emirates is also at great risk because its groundwater use is 20 times higher than the natural recharge rate, where 60 percent of its consumption comes from aquifers, compared with 29 percent from desalination plants and 6 percent from water recycling (Construction Week 2015). And Alexandria, Egypt, is a well-known example of sediment compaction in the Nile delta that provokes land subsidence, thereby enhancing the effects of climateinduced SLR, as further described in the SLR subsection below (Syvitski et al. 2009).
Dredging
The Gulf region has been active in dredging for both navigation (that is, channels for ships) and land reclamation in the past few years (Kloosterman 2010). Efforts to facilitate commercial, recreational, and navigational activities have important effects on coastal waterways, inlets, and bays—altering currents and wave patterns, creating hydraulic mining, and moving sediment. Shallow deltas and inlets that once constrained the outward flow of freshwater and held the salt sea at bay are now hydraulic superhighways because of dredging. This process also fosters the loss of coastal freshwater aquifers to saltwater infiltration, affecting water treatment and distribution plants and potable water sources for human consumption.
Sand Mining
Sand mining—extraction of sand from sandy areas on the coasts or along riverbanks, mostly for construction and industrial uses—has been a problem in the Middle East and North Africa, particularly in Morocco. In Morocco, coastal sand mining, often illegal, has been rising with the increase in construction and real estate development (Aldar.ma 2019) and has increased erosion along vulnerable coastlines. Around half of the sand used annually in Morocco (about 10 million cubic meters) is from illegal coastal sand mining.
Illegal sand mining operations can, at the extreme, leave behind bare beaches such as a large beach between Safi and Essaouria (along the Atlantic coast of Morocco) that became rocky terrain (UNEP 2019). Coastlines weakened by mining are also more vulnerable to the impact of storms, further accelerating beach erosion. The coastline of Asilah, Morocco, has been severely damaged because of the increased demand for sand to mix with cement for urban construction. Similar operations have been documented along the Atlantic shoreline in Larache or Kenitra and farther south in Morocco, as well as in Algeria (Coastal Care 2009, 2020; Greene 2016). Sand mining can also affect dune replenishment as well as the integrity of coastal marshes.
Storm Surge
Storm-induced erosion and coastal flooding are the two most important natural hazards to coastal systems worldwide and are interdependent (Kron 2013). In some cases, storms and storm surges, exacerbated by SLR, are the principal cause of erosion (Katz and Mushkin 2013; Nicholls et al. 2007).
Storm surges severely affect coastal regions in the southern Mediterranean, and low-lying areas are especially vulnerable (Satta et al. 2017). Middle East and North Africa countries exposed directly to the Indian Ocean (for example, Djibouti, Oman, and the Republic of Yemen) are also regularly exposed to tropical storms, whereas the west coast of Morocco is exposed to Atlantic storms (Becker et al. 2013; Knapp et al. 2010).
By 2100, SLR and storm surges in Tangier, Morocco, will affect a projected 34.8 percent of its urban area, 99.9 percent of its port infrastructure, and 36 percent of its roads (Snoussi et al. 2009; World Bank 2014, 127). Storm-surge zones are also projected to increase this century by 84 percent in Egypt, 57 percent in Algeria, 54 percent in Libya, 30 percent in Morocco, and 27 percent in Tunisia (Dasgupta et al. 2009).
Sea Level Rise
Rising seas contribute to faster coastline retreat, particularly in low-lying areas (Stive, Ranasinghe, and Cowell 2010). Since 1990, the rate of SLR in the Mediterranean has been above the global average (Tsimplis and Baker 2000). Atmospheric influence is thought to be the primary driver: pressure and wind variations associated with the North Atlantic Oscillation control water flow through the Straits of Gibraltar (Gomis et al. 2006; Landerer and Volkov 2013; Tsimplis et al. 2013). Compared with the well-studied Mediterranean, tide-gauge records in the Red Sea and the RSA are much sparser because they are noncontinuous and limited to a few years.11
A stronger rise in the Arabian Sea than in the Mediterranean is projected under both a Representative Concentration Pathway (RCP) 2.6 scenario (a 1.5 degrees Celsius world) and an RCP 8.5 scenario (a 4 degrees Celsius world).12 Under the latter scenario, Muscat is expected to experience a median SLR of 0.64 meters, and Tunis an SLR of 0.56 meters, by the last decades of the century (2081–2100). The most-affected cities in the region include Muscat (12.0 millimeters per year), Alexandria (10.9 millimeters per year), Tangier (10.2 millimeters per year), and Tunis (10.1 millimeters per year) under an RCP 8.5 scenario (World Bank 2014). Among these cities, Alexandria is projected to lose the most local value added as a result of damages from SLR by 2050 (Hallegate et al. 2013). These changes in the sea level are a major
potential threat to coastal areas because of the cumulative effect of SLR and long-term shoreline retreat.
As discussed above, data, monitoring, and analysis form the cornerstone of effective coastal erosion mitigation and management, specifically for ICZM plans. Data on factors such as sediment flows, erosion rates, coastal and marine physical processes, and infrastructure and development are critical for monitoring, analysis, and determination of informed engineered and other solutions and interventions. These data will help all stakeholders to understand areas of accretion, areas of erosion, and sediment feed, which in turn help to identify hot spots, erosion sources, and zones for intervention.
Monitoring the coasts for risk management, identifying threat levels, and implementing immediate interventions are also important. Monitoring also aids the process of keeping records that could also be used for analysis. Both data and monitoring aid the analysis process through various tools and computational modeling to identify sources, risks, hot spots, and potential solutions.
First, it is necessary to understand the degree of coastal erosion in a location-specific way—by identifying and analyzing the hot spots. Coastal erosion is highly dependent on localized physical processes such as fluid mechanics and sediment balance and flows, meaning that although there may be severe erosion in one area, the adjacent area can behave very differently. Analyzing hot spots at a comprehensive yet granular scale (as done in the close analyses of Moroccan and Tunisian coastlines, elaborated earlier in the chapter) is an important first step. Extending the hot-spot analysis to cover as much of the Middle East and North Africa’s coasts as possible is desirable. With such analyses in hand, sites where actions are needed in a timely manner can be identified, and policy makers and researchers could prioritize these sites.
Second, why does coastal erosion occur in a selected hot spot? Once the hot spots of erosion along the coast have been identified, more-detailed analyses of prevalent dynamics (for example, the morphological cycle or sediment transport) of these sites is crucial. In addition, anthropogenic perturbations, such as those highlighted earlier (dam construction, harbor construction, sand mining, coastal subsidence, SLR, and so forth) must be modeled covering larger spatial scales because, for example, changes up-current can have down-current effects. Implementing measures without precise knowledge of coastal dynamics (spatially and temporally) can worsen the effects of coastal erosion. This was the case for the Rosetta promontory in Egypt’s Nile delta region, where the construction of defense structures has exacerbated the effects of coastal erosion at other
sites (Ghoneim et al. 2015). It is important to study the effects of different measures at different sites to avoid unintended side effects.
Measures to combat coastal erosion also require knowledge of geomorphological characteristics. In addition to knowing how sediment is transported along the coast, it is important to know what types of sediments are predominant in certain areas such as beaches. For some defense solutions, it is important to consider existing structure and granularity. Using sand that is too different in its characteristics (for example, desert sand versus coastal sand) to refill beaches will undermine these efforts and will get washed away quickly.
Erosion Data Gathering, Monitoring, and Modeling within the Region
Detailed sediment budgets and numerical models are important tools to understand coastal changes in the Middle East and North Africa. Such analyses have the potential to uncover important sediment dynamics along coasts influenced not only by coastal developments such as ports but also by inland structures such as dams. Although such models have been employed at some specific sites along the region’s coasts, a comprehensive analysis of these dynamics would allow for the incorporation of transboundary effects of sediment transport and its effects on coastal erosion. In West Africa, such modeling exercises were recently undertaken (box 5.2). Such analysis provides policy makers with a comprehensive and easy-to-use tool to simulate the impact of different coastal developments and climate change on coastal sediment transport and in turn on coastal erosion.
In the Middle East and North Africa, monitoring and analyses of sediments, coastal changes, and human intervention relevant to coastal erosion have been carried out only for some areas, but comprehensive modeling for the entire coast is needed. For example, a 25-year study (1990–2014) investigated coastal erosion rates and sources along the Nile delta coast (Ali and El-Magd 2016).
Tools such as geographic information systems (GIS) and sedimentbudget computational modeling are normally used for such analysis, including statistical and physical data. Studies that investigate the behavior of sediment transport on a large scale have the advantage of incorporating and allowing for evaluation of effects that various changes in certain parts of the coastal landscape have on other parts of the shoreline. Identifying sources and sediment flows can inform the analysis to identify potential solutions and analyze their potential to prevent coastal erosion, mitigate its impacts, or both. The sources and hot spots of coastal erosion become part of the input that aids such analysis to come up with sustainable measures, policies, and designs of engineered solutions. The information from sediment studies provides useful inputs in
