Introduction

The coastal zone is more than a narrow strip of land and sea subjected to development but is also among the most complex, vulnerable, and sensitive of all natural ecosystems. Thus, it has historically attracted humans and human activities due to the abundant amenity, esthetic value, and diverse ecosystem services that they provide. One of the economic sectors that would most likely increase in future global economic development is the tourism sector. The concept of tourism destinations’ competitiveness is multifaceted and encompasses benefits on the economic, social, cultural, political, technological, and environmental aspects (Weidenfeld 2018). The appropriate combination of these components makes each tourism destination a unique creation highly attractive to tourists. However, the cumulative effects of tourism impacts can still be inordinate (Lemma 2014). Local economic development has been primarily driven by tourism; thus, other activities that emerged as a result of tourism have started to have negative effects on sustainability that, in many cases, outweigh the advantages of tourism development. Indeed, a key component of the execution of public policies and initiatives for sustainable development is understanding the causal link between tourism and economic growth (Khan et al. 2020). However, other causal relationships must be considered in the local development of this activity, such as coastal erosion and accretion. Sandy beaches, for instance, are quite developed and crowded because of the beauty and amenities they offer. Therefore, accurate estimates of these beaches’ rates of shoreline change are essential for efficient spatial planning, sustainable coastal development, coastal engineering initiatives, and mitigating the impacts of climate change along high-value coastlines around the world (Luijendijk et al. 2018).

In this context, the environmental quality of the beach is the key factor in choosing the tourism destination, since tourists are concerned with the natural values of the beach. Construction of the coastal structures and the dredging activities for the tourism development and building of ports and marinas interfere with the coastal processes of this region. The shoreline may be significantly impacted by the changes to the coastal processes. In addition, because of incomplete knowledge and the complexity of coastal processes, the behavior of the applied system may occasionally deviate from expectations. Recent coastal developments also have had detrimental effects on the coastline.

The Egyptian Mediterranean North Coast offers about 970 km of beachfront, from Arish to El-Salloum. However, some of Egypt’s prime tourism destinations cover only a quarter of the beachfront spanning two governorates (Alexandria & Matrouh). Throughout history, the western coast of Egypt, which includes the study region, has maintained a significant equilibrium. It is about 550 km long and extends from Sallum in the west to Alexandria in the east. This region’s tourism potential is yet mostly unrealized.

The Western North Coast Development Project is the third national project in the National Strategic Plan for Urban Development (2052) series of national projects for development across the country, toward which the government has achieved notable recent progress. Tourism can expedite economic growth and job creation if it develops successfully. As natural resources and cultural endowments can be used to generate possibilities for local populations, this sector also has the potential to considerably advance the cause of social inclusion.

Sidi Abd El-Rahman coastal area (the study area) between Lazord Bay (E) and Hacienda Red (W) resorts seems to behave as a complex system where zones of evident shoreline advance, and retreat could coexist within a delicate sedimentary balance. Since the 1990s, there was ongoing erosion of beaches at Sidi Abd El-Rahman Gulf on the North Coast (Saleh et al. 2017). Recently, the erosion problem is a major issue along this coastal strip, particularly at Marassi resort. Consequently, the Egyptian Ministry of Environment indicated that the turbidity in seawater in the coastal area adjacent to Marassi resort at Sidi Abd El-Rahman coastal area was due to dredging work related to the project construction of the new marina. Although a committee was established to investigate and assess this area, the Environment Minister decided to halt dredging operations; however, the erosion process damaged beaches adjacent to this project.

In Egypt, several surveys have been executed on the rates of shoreline changes along the Mediterranean coast of Egypt using a comparison of beach profiles (Frihy et al. 2002; Frihy and Dewidar 2003; El-Asmar et al. 2014; Nassar et al. 2019; Emam and Soliman 2020; Sarhan et al. 2020; Awad and El-Sayed 2021; El-Masry 2022). However, only a few studies include that part of the Sidi Abd El-Rahman coastal zone.

In this framework, the major issue to be addressed here is to justify the causes of coastal erosion using the application of remote sensing and (GIS) to avoid revenue losses from the tourism business in tourism resort destructions. Motivated by this, the present paper aims to assess the shoreline change rate over the last 27 years (1995–2022) at Sidi Abd El-Rahman coastal zone since it is crucial in ensuring the sustainability of this destination. Moreover, it offers estimations considering the negative economic impact due to beach erosion and suggests a solution for the control of this problem.

Study area

General description and climate

The study area is located on the north-western coast of the Mediterranean Sea in Egypt. It extends for about 24 km at Sidi Abd El-Rahman coastal zone between longitudes 28°38′56.03″E and 28°49′50.10″E and latitudes 30°57′8.57″N and 31° 0′18.94″N (Fig. 1).

Fig. 1
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Map of the study area showing main tourism resorts and locations of beach sediment samples

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Sidi Abd El-Rahman is Egypt’s prime tourism destination on the north coast. It has a very specific weather requirement for light outdoor activities including beach tourism and its related activities.

The study area has a semi-arid Mediterranean climate. The summer season, which extends from May until September, is characterized by a clear sunny sky and no rain. The winter season, starting in October up until March, is mainly windy with certain periods of heavy rains. Climatic factors, such as temperature, sunshine hours, and precipitation, determine a large share of the tourism flows within this area. Summer and winter monthly averages of air temperatures do not reach extreme values. The average monthly air temperature reaches 9 °C (minimum) in January and 31 °C (maximum) in July. The amount of rainfall in the study area is approximately 104 mm/year. The best time to visit is May, June, July, August, September, and October. June has the fewest days with precipitation (0.07 days). The month with the highest relative humidity is August (68.31%). February is the month with the lowest relative humidity (59.84%) (NASA website). June the highest number of daily hours of sunshine is measured in Sidi Abdelrahman on average. In the same month, there is an average of 11.85 h of sunshine a day and a total of 367.27 h of sunshine.

Geomorphological and geological settings

The coastal plain, the piedmont plain, and the tableland are the three distinct geomorphologic units that may be identified in the study area. The coastal plain is a narrow land area stretching adjacent to the Mediterranean Sea; its elevation ranges between 0 and 30 m above sea level with a northward slope. This plain’s maximum inland extension, measured from the sea in a north-to-south direction, is around 5 km. The coastal plain features many landforms along its several parts, being influenced by the local structures (El Shazly and Shata1971). Generally, it slopes in the northward direction.

Materials and methods

Shoreline analysis

Data (products and sources)

The main goal of using satellite images was to evaluate the dynamics of the shoreline, track the annual rate of erosion and accretion, and determine how the intertidal zone changed over time (Kabir et al. 2020). In the present study, four satellite images were employed to assess shoreline dynamics along Sidi Abd El-Rahman coastal zone from 1995 to 2022, that is, over 27 years (Table 1). All images were chosen to be at or near acquisition dates to remove the effects of seasonal differences. All images were from the US Geological Survey (USGS) (http://www.earthexplorer.usgs.gov). Landsat images were chosen to be of good quality (IQ = 9), cloud-free (less than 10%), and with level-1 precision terrain corrected to the Universal Transverse Mercator map projection system, zone 35 north on the World Geodetic Datum of 1984 (WGS 84). USGS rectified all images with a total root-mean-square error less than 0.4 m. A false-color composite was used.

Table 1 Data products and their specifications
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Shoreline extraction

Image scenes were subjected to image pre-processing using ArcMap version 10.8. The image data were then geometrically corrected, which co-registered them with each other for comparison (e.g., change detection) or integration (e.g., analysis of multi-temporal data for land use classification). After that, all image data were radiometrically calibrated and converted to reflectance values. The reflectance values for each date were atmospherically corrected.

Several various features, such as the vegetation line, the high water line, the low water line, or the wet/dry line, can be used to determine shoreline positions (Thieler et al. 2009). In the present study, the spectral and spatial enhancement of pixel properties has been carried out using histogram equalization and convolution image processing techniques to improve the discrete line (shoreline) lying between the land and sea surface (Beheroo et al 2016). This discrete line was extracted automatically by using binary classification techniques of land and water features based on their spectral signatures of the aerial images, and the extracted linear geometric shapefile was then exported into the ArcGIS platform (Moore 2000). The ground truthing shapefile has been positioned on the extracted shoreline to validate it. A set zooming scale has been used for manual digitizing whenever inconsistencies have been discovered (Kabir et al. 2020). Thereafter, the different time series layers of the coastal area were added to a personal geo-database with the following attributes: namely feature id, name, length, and feature characteristics. The Digital Shoreline Analysis System (DSAS) tool for shoreline displacement analysis also used this geo-database to store and retrieve information on multiple shorelines. As per the position of the shoreline concerning the baseline, the coast has been categorized as erosion or accretion.

Digital Shoreline Analysis System

DSAS version 5.1, an extension of ArcGIS 10.8, is employed by the present study to assess the shoreline dynamics. The study created a hypothetical baseline buffered by 300 m from the shoreline position for the year 2022. This work carried out the shoreline analysis along 24 km, through which DSAS casts 485 transects (T) orthogonal to the baseline at 50-m intervals to intersect the four shoreline vector layers. The entire coastline was divided into 4 zones according to the characteristics of each zone and its response to the established structures, as follows (Fig. 2).

Fig. 2
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Sidi Abd El-Rahman coast (2022) map showing 4 different zones according to their erosion/accretion behavior (T, transect)

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The commonly used statistical methods, which have been conducted to quantify the shoreline dynamics in the current study, are the net shoreline movement (NSM) and the end point rate (EPR) following Genz et al. (2007) and El-Masry (2022), where NSM is the total distance between the youngest and the oldest shoreline in every transect in meter unit and EPR is the rate, which was calculated by dividing the net movement by the time elapsed in the oldest and the youngest shoreline in every transect in meter per year (Thieler et al. 2009), where a positive value indicates seaward movement (beach sediment accretion) and a negative value indicates landward movement (beach sediment erosion) of the shoreline. Statistical analysis has been conducted through MS Excel software.

Grain Size Analysis

Twelve sand samples were collected along the study area’s beach at a low water mark. The collected beach sediments were subjected to grain size analysis. The sieving technique (dry) was only applied owing to the lack of fractions smaller than 0.63 mm (4\(\phi\) ). Samples were sieved through a standard set of sieves arranged in a 1\(\phi\) class interval from top to bottom.

The graphic measures of Folk and Ward (1957) were employed for the results of the grain size analysis using the phi-notation. Cumulative percentages were plotted against the grain size interval. The \(\phi\) value was directly interpolated from the cumulative curves. The graphic mean size (Mz\(\phi\)), and inclusive graphic standard deviation (бI), were calculated according to the following equations (Folk and Ward, 1957).

$$\mathrm M\mathrm{z\phi}=(\phi16+\phi50+\phi84)/3$$
$$6I=(\phi84-\phi16)/4+(\phi95-\phi5)/6.6$$

Results and discussions

Since the 1990s, Sidi Abdel Rahman Gulf’s western portion on the North Coast has been eroded. Tourism development along the North Coast at Sidi Abdel-Rahman has come to a halt over concerns about water quality and beach erosion. One of the critical and most recent issues for the study area (Sidi Abd El-Rahman) is beach erosion and shoreline retreat, particularly after the construction of Sidi Abd El-Rahman Port.

The shoreline is a crucial coastal geomorphological feature in determining a beach’s state, particularly the issues related to coastal erosion. It is an active system with evolution and quick reactions. Its shift can be determined by mapping on different dates through data collection in the field or via satellite imaging (Mendonça Diniz et al. 2020). Accordingly, the following section discusses the beach sediment grain size analysis, kinematics of the shoreline (1995–2022), overall beach area (loss/gain), and economic valuation of irrational tourism developments.

Kinematics of the shoreline: a diachronic analysis

Due to issues with access to the coast, particularly private tourism resorts, it is nearly difficult to conduct a study of the evolution of the shoreline using primarily field data in the study area. However, by examining several historical and recent satellite images, we can evaluate the changes that have taken place. Table 2 and Fig. 3 summarize the results of NSM and EPR for the study area of the intermediate periods. The results revealed that Sidi Abd El-Rahman shoreline presents an active sediment transport with well-defined alternation between erosion and accretion which is in agreement with results obtained from other studies (Iskander et al. 2007; Frihy et al. 2010; El-Masry 2022).

Table 2 The results of shoreline changes in Sidi Abd El-Rahman (1995–2022)
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Fig. 3
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The variations in the shoreline of Sidi Abd El-Rahman; illustrate the evolution of the coastline for the periods 1995–2005, 2005–2015, and 2015–2022

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Period 1995–2005

The evolution of the shoreline during this period oscillates between advanced-retreat and advanced-retreat stability. The overall result for this period shows negative values of the shoreline position of about (44%). But, in detail, there are some differences between the situated shore in which 19.7% is stable while 36.25% is in an advanced position.

Indeed, the entire study area fluctuated between stability, erosion, and accretion. The net rates of evolution vary between − 50 m (EPR: − 5 m/year) (T#403) on the eastern side and 85 m (EPR: 8.5 m/year) (T#220) with an average value of − 0.8 m (EPR: − 0.08 m/year).

Period 2005–2015

During this period, the shoreline shows equilibrium between advancing and retreating of the shoreline position along the study area (i.e., advancing, 50%, and retreating, 50%). The western part of the shoreline shows sectors in erosion and others in accretion while the center (Ras Gobis) and the eastern parts of the study area are dominated by advanced transects. The shoreline retreat reaches 98 m, with an annual speed of − 9.8 m/year at T#311 while the maximum shoreline advance is observed at T#452 and 457 at the eastern side of the study area which shows a generalized shoreline advance with a value of 43 m (EPR: 4.3 m/year).

Period 2015–2022

The shoreline shows a position of advanced retreat throughout this period when extensive tourism development was established along the study area coastal zone after the year 2015. Most of this coastal stretch shows an extensive shoreline retreat of about 63% of the total number of transects, while the shoreline advance is about 37% of the total number of transects. Significant rates of shoreline changes (i.e., retreat and advance) were found during this period, which is relatively large in comparison with rates obtained in other studied periods. This occurred in response to the intensification of construction activities occurring during this period. For instance, erosion rates of − 14.19 m/year at T#267and T#268 with a total shoreline movement of − 99.4 m were found to the west of the new marina built at the center of the study area (at Marassi resort) and T #347 at the eastern part of the study area. On the other hand, the evolution rate reaches 99 m or an annual enlargement rate of 14 m/year at (T#276). It is worth mentioning that the evolution of the shoreline of the Marassi resort is marked by a progressive retreat, reaching about 80% of the total transects of this zone. It may be attributed to the irrationally extensive development of this zone and the building of the new Marina at the center of this resort which disturbs the role of sediment transport.

Overall beach area (loss/gain)

A simple method is proposed to quantify the gains and the losses of sediment along the study area; the shoreline displacements were expressed in terms of surfaces. The following results show a spatial–temporal variability of the beach’s area. Throughout 27 years, the lost beach surfaces dominate those gained by accretion, and the overall sediment budget is negative (Figs. 4 and 5). Regarding the change in the beach area, about 332 km2 of the beach area showed a remarkable loss, while about 240 km2 of the beach area was expanded with an overall erosion reaches of − 90 km2. The maximum area of beach loss of about − 6.7 km2 was noticeable in zone 3, which may be attributed to the construction of a new marina at the Marrassi tourism resort which made a strong sediment disturbance in this zone. In addition, the turbidity of the water was reported by visitors in the area neighboring the Marassi Resort and was the result of dredging near that part of the beach.

Fig. 4
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The percentage of total erosion/accretion of the study area over 27 years

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Fig. 5
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The overall (NSM) of the study area (1995–2022)

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Grain size analysis

The sediment grain size analyses helped in proposing the solution measures for the erosion problem along the study area’s coast. The results of the grain size analysis are presented in Fig. 6. The average mean grain size in the beach sediments is 1.3 (± 0.18) Ø (medium sand). The mean grain size was coarsening westwards. All the studied samples were sandy as most of the study areas were subjected to direct wave effects. The average value of sorting is 0.4 (± 0.1) (well sorted). The sorting of sediments attends to the purpose of dynamic conditions since the study area is affected by wave action.

Fig. 6
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Mean size and sorting of the study area’s sediment

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The beaches of the study area were covered by white medium to coarse sand; there was almost no variation in the type of sediments covering these beaches. This may be attributed to the source of the beach sediments in this area being authigenic, as it originates from the erosion of the nearshore and the submerged carbonate ridges. These results and findings agree with (Iskander et al. 2007).

Economic valuation of irrational tourism developments

The current economic value for the tourism resorts was estimated in Egyptian Pound (EGP) per square meter (https://www.savills.com.eg & personal inquiring) (Table 3), taking into account the type of unit to be evaluated. The estimations of average rental values consider 120 days season, which, for the study area, represents the high tourism season. The highest value per square meter in the study area is found in Marassi Resort for chalet (47,940 EGP/m2). In this resort, the prices of apartments range from 7,971,888 up to 44,530,888 million Egyptian pounds, depending on the number of bedrooms. In addition, townhouse prices range from 17,269,888 up to 17,505,888 million Egyptian pounds while the prices of standalone villas range from 9,373,300 million up to 34,907 million Egyptian pounds. The lowest value per square meter (15,7EGP/m2) is presented in Hacienda Bay resort for the chalet. This variation in the prices of the different units and rental values may be attributed to the dissimilarity in the services and facilities at each resort.

Table 3 The average value of tourism units in different resorts subjected to beach erosion (EGP/m2)
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The econometric analysis indicates that the shoreline retreat reduces the beach area, lowering its value. Reductions in the beach width will have further negative effects on the tourism sector in terms of loss of properties. The quality of beaches is an important factor in maintaining coastal development and the recreational function of beaches (de Paula et al. 2022). In addition, applying measures for coastal environment protection and monitoring is vital for the municipality’s economic development, particularly in the tourism industry (de Paula et al. 2021). In the present study, the cost of loss in property arises from the loss in beach, property, and infrastructures of tourism villages. The increase in this cost resulted from growing estimated prices of units and an increasing number of damaged tourism villages. Due to the absence of basic data on the number and area of units in the various tourism resorts, the estimations take into consideration the beach loss in each resort and the calculated value per square meter for different unit types.

Conclusions and recommendations

The shoreline position is a significant indicator of analysis that reflects beach vulnerability trends to erosion, having implications for tourism development and its related recreational activities. This indicator can be used by coastal managers for a short-term assessment of the coastal problem associated with erosion to avoid loss of revenue from tourism and high costs of coastal protection.

The present study suggests a nourishment scheme employing the placement of borrowed compatible sand in terms of grain size and sand color directly onto the eroded beaches. In addition, mitigating the impact of the new marina built at Marassi resort using environmental assessment and coastal modeling techniques or editing its design takes Dubai Palm Island as a reference to reduce its impact on adjacent beaches. It is worth noting that the adaptive solution of using piling sandbags along the eroded beaches transports the erosion to other beaches and is not recommended.

Finally, the changes regarding both natural and human activities subject the coast to change; thus, the study suggests regular and continuous analyses of the shoreline, to know, understand and predict shoreline changes.