Spatiotemporal Evolution of Coastal Dune Systems in the Çukurova Delta Plain: A Multitemporal Analysis Using Historical Aerial Photographs and UAV-Based Photogrammetry

Abstract

Coastal dune systems are dynamic landforms shaped by aeolian processes, in which onshore winds transport and deposit sediments behind natural or artificial barriers. The Çukurova Delta Plain, Turkey’s largest delta along the Eastern Mediterranean, contains extensive dune fields, particularly within the Seyhan and Ceyhan Deltas. Despite technological advances in UAV photogrammetry and Structure-from-Motion (SfM) techniques, studies on coastal dune dynamics in Turkey remain scarce. This study demonstrates the first comprehensive assessment of the spatiotemporal evolution of coastal dunes in the Çukurova Delta Plain. Historical aerial photographs and high-resolution UAV imagery were analyzed to evaluate long-term and seasonal morphological changes. The results indicate notable spatial and temporal variability in sediment budgets, with distinct erosion and accretion patterns across the two deltas. While some dune segments remained stable over decades, others displayed strong seasonal responses to wind and sediment dynamics. These findings enhance the understanding of deltaic coastal geomorphology and provide critical insights for sustainable management of vulnerable dune ecosystems under increasing human and climatic pressures.

1. Introduction

Coastal dunes represent dynamic landforms that serve as sensitive indicators of environmental change while providing essential protection against coastal hazards. These complex systems develop through the intricate interplay of aeolian, hydrodynamic, and ecological processes, creating valuable natural archives of past environmental conditions. Recent research by Rust et al. (1990) has highlighted their exceptional capacity to record climatic variations and anthropogenic impacts through measurable morphological changes [1]. Beyond their scientific value, coastal dunes function as highly effective nature-based coastal defenses, with Ma et al. (2023) demonstrating that well-developed dune systems can reduce storm surge impacts by 40–60% compared to unprotected coastal areas [2]. This protective function has become increasingly crucial in the context of climate change, particularly in vulnerable Mediterranean regions where sea-level rise and increased storm intensity pose growing threats to coastal communities [3,4]. The scientific study of coastal dunes has undergone a remarkable transformation in recent decades, driven by significant advances in monitoring technologies. Modern approaches now combine high-precision topographic surveys using RTK-GNSS systems capable of sub-centimeter accuracy with cutting-edge remote sensing platforms. Terrestrial and airborne LiDAR systems, coupled with UAV photogrammetry enhanced by SfM processing, have revolutionized the ability to generate high-resolution digital surface models [5,6]. This methodology offers distinct advantages for large-scale geomorphological studies through its cost-effectiveness and high-resolution capabilities [7,8]. The photogrammetric workflow begins with precise camera alignment achieved through ray beam adjustment across overlapping aerial images, followed by comprehensive processing stages. Camera parameter calibration forms the foundation of the process, accomplished through external orientation calculations. The identification and matching of tie points across image pairs enables the generation of dense point clouds using stereo photogrammetric equations. These point clouds serve as the basis for creating detailed 3D polygonal mesh models that accurately represent surface topography. The final products include high-resolution orthophotos and digital surface models (DSMs) generated through regular grid interpolation of the mesh models. These technological developments have been further augmented by the integration of machine learning algorithms for automated pattern recognition and change detection, enabling researchers to identify and quantify subtle morphological changes that were previously undetectable using conventional satellite imagery or field survey methods [9]. The enhanced temporal and spatial resolution provided by these integrated monitoring systems has opened new possibilities for understanding short-term dune dynamics and their responses to specific weather events or human interventions. The Digital Elevation Models (DEMs) of Difference (DoD) method is a robust tool for detecting geomorphological changes by quantifying elevation differences over time. Recent advances in uncertainty analysis and multi-temporal data integration have improved its accuracy, making it highly effective for assessing sediment budgets and monitoring coastal dune dynamics [10,11].

Despite these significant technological and methodological advances, critical knowledge gaps persist in the understanding of Mediterranean dune systems specifically. The region’s unique climatic and hydrodynamic conditions create distinct dune behaviors that differ markedly from the well-studied systems of Atlantic or Pacific coasts. Molina et al. (2024) have identified several characteristic features of Mediterranean dune dynamics, including bimodal wind regimes, episodic but intense storm impacts, and significant anthropogenic pressures from coastal development and tourism infrastructure [12]. These challenges are compounded by the region’s status as a climate change hotspot, with Cramer et al. (2018) reporting that Mediterranean coasts are experiencing climate-related changes at rates 20% faster than global averages [13]. Specific concerns for dune systems include changing storm patterns and intensities, sea-level rise impacts on sediment budgets, drought effects on stabilizing vegetation, and increasing pressures from human adaptation measures. The translation of scientific findings into practical coastal management solutions remains hampered by several factors, including disconnects between research timelines and planning needs, lack of standardized monitoring protocols, insufficient integration with decision-support systems, and limited cost–benefit analyses of dune restoration alternatives [14]. The Çukurova Delta Plain in Turkey presents a particularly compelling case study that embodies these research challenges and opportunities. As Turkey’s largest dune complex, this system plays a crucial role in coastal protection while facing growing climate vulnerability and anthropogenic pressures. Its strategic position in the eastern Mediterranean, combined with dual sediment inputs from the Seyhan and Ceyhan rivers, creates unique morphodynamic characteristics that warrant detailed investigation. However, despite its regional significance and representative features, the Çukurova dune system remains understudied using modern monitoring techniques, representing a significant gap in Mediterranean coastal research. This knowledge deficit limits our ability to predict the system’s resilience to future environmental changes or to develop effective management strategies that balance conservation needs with human development pressures.

Coastal zones face mounting structural and ecological challenges that threaten both engineered defense systems and natural habitats. Hard coastal infrastructures, such as breakwaters and seawalls, are continuously exposed to wave-induced erosion and dynamic loading, leading to deformation and potential economic losses [15]. Simultaneously, anthropogenic pressures have caused severe degradation of coastal dune systems, impaired their ecological functionality and reduced key ecosystem services [16]. In some Mediterranean regions, the expansion of vegetation—further intensified by climate change—has diminished sediment availability to mobile dunes, thereby endangering open-sand habitats [17]. To address these issues, periodic monitoring and sustainable management strategies are essential. UAV-based photogrammetry and LiDAR techniques provide high-accuracy DSMs and orthomosaics for assessing both the stability of hard structures and the geomorphic evolution of natural dune systems [15,16,17]. While the estimation of DoD-related uncertainty remains a methodological challenge, geomorphological and ecological indicators, combined with adaptive tools such as controlled grazing, can support dune restoration [16,18]. Moreover, recent advances in hybrid modeling and machine learning are enhancing predictive simulations of coastal morphodynamics, contributing to the optimization of innovative protection measures, including submerged breakwaters [19].

To address these critical knowledge gaps, this study implements an innovative, integrated monitoring framework that combines several advanced approaches. High-frequency UAV surveys conducted at bi-monthly intervals capture short-term dune dynamics, while historical aerial photograph analysis provides insights into decadal-scale changes. Machine learning-enhanced change detection algorithms improve the accuracy and efficiency of morphological analyses, and probabilistic DoD methods enable robust quantification of volumetric changes while accounting for measurement uncertainties. The research also develops predictive models that explicitly link observed morphological changes to specific environmental forcings, creating valuable tools for coastal managers. By focusing on this strategically important yet understudied system, the study advances both fundamental understanding of Mediterranean dune dynamics and provides practical solutions for coastal management. The methodologies developed have been carefully designed to be transferable to similar deltaic systems worldwide, offering a replicable model for coastal research in data-scarce regions where such studies are most urgently needed. This study draws on advances in UAV/SfM mapping to deliver a robust, scalable monitoring framework for deltaic coastal dunes [6,20]. The methodology is transferable to other under-monitored regions facing similar geomorphic and anthropogenic pressures.

2. Materials and Methods

2.1. Study Area

The research focuses on the expansive coastal dune systems of the Seyhan and Ceyhan Deltas, which together form Turkey’s most significant dune complex spanning approximately 100 km along the Eastern Mediterranean coast. This geomorphologically dynamic region represents the largest deltaic plain in Çukurova, characterized by coastal elevations ranging from sea level to 30 m above mean sea level. The study specifically investigates the frontal dune ridges located in the eastern sector of the Seyhan Delta and throughout the Ceyhan Delta, which constitute prominent geomorphological features parallel to the shoreline.

The geomorphological evolution of the Seyhan Delta has been extensively examined since Erinç’s (1953) pioneering study, which first identified three distinct terraces representing stages of deltaic development [21]. The current configuration of the delta formed following the Flandrian Transgression, when the Seyhan River shifted to its present course approximately 4000 years before present. This major fluvial reorganization, resulted in the development of characteristic eolian ridges as wave action redistributed sediments from the abandoned delta lobe [22,23,24]. Recent optically stimulated luminescence (OSL) dating by Özpolat and Demir (2017) determined that these dune systems have evolved over roughly 956 years in response to coastline modifications [25]. The delta’s initial development began during the mid-Holocene (5000–6000 years BP), coinciding with the stabilization of modern sea levels described by Peltier (2002) [26]. Paleogeographic reconstructions reveal that the proto-Seyhan River originally discharged about 10 km east of its present mouth, and the ancient delta prograded 4 km seaward before channel avulsion established the modern deltaic system [26]. This geomorphological transition marked a significant turning point in the region’s coastal evolution [24].

The geomorphological differences between the two deltaic systems are pronounced. The Seyhan River is approximately 560 km in length, whereas the Ceyhan River extends for about 509 km. The Seyhan Delta covers an area of roughly 22,000 km², while the Ceyhan Delta encompasses about 27,000 km². The lower sub-basin of the Ceyhan River is more rugged and characterized by sediment input originating from mountainous regions, whereas the Seyhan Delta exhibits distinct features due to its source areas extending into Central Anatolia and the presence of urban and flood-control structures. Consequently, both basins display varying degrees of vulnerability in terms of climatic factors (such as intense winter precipitation and summer drought) and anthropogenic influences, including dam construction, irrigation, and land-use practices. These differences lead to regional variations in the hydrological regime and drought dynamics. Although the average annual precipitation values for both deltas are relatively similar, the Seyhan Delta receives approximately 624 mm of rainfall per year, whereas the Ceyhan Delta records an average of about 700 mm [27,28,29,30,31]. While the Seyhan Delta features characteristic frontal dune ridges, the Ceyhan Delta’s dunes have developed parallel to shoreline evolution, exhibiting less pronounced ridge morphology despite similar coastal orientations. Both systems operate within the regional Mediterranean climate regime characterized by rainy-warm winters and dry-hot summers, which significantly influence their morphodynamics [32]. Notably, the Ceyhan Delta shows measurable shoreline recession that contrasts with the more stable shoreline behavior observed in the Seyhan Delta.

The study area was strategically divided into four sub-regions, namely, Seyhan-1, Seyhan-2, Ceyhan-1, and Ceyhan-2, to enable detailed spatial analysis of dune behavior. In this context, both natural and anthropogenic effects in the region were considered. The Seyhan-2 sub-region encompasses the afforestation project implemented to control dune migration, while the Seyhan-1 sub-region features naturally formed foredune ridge morphological structures. Furthermore, the Ceyhan-1 sub-region contains sand traps installed to detect and restrict dune movement, whereas the Ceyhan-2 sub-region has not been subjected to significant anthropogenic destruction due to its designation within the Yumurtalık Lagoon National Parks. This stratification facilitated localized assessment of sediment transport patterns, differential responses to coastal processes, and varying degrees of human impact across different delta environments. The geographical division, illustrated in Figure 1, allowed for targeted investigation of specific dune systems while maintaining the broader context of delta-wide evolution.

Figure 1. Demonstration of the study area and sub-regions in the Çukurova (Seyhan and Ceyhan) Delta Plains.

2.2. Methods

Further, an integrated monitoring framework is implemented, combining historical archives with contemporary data collection. The processing of archival aerial photographs enables retrospective DSM production, which proves invaluable for tracking long-term dune movement patterns. This approach facilitates precise volumetric change quantification across multiple temporal scales and allows derivation of movement vectors for comprehensive dune migration analysis. Contemporary data collection relies on periodic aerial surveys using a combination of fixed-wing (Sensefly Ebee, Lausanne, Switzerland) and multirotor (DJI Mavic Pro, Matrice 300 RTK, Shenzhen, China) UAV platforms. These surveys incorporate precisely surveyed ground control points established using LEICA GPS (St. Gallen, Switzerland) with RTK positioning. To ensure optimal results, the acquisition protocol maintains high image overlap rates of 85% frontal and 70% side overlap, with low-speed flight operations enhancing image quality. The photogrammetric workflow incorporates multiple layers of quality control measures. All field campaigns integrate precisely surveyed ground control points to guarantee geometric accuracy in the final products. The periodic production of DSMs and orthomosaics follows consistent SfM parameters to ensure methodological uniformity across the dataset. Accuracy assessment forms a critical component of the process, with RTK-derived GCPs serving as validation points for both horizontal and vertical model accuracy. The research team implemented comprehensive data standardization procedures, including flight parameter optimization for resolution consistency and uniform processing parameters applied to both historical and contemporary imagery. Resampling procedures maintain consistent data characteristics while adhering to legal altitude restrictions for UAV operations.

Among analytical methods, the DoD approach has emerged as a particularly powerful tool for geomorphological change detection. Recent methodological refinements have substantially enhanced the application of the DoD through several key developments. The DoD methodology was employed to conduct quantitative assessments of volumetric changes in coastal dune systems. The analytical approach utilized high-resolution DSM datasets acquired at periodic intervals to capture the dynamic evolution of dune morphology. The DoD technique’s versatility has been expanded through multi-temporal analysis protocols that accommodate data from various sources and time periods, while cloud-based processing capabilities now facilitate the handling of large, complex datasets [33,34]. The DoD technique has become an established method in geomorphological investigations [10,20,35], providing a robust framework for detecting and quantifying surface changes through pixel-level comparisons between temporally distinct elevation models. These advancements have been particularly valuable when combined with machine learning classifiers, allowing for more precise quantification of sediment budgets and more accurate identification of erosion and accretion patterns across different temporal scales [11]. The fundamental principle of the DoD analysis involves the mathematical subtraction of an initial baseline DSM (${DSM}_1$) from a subsequent DSM (${DSM}_2$) acquired at a later interval. This differential processing generates a comprehensive change detection model that simultaneously provides both visual representation and numerical quantification of topographic modifications. The resulting output effectively highlights areas of erosion, deposition, and stability across the dune landscape, enabling detailed spatiotemporal analysis of geomorphological processes.

A critical aspect of the DoD methodology involves addressing inherent uncertainties in the elevation data to ensure accurate detection of true morphological changes. The analysis incorporated a statistically derived minimum detection threshold (Level of Detection—LoD) to differentiate between actual geomorphological transformations and measurement noise. This threshold determination followed established protocols [36], by calculating the root mean square error of vertical position errors present in both input DSMs. The mathematical expression for this uncertainty threshold ($U_{DoD}$) incorporates the vertical error components from each DSM (${\delta }_1$ and ${\delta }_2$, respectively). The implementation of this rigorous error analysis framework served multiple purposes in the research methodology. Primarily, it allowed for the effective discrimination between genuine surface changes and artifacts resulting from data acquisition or processing limitations. Additionally, the thresholding approach provided a statistically robust basis for identifying significant geomorphological changes while filtering out minor variations that could be attributed to measurement uncertainty. Areas exhibiting changes below the calculated $U_{DoD}$ value were conservatively classified as showing no substantial morphological alteration, thereby enhancing the reliability of the detected changes.

In order to validate the calculated Level of Detection (LoD = U_DoD) threshold and assess its effectiveness in distinguishing meaningful geomorphological change from measurement noise, representative zones characterized by low relief and partial vegetation cover were selected for demonstration. In the Ceyhan-2 sub-region, areas with elevation changes falling just below the threshold were confirmed by field inspection to correspond to stable surfaces, such as vegetated dune crests and interdune hollows, and were therefore conservatively excluded from change counts. In contrast, zones exceeding the threshold corresponded to observable dune migration or sediment accumulation and depletion features, as verified through orthomosaic overlays. Additionally, a sensitivity analysis was performed by varying the threshold by ±5 cm around the originally calculated value (based on propagation of vertical RMSE components δ₁ and δ₂). The areal proportion of ‘no-change’ classification under each threshold scenario (−5 cm, original, +5 cm) showed variations of <3% in stable areas and negligible change (<1%) in dynamic dune ridges. These results confirm that the adopted threshold value robustly separates geomorphologically meaningful change from instrumentation or processing noise, especially in low-relief or vegetated settings. The methodological transparency of the DoD workflow is thus enhanced.

The accuracy and precision of the volumetric calculations were fundamentally dependent on the quality of the input DSM data. To optimize results, the study incorporated several quality assurance measures throughout the data acquisition and processing chain. These included rigorous ground control point networks, consistent photogrammetric processing parameters, and comprehensive error propagation analysis. The methodological approach maintained sensitivity to the challenges of monitoring dune systems, where subtle changes in surface elevation can represent significant sediment flux while being potentially obscured by surface texture variations or vegetation cover. The application of this advanced analytical framework enabled the research to capture both the magnitude and spatial distribution of dune morphodynamics with unprecedented precision.

In this context, potential limitations associated with the integration of multi-temporal datasets must be considered. Historical aerial photographs and modern UAV datasets differ in spatial resolution, image quality, and ground sampling distance (GSD). The historical datasets (1950–2016) exhibited GSD variations between 0.6 and 2.5 m, while UAV-derived models achieved 0.05–0.1 m resolution. These discrepancies inevitably influence the precision of multi-temporal DSMs and DoD outputs. The propagation of vertical errors from GCP uncertainty (ranging from 5 to 13 cm) and image alignment residuals was assessed using error propagation analysis, resulting in a cumulative uncertainty of ±0.18 m in long-term volume change estimates. To mitigate these effects, uniform resampling and standardized SfM parameters were applied across all epochs. While these measures reduced systematic errors, residual spatial discrepancies may still contribute up to 3–5% variation in computed volumetric change and migration distances.

2.3. Dataset

This research presents a comprehensive approach to analyzing coastal dune evolution through the synthesis of multi-temporal remote sensing data and advanced geospatial techniques. The methodology combines historical aerial photography with contemporary UAV surveys to establish a robust observational framework spanning seven decades of coastal change. The foundation of this research lies in its systematic compilation of archival aerial photographs acquired by Turkey’s General Directorate of Mapping (HGM) across six distinct periods between 1950 and 2019. This temporal series, captured at approximately 20-year intervals, provides a unique window into long-term coastal evolution. The digitized photographic collection includes 134 images from 1950, 170 from 1975, 96 from 1992, 26 from 2003, 233 from 2009, and 122 from 2016. The archival aerial photographs acquired by the HGM were originally obtained with known overlapping stereo coverage (typically > 60% forward overlap) and documented calibration parameters. These analogue photographs were digitized at 1200 dpi, radiometrically corrected and georeferenced via a bundle-adjustment SfM workflow [20]. GCPs collected during UAV campaigns were reused, in combination with tie-points in the archival campaigns, to anchor each epoch in the same coordinate frame. The vertical RMSE of the resulting DSMs was subsequently validated against independent RTK-GNSS checkpoints, yielding RMSE ≤ 0.5 m for all historical datasets—a precision considered sufficient for decadal-scale dune migration and volumetric budgeting [25]. To extend the temporal analysis, a seasonal UAV monitoring program was implemented, capturing quarterly high-resolution data to observe short-term dune dynamics. This approach aimed to identify fine-scale morphological responses to seasonal conditions and human activities, providing the spatial and temporal detail necessary to complement long-term geomorphic change detection.

All aerial photographs, whether historical or contemporary, underwent uniform SfM processing with identical parameter sets. The integration of precisely surveyed RTK-GNSS GCPs guaranteed positional accuracy across all generated DSMs. Potential error sources such as wetlands and vegetated areas were systematically identified and masked during processing, and the orthomosaics were generated. It is important to note that while the UAV-SfM workflow delivers high-resolution DSMs with centimetric accuracy, the archival aerial photograph-derived DSMs inherently possess higher uncertainty (vertical RMSE ≤ 0.5 m) and were applied only for decadal-scale morphological trends, not fine seasonal dynamics. UAV-derived data were used exclusively for high-frequency (quarterly) monitoring, whereas archival datasets underpin long-term DoD analyses. To avoid methodological conflation, results from each dataset are clearly distinguished in the discussion and figures, noting that absolute height precision differs between the two sources.

This study applied a photogrammetric workflow to generate high-precision orthomosaics and DSMs from archival aerial photographs (1950–2016) and UAV-based photogrammetry. Using the DoD method, elevation changes between successive periods were quantified to precisely assess the long-term morphological evolution of the deltaic dune systems. Figure 2 shows the comprehensive photogrammetric process workflow in the study.

Figure 2. The comprehensive photogrammetric process workflow.

The UAV-based monitoring program commenced in October 2020 with an initial flight campaign to establish baseline conditions for the dune systems. Subsequent data collection occurred at quarterly intervals (February, June, and September 2021) to capture seasonal variations in dune morphology. The varying spatial extent of each study sub-region necessitated multiple UAV flights for complete coverage, with the total photographic yield for each area systematically documented in Table 1. This stratified acquisition strategy ensured comprehensive spatial representation while maintaining consistent temporal resolution across all study sites. Also, photogrammetric parameters and data accuracy values used in the study are shown in Table A1 in Appendix A.

Table 1. Number of photographs for the sub-regions.

Sub-Region	October 2020	February 2021	June 2021	September 2021
Seyhan-1	504	503	613	454
Seyhan-2	569	512	176	219
Ceyhan-1	666	627	960	1087
Ceyhan-2	1699	1076	679	679

Binary masks were applied to orthomosaic images to exclude transient water bodies (sea, lagoon, and ephemeral pools) from DSM differencing. Black areas indicate masked water or open-water pixels, while white areas correspond to retained land surfaces (Figure 3). Masks were generated using the Magic Wand tool in Agisoft Metashape Pro v1.8, which selects pixels based on color/tonal similarity, with manual adjustments to ensure only relevant water features were masked, followed by morphological opening and closing to remove small artifacts (<5 m²). This process ensures that elevation artifacts caused by seasonal water coverage or shoreline fluctuations do not erroneously contribute to the DoD change detection analysis.

Figure 3. An example of masking sea areas in UAV-based aerial photographs.

The integration of historical and UAV-derived datasets established a consistent framework for analyzing spatiotemporal dune evolution. Multi-temporal DSMs enabled precise volumetric change detection across decadal and seasonal scales, while high-resolution orthomosaics supported detailed visual interpretation—together providing a robust basis for understanding long-term and short-term dune dynamics.

The study employed a strategic UAV deployment approach tailored to the specific requirements of each data acquisition period. During the initial phases of data collection in October 2020 and February 2021, conventional non-RTK UAV platforms including the eBee Sensefly fixed-wing system and Mavic 2 quadcopter were utilized. These missions incorporated an extensive network of GCPs strategically positioned throughout the study area to ensure the geometric accuracy of derived DEMs. The subsequent monitoring campaigns in June and October 2021 transitioned to an advanced RTK-enabled platform, the DJI Matrice 300RTK (Shenzhen, China), which provided centimeter-level positioning accuracy through real-time kinematic correction. This technological advancement eliminated the requirement for physical GCPs while maintaining survey precision through direct georeferencing capabilities.

For the temporal change analysis, the June 2021 dataset was established as the reference epoch due to its optimal data quality and seasonal conditions. A comprehensive geodetic control network was implemented across all four study sub-regions (Seyhan-1, Seyhan-2, Ceyhan-1, and Ceyhan-2), with GCPs established during both the October 2020 and February 2021 campaigns. The spatial distribution of control points was carefully designed to account for varying terrain characteristics, with 13 GCPs deployed in Seyhan-1, 7 in Seyhan-2 (limited by dense forest canopy coverage), 15 in Ceyhan-1, and 9 in Ceyhan-2. This configuration ensured adequate coverage while accommodating site-specific constraints, particularly in the vegetated Seyhan-2 sector where optimal GCP placement was challenging. The same control network specifications were applied to the georeferencing of historical aerial photographs to maintain methodological consistency across all temporal datasets.

The incorporation of GCPs into the photogrammetric workflow yielded horizontal and vertical accuracies ranging from 1 cm to 13 cm, consistently meeting or exceeding the project’s stringent accuracy requirements. Following comprehensive error assessment and validation procedures, each dataset underwent processing through advanced SfM algorithms. Figure 4 presents (a) the October 2020 orthomosaic of sub-region Seyhan-1 at 10 cm resolution, and (b) a zoomed inset (1:2) illustrating dune ridge morphology and sand-trap structures. The enhanced insets highlight features such as linear aeolian dune ridges, pioneer vegetation bands and dune–shoreline transitions, thus providing readers with evidence of the image resolution and geomorphological context used in our DSM generation. The standardized 10 cm resolution across all outputs facilitated direct spatiotemporal comparisons, while the systematic error validation protocol ensured the reliability of subsequent change detection analyses. This methodological framework proved particularly effective in maintaining data consistency between conventional and RTK-derived datasets, with the comprehensive accuracy assessment procedures compensating for differences in acquisition methodologies. The resulting geospatial products provided an unprecedented level of detail for analyzing coastal dune dynamics across multiple temporal and spatial scales.

Figure 4. Demonstration of (a) orthomosaic and (b) DSM for October 2020.

2.4. Coast Dune Change Detection

2.4.1. 2020–2021 Seasonal Change Detection

The comprehensive field studies conducted between 2020 and 2021 employed a systematic approach to analyze seasonal dune dynamics across the four sub-regions (Seyhan-1, Seyhan-2, Ceyhan-1, and Ceyhan-2). Through the generation of precise DSMs derived from UAV flights, cross-sectional profiles were systematically extracted at regular intervals to quantify morphological changes. This analytical framework enabled detailed examination of volumetric fluctuations and spatial patterns in dune behavior throughout the seasonal cycle. The DoD analysis for Ceyhan-1 (Figure 5) reveals complex volumetric changes between June 2021 and October 2020. While the region demonstrated an overall net accumulation, the profile analysis shows a distinct pattern of initial erosion followed by subsequent deposition, highlighting the dynamic equilibrium of the dune system. These fluctuations reflect the interplay between aeolian transport processes and seasonal wind regimes that characterize this coastal environment.

Figure 5. Demonstration of DoD analysis between October 2020 and June 2021 in the Ceyhan-1 region. A–A’ represents the section inland from the coastline.

In the Seyhan-1 region, monitoring revealed a clear seasonal cycle in dune behavior. Winter months exhibited dune stabilization followed by pronounced inland migration during late spring and summer, as evidenced by the E–E’ profile. The volumetric analysis shows distinct seasonal signatures—winter months typically showed erosion due to marine influences, while summer months demonstrated accumulation from wind-driven sand transport (Figure 6). This cyclic pattern underscores the delicate balance between marine and aeolian processes shaping the dune morphology.

Figure 6. The seasonal changes of the dunes between the years 2020 and 2021 in the Seyhan-1 region. A–A’ to E–E’ represent the sections drawn inward from the coastline.

The Seyhan-2 region displayed similar seasonal patterns to Seyhan-1, but with notable modifications due to ongoing reforestation efforts. The established coastal forest buffer has significantly altered natural dune dynamics, particularly in areas immediately landward of the pioneer dunes. Profile analyses (B–B’ and E–E’) demonstrate how vegetation has disrupted typical seasonal transport patterns, resulting in localized recession of dune fronts due to combined marine and biotic influences (Figure 7). This intervention highlights the complex interactions between natural processes and management strategies in coastal dune systems.

Figure 7. The seasonal changes of the dunes between the years 2020 and 2021 in the Seyhan-2 region. A–A’ to E–E’ represent the sections drawn inward from the coastline.

The implementation of sand traps in Ceyhan-1 has created distinct morphological signatures visible in the A–A’ and B–B’ profiles. These structures have effectively created zones of accelerated accumulation, particularly evident during summer months when wind transport is most active. The profile data reveals pronounced peaks in dune height adjacent to these interventions, demonstrating their efficacy in modifying sediment transport patterns (Figure 8).

Figure 8. The seasonal changes of the dunes between the years 2020 and 2021 in the Ceyhan-1 region. A–A’ to E–E’ represent the sections drawn inward from the coastline.

Ceyhan-2 exhibited atypical behavior compared to other sub-regions, maintaining relatively stable volumes from October through June before showing September declines. This distinctive pattern is attributed to the region’s southwest-facing orientation, which modifies its response to prevailing wind directions. The resulting dynamics create a unique seasonal signature in this sector, emphasizing the importance of coastal aspect in dune system behavior (Figure 9).

Figure 9. The seasonal changes of the dunes between the years 2020 and 2021 in the Ceyhan-2 region. A–A’ to E–E’ represent the sections drawn inward from the coastline.

The comparative analysis across all four sub-regions reveals how local factors including wind patterns, coastal orientation, and human interventions create distinct morphological responses within the larger dune system. While fundamental seasonal patterns are consistent across the study area, the specific manifestations of these patterns vary significantly based on these modifying factors. This comprehensive assessment provides valuable insights for coastal management strategies, demonstrating both the effectiveness and limitations of various stabilization approaches in different geomorphological contexts.

2.4.2. 1950–2016 Long-Term Change Detection

A comprehensive multi-temporal approach was employed to analyze coastal dune evolution across six decades, utilizing archival aerial photographs from 1950 to 2016 (Figure 10). The methodology incorporated high-resolution DSMs derived from historical imagery to systematically examine morphological changes in first-, second-, and third-generation dune ridges within the deltaic system. Comparative topographic profiles and slope analyses between the 1950 and 2016 datasets revealed significant alterations in dune morphology, while historical orthomosaics provided clear visualization of both dune field transformations and coastline modifications.

Figure 10. Demonstration of dune movement and coastline change; (a) Dune trap zones for the dune detection project in the Ceyhan-1, (b) afforested areas to restrict dune movement in Seyhan-2 based on the orthomosaics between the years 1950–2016.

The analysis also documented the measurable impacts of various dune stabilization initiatives, including sand trapping structures and afforestation projects, on the natural dune migration patterns. The DoD analysis revealed distinct spatiotemporal patterns of dune movement across the study regions:

For the Seyhan-1 Sector, the 2016–2009 period showed consistent dune migration of 15–20 m in the north-northwest (N-NW) direction, with reduced displacements of 7–10 m observed along agricultural margins (Figure 11).

Figure 11. Seyhan-1 sub-region: (a) 2016–2009; (b) 2009–1992 DoD analyses. A–A’ and B–B’ represent the sections drawn inward from the coastline.

The preceding 2009–1992 interval demonstrated accelerated movement rates of 20–40 m in the same predominant direction, suggesting potential changes in wind regimes or sediment availability over time. The Seyhan-2 Sector exhibited more moderate migration rates, with 5–12 m of N-NW displacement during 2016–2009 and 10–20 m during 2009–1992 (Figure 12).

Figure 12. Seyhan-2 sub-region: (a) 2016–2009; (b) 2009–1992 DoD analyses. A–A’ and B–B’ represent the sections drawn inward from the coastline.

The constrained movement patterns in this sector likely reflect the stabilizing influence of vegetation and anthropogenic modifications to the coastal landscape. The Ceyhan-1 Sector displayed the most pronounced migration rates, with 25–40 m of N-NW movement during 2009–2016 and even greater displacements of 35–60 m in predominantly northern directions during the 1992–2009 period (Figure 13). These accelerated rates suggest higher sediment availability or stronger wind forcing in this portion of the delta.

Figure 13. Ceyhan-1 sub-region: (a) 2016–2009; (b) 2009–1992 DoD analyses. A–A’ and B–B’ represent the sections drawn inward from the coastline.

The Ceyhan-2 Sector demonstrated a distinct northeastward (N-NE) migration trend, with 50–70 m of movement during 2009–2016, while coastal areas showed modified N-NW vectors of 30–40 m (Figure 14). The 1992–2009 period maintained this pattern with 45–65 m of N-NE displacement, indicating consistent long-term transport dynamics in this uniquely oriented coastal sector.

Figure 14. Ceyhan-2 sub-region: (a) 2016–2009; (b) 2009–1992 DoD analyses. A–A’ and B–B’ represent the sections drawn inward from the coastline.

Furthermore, complementary analysis of historical orthomosaics provided additional validation of these migration patterns, with the 2016–2009 interval documenting 44 m of northeastward movement in Ceyhan-1 and 32 m of northwestward displacement in Ceyhan-2 (Figure 15 and Figure 16), while the longer 2009–1950 timeframe revealed more extensive migrations of 120 m northward in Ceyhan-1 and 180 m northwestward in Ceyhan-2 (Figure 17 and Figure 18). The positions of dune-crest lines across historical epochs were interpreted consistently from orthophoto stereo-pairs. While differences in radiometric quality across years limit the direct superimposition of these crest lines on a single modern orthomosaic, the spatial relationships between crest positions and the quantified migration distances remain clearly represented in Figure 17 and Figure 18.

Figure 15. A dune movement of 44 m in the NE direction in the Ceyhan-1 region, based on the analysis of the orthomosaics from the years 2009 to 2016.

Figure 16. A dune movement of 32 m in the NW direction in the Ceyhan-2 region, based on the analysis of the orthomosaics from the years 2009 to 2016.

Figure 17. A dune movement of 120 m in the N direction in the Ceyhan-1 region, based on the analysis of the orthomosaics from the years 1950 to 2009.

Figure 18. A dune movement of 180 m in the NW direction in the Ceyhan-2 region, based on the analysis of the orthomosaics from the years 1950 to 2009.

These quantified movements demonstrate the persistent directional trends in dune migration while highlighting the substantial cumulative displacements that can occur over multi-decadal timescales. The differential migration rates between sectors underscore the importance of local geomorphological controls, including coastal orientation, sediment supply, and anthropogenic modifications, in shaping dune field evolution.

3. Results and Discussion

In the context of Mediterranean dune systems, our observed annual migration rates (1–8 m·yr⁻¹) align with those reported for similarly dynamic sectors—for example, Molina et al. (2024) found foredune translation rates of 2–6 m·yr⁻¹ along the Spanish Mediterranean coast [12]. The volumetric accumulation values in our Ceyhan-2 sub-region (~0.015 m³·m⁻²·yr⁻¹) are of the same order of magnitude reported in Andalusian systems (~0.012 m³·m⁻²·yr⁻¹) [12]. These similarities underscore the relevance of our results beyond the Turkish context and suggest common aeolian forcing and sediment budget behaviors across the eastern Mediterranean. Furthermore, the reduction in migration rates in afforested sectors (Seyhan-2: ~0.5 m·yr⁻¹) compared to open dune ridges (Ceyhan-1: ~4 m·yr⁻¹) supports process–control relationships previously highlighted by Ferreira et al. (2023) [6], who demonstrated that UAV-SfM monitoring in coastal dunes reveals clear wind-direction and vegetation buffer signals. Our study thus advances this understanding by linking volumetric budgets, orientation effects and anthropogenic stabilization over both seasonal and decadal timescales [6]. The discussion also emphasizes key drivers of dune behavior in our system: (i) bimodal wind regimes combining dominant on-shore spring winds and episodic storm winds [12]; (ii) sediment supply variability from the Seyhan and Ceyhan rivers modulated by upstream dam regulation; and (iii) human interventions—such as sand fences and afforestation—that led to a ~30% reduction in volumetric mobility in targeted zones. This integrated comparison with other systems enhances the scientific impact of our findings and situates the Çukurova Delta Plain within the broader Mediterranean dune-dynamics literature.

This study employed an integrated approach combining archival aerial photographs and contemporary UAV imagery to analyze morphological changes in coastal dune ridges across four key sub-regions (Seyhan-1, Seyhan-2, Ceyhan-1, and Ceyhan-2) within the expansive dune systems east of the Seyhan and Ceyhan Deltas. The methodological framework generated high-resolution DSMs from two distinct temporal datasets: historical aerial photographs captured at 20-year intervals and recent UAV images acquired quarterly during 2020–2021. This dual-temporal approach enabled comprehensive assessment of both decadal-scale evolutionary patterns and seasonal dune dynamics influenced by coastal processes.

Anthropogenic impacts affect the natural state of the dunes, as evidenced by field observations and UAV-based data collected during 2020–2021, which revealed distinct seasonal mobility patterns in the Seyhan sectors. During the winter months, dune stabilization was observed, followed by inland migration of approximately 0.5–1 m in late spring and summer under prevailing wind regimes. Human interventions such as afforestation and the installation of sand fences have altered natural sediment transport pathways, leading to localized dune recession rather than typical coastal progradation. These measures physically restrict sand movement, and their effects are evident in the volumetric analyses. In Ceyhan-1, strategically placed sand fences proved effective, showing notable volumetric increases during the summer months due to sediment accumulation along the coastline.

The quarterly UAV campaigns (October 2020–September 2021) produced DSMs at 10 cm resolution, enabling volumetric calculations for each sub-region. In Seyhan-1, an average summer accretion of +0.02 m³·m⁻² and winter erosion of –0.015 m³·m⁻² were observed. Predominant N–NW (330–360°) migration in the Seyhan sectors corresponded to regional onshore wind trajectories, while in Ceyhan-2 the dominant direction was N–NE (~20°) with higher magnitude (~0.010 m displacement per quarter), consistent with exposure to the WNW summer wind component. Additionally, sand-trap installations in Ceyhan-1 resulted in localized volumetric gains of up to +0.03 m³·m⁻² during the summer months, indicating effective managed sediment accretion. These quantified outcomes illustrate the capability of our methodology to resolve seasonal dune morphodynamics, vectorially and volumetrically. By linking these seasonal metrics to the long-term DoD results (1950–2016), we demonstrate that sectors exhibiting higher seasonal mobility (Ceyhan-1, Ceyhan-2) also present greater decadal migrations (~4–8 m·yr⁻¹) compared to stabilized sectors (~1 m·yr⁻¹). This linkage provides a process-based framework for predicting future dune behavior under changing environmental forcings.

The seasonal DoD analysis indicated net volumetric gains across most study areas, though profile examinations revealed complex temporal variations in sediment transport. Ceyhan-2 exhibited anomalous behavior with September 2021 volume reductions, attributed to unique wind exposure from the WNW direction during summer months combined with the region’s distinctive westward coastal orientation that modified typical sediment transport pathways. From a meteorological perspective, studies based on data from the Adana–Karataş meteorological station indicate a distinct prevailing wind orientation from the south–southwest (S–SW) toward the land during the summer months between 1983 and 2009, accompanied by a gradual increase in wind velocity. In general, the Adana region experiences mean monthly wind speeds of approximately 3.3 m/s (~11.8 km/h) in July, with southerly onshore winds prevailing about 68% of the time throughout the year [37,38]. These observations support the interpretation that during the dry summer season, onshore winds play a significant role in triggering sediment transport and intra-dune migration processes. From a sedimentological perspective, field observations conducted across the Seyhan Delta indicate that samples collected from the frontal dune ridges are predominantly composed of fine- to medium-grained sand, with maximum grain diameters reaching ~0.5 mm [39]. The sediments exhibit good to moderate sorting, corresponding to grain-size distributions in the range of approximately 0.22–0.35 mm. This granulometric composition suggests a high potential for aeolian transport under the prevailing wind regime, which is consistent with the volumetric variations and migration distances identified in our analysis. Long-term analysis of archival imagery quantified persistent migration trends across all sub-regions. Seyhan-1 demonstrated consistent annual displacements of approximately 2 m in the NW-NNW direction during both 1992–2009 and 2009–2016 intervals, though agricultural expansion has progressively flattened dune topography, restricting major sediment transport to field margins with reduced movement rates of about 1 m/year. Comparative analysis revealed regional variability in migration rates, with Seyhan-2 and Ceyhan-1 showing annual movements of 1 m (N-NW) and 3.5 m (W-SW), respectively. Ceyhan-2 exhibited the most dynamic changes, with annual displacements of 3–8 m between 1992 and 2016, including coastal-fronting primary dunes moving approximately 4 m/year in the WNW direction. Orthomosaic-based measurements provided complementary data, showing Ceyhan-1 migrations of 6 m/year (SW) during 2009–2016 and 2 m/year (W) from 1950 to 2009, while Ceyhan-2 moved 5 m/year (SW) and 3 m/year (SW) during corresponding periods.

The study’s quantitative assessment of coastal dune evolution through aerial photographic monitoring has successfully characterized both short-term seasonal behaviors and long-term morphological changes. The detailed documentation of spatiotemporal volumetric variations provides critical insights into coastal system dynamics, offering a robust foundation for understanding deltaic evolution patterns and informing future coastal management strategies. These findings particularly highlight the complex interplay between natural aeolian processes and anthropogenic landscape modifications in shaping dune field development over multiple temporal scales.

In the contemporary period, the cessation of sediment supply to the former delta lobe has triggered extensive coastal reworking by marine processes. Wave and current action have eroded the abandoned delta front, generating significant sediment deficits along adjacent shorelines [40,41]. This natural erosional trend has been greatly intensified by anthropogenic influences, particularly the rapid expansion of agricultural lands across the Çukurova Plain. Land-use changes, the degradation of the plant–soil system, the interruption of sediment supply, and the alteration of moisture and groundwater regimes have led to the fragmentation of the dune system. With the expansion of agricultural activities within dune areas and the surrounding basin, the structural integrity of the dunes has been disrupted, altering sediment transport and deposition processes, which in turn has resulted in the gradual decline of dune formations over time [42,43]. Quantitative analyses indicate that between 1948 and 2013, agricultural areas increased from 990 to 5499 hectares, while coastal dune coverage decreased from 3540 to only 285 hectares [44]. These substantial land-use changes have disrupted sediment budgets and accelerated dune degradation, especially around Tuzla Lake, where dune systems have nearly vanished since the 1980s. The detailed analysis provides essential baseline data for understanding anthropogenic impacts on this fragile coastal ecosystem. Historical imagery confirms notable transformations in dune morphology over time within the Seyhan Delta, in contrast to the Ceyhan Delta’s more continuous and linear dune systems extending over approximately 100 km of coastline and 7250 hectares of protected area within the Yumurtalık Lagoon National Parks (Figure 1). Although the Ceyhan Delta’s protected status has mitigated anthropogenic degradation, both systems exhibit substantial dune mobility between 1984 and 2017 [44].

4. Conclusions

This comprehensive investigation of coastal dune dynamics in the Seyhan and Ceyhan Deltas has yielded significant insights into both natural aeolian processes and anthropogenic influences on dune morphodynamics across multiple temporal scales. Through the innovative integration of historical aerial photographs (1950–2016) and contemporary UAV surveys (2020–2021), the study has successfully quantified and characterized dune evolution patterns that were previously undocumented in this region of the Eastern Mediterranean. The research demonstrates distinct spatial and temporal patterns in dune behavior across the four sub-regions, revealing average annual migration rates ranging from 1 m in stabilized areas to 8 m in more dynamic sectors. Notably, the study documents how anthropogenic interventions—particularly afforestation projects and sand fencing—have measurably altered natural sediment transport patterns, with afforested zones reducing migration rates by approximately 50% and sand fences demonstrating 20–30% efficiency in promoting dune accumulation during summer months.

The seasonal analysis has identified critical temporal patterns in dune mobility, with winter stabilization periods followed by active summer migration phases showing 0.5–1 m displacements. The exceptional case of Ceyhan-2, where unique coastal orientation resulted in September volume reductions, underscores the importance of local geomorphological controls in modifying regional wind patterns. Long-term assessments reveal persistent directional trends in dune migration, particularly the dominant NW movement in Seyhan sectors and SW trajectories in Ceyhan areas, while simultaneously documenting the progressive flattening of dune topography due to agricultural expansion. The multi-decadal orthomosaic analysis provides particularly valuable baseline data, showing cumulative displacements of 120–180 m since 1950 that highlight the substantial landscape modifications possible over engineering timescales.

These findings carry important implications for coastal zone management, demonstrating both the effectiveness and limitations of various stabilization approaches while providing quantitative benchmarks for predicting future dune migration. The study establishes a methodological framework for ongoing monitoring that combines historical analysis with modern remote sensing techniques, offering a replicable model for similar coastal environments worldwide. Future research directions should focus on extending the temporal dataset through continued UAV monitoring, investigating sediment budget linkages between dune and nearshore systems, and evaluating the ecological impacts of stabilization measures. In this study, all analyses were conducted using UAV-based methods without incorporating ground measurements; therefore, integrating field measurements should be considered as a potential avenue for future research. This work ultimately contributes to our broader understanding of deltaic system evolution in the context of climate change and increasing anthropogenic pressures along vulnerable Mediterranean coastlines.