Evaluating Sea Level Rise Impacts on the Southeastern Türkiye Coastline: a Coastal Vulnerability Perspective

PFG – Journal of Photogrammetry, Remote Sensing and Geoinformation Science https://doi.org/10.1007/s41064-024-00284-0 ORIGINAL ARTICLE Evaluating Sea Level Rise Impacts on the Southeastern Türkiye Coastline: a Coastal Vulnerability Perspective Fahri Aykut1 · Devrim Tezcan1 Received: 30 November 2023 / Accepted: 5 March 2024 © The Author(s) 2024 Abstract Coastal areas are inherently sensitive and dynamic, susceptible to natural forces like waves, winds, currents, and tides. Human activities further accelerate coastal changes, while climate change and global sea level rise add to the challenges. Recognizing and safeguarding these coasts, vital for both socioeconomic and environmental reasons, becomes imperative. The objective of this study is to categorize the coasts of the Mersin and İskenderun bays along the southeastern coast of Türkiye based on their vulnerability to natural forces and human-induced factors using the coastal vulnerability index (CVI) method. The study area encompasses approximately 520 km of coastline. The coastal vulnerability analysis reveals that the coastal zone comprises various levels of vulnerability along the total coastline: 24.7% (128 km) is categorized as very high vulnerability, 27.4% (142 km) as high vulnerability, 23.7% (123 km) as moderate vulnerability, and 24.3% (126 km) as low vulnerability. Key parameters influencing vulnerability include coastal slope, land use, and population density. High and very high vulnerability are particularly prominent in coastal plains characterized by gentle slopes, weak geological and geomorphological features, and significant socioeconomic value. Keywords Climate Change Impacts · Global Sea Level Projections · Mersin · Socio-Economic Vulnerability · Eastern Mediterranean 1 Introduction Coastal regions play a vital role in human activities, economic activities, and the preservation of coastal ecosystems. It is reported that approximately 37% of the global population resides within 10 km of the coast (OC 2017). Coastal economic activities, including trade, tourism, fisheries, and various industries, constitute a substantial portion of the global economy (WOR 2017; EC Report 2016; Randone et al. 2017). Additionally, coastal areas serve as critical providers of essential marine ecosystem services. On the other hand, coastal areas are highly vulnerable and dynamic ecosystems, susceptible to rapid changes caused by both human-induced factors and climate-related impacts (De La Cruz 2021). Climate change has many significant impacts on coastal areas, with sea level rise (SLR) being among the major climate change-induced risks of  Devrim Tezcan 1 Institute of Marine Sciences, Middle East Technical University, Mersin, Turkey the 21th century for coastal areas (Nicholls and Cazenave 2010). SLR is primarily driven by global warming which results from increased concentrations of greenhouse gases in the Earth’s atmosphere. Additionally, human activities in recent decades have accelerated the warming of the planet and contributed to the rise in sea levels. The Intergovernmental Panel on Climate Change (IPCC) has projected SLR scenarios for 2100 based on climate mitigation success. Even the best scenario predicts a rise of 0.28–0.55 m, while the worst-case scenario reaches 1 m (IPCC 2014). SLR leads to increased coastal erosion, higher storm surges, and saltwater intrusion into freshwater sources, severely affecting low-lying coastal areas (IPCC 2019). Unpredictable weather events and extreme precipitation further exacerbate these threats. Authorities and coastal planners need a coastal vulnerability assessment to address these threats. The Mediterranean basin, identified as one of the primary hotspots for climate change, is warming at a rate 20% faster than the global average, according to Med (2020). Compared to other coastal regions worldwide, Mediterranean cities, wetlands, and drylands are projected to suffer the K PFG – Journal of Photogrammetry, Remote Sensing and Geoinformation Science most damage due to SLR in the 21st century (Marcos et al. 2016). The southeastern coastal region of Türkiye, characterized by low-lying areas, deltas, and natural preserves, faces significant risks from global threats such as SLR. The vulnerability of coastal areas depends on both the physical characteristics of the coast and human activities along the coast. To assess vulnerability, various coastal vulnerability index (CVI) tools have been developed (Gornitz 1990, Gornitz et al. 1997, Thieler and Hammar-Klose 1999, Szlafsztein and Sterr 2007, McLaughlin and Cooper 2010). The Thieler and Hammar-Klose (1999) model, which is an adapted version of Gornitz (1990), is the most widely used CVI method for assessing coastal vulnerability against SLR. Owing to the widespread availability of satellite data, this method has been employed by researchers globally (Charuka et al. 2023, Mendoza et al. 2023, Kuleli and Bayazıt 2023, Ozsahin et al. 2023, Gaki-Papanastassiou et al. 2010, Addo 2013, Gorokhovich et al. 2014, Kunte et al. 2014, Diez et al. 2007). However, this model only considers the physical attributes of coastal areas, including coastal geomorphology, coastal slope, historical shoreline change, mean tidal change, mean wave height, and the rate of sea level rise. Similar to the physical factors, socioeconomic factors also have significant impacts on coastal vulnerability (Boruff et al. 2005). Socioeconomic factors encompass all human activities on coastal areas such as infrastructures, settlements, sensitive coastal and marine ecosystems. Socioeconomic transformations tend to happen more rapidly than physical alterations when considering both physical and socioeconomic aspects of vulnerability (Szlafsztein and Sterr 2007). As an example, population and tourist density are identified as key influencers of coastal vulnerability, particularly in Goa, India, where the escalating population and tourism’s crucial economic role intertwine to shape the region’s coastal resilience (Kunte et al. 2014). Another important socioeconomic factor, the land use, provides a more comprehensive representation of the cultural, economic, and environmental values of coastal areas (Maanan et al. 2018). Also, the conservation areas should be included in vulnerability assessments to effectively identify regions with significant ecological and biological importance (Maanan et al. 2018). The model by Thieler and Hammar-Klose (1999) was adapted in some studies to incorporate socioeconomic parameters into vulnerability assessments (Dada et al. 2024, Charuka et al. 2023). In this adapted approach, both physical and socioeconomic factors contribute equally to the overall assessment. Another methodology, the multi-scale CVI method developed by McLaughlin and Cooper (2010), described the vulnerability as a combination of factors including coastal characteristics (such as geomorphology, K coastline type, and elevation), coastal forces (like wave (...truncated)