Karst-Based Geotourism in Eastern Carphatian Serbia: Exploration and Evaluation of Natural Stone Bridges

Introduction

Geotourism research is intended to improve the value-added component of the geosite visitor experience (Hose 2006). The assessment of geoheritage assets, values and benefits enables a more holistic approach to geotourism, recognizing the connections between people, geoheritage and the landscape (Gordon 2018). Geotourism is appreciated and accepted as a useful tool for promoting natural and cultural heritage as well as fostering local and regional economic development (Kubalíková 2019). This underlines the importance of exploring geoheritage and geotourism potentials and values for the establishment of geoconservation strategies.

A geoconservation focus gives geotourism an overlap with other forms of natural heritage tourism such as ‘environmental’ and ‘nature-based’ (Hose 2012), but the main purpose is the conservation of geosites and geomorphosites through the implementation of specific inventory, evaluation, conservation and monitoring procedures (Henriques et al. 2011). Geoconservation research has been undertaken elsewhere on different geosites, mainly caves (Stephens et al. 2013; Guzmán & Fernández 2016; Larwood 2016; Murphy & Allshorn 2018; Lewis 2019; Tomić et al. 2019; Antić et al. 2019; Zafra-Otero et al. 2019; Gordon 2019) and loess geosites (Vasiljević et al. 2011; Solarska et al. 2013; Vasiljević et al. 2014; Dong et al. 2014; Marković et al. 2014). A crucial aspect of geoconservation is the ability to establish the sustainability of local development (Piranha et al. 2011), geo-knowledge (Farsani et al. 2014) and geoethical values (Peppoloni et al. 2019). Moreover, professional and responsible geoconservation management and continuous geodiversity monitoring are prerequisites for carrying out successful geotourism strategies (Gordon, 2018).

Karst landscapes and features are one of the most vulnerable (Williams 2008) and visited (Lobo 2013) geosites. Caves, gorges, canyons, karst springs, waterfalls and natural stone bridges are the main representatives of karst resources (Ruban 2018) and karst-based geotourism potential. However, due to their fragility, the conceptual frameworks of karst geotourism strategies must include protection, education and socio-economic perspective (Sánchez-Botello et al. 2018). Furthermore, the promotion of scientific, educational and aesthetic values of rare and unique karst geosites establishes an adequate starting point of the geotourist affirmation. Bearing in mind the many benefits that local people can derive from tourism, both marketing and spatial planning must be carefully implemented to bring sustainable and ethical concepts of prosperity to geotourism.

Natural Arch and Bridge Society defines natural arches as “rock exposures that have holes through them formed by the natural, selective removal of rock, leaving a relatively intact frame”. There are many different processes of erosion that can contribute to the natural, selective removal of rock. These processes usually only cause a natural arch to form when certain combinations of them act on a rock exposure of a specific shape. Water, gravity, and temperature fluctuation are the principal forces involved in carving natural arches out of rock (www.naturalarches.org). Furthermore, Ćalić-Lubojević (2000) argues that there are two theories on the genesis of the natural bridges. The first one was elaborated by Cvijić (1918) and relies on the former presence of a cave whose roof collapsed, leaving only tiny stone arches—natural bridges. The second theory refers to situations when a river flowing across a thin limestone ridge cannot entrench into the ridge but sinks at the contact and resurges on the other side (Petrović 1969).

The diversity of karst areas in eastern Carpathian Serbia enables numerous exploitations of geosites for geotourism development purposes. The main focus of this paper is to identify and evaluate natural stone bridges as important resources for the development of karst geotourism in eastern Serbia. Additionally, the paper mentions other karst features in the area which could enrich the geotourism offer in this part of the Carpathians. The results of the paper are of particular importance for tourism workers, management structures and decision makers, as well as for the local population and NGOs.

Study area

The Carpathian branches in eastern Serbia extend from the Timok and Crna rivers in the east to the Velika Morava River in the west and from the Balkan Mountains in the Nišava River basin in the south to the Danube in the north.

The explored geosites are positioned in the karst the environment of the Carpathians in eastern Serbia (Figure 1). The evaluation was conducted on seven selected natural stone bridges, which are the most representative and possess great potential for geotourism development. Table 1 provides detailed descriptions of the sites that are analyzed and evaluated in this paper. It can be observed that out of seven selected geosites, four are located in the Negotin municipality. Also, Rajska has the longest tunnel (155 m), because it is a cave that has the characteristics of a natural stone bridge. Moreover, it is evident that Valja stone bridge near Majdanpek is the highest (44.8 m), which indicates its aesthetic uniqueness while the smallest natural stone bridge is Osanica, which can be very attractive for adventure tourists.

Figure 1. Location of analyzed stone bridges and the spread of karst areas in Carpathian Serbia

 In addition, there are numerous caves in this area that are already developed speleotouristic destinations, such as Resava cave, Rajkova cave, Lazareva cave, Ceremošnja and Ravništarka caves. Numerous waterfalls are also found in this karst area: Buk, Siga, Blederije, as well as many gorges, canyons and paleo-volcanic sites.

Table 1. Natural stone bridges in Eastern Serbia

Vratna River Stone Bridges are located in the Vratna canyon in eastern Serbia, more precisely about 30 km from the city of Negotin. The Vratna canyon can be reached via the Negotin-Kladovo road leading to the Vratna monastery and three stone bridges that cover a watercourse of 94 m in length (Tomić 2016).

The area of the Vratna River, which is cut in limestones, used to be a large cave with the main channel about 150 m long. It was through this channel that the Vratna River flowed. The simultaneous existence of surface and underground watercourses were connected by numerous sinkholes. While the underground flow was constantly active, the surface only existed occasionally, during the wetter period of the year when the underground cavities could not receive all the water. Due to the surface denudation (lowering of the surface area) and the simultaneous increase in the dimensions of the cave channel, or due to its expansion, the cave ceiling collapsed over a distance of about 100 meters, leaving only two specific limestone ports today called Mala (small) stone bridge and Velika (big) stone bridge (Petrović & Gavrilović 1969).

Figure 2. Mala Vratna stone bridge

Mala Vratna stone bridge is located about 200 meters upstream of the Vratna Monastery. The bridge is 15 m long, 33 m wide and 34 m high (Figure 2). The Velika Vratna stone bridge (Figure 3) is located 100 meters upstream of the Mala stone bridge and it has an opening in the form of a tunnel 45 m long, 22–33 m wide and 26 m high. There are more openings of cave channels on the walls and ceiling. The largest and longest cave system is located in the right wall and represents a maze of channels at different levels and heights (Tomić 2016). Suva Vratna stone bridge is not a part of the Vratna protected area and is approximately three kilometers from the previous two stone bridges. It is quite inaccessible, but the marked trail is extremely attractive to all adventurer tourists (Figure 4). This imposing and final stone bridge of the Vratna area is 34 m long, 20 m wide and 15 m high (Petrović & Gavrilović 1969).

  Figure 3. Velika Vratna stone bridge

The Vratna Canyon is protected by the Institute for Nature Conservation of Serbia as a natural monument. The protected area encompasses the river canyon on either side of the river bed. The Vratna canyon also has a very specific flora dating back to the Ice Age, as well as about 50 bird species and mammal species such as mouflon and musk deer (Petrović & Gavrilović 1969).

Figure 4. Suva Vratna stone bridge

Samar Stone Bridge. This natural bridge is located on the border of Homolje and Kučaj mountains, near the small city of Žagubica. The Samar stone bridge karst formation (Figure 5) is in the limestones of the easternmost part of Beljanica Mountain. Also, the Borsko Lake is only 12.5 km south of this geosite. The Ravna River flows through the Samar stone bridge, in a west-east direction. The length of this natural bridge is 10 m, while the width is 14 m and its height is 15m (Cvijić 1918). The Samar Geomorphologic Nature Monument was protected in 1979.

  Figure 5. Samar stone bridge

              Figure 6. Valja stone bridge

Valja Stone Bridge.

The natural stone bridge Valja (Figure 6) is protected by the state as a natural monument of exceptional importance. The bridge is located about 12 km from Majdanpek. From a regional road Majdanpek-Rudna Glava a 1300m long pedestrian track leads to this geosite. The impressive height of the bridge is 44.8m, making it the highest in Serbia, while the width of its opening at the bottom is 9.7m. The protected area also includes a mountain river of the same name that runs below the stone bridge. Together they make an attractive and very significant geotourism destination (Gavrilović 2005).

The Osanica Stone Bridge. This geositeis in the north western part of Homolje Mountains, in the narrowest part of the Osanica epigenetic gorge. It is 2 km upstream of the Osanica River. The total length of this stone bridge is 18 m and the height of the vault varies from 1 m up to 3 m, while the average width is 3 m (Figure 7).

Figure 7. Osanica stone bridge

The thickness of the stone vault is 5 m below which the Osanica River flows. Due to its proximity to Osanica village, it is very accessible to all visitors. The macadam road along the river leads to the stone bridge, but for the last few tens of meters the stone bridge can only be reached by walking into the river. Therefore, the stone bridge can only be reached when the water level is low.

Rajska Stone Bridge. This geosite is located in the valley of the Zamna River, close to the Plavna village, which belongs to the municipality of Negotin. Zamna River Canyon and the stone bridge are both protected as a natural monument, but it should be emphasized that Rajska is also a tunnel cave. The river flows through a 155 m long cave with bridges at both sides (Figure 8). Water erosion has created openings in the cave vault through which daylight reaches almost its entire length (Gavrilović 1998).

  Figure 8. Rajska stone bridge

Methodology

 The methodology of this study is based upon the ‘Modified GeositeAssessment Model’ (M-GAM), as developed by Tomić & Božić (2014). This method is mainly based on the Importance factor (Im) first introduced by Tomić (2011) and the GAM model created by Vujičić et al. (2011). The method is also based on previous geosite assessment methods developed by different researchers (Bruschi & Cendrero 2005; Coratza & Giusti 2005; Erhartič 2010; Hose 1997; Pereira et al. 2007; Pralong 2005; Reynard 2008; Reynard et al. 2007; Serrano & González-Trueba 2005; Tomić 2011; Zouros 2007). It combines the opinions of both sides of the tourism experience, tourists and experts, in such a way that neither side is favored in the assessment process. It has been successfully tested and applied numerous times for the assessment of various geosites in Serbia (Antić & Tomić 2017; Boškov et al. 2015; Božić et al. 2014; Božić & Tomić 2015; Tomić et al. 2019; Tomić et al. 2020; Vukoičić et al. 2018; Antić et al. 2019; Antić & Tomić 2019; Vuković & Antić 2019), Slovenia (Tičar et al. 2018), the USA (Tomić et al. 2015; Jonić 2018), Iran and in the Hungarian Bakony-Balaton geopark (Pál & Albert 2018).

The M-GAM model consists of two key indicators: Main Values and Additional Values, which are further divided into 12 and 15 indicators respectively, each individually marked from 0 to 1. This division is made due to two general kinds of values: Main Values - that are mostly generated by geosite’s natural characteristics; and Additional Values - that are mostly human-induced and generated by modifications for a geosite’s use by visitors. The Main Values comprise three groups of indicators: scientific/educational (VSE), scenic/aesthetic values (VSA) and protection (VPr) while the Additional Values are divided into two groups of indicators, functional (VFn) and touristic values (VTr). The Main and Additional Values are presented in more detail in Table 2.

The evaluation process is based on careful consideration of the different characteristics of investigated speleological objects. With the help of field research (visiting each geosite), scientific, aesthetic, conservation, tourist and functional parameters related to the M-GAM subindicators were observed in order to determine the current state and perspectives of tourism development of each geosite.

       Table 2. The structure of the Modified Geosite Assessment Model (M-GAM)

In total sum, there are 12 subindicators of Main Values, and 15 subindicators of Additional Values, which are graded from 0 to 1 that define M-GAM as a simple equation:

                                                           M-GAM = MV + AV                                                           (1)

where MV and AV represent symbols for Main and Additional Values. Since Main and Additional Values consist of three or two groups of subindicators, we can derive these two equations:

                                                           MV = VSE + VSA + VPr,                                                   (2)

                                                           AV = VFn + VTr,                                                                (3)

            Now that we know that each group of indicators consists of several subindicators, equations (2) and (3) can be written as follows:

                                                                                                                                                                           (4) and (5)

Here, SIMV_i and SIAV_j represent 12 subindicators of Main Values(i = 1,...,12) and 15 subindicators (j = 1,...,15) of Additional Values.

The main feature of M-GAM is that it does not focus only on the expert’s opinion but also on the opinion of visitors and tourists regarding the importance of each indicator in the assessment process. Visitor inclusion in the assessment process is done through a survey where each respondent is asked to rate the importance (Im) of all 27 subindicators (from 0.00 to 1.00) in the M-GAM model (Table 3). The importance factor (Im) was first introduced by Tomić (2011) in his research and later used for the creation of the M-GAM model, CREM model (Cultural Route Evaluation Model) created by Božić & Tomić, 2016 and SAM Model (Spa Assessment Model) created by Tomić & Košić, 2020. It gives visitors the opportunity to express their opinion about each subindicator in the model and how important it is for them when choosing and deciding between several geosites that they wish to visit. After each respondent rates the importance of every subindicator, the average value of each subindicator is calculated and the final value of that subindicator is the importance factor. Afterwards, the value of the importance factor (Im) is multiplied with the value that was given by experts (also from 0.00 to 1.00) who evaluate the current state and value of each subindicator (Table 3).

This is done for each subindicator in the model after which the values are added up according to the M-GAM equation but this time with more objective and accurate results due to the addition of the importance factor (Im). This parameter is determined by visitors who rate it in the same way as experts rate the subindicators for Main and Additional Values by giving them one of the following numerical values: 0.00, 0.25, 0.50, 0.75 and 1.00, marked as points. The importance factor (Im) is defined, as:

                                                                                                                       (6)

Where Iv_k is the assessment/score of one visitor for each subindicator and K is the total number of visitors. Note that the Im parameter can have any value in the range from 0.00 to 1.00.

Finally, the M-GAM equation is defined and presented in the following form:

                                                                               M - GAM = MV + AV                     (7)                                                                                                            

                                                                                                                                                                   (8) and (9)     

As it can be seen from the M-GAM equation, the value of the importance factor (Im), which is rated by visitors (for each subindicator separately) is multiplied with the value given by experts (also separately for each subindicator). This is done for each subindicator in the model.

 In their research about different geotouristic segments, Božić & Tomić (2015) conducted a survey and calculated the importance factor for each subindicator in the M-GAM model. Their research was carried out in order to calculate the importance factor for Serbian geotourists. Since then, these values have been used numerous times for the assessment of different geosites in Serbia for the needs of Serbian tourists (Antić & Tomić 2017; Tomić et al. 2019; Tomić et al. 2020; Antić et al. 2019; Antić & Tomić 2019; Vuković & Antić 2019) and therefore can be applied in this case as well given the fact that the assessment is also done for Serbian tourists. Therefore, the values of the importance factor in this paper have been adopted from the mentioned paper.

Based on the assessment results, a matrix of Main (X axes) and Additional Values (Y axes) is created (Figure 9). The matrix is divided into nine fields represented with Z(i,j), (i,j=1,2,3). Depending on the final score, each geosite will fit into a certain field. For example, if a geosite's Main Values are 7 (X axes) and additional are 4 (Y axes), the geosite will fit into the Z₂₁field at the point where these two values (7 and 4) meet.

Figure 9. Position of analyzed geosites in the M-GAM matrix

Results and Discussion

Considering the vastness of karst terrain in the eastern Carpathian region of Serbia (Figure 1), natural stone bridges are most certainly a regional phenomenon. The Carpathian region in Serbiais an area with the largest number of these geosites, which points out a unique advantage that can be utilized in the tourism market. Due to these facts, all natural stone bridges are rated 0.50 for the rarity subindicator. Moreover, the representativeness of the explored geosites was assessed more diversely. The utmost values (1.00) are given to the Velika Vratna, Valja stone bridge and Rajska stone bridge geosites while high values (0.75) are given to all other geosites, except Osanica, which received a moderate value of 0.50. This is the result of various attractive features. The best rated geosites have larger dimensions, which also affects the level of visits they receive. Furthermore, the interpretation subindicator is highly rated for all geosites, because the possibility of presenting it to potential tourists is high. There are the good examples of processes that are easy to explain to a common visitor. Although scientific research and publications related to the knowledge of these geosites are very scarce, the natural stone bridges in the Vratna river basin have been explored and papers have been published on this topic in international journals (Ćalić-Ljubojević 2000; Petrović & Carević 2015) while for other sites this is not the case.

The evaluation results for aesthetic values are very similar for all geosites. The natural stone bridges in the Vratna river basin have higher ratings because they possess a larger number of viewpoints compared to other geosites. The area covered by the explored geosites is also similarly evaluated. The majority of the geosites have medium size, while Rajska as the largest and Osanica stand out as the smallest. Considering the researched geosites, it is evident that these localities are unique for the Carpathian region of Serbia. Thus, they are authentic representative tourist potentials for this area. Given the uniqueness of the natural environment in which these geosites are located, they are all rated with maximum score when it comes to subindicators of landscape, nature and environmental fitting. Furthermore, all natural stone bridges are protected at the national level by the Institute for Nature Conservation of Serbia and have no major damage. According to the presented data and results for the Main Values, we can conclude that these geosites possess significant geotourism potential that could be used for the creation of an attractive geotourism destination. Therefore, it is necessary to explore the functional, infrastructural and tourist values to determine the measures for the creation, improvement and modernization of the potential geotourism product.

          Table 3.Subindicator values given by experts for Natural Stone Bridges in Eastern Serbia

Additional values of the analyzed geosites are significantly lower than the Main Values. Apart from the Vratna andValjа stone bridge near the Đerdap National Park, accessibility is low for each of the analyzed sites. Walking with special equipment and expert guide tours is mandatory for safe access to the explored sites. This is the primary reason that these sites have few visitors, because most tourists require adequate tourist infrastructure. On the other hand, this is an advantage for those tourists who enjoy adventurous trips to destinations that are completely free from conventional tourist activities. An appropriate solution is to provide both groups with quality conditions that will inspire them to visit these destinations continuously. This would mean arranging a part of the site, which is in the immediate vicinity of the stone bridges (access and information units), without changing the natural environment by opening large tourist complexes and camps.