DOI: 10.3897/jbgs.e168786

Authors: Davis Dinkov, Lyubka Pashova

Abstract: High-resolution Digital Elevation Models (DEMs) are critical for accurate coastal flood risk assessment, particularly in low-lying areas vulnerable to sea-level rise, storm surges, and other natural hazards. This study presents a comparative evaluation of five DEMs with varying spatial resolutions and data sources for a test area along the northeastern Bulgarian Black Sea Coast around the Durankulak Lake—an area identified as at risk of coastal flooding. A high-resolution Uncrewed Aerial Vehicle (UAV) derived DEM was generated using Structure-from-Motion and Multi-View Stereo (SfM-MVS) photogram-metry and compared against three other DEMs: BG DSM (4 m), MGS DEM (10 m), and re-sampled TanDEM-X (10 m). The vertical accuracy of DEMs was assessed using control points (CPs), including GNSS-measured and geodetic reference points, and parametric and non-parametric statistical methods, along with statistical tests to assess the error distribution. Results indicate that the UAV and BG DSM models exhibited normal error distributions with high vertical accuracy (root mean square error: 0.098 m and 0.776 m, respectively), while the MGS and TanDEM-X models display significant deviations from normality and lower precision. The UAV-derived DEM has offered the highest accuracy and reliability, though it requires significant field and processing resources. The findings highlight the importance of selecting DEMs based on the required precision, available resources, and application-specific context, particularly for hydrologic and hydrodynamic modeling and flood risk mapping under the EU Floods Directive. This study provides a robust methodological framework for evaluating DEM quality and suitability in coastal hazard assessments and contributes to improved geospatial data practices in flood-prone regions.

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DOI: 10.3897/jbgs.e177296

Authors: Dmytro Kasiyanchuk, Yaroslava Atamaniuk, Mykola Deputat, Svitlana Gavdey, Pavlo Horishevskyi

Abstract: The objective of the present study is to undertake a quantitative assessment of the spa-tial impact of tourism on natural complexes in the Carpathian region. This is achieved by employing geostatistical modelling methods. The present study deviates from con-ventional buffer methodologies insofar as it employs an integrated algorithm founded upon Kernel Density Estimation (KDE), thereby amalgamating multivariate analysis with detailed land use classification (LULC). In the analysis, each of the seven factors ̶ hydro-graphic network, relief, transport accessibility, hotels, tourist routes, land use types and nature conservation areas ̶ is standardised on a scale of 1–10 and synthesised into a single model of the vulnerability of natural landscapes to tourist pressure. The spatial integration of the factors demonstrates that areas exhibiting high and very high vul-nerability encompassed a total area of more than 310 km², constituting approximately 34% of the total area under consideration. These areas are predominantly concentrated within mountain valleys and along major transport axes. The findings demonstrate the substantial analytical superiority of KDE in comparison to buffer models, owing to its capacity to accommodate continuous impact gradients and its strong alignment with actual urbanisation patterns. The proposed approach can be applied to spatial planning for sustainable tourism and environmental monitoring in mountain regions.

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DOI: 10.3897/jbgs.e159980

Authors: Aditya Kumar, Pankaj Kumar, Rumi Rongpi, Prabhat Ranjan, Aditi Kumari, Anju Singh

Abstract: Forests are vital to terrestrial ecosystems and they offer essential services for climate regulation and human welfare. However, the increasing trend in forest fires poses a significant threat to these ecosystems. This study aims to map and assess forest fire vulnerability zones within Almora district, Uttarakhand, India, using geospatial technologies and the Artificial Neural Network (ANN) technique. Twelve environmental indicators related to forest fire vulnerability, including elevation, slope, land use/land cover (LULC), Normalized Difference Vegetation Index (NDVI), Vegetation Health Index (VHI), temperature, precipitation, humidity, wind speed, Land Surface Temperature (LST), and distance from settlements and roads, were considered. The study revealed that a strip running from northern to southern Almora, including Someshwar, Dwarahat, and Ranikhet, is highly vulnerable to forest fires. This region is characterized by moderate to high elevation, a moderate to steep slope, and well-connected roads and settlements, particularly in Dwarahat and Ranikhet tehsils. The central and southern parts of Almora also exhibit good road connectivity, dense human settlements, and receive moderate to low precipitation, all of which contribute to a higher fire risk. In contrast, the eastern and western parts of Almora, comprising northern Sult, northern Bhikiyasain, and Banoli tehsils, are significantly less vulnerable to forest fires. These areas have moderate slopes, low to moderate elevation, higher precipitation in the eastern parts, and lower precipitation in the western parts, making them comparatively less prone to fire incidents. Validation through the Receiver Operating Characteristic (ROC) curve confirmed the accuracy of the model, with an 82% area under the curve.

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DOI: 10.3897/jbgs.e126690

Authors: Tabaro Kabanda

Abstract: This study examines the effects of extreme temperature events, defined explicitly as the 98th percentile temperature for heat, in Tanzania from 1981 to 2023. The study utilises percentile analysis, z-score calculations, and trend mapping to highlight the prevalence of extreme temperatures. The z-score analysis examines the occurrence of extreme temperatures and their distribution in terms of frequency and space. It identified Tanzania’s mid-eastern and north-western regions as areas with a high concentration of extreme temperatures over the previous 43 years. The study analyses the length of extreme occurrences and reveals changing patterns. In 2020, the events were shorter, while in 2021 and 2022, they became longer-lasting, and there was a notable concentration of extended anomalies near the northern coastline. In 2023, the highest temperatures ever recorded were observed, with more than half of the regions seeing prolonged periods of extreme temperatures lasting for a week and significant deviations from the norm staying for four weeks or more. This was particularly notable in the southern regions of Lindi and Mtwara. The harmonic trend analysis of temperature shows an upward temperature trend noticeably in regions such as Arusha, Kilimanjaro, Kagera, Morogoro, Simiyu, and Shinyanga and is somewhat inconspicuous in most areas.

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DOI: 10.3897/jbgs.e116695

Authors: Boyko Berov, Antoaneta Frantzova, Plamen Ivanov, Nikolai Dobrev, Miroslav Krastanov, Rosen Nankin

Abstract: As part of the Reimbursable Advisory Services on Accelerating Resilience to Disaster Risks, the World Bank worked with the Interior Ministry of Bulgaria to develop a proposal for the National Disaster Risk Profile of Bulgaria. The purpose of this document, which is the fourth technical annex to the proposal for the National Disaster Risk Profile, is to provide particular conclusions, information, and techniques that were utilised to evalu-ate the risk of landslides in Bulgaria. For the first time at the national level, landslide risk assessment procedures based on ISO/IEC 31010:2019 Risk assessment techniques are being developed and applied in Bulgaria. The five primary categories in which the results are presented are physical safety, economic security, social well-being, environmental security, and security of tangible assets and critical infrastructure. The uncertainty (confidence) parameter is utilised, and it is subdivided into the following three basic categories: low uncertainty, medium uncertainty, and high uncertainty. The produced results demonstrate consistent applicability to empirical data analysis and real-world situations.

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DOI: 10.3897/jbgs.e114156

Authors: Nadezhda Nikolova

Abstract: In the period from 1955 to 1992, uranium ore was mined and processed in the Mesta River basin around the village of Eleshnitsa, region of Razlog. The ore processing plant was built and a tailings storage facility was built next to it. In the period 2002–2006, the tailings storage was reclaimed, and in 2011–2012 the ore mines were also reclaimed. For the treatment of drainage water, a treatment plant was built in the valley of Valchoto Dere River, a left tributary of the Mesta River. The radiological monitoring carried out by the Basin Directorate “West Aegean Sea Region” reveals a generally good quality of the surface waters in terms of the content of uranium and radium (226Ra) outside the area of the former uranium mining and the tailings storage facility. In this area, in some years a high content of natural uranium was found, with concentrations from 0.54 to 67.40 mg/l on average per year. The values significantly exceed (by 1.8 to 224.6 times) the norm regulated in the regulation for radiation protection and safety from the liquidation of the consequences of uranium mining. The spread of uranium is limited to a small area shortly downstream from the sources of contamination, but the potential risk to the local ecosystem should not be neglected. Radium, in contrast to uranium, has concentrations below the permissible limits in the twelve years studied. Its content varied from 0.025 to 0.11 Bq/l on average annually. The results show that the Mesta River near the border with the Republic of Greece is not contaminated with the studied radionuclides.

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DOI: 10.3897/jbgs.e106818

Authors: Eugenia Sarafova

Abstract: Natural disasters can significantly impact children's well-being, making it essential to effectively communicate risks and potential hazards to them. This paper outlines a data-driven holistic approach to enhance resilience among children by leveraging geospatial data and maps used in the classroom. By providing easy-to-understand information about the location, extent, and intensity of potential hazards, geospatial data, and maps can help children better understand the risks and prepare for emergencies. Also, the integration of geospatial data and maps can facilitate improved comprehension of risks among children while concurrently fostering their preparedness for emergency situations. During the primary research phase, various mediums were explored for effective communication of disasters. Presentation templates were developed to present information about different types of disasters, their causes, and appropriate actions during and after such events. Various practical activities that students can engage in to learn about natural disasters and their impact were developed. These activities include exploring flooding in different areas using a virtual globe, visualizing wildfires using satellite data platforms, and studying plate tectonics using a virtual globe. Students can also work with KML datasets containing fault lines and point GIS layers of all the earthquakes in the country since the beginning of the XX century, as well as explore the country’s landslide register using various maps and layers. These activities provide students with hands-on experience in using technology and data to understand natural disasters and their impact.

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DOI: 10.3897/jbgs.e105178

Authors: Patrick Sunday Asa, Idris Shehu Umar, Ambrose Audu Zemba

Abstract: The paper presents the results of studying the spatial and seasonal atmospheric temperature characteristics of Jalingo metropolis, Nigeria, with the aim of assessing seasonal temperature variations for thermal comfort planning. Temperature data for this study was collected across the local climate zones, otherwise known as thermal climate zones (TCZ), following the TZC classification of the area. Temperature data was collected for 30 days continuously and simultaneously across the TCZ. The collection of temperature data was done in the months of April and August 2021, and January 2022 – representing the dry season, the rainy season and the Harmattan period respectively. A Thermochron Ibutton sensor by Maxim Incorporation was used to collect temperature data, while the specific series used was DS1921. An improvised automated weather station was constructed to house the sensor. The result of the study indicates that air temperature varies considerably within Jalingo metropolis, as well as throughout the seasons, thus affecting human thermal comfort in the study area, as temperature is found to correlate well with both human morbidity and mortality, especially regarding cardiovascular diseases. The paper recommends increasing ventilation and nature-based solution to reduce high temperatures through tree planting in order to improve human thermal comfort in Jalingo metropolis area.

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DOI: 10.3897/jbgs.e101301

Authors: Petar Stefanov, Hristina Prodanova, Dilyana Stefanova, Vanya Stoycheva, Gergana Petkova

Abstract: Karst is a widely spread natural phenomenon which provides essential benefits to human society, such as drinking water. The water cycle in the karst geosystems is the main factor for their formation and at the same time one of the main drivers for ecosystem services (ES) provision. The monitoring of the water cycle can provide valuable information regarding its functioning and ensure data for ES assessment. This paper aims to present an overview of the monitoring of the water cycle in the karst geosystems and the opportunities to integrate the monitoring data into the water regulation ES assessment. The monitoring of the water cycle is based on the methodological framework ProKARSTerra. It is applied in model karst geosystems, which are representative of the main karst types in Bulgaria. One of them is the Brestnitsa karst geosystem, which is the case study of this work. The monitoring ensures data for analyses of the water cycle which can be used in the assessment of water-related ecosystem services. The results from the analyses of the data requirements and availability show that some services such as water flow regulation and regulation of chemical condition of freshwaters can be easily provided through data for quantification, while for others further studies are needed. The results of the long-term integrated monitoring in Brestnitsa karst geosystem provide the foundation for important conclusions and models for the karst genesis and function under global changes and active anthropogenic pressure. Their integration into the assessment framework and mapping of ecosystem services is an essential step towards the development of models for sustainable use of natural resources in the karst areas.

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DOI: 10.3897/jbgs.e99206

Authors: Zvezdelina Marcheva, Tsvetan Kotsev, Assen Tchorbadjieff, Velimira Stoyanova

Abstract: This study aims to reveal the arsenic dynamics in groundwater of а river floodplain contaminated with mine tailings under temperate climate conditions and natural river hydrodynamics. Arsenic concentrations were monitored in the primary morphological units of the floodplain in the upper stretch of the Ogosta River in NW Bulgaria. Iron, lead-silver, and gold mining heavily affected the river valley in the second half of the 20th century. We used groundwater monitoring data from 21 piezometers for the period 2016-2020. Based on the geochemical and geomorphological conditions in the valley, the piezometers were grouped into three clusters. Regression models were developed for each cluster and representative piezometers to predict arsenic concentrations. In the active floodplain, seasonal fluctuations in arsenic concentrations followed the river and groundwater regime. In this part of the valley floor, we determined two periods of elevated arsenic concentrations during the spring and autumn/winter seasons that coincide with high river water stages. Arsenic content in the groundwater of the higher floodplain was less dependent on the water level fluctuations but followed changes in redox potential, electrical conductivity, and water temperature. The obtained results showed the elaborated models as valuable tools for studying arsenic dynamics in alluvial aquifers of contaminated river floodplains. The suggested models could be coupled with groundwater monitoring systems to monitor arsenic concentrations and identify periods of the year with levels below and above threshold values.

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DOI: 10.3897/jbgs.e97971

Authors: Kalin Seymenov

Abstract: The present article seeks to estimate water pollution with nitrogen and phosphorus and to analyse the territorial specifics in the content of those physicochemical variables along the length of a river. As a case area, the watercourse of the Osam River (Northern Bulgaria) is selected. Data concern the values of the following parameters: ammonium nitrogen (N-NH4), nitrate nitrogen (N-NO3), nitrite nitrogen (N-NO2), total nitrogen (N-tot), orthophosphates (P-PO4), and total phosphorus (P-tot), collected at four sampling points during the period 2015–2020. The assessment is based on the guidelines of Regulation 4/2012 for characterization of the surface waters. The spatial changes in the content of the examined variables are related to land use and for this purpose a map of CORINE Land Cover (2018) is prepared. The resulting information reveals that parameters with the most frequent excesses over the reference norm include N-NO3, N-tot, P-PO4, and P-tot, whose highest observed concentrations remain up to four times above the permissible limits for ”Good status” recommended in Regulation 4/2012. However, the reported values appear to be lower than those established for previous periods, which shows a positive tendency in water quality. There are also spatial features as moving from upstream to downstream – the upper part is contaminated with P-PO4 and P-tot due to the release of raw municipal and industrial effluents, while the lower section is loaded with N-NO3 and N-tot as a result of the excessive fertilization of arable lands. This work enriches past studies with new data for a recent period.

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DOI: 10.3897/jbgs.e97168

Authors: Tsvetan Kotsev, Velimira Stoyanova

Abstract: The present study aims to determine the spatial distribution of soils with lead (Pb) content above the quality thresholds in a section of the Ogosta River valley (NW Bulgaria). The study area was contaminated with mine waste from the extraction and flotation of iron, lead-silver, and gold-bearing ores in the second half of the XX century. Predictive modeling was performed with the software Maximum Entropy Species Distribution Modeling (MaxEnt), Version 3.4.4, which uses machine learning algorithms and applies the maximum entropy method. The choice of predictors of contaminated soil distribution is consistent with the main factor for Pb dispersal within the valley floor - flooding from the Ogosta River. The following six parameters explained the environmental settings related to the accumulation of contaminated floodplain sediment: vertical distance to the river channel, lateral distance to the Ogosta River, terrain slope, land cover (CORINE Land Cover, 2019), morphographic units of topography, and elevation. The results represent the average values of 10 replicates of the model. We evaluated the individual models by the value of the area under the relative operating characteristic curve (AUC) and the geographic logic of the obtained results. The AUC score for the test samples was 0.666 for the soil group 1 with Pb ≤120 mg/kg, 0.782 for group 2 with Pb (120-500] mg/kg, and 0.934 for group 3 with Pb>500 mg/kg. The most significant predictors for the models are the vertical and lateral distance to the river and the slope of the terrain. Lead concentrations tend to decrease with the distance from the main river and by increasing the elevation above the river channel due to lower inundation frequency and deposition rate of polluted river sediments. The soils with a Pb concentration below the permissible threshold of 120 mg/kg cover more than 58.42% of the valley floor of the studied section, and lands with Pb content above the intervention value of 500 mg/kg occupy nearly 10.82% of the investigated territory. The selected predictors describe the distribution of highly contaminated soils well and define the range of soils with lower Pb content worse. Combining clean and contaminated soil samples into one group is considered the main reason for the poor performance of MaxEnt for soils with Pb ≤120 mg/kg. However, the results prove the model's ability to predict the spatial distribution of not only biological species but also the dispersal of hazardous substances in soil.

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DOI: 10.3897/jbgs.e87743

Authors: Julia Cardwell

Abstract: This review essay considers the development of the field of disaster studies and specifically, examines the myriad ways in which the role of the human has shifted during this development. The essay focuses on four major periods of development within disaster studies, including: the hazard-risk paradigm, the bounded rationality paradigm, the concept of social vulnerability and critiques of social vulnerability.

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DOI: 10.3897/jbgs.e85567

Authors: Eugenia Sarafova

Abstract: Bulgaria, located in the Balkans, is subject to a number of natural disasters including floods, earthquakes, landslides, forest fires, strong winds, droughts, heavy snowfall and extreme temperatures. In addition to natural disasters, the country is at risk for man-made events like industrial and nuclear accidents, transport accidents, and infectious diseases. Disaster planning and prevention is a complex process that requires multiple data sources. At the same time, spatial data are often not available on-line, so the country's GIS specialists may find existing spatial data to be a great challenge. This research analyses the application of the health sector data provided by the Copernicus Climate Change Service to support the development, implementation and evaluation of disaster risk management plans in Bulgaria. The climate data visualizations provided by the service enable scientists and other stakeholders to view climate change data in a format that is simple to use, visually understandable, and usable for decision makers in government, business, and non-governmental organizations. Many of these visualizations are interdisciplinary and may be critical for gathering and applying information needed to develop disaster risk reduction plans.

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DOI: 10.3897/jbgs.2020.43.11

Authors: Stefan Petrov, Ivan Drenovski

Abstract: Air as a component of the natural environment is subjected to constant pollution caused by anthropogenic impact. Air can be considered polluted when the concentration of pollutants is higher than in a normal environment and this leads to a deterioration of the ambient air quality. This problem is also relevant for the region of Vidin and the town of Vidin in particular. Every year the city holds one of the highest ranks for the most polluted air in Bulgaria, even though the city has not been a place with a developed industrial activity that can be linked to air pollution for years. This report aims at identifying the causes of pollution and whether the measures taken in the “Programme for reducing the levels of PM10 and reaching the established norms of their content in the air in the region of Vidin for the period 2015-2020” are effectively implemented.

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DOI: 10.3897/jbgs.2020.43.4

Authors: Rumen Penin, Dimitar Zhelev

Abstract: The article depicts the biogeochemical properties of the landscapes in the area of the Ada Tepe gold mine (Krumovitsa River Catchment, Eastern Rhodopes) before its launching as an active ore-extraction site. The research is conducted by examination of heavy metals content in particular samples of representative native plant species in the local landscapes. The conducted research surveyed the content of 7 chemical elements (heavy metals) in the tissues of native plants from the landscapes in the Eastern Rhodopes. These microelements are generally prioritized in terms of environmental protection. The interpretation of the obtain results was made by applying the Coefficient of Biological Absorption (Ax). It is as a result of the proportions between the chemical content in the plant tissue (lx) and the chemical content in the local soil/bedrock (nx). By default, this coefficient represents the absorption (and accumulation) intensity of chemical elements in the plants.

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DOI: 10.3897/jbgs.2020.42.17

Authors: Hristina Prodanova, Mariya Petrova

Abstract: The paper is devoted to Assoc. Prof. PhD Nikola Todorov’s life and professional contributions (1955- 2018) – a prominent Bulgarian geographer, unreservedly dedicated to the science and field researches, who left а rich creative heritage in the field of Physical Geography and Landscape Science. He was the leading author in the development of the second landscape classification system of Bulgaria and in the creation of а landscape map of Bulgaria on a 1:500 000 scale, which is one of his main contributions. An important contribution in his research activity is the developed classification system of anthropogenic changes and landscape disturbances in Bulgaria, which is applicable to the whole country and encompassing the enormous variety of natural-territorial complexes and their changes. He was a scientific mentor for 26 master students and 4 PhD students. Assoc. Prof. Nikola Todorov was a Lecturer who inspired generations of students and many young researchers with his erudition and oratory skills.

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DOI: 10.3897/jbgs.2019.40.4

Authors: Zornitza Cholakova

Abstract: The essence of karst landscapes is considered. The content of Cu, Zn, Pb, Cr, Ni, Co, Mn, Cd trace elements in the soils of karst landscapes in the Ponor, Vrachanska and Vlahina Mountains, as well as those in The Western and Middle Fore-Balkan (Arbanassi Plateau), Bulgaria, is analyzed using landscape-geochemical, laboratory, mathematical and statistical methods. The obtained results are compared with the average content in the carbonate rocks of Bulgaria (Kuikin et al., 2001), the rendzina (Rendzic Leptosols, LPk, FAO) and the gray forest soils (Haplic Luvisols, LVh, FAO) in the country (according to Atanassov et al., 2002). The importance of the carbonate rock substrate on the concentration of the chemical elements - heavy metals in the studied zonal and azonal soil types was determined.

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DOI: 10.3897/jbgs.2018.39.7

Authors: Rumen Penin, Dimitar Zhelev

Abstract: The mud volcanoes in the valley of the Sazliyka River and its tributaries are a geological phenomenon that has attracted scientific attention for decades. They are a specific element for the local lowland landscapes. This study focuses on the content of heavy metals in mud volcanoes. The total content of the elements: copper (Cu), zinc (Zn), lead (Pb), manganese (Mn), nickel (Ni), cobalt (Co) and chromium (Cr) in mg/kg (ppm) has been identified. The obtained contents have been analyzed by the clarke of concentration indicator (KK) - the ratio between the content of a given element in a given natural component (soil horizon, vegetation, surface water, etc.) - Ci, and a clarke of the same element in the lithosphere - K: The researched geochemical nature of the local litho-geochemical and soil-geochemical conditions may have been influenced by the geochemical specifics of the materials entering the earth’s surface upon activation of mud volcanoes in the area of study. They might have an impact on the geochemical structure of the bottom sediments in the local river currents and hence the influence on the main river artery Sazliyka River. The obtained results give to some extent information about the geochemical nature of this rare phenomenon for our country.

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