Storms are one of the phenomena determining the short-term evolution of coasts by influencing the... more Storms are one of the phenomena determining the short-term evolution of coasts by influencing the erosion and accretion patterns of the beaches. Some severe storms could cause loss of beach sediments, partial or complete destruction of coastal structures and even threaten human life and occupation. Bearing this in mind, it is essential to comprehend, which storms could evoke transient, although in some instances, significant morphological changes, and which could be considered as hazardous and result in catastrophic damage. This issue implies establishment of a set of critical thresholds for storm impact on coastal morphology. The paper presents a regional scale analysis of the near-shore morphological response of five beaches to storms of varying intensity. The analysis is accomplished by coupling of offshore wave and cross-shore profile data obtained for the Bulgarian Black sea coast. The historical storm pattern is reconstructed through hindcast using a coupled wave model system, while resulting morphological changes, such as shoreline alteration and cross-shore profile evolution, are estimated by analysis of long-term series of coastal measurements performed in 1970-1977 and 2008-2010. The storm impact thresholds are set in terms of integral wave energy taking into account both storm pattern and duration. It was found that the morphological response to storm impact is site specific and single-value thresholds are difficult to be established even at regional scale. Nevertheless, a range of critical storm thresholds is proposed. Thus, storms with integral wave energy varying within threshold values 0.4-0.7 × 10 6 J m −2 are regarded as capable of significant morphological changes, while less energetic events are supposed to influence predominately the seasonal beach dynamics. Furthermore, storms with integral wave energy higher than 0.7 × 10 6 J m −2 represent potentially destructive events that can change irreversibly the beach pattern or damage impact.
Winds over the ocean play an important role in meteorology, oceanography and climatology. They af... more Winds over the ocean play an important role in meteorology, oceanography and climatology. They affect air-sea variations in heat, humidity, gases and particles, regulating the crucial relation between the ocean and the atmosphere that establishes and supports the climate on regional and global scale. Therefore, the knowledge of wind fields over the oceans is essential for global weather forecast purposes.
Proceedings of ... Conference on Coastal Engineering, Jun 23, 2017
Storms and related disasters are phenomena producing coastal hazards and endangering human life a... more Storms and related disasters are phenomena producing coastal hazards and endangering human life and occupation. The study evaluates coastal receptors' exposure and their vulnerability to storm-induced flooding hazard along Varna regional coast in Western Black Sea, Bulgaria. The assessment is performed employing the Coastal Risk Assessment Framework (CRAF) developed within EU FP7 RISC-KIT project. It constitutes a screening process that allows determination of susceptible alongshore sectors (hotspots) by assessing relevant hazard intensities, hazard extents and potential receptors' exposure vulnerability within them by means of coastal indices approach. The ultimate goal is to evaluate potential risk posed by flooding in support to coastal managers, decision and policy makers. Assessment of coastal receptors' exposure vulnerability is done by exposure indicators approach, using hazard intensities and flooding extents relevant to return period of 100 years. The approach consists of combining several indicators into a single index, thereby allowing a rapid comparison of coastal sectors. Five types of receptors are considered to formulate the relevant exposure indicators: Land Use, Population, Transport, Utilities and Business, which subsequently are combined into an Overall Exposure Indicator to evaluate potential direct and indirect impacts. Results show that the most vulnerable to coastal flooding in terms of exposure are coastal sectors located within Varna Bay, comprising port and industry facilities with regional, national and international significance.
This paper examines the vulnerability to flooding and erosion of four open beach study sites in E... more This paper examines the vulnerability to flooding and erosion of four open beach study sites in Europe. A framework for the quantitative estimation of present and future coastal flood and erosion risks is established using methods, data and tools from across a range of disciplines, including topographic and bathymetric data, climate data from observation, hindcast and model projections, statistical modelling of current and future climates and integrated risk analysis tools. Uncertainties in the estimation of future coastal system dynamics are considered, as are the consequences for the inland systems. Different implementations of the framework are applied to the study sites which have different wave, tidal and surge climate conditions. These sites are: Santander, Spain-the Atlantic Ocean; Bellocchio, Italy-the Adriatic Sea; Varna, Bulgaria-the Black Sea; and the Teign Estuary, UK-the northern Atlantic Ocean. The complexity of each system is first simplified by subdivision into coastal "impact units" defined by homogeneity in the local key forcing parameters: wave, wind, tide, river discharge, runoff , etc. This reduces the simulation to that of a number of simpler linear problems which are treated by applying the first two components of the Source-Pathway-Receptor-Consequence (S-P-R-C) approach. The case studies reveal the flexibility of this approach, which is found useful for the rapid assessment of the risks of flooding and erosion for a range of scenarios and the likely effectiveness of flood defences.
The study aims to assess in probabilistic terms the magnitude of storminduced flooding hazard and... more The study aims to assess in probabilistic terms the magnitude of storminduced flooding hazard and vulnerability along Burgas regional coast (Bulgaria, western Black Sea) and to identify susceptible coastal sectors (hotspots). It employs the Coastal Risk Assessment Framework-a screening process that allows estimation of hazar'1d intensities, extents and potential receptors' exposure vulnerability within predefined sectors. Total water level, consisting of maximum wave run-up estimated using empirical models relevant for sandy beaches, artificial or rocky coastal slopes and storm surge level, is considered for calculation AQ1 of coastal flooding hazard. Furthermore, hazard extents (flooded areas) are determined by two approaches to form the hazard indicator, while land use, social vulnerability, transport systems, utilities and business settings are considered as exposure indicators. Finally, the potential risk is assessed by combining the hazard and exposure indicators into a single index, thereby allowing rapid comparison of coastal sectors' vulnerability. The study found that the main concentration of hotspots is in the town of Pomorie and its surroundings, while other candidates are scattered across the innermost Burgas bay.
The study aims to assess in probabilistic terms the magnitude of storminduced flooding hazard and... more The study aims to assess in probabilistic terms the magnitude of storminduced flooding hazard and vulnerability along Burgas regional coast (Bulgaria, western Black Sea) and to identify susceptible coastal sectors (hotspots). It employs the Coastal Risk Assessment Framework-a screening process that allows estimation of hazar'1d intensities, extents and potential receptors' exposure vulnerability within predefined sectors. Total water level, consisting of maximum wave run-up estimated using empirical models relevant for sandy beaches, artificial or rocky coastal slopes and storm surge level, is considered for calculation AQ1 of coastal flooding hazard. Furthermore, hazard extents (flooded areas) are determined by two approaches to form the hazard indicator, while land use, social vulnerability, transport systems, utilities and business settings are considered as exposure indicators. Finally, the potential risk is assessed by combining the hazard and exposure indicators into a single index, thereby allowing rapid comparison of coastal sectors' vulnerability. The study found that the main concentration of hotspots is in the town of Pomorie and its surroundings, while other candidates are scattered across the innermost Burgas bay.
The study examines the relationships between the beach-face slopes and sediment sizes for several... more The study examines the relationships between the beach-face slopes and sediment sizes for several coastal stretches located in Burgas Bay using limited field data, and explores the applicability of a number of previously developed formulations for local geomorphic, lithologic and wave conditions. Knowledge on the clear dependence between considered parameters is of particular importance for many engineering applications such as calculation of maximum run-up, shoreline changes, beach berm erosion potential, and assessment of coastal flood and erosion hazards. The results have shown that none of the considered empirical relationships can be used straightforwardly, although some of them might be considered for future analysis. Hence, it is necessary to enrich the database with wider ranges of beachface slopes, sediment sizes coming from areas with different wave exposure and morphodynamics state in order to elaborate a reliable native relationship suitable for local to regional specifi...
In this paper we present the first results of beach profile hindcasting with XBeach using recentl... more In this paper we present the first results of beach profile hindcasting with XBeach using recently measured coastal data acquired under storm conditions at eight European sites, including a comparison to model results obtained with off-the-shelf models. The results show consistently that the XBeach has skill in predicting the coastal profile, albeit that in most cases the erosion around the mean water line is overpredicted and the depositions at the lower beach face are overpredicted. The causes for this model effect are under active investigation but not resolved yet. Likely candidates are the modeling of onshore (asymmetry) transports which reduces the offshore transports due to undertow (currents) or the modeling of sediment motion in the swash zone.
This chapter presents the GIS-based hazard maps that are set-up for the project area in Bulgaria.... more This chapter presents the GIS-based hazard maps that are set-up for the project area in Bulgaria. The maps have been compiled by Professor Fridtjof Nansen Institute of Oceanology - Bulgarian Academy of Sciences. The text herein represents an excerpt from Deliverable 5.1 GIS-Based Hazard Maps, WP 5: Early Warning System, project "Morphological Impacts and Coastal Risks Induced by Extreme Storm Events" (Acronym: MICORE), funded under the EU's 7FP, GA No 2002798.
The study examines the relationships between the beach-face slopes and sediment sizes for several... more The study examines the relationships between the beach-face slopes and sediment sizes for several coastal stretches located in Burgas Bay using limited field data, and explores the applicability of a number of previously developed formulations for local geomorphic, lithologic and wave conditions. Knowledge on the clear dependence between considered parameters is of particular importance for many engineering applications such as calculation of maximum run-up, shoreline changes, beach berm erosion potential, and assessment of coastal flood and erosion hazards. The results have shown that none of the considered empirical relationships can be used straightforwardly, although some of them might be considered for future analysis. Hence, it is necessary to enrich the database with wider ranges of beachface slopes, sediment sizes coming from areas with different wave exposure and morphodynamics state in order to elaborate a reliable native relationship suitable for local to regional specifi...
The study investigates cross-shore outer sand bar dynamics in an open-coast non-tidal beach at th... more The study investigates cross-shore outer sand bar dynamics in an open-coast non-tidal beach at the Bulgarian Black Sea due to wave climate. On seasonal to short-term (1–2 years) time scale, monthly field measurements of the outer bar profiles were related to respective modeled nearshore wave data. Hereby, seaward-shoreward bar migration was examined depending on the wave forcing, wave non-linearity, wave transformation scenarios, storms and direction of wave incidence. Analysis revealed that intra-annually highly non-linear waves were responsible for outer bar displacement, while the direction of migration depended on wave period, duration of conditions with wave steepness >0.04, angle of approach and total duration of storms. Short-term bar evolution was mainly governed by wave height and storms’ parameters as the angle of approach and duration. The correlation between the outer bar location and wave height annual variations initiated the first for the explored Black Sea region ...
Palgrave Studies in Climate Resilient Societies, 2020
The study explores the cultural, socio-ecological, and institutional factors responsible for the ... more The study explores the cultural, socio-ecological, and institutional factors responsible for the present ways of handling natural hazards and coping with climate change challenges in Varna, a coastal city situated on the western Black Sea, Bulgaria. Diving into cultural perceptions of risk, governmental, social, and economic circumstances triggered after the political changes in 1989, and present state of development and implementation of disaster risk reduction, coastal management and climate adaptation legislation framework helped to reveal the main reasons behind the relatively low adaptive capacity and climate resilience of Varna.
European coasts suffer significantly from hazards caused by low-probability and high-impact hydro... more European coasts suffer significantly from hazards caused by low-probability and high-impact hydro-meteorological events. The aim of the study is to assess in probabilistic terms the magnitude of storm‐induced flooding and erosion hazards along Varna regional coast (Bulgaria, western Black Sea). The study is performed employing the Coastal Risk Assessment Framework (CRAF) developed within EU FP7 RISC-KIT project. It constitutes a screening process that allows estimation of relevant hazard intensities and extents within predefined sectors. Since total water level was the chief property considered for determination of coastal flooding hazard, the accurate calculation of maximum wave induced run-up is of utter importance. Therefore, a central part of the study is testing the applicability and validation of three empirical models – from which the Holman model was preferred to be applied on sandy beaches, as well as EurOtop formulation for artificial or rocky slopes. As for erosion hazard...
The coastal morphology is highly sensitive to storm-induced impacts. All components of the coasta... more The coastal morphology is highly sensitive to storm-induced impacts. All components of the coastal system-aerial beach and dunes, submerged beach, nearshore barsundergo changes during an extreme storm event (Sallenger et al., 1985; Morton and Sallenger, ...
Comptes rendus de l'Académie bulgare des sciences: sciences mathématiques et naturelles
Recent natural disasters in coastal areas have highlighted the devastating effects that hazards o... more Recent natural disasters in coastal areas have highlighted the devastating effects that hazards of marine origin can cause. This problem is addressed by set up of an on-line Early Warning System (EWS) for reliable prediction of morphological impacts due to marine storm events in support to civil protection strategies. The system involves a train of hydro- and morphodynamic models, predicting the storm impact on the beach, and a set of indicators, which convert model results in terms of key physical parameters to adequate warnings and series of actions to be undertaken by responsible authorities. The prototype consists of five interconnected key modules and lays the foundation for a greater national scale roll-out by adopting the following principles: using a generic structure adaptable to a range of different coastal environments; using free and open-source software; and tailoring the functionality of the EWS to the needs of end-users.
The study presents evaluation and comparative analysis of storm induced flooding impacts on diffe... more The study presents evaluation and comparative analysis of storm induced flooding impacts on different coastal receptors at a scale of Varna region using INtegrated DisRuption Assessment (INDRA) model. The model was developed within the FP7 RISC-KIT project, as a part of Coastal Risk Assessment Framework (CRAF) consisting of two phases. CRAF Phase 1 is a screening process that evaluates coastal risk at a regional scale by means of coastal indices approach, which helps to identify potentially vulnerable coastal sectors: hot spots (HS). CRAF Phase 2 has the objective to assess and rank identified hotspots by detailed risk analysis done by jointly performing a hazard assessment and an impact evaluation on different categories (population, businesses, ecosystems, transport and utilities) using INDRA model at a regional level. Basically, the model assess the shock of events by estimating the impact on directly exposed to flooding hazard receptors of different vulnerability, as well as the potential ripple effects during an event in order to assess the "indirect" impacts, which occur outside the hazard area and/or continue after the event for all considered categories. The potential impacts are expressed in terms of uniform "Impact Indicators", which independently score the indirect impacts of these categories assessing disruption and recovery of the receptors. The ultimate hotspot ranking is obtained through the use of a Multi Criteria analysis (MCA) incorporated in the model, considering preferences of stakeholders. The case study area-Varna regional coast-is located on the western Black Sea, Bulgaria. The coastline, with a length of about 70 km, stretches from cape Ekrene to cape St. Atanas and includes Varna Bay. After application of CRAF Phase 1 three hotspots were selected for further analysis: Kabakum beach (HS1), Varna Central beach plus Port wall (HS2) and Artificial Island (HS3). For first two hotspots beaches and associated infrastructure are the assets that attract holiday-makers and tourists in summer season. For HS3 the exposed area is occupied by storage premises for industrial goods and oil/fuel tanks. Flooding hazard was assessed through coupled use of XBeach 1D and LISFLOOD 2D inundation models at the selected hotspots. The "response" approach was adopted as 75 extreme storm events were simulated to obtain storm maxima series of overtopping discharges, flood depth, depth-velocity and berm retreat. The selected return periods within the extreme value analysis were 20, 50 and 100 years. For impact evaluation by INDRA model the categories "Population" and "Business" were considered. Impacts on Population were addressed by 3 impact indicators: "Risk to Life", "Household Displacement Time" and "Household Financial Recovery", while for Business category only by "Business Financial Recovery". Hotspots ranking was done using MCA by weighting of the evaluated indicators: focused on Risk to Life (F1) and on Business Financial Recovery (F2). MCA scoring focused on Household displacement/recovery was not evaluated because modelling results revealed quite a low number of flooded household receptors. Results show that for both F1 and F2 and for all considered return periods HS2 has the highest scores, which makes it a final hotspot.
In this paper we present the first results of beach profile hindcasting with XBeach using recentl... more In this paper we present the first results of beach profile hindcasting with XBeach using recently measured coastal data acquired under storm conditions at eight European sites, including a comparison to model results obtained with off-theshelf models. The results show consistently that the XBeach has skill in predicting the coastal profile, albeit that in most cases the erosion around the mean water line is overpredicted and the depositions at the lower beach face are overpredicted. The causes for this model effect are under active investigation but not resolved yet. Likely candidates are the modeling of onshore (asymmetry) transports which reduces the offshore transports due to undertow (currents) or the modeling of sediment motion in the swash zone.
Storms are one of the phenomena determining the short-term evolution of coasts by influencing the... more Storms are one of the phenomena determining the short-term evolution of coasts by influencing the erosion and accretion patterns of the beaches. Some severe storms could cause loss of beach sediments, partial or complete destruction of coastal structures and even threaten human life and occupation. Bearing this in mind, it is essential to comprehend, which storms could evoke transient, although in some instances, significant morphological changes, and which could be considered as hazardous and result in catastrophic damage. This issue implies establishment of a set of critical thresholds for storm impact on coastal morphology. The paper presents a regional scale analysis of the near-shore morphological response of five beaches to storms of varying intensity. The analysis is accomplished by coupling of offshore wave and cross-shore profile data obtained for the Bulgarian Black sea coast. The historical storm pattern is reconstructed through hindcast using a coupled wave model system, while resulting morphological changes, such as shoreline alteration and cross-shore profile evolution, are estimated by analysis of long-term series of coastal measurements performed in 1970-1977 and 2008-2010. The storm impact thresholds are set in terms of integral wave energy taking into account both storm pattern and duration. It was found that the morphological response to storm impact is site specific and single-value thresholds are difficult to be established even at regional scale. Nevertheless, a range of critical storm thresholds is proposed. Thus, storms with integral wave energy varying within threshold values 0.4-0.7 × 10 6 J m −2 are regarded as capable of significant morphological changes, while less energetic events are supposed to influence predominately the seasonal beach dynamics. Furthermore, storms with integral wave energy higher than 0.7 × 10 6 J m −2 represent potentially destructive events that can change irreversibly the beach pattern or damage impact.
Winds over the ocean play an important role in meteorology, oceanography and climatology. They af... more Winds over the ocean play an important role in meteorology, oceanography and climatology. They affect air-sea variations in heat, humidity, gases and particles, regulating the crucial relation between the ocean and the atmosphere that establishes and supports the climate on regional and global scale. Therefore, the knowledge of wind fields over the oceans is essential for global weather forecast purposes.
Proceedings of ... Conference on Coastal Engineering, Jun 23, 2017
Storms and related disasters are phenomena producing coastal hazards and endangering human life a... more Storms and related disasters are phenomena producing coastal hazards and endangering human life and occupation. The study evaluates coastal receptors' exposure and their vulnerability to storm-induced flooding hazard along Varna regional coast in Western Black Sea, Bulgaria. The assessment is performed employing the Coastal Risk Assessment Framework (CRAF) developed within EU FP7 RISC-KIT project. It constitutes a screening process that allows determination of susceptible alongshore sectors (hotspots) by assessing relevant hazard intensities, hazard extents and potential receptors' exposure vulnerability within them by means of coastal indices approach. The ultimate goal is to evaluate potential risk posed by flooding in support to coastal managers, decision and policy makers. Assessment of coastal receptors' exposure vulnerability is done by exposure indicators approach, using hazard intensities and flooding extents relevant to return period of 100 years. The approach consists of combining several indicators into a single index, thereby allowing a rapid comparison of coastal sectors. Five types of receptors are considered to formulate the relevant exposure indicators: Land Use, Population, Transport, Utilities and Business, which subsequently are combined into an Overall Exposure Indicator to evaluate potential direct and indirect impacts. Results show that the most vulnerable to coastal flooding in terms of exposure are coastal sectors located within Varna Bay, comprising port and industry facilities with regional, national and international significance.
This paper examines the vulnerability to flooding and erosion of four open beach study sites in E... more This paper examines the vulnerability to flooding and erosion of four open beach study sites in Europe. A framework for the quantitative estimation of present and future coastal flood and erosion risks is established using methods, data and tools from across a range of disciplines, including topographic and bathymetric data, climate data from observation, hindcast and model projections, statistical modelling of current and future climates and integrated risk analysis tools. Uncertainties in the estimation of future coastal system dynamics are considered, as are the consequences for the inland systems. Different implementations of the framework are applied to the study sites which have different wave, tidal and surge climate conditions. These sites are: Santander, Spain-the Atlantic Ocean; Bellocchio, Italy-the Adriatic Sea; Varna, Bulgaria-the Black Sea; and the Teign Estuary, UK-the northern Atlantic Ocean. The complexity of each system is first simplified by subdivision into coastal "impact units" defined by homogeneity in the local key forcing parameters: wave, wind, tide, river discharge, runoff , etc. This reduces the simulation to that of a number of simpler linear problems which are treated by applying the first two components of the Source-Pathway-Receptor-Consequence (S-P-R-C) approach. The case studies reveal the flexibility of this approach, which is found useful for the rapid assessment of the risks of flooding and erosion for a range of scenarios and the likely effectiveness of flood defences.
The study aims to assess in probabilistic terms the magnitude of storminduced flooding hazard and... more The study aims to assess in probabilistic terms the magnitude of storminduced flooding hazard and vulnerability along Burgas regional coast (Bulgaria, western Black Sea) and to identify susceptible coastal sectors (hotspots). It employs the Coastal Risk Assessment Framework-a screening process that allows estimation of hazar'1d intensities, extents and potential receptors' exposure vulnerability within predefined sectors. Total water level, consisting of maximum wave run-up estimated using empirical models relevant for sandy beaches, artificial or rocky coastal slopes and storm surge level, is considered for calculation AQ1 of coastal flooding hazard. Furthermore, hazard extents (flooded areas) are determined by two approaches to form the hazard indicator, while land use, social vulnerability, transport systems, utilities and business settings are considered as exposure indicators. Finally, the potential risk is assessed by combining the hazard and exposure indicators into a single index, thereby allowing rapid comparison of coastal sectors' vulnerability. The study found that the main concentration of hotspots is in the town of Pomorie and its surroundings, while other candidates are scattered across the innermost Burgas bay.
The study aims to assess in probabilistic terms the magnitude of storminduced flooding hazard and... more The study aims to assess in probabilistic terms the magnitude of storminduced flooding hazard and vulnerability along Burgas regional coast (Bulgaria, western Black Sea) and to identify susceptible coastal sectors (hotspots). It employs the Coastal Risk Assessment Framework-a screening process that allows estimation of hazar'1d intensities, extents and potential receptors' exposure vulnerability within predefined sectors. Total water level, consisting of maximum wave run-up estimated using empirical models relevant for sandy beaches, artificial or rocky coastal slopes and storm surge level, is considered for calculation AQ1 of coastal flooding hazard. Furthermore, hazard extents (flooded areas) are determined by two approaches to form the hazard indicator, while land use, social vulnerability, transport systems, utilities and business settings are considered as exposure indicators. Finally, the potential risk is assessed by combining the hazard and exposure indicators into a single index, thereby allowing rapid comparison of coastal sectors' vulnerability. The study found that the main concentration of hotspots is in the town of Pomorie and its surroundings, while other candidates are scattered across the innermost Burgas bay.
The study examines the relationships between the beach-face slopes and sediment sizes for several... more The study examines the relationships between the beach-face slopes and sediment sizes for several coastal stretches located in Burgas Bay using limited field data, and explores the applicability of a number of previously developed formulations for local geomorphic, lithologic and wave conditions. Knowledge on the clear dependence between considered parameters is of particular importance for many engineering applications such as calculation of maximum run-up, shoreline changes, beach berm erosion potential, and assessment of coastal flood and erosion hazards. The results have shown that none of the considered empirical relationships can be used straightforwardly, although some of them might be considered for future analysis. Hence, it is necessary to enrich the database with wider ranges of beachface slopes, sediment sizes coming from areas with different wave exposure and morphodynamics state in order to elaborate a reliable native relationship suitable for local to regional specifi...
In this paper we present the first results of beach profile hindcasting with XBeach using recentl... more In this paper we present the first results of beach profile hindcasting with XBeach using recently measured coastal data acquired under storm conditions at eight European sites, including a comparison to model results obtained with off-the-shelf models. The results show consistently that the XBeach has skill in predicting the coastal profile, albeit that in most cases the erosion around the mean water line is overpredicted and the depositions at the lower beach face are overpredicted. The causes for this model effect are under active investigation but not resolved yet. Likely candidates are the modeling of onshore (asymmetry) transports which reduces the offshore transports due to undertow (currents) or the modeling of sediment motion in the swash zone.
This chapter presents the GIS-based hazard maps that are set-up for the project area in Bulgaria.... more This chapter presents the GIS-based hazard maps that are set-up for the project area in Bulgaria. The maps have been compiled by Professor Fridtjof Nansen Institute of Oceanology - Bulgarian Academy of Sciences. The text herein represents an excerpt from Deliverable 5.1 GIS-Based Hazard Maps, WP 5: Early Warning System, project "Morphological Impacts and Coastal Risks Induced by Extreme Storm Events" (Acronym: MICORE), funded under the EU's 7FP, GA No 2002798.
The study examines the relationships between the beach-face slopes and sediment sizes for several... more The study examines the relationships between the beach-face slopes and sediment sizes for several coastal stretches located in Burgas Bay using limited field data, and explores the applicability of a number of previously developed formulations for local geomorphic, lithologic and wave conditions. Knowledge on the clear dependence between considered parameters is of particular importance for many engineering applications such as calculation of maximum run-up, shoreline changes, beach berm erosion potential, and assessment of coastal flood and erosion hazards. The results have shown that none of the considered empirical relationships can be used straightforwardly, although some of them might be considered for future analysis. Hence, it is necessary to enrich the database with wider ranges of beachface slopes, sediment sizes coming from areas with different wave exposure and morphodynamics state in order to elaborate a reliable native relationship suitable for local to regional specifi...
The study investigates cross-shore outer sand bar dynamics in an open-coast non-tidal beach at th... more The study investigates cross-shore outer sand bar dynamics in an open-coast non-tidal beach at the Bulgarian Black Sea due to wave climate. On seasonal to short-term (1–2 years) time scale, monthly field measurements of the outer bar profiles were related to respective modeled nearshore wave data. Hereby, seaward-shoreward bar migration was examined depending on the wave forcing, wave non-linearity, wave transformation scenarios, storms and direction of wave incidence. Analysis revealed that intra-annually highly non-linear waves were responsible for outer bar displacement, while the direction of migration depended on wave period, duration of conditions with wave steepness >0.04, angle of approach and total duration of storms. Short-term bar evolution was mainly governed by wave height and storms’ parameters as the angle of approach and duration. The correlation between the outer bar location and wave height annual variations initiated the first for the explored Black Sea region ...
Palgrave Studies in Climate Resilient Societies, 2020
The study explores the cultural, socio-ecological, and institutional factors responsible for the ... more The study explores the cultural, socio-ecological, and institutional factors responsible for the present ways of handling natural hazards and coping with climate change challenges in Varna, a coastal city situated on the western Black Sea, Bulgaria. Diving into cultural perceptions of risk, governmental, social, and economic circumstances triggered after the political changes in 1989, and present state of development and implementation of disaster risk reduction, coastal management and climate adaptation legislation framework helped to reveal the main reasons behind the relatively low adaptive capacity and climate resilience of Varna.
European coasts suffer significantly from hazards caused by low-probability and high-impact hydro... more European coasts suffer significantly from hazards caused by low-probability and high-impact hydro-meteorological events. The aim of the study is to assess in probabilistic terms the magnitude of storm‐induced flooding and erosion hazards along Varna regional coast (Bulgaria, western Black Sea). The study is performed employing the Coastal Risk Assessment Framework (CRAF) developed within EU FP7 RISC-KIT project. It constitutes a screening process that allows estimation of relevant hazard intensities and extents within predefined sectors. Since total water level was the chief property considered for determination of coastal flooding hazard, the accurate calculation of maximum wave induced run-up is of utter importance. Therefore, a central part of the study is testing the applicability and validation of three empirical models – from which the Holman model was preferred to be applied on sandy beaches, as well as EurOtop formulation for artificial or rocky slopes. As for erosion hazard...
The coastal morphology is highly sensitive to storm-induced impacts. All components of the coasta... more The coastal morphology is highly sensitive to storm-induced impacts. All components of the coastal system-aerial beach and dunes, submerged beach, nearshore barsundergo changes during an extreme storm event (Sallenger et al., 1985; Morton and Sallenger, ...
Comptes rendus de l'Académie bulgare des sciences: sciences mathématiques et naturelles
Recent natural disasters in coastal areas have highlighted the devastating effects that hazards o... more Recent natural disasters in coastal areas have highlighted the devastating effects that hazards of marine origin can cause. This problem is addressed by set up of an on-line Early Warning System (EWS) for reliable prediction of morphological impacts due to marine storm events in support to civil protection strategies. The system involves a train of hydro- and morphodynamic models, predicting the storm impact on the beach, and a set of indicators, which convert model results in terms of key physical parameters to adequate warnings and series of actions to be undertaken by responsible authorities. The prototype consists of five interconnected key modules and lays the foundation for a greater national scale roll-out by adopting the following principles: using a generic structure adaptable to a range of different coastal environments; using free and open-source software; and tailoring the functionality of the EWS to the needs of end-users.
The study presents evaluation and comparative analysis of storm induced flooding impacts on diffe... more The study presents evaluation and comparative analysis of storm induced flooding impacts on different coastal receptors at a scale of Varna region using INtegrated DisRuption Assessment (INDRA) model. The model was developed within the FP7 RISC-KIT project, as a part of Coastal Risk Assessment Framework (CRAF) consisting of two phases. CRAF Phase 1 is a screening process that evaluates coastal risk at a regional scale by means of coastal indices approach, which helps to identify potentially vulnerable coastal sectors: hot spots (HS). CRAF Phase 2 has the objective to assess and rank identified hotspots by detailed risk analysis done by jointly performing a hazard assessment and an impact evaluation on different categories (population, businesses, ecosystems, transport and utilities) using INDRA model at a regional level. Basically, the model assess the shock of events by estimating the impact on directly exposed to flooding hazard receptors of different vulnerability, as well as the potential ripple effects during an event in order to assess the "indirect" impacts, which occur outside the hazard area and/or continue after the event for all considered categories. The potential impacts are expressed in terms of uniform "Impact Indicators", which independently score the indirect impacts of these categories assessing disruption and recovery of the receptors. The ultimate hotspot ranking is obtained through the use of a Multi Criteria analysis (MCA) incorporated in the model, considering preferences of stakeholders. The case study area-Varna regional coast-is located on the western Black Sea, Bulgaria. The coastline, with a length of about 70 km, stretches from cape Ekrene to cape St. Atanas and includes Varna Bay. After application of CRAF Phase 1 three hotspots were selected for further analysis: Kabakum beach (HS1), Varna Central beach plus Port wall (HS2) and Artificial Island (HS3). For first two hotspots beaches and associated infrastructure are the assets that attract holiday-makers and tourists in summer season. For HS3 the exposed area is occupied by storage premises for industrial goods and oil/fuel tanks. Flooding hazard was assessed through coupled use of XBeach 1D and LISFLOOD 2D inundation models at the selected hotspots. The "response" approach was adopted as 75 extreme storm events were simulated to obtain storm maxima series of overtopping discharges, flood depth, depth-velocity and berm retreat. The selected return periods within the extreme value analysis were 20, 50 and 100 years. For impact evaluation by INDRA model the categories "Population" and "Business" were considered. Impacts on Population were addressed by 3 impact indicators: "Risk to Life", "Household Displacement Time" and "Household Financial Recovery", while for Business category only by "Business Financial Recovery". Hotspots ranking was done using MCA by weighting of the evaluated indicators: focused on Risk to Life (F1) and on Business Financial Recovery (F2). MCA scoring focused on Household displacement/recovery was not evaluated because modelling results revealed quite a low number of flooded household receptors. Results show that for both F1 and F2 and for all considered return periods HS2 has the highest scores, which makes it a final hotspot.
In this paper we present the first results of beach profile hindcasting with XBeach using recentl... more In this paper we present the first results of beach profile hindcasting with XBeach using recently measured coastal data acquired under storm conditions at eight European sites, including a comparison to model results obtained with off-theshelf models. The results show consistently that the XBeach has skill in predicting the coastal profile, albeit that in most cases the erosion around the mean water line is overpredicted and the depositions at the lower beach face are overpredicted. The causes for this model effect are under active investigation but not resolved yet. Likely candidates are the modeling of onshore (asymmetry) transports which reduces the offshore transports due to undertow (currents) or the modeling of sediment motion in the swash zone.
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Papers by Petya Eftimova