Vasilis Baltikas - Academia.edu (original) (raw)

Papers by Vasilis Baltikas

Continental Shelf Research, 2021

Thermaikos Gulf is a typical, river-fed, microtidal, semi-enclosed, coastal inlet of the east-cen... more Thermaikos Gulf is a typical, river-fed, microtidal, semi-enclosed, coastal inlet of the east-central Mediterranean Sea. It is an important coastal ecosystem susceptible to several anthropogenic pressures, strong river discharges and variable meteorological and ocean (met-ocean) conditions. One of the most significant environmental problems of the region is the occasional formation of extended eutrophication phenomena (red tides, mucilaginous aggregates), especially over the Northern Thermaikos Gulf (NTG). Herein, we investigate the contribution of hydrodynamic processes on the formation of such events, under the effects of different meteorological and river discharge conditions during the annual cycle. We conducted field observations (physical-chemical measurements), microscopy analysis of phytoplankton samples, satellite ocean color image analysis, and implemented high-resolution numerical hydrodynamic simulations with updated river discharge outflows to detect eutrophication even...

Environmental Modeling & Assessment, 2021

In deltaic areas, riverine and coastal waters interact; hence, these highly dynamic environments ... more In deltaic areas, riverine and coastal waters interact; hence, these highly dynamic environments are particularly sensitive to climate change. This adds to existing anthropogenic pressures from irrigated agriculture, industrial infrastructure, urbanization , and touristic activities. The paper investigates the estimated future variations in the dynamics of surface and coastal water resources at a Mediterranean deltaic environment for the twenty-first century. Therefore, an Integrated Deltaic Risk Index (IDRI) is proposed as a vulnerability assessment tool to identify climate change impact (CCI) on the study area. For this purpose, three regional climate models (RCM) are used with representative concentration pathways (RCPs) 4.5 and 8.5 for short-term (2021-2050) and long-term (2071-2100) future periods. Extensive numerical modeling of river hydrology, storm surges, coastal inundation, water scarcity, and heat stress on irrigated agriculture is combined with available atmospheric dat...

Global OCEANS 2020 Online Proceedings, 2020

The ability to reliably forecast sea states (most importantly sea level, wind, and wave condition... more The ability to reliably forecast sea states (most importantly sea level, wind, and wave conditions) within or close to the entrance of ports is a critical tool for all involved stakeholders. In this paper, we present our work on a prototype decision support system capable of providing accurate sea state forecasts based on three high-resolution hydrodynamic models, i.e. a spectral wave model (model A), a mild-slope equation wave model (model B), and a barotropic hydrodynamic circulation model (model H). We present an end to end novel data processing pipeline, capable of handling the challenges posed by the volume of related data and capable of providing high-resolution wave forecasts by exploiting parallelization.

Proceedings of virtual Conference on Coastal Engineering 2020, 2020

Karambas and Memos (2009) have presented a protocol version of a post-Boussinesq type wave model ... more Karambas and Memos (2009) have presented a protocol version of a post-Boussinesq type wave model with a system of 2-DH equations for fully dispersive and weakly nonlinear irregular waves over any finite water depth. The model in its two-dimensional formulation, involves in total five terms in each momentum equation, including the classical shallow water terms and only one frequency dispersion term. The latter is expressed through convolution integrals, which are estimated using appropriate impulse functions. In this work, an updated version of the aforementioned model is introduced. It is implemented for wave propagation and transformation (due to shoaling, refraction, diffraction, bottom friction, wave breaking, runup, wave-structure interaction etc.) in nearshore zones and inside ports. One of the main goals is the model's thorough validation, thus it is tested against experimental data of wave transmission over and through breakwaters, uni-and multi-directional spectral wave ...

<p&amp... more <p>Thermaikos Gulf, located in the Northwestern Aegean Sea (Greece), is a marine ecosystem of major importance, not only environmentally (as an area of the deep water formation with contribution to the renewal of the North Aegean deep waters), but also due to the various socioeconomic activities associated with the area. Observational and simulated data are used to investigate the evolution of eutrophication events during the last two years in order to evaluate the current (2017-2019) quality state of the seawater in the Gulf. The quality of the marine environment of Thermaikos Gulf was appraised by measuring physical, chemical and biological parameters. Specific physical-chemical characteristics (temperature, salinity, density along with pH and dissolved oxygen) and biological parameters (chl-a and phytoplankton biomass) throughout the water column were evaluated by conducting in situ measurements during the sampling campaigns. Current fields, derived from a high-resolution 3-D ocean model, together with ADCP measurements, are used to describe the major circulation patterns, the river plume dynamics and the renewal pathways of the Gulf. The obtained results are discussed with regards to seasonal and spatial variability, and the water column stratification. Satellite ocean color data were also used to discuss the in-situ findings and confirm “Dirty” Sea and Red Tide phenomena, that were detected and analyzed based on the physical dynamics and especially the renewal patterns of the Gulf. Moreover, we compare these recent findings to respective observations from a previous period (1997 to 2007) to evaluate potential changes in the quality state of the Gulf with respect to meteorological and river discharge conditions.     </p>

The aim of the present research is the development of a state-of-the-art, high resolution, sea-st... more The aim of the present research is the development of a state-of-the-art, high resolution, sea-state forecasting system (WaveForUs) in the Thermaikos Gulf. The operational system includes mathematical models for the prognosis of: waves (WaveWatch-III), circulation (POM) and storm surges (HRSS). Atmospheric forcing is obtained by the WRF-ARW meteorological model. The WaveForUs system provides 3-day forecasts of waves, circulation, seawater thermohaline properties and sea level height via television broadcasts and web-based applications. The present paper focuses on the basic parameters of the forecasting system and on results from the calibration and validation of the sea-state forecasting models.

Proceedings of the ASLO 2015 Aquatic Sciences Meeting, Feb 26, 2015

Extreme storm surge events pose a great threat to densely populated, low-elevation areas at the c... more Extreme storm surge events pose a great threat to densely populated, low-elevation areas at the coastal zones of the Aegean, Ionian and (northern) Libyan Seas (regional Greek seas of the Mediterranean). Historically, similar events have caused human casualties, damages to coastal structures, and environmental pressures on ecologically sensitive and protected Greek sites (RAMSAR, NATURA 2000). Hereby, we explore the trends of meteorologically induced extremes of sea level, the variability and the occurrence frequency of storm surge extremes at the near-shore regions of Greek Seas for a period of 150 years (1951-2100), under IPCC’s A1B climate scenario (increasing future concentrations of greenhouse gases). In this framework, we use a high resolution (1/20˚) model of 2-D shallow water equations, which is nested to the coarser Mediterranean Climate Surge Model (MeCSM). In situ measurements from Greek tidal gauges are used to evaluate the results. Statistical indexes, high-order percent...

Proceedings of the ASLO 2015 Aquatic Sciences Meeting, Feb 26, 2015

WaveForUs is a high-resolution forecasting system for public and emergency use that delivers 3-da... more WaveForUs is a high-resolution forecasting system for public and emergency use that delivers 3-day sea-state prognoses. In this framework, a prognostic tool for total coastal surges (storm surge, tidal extremes and wave-induced setup) was implemented, aiming at the notification of the authorities and the public in cases of high coastal inundation risk; more specifically, the results of a 2D hydrodynamic model (HRSS) that simulates the free surface elevation due to the combined effect of atmospheric forcing (pressure and wind) and tides and the results of a spectral wave model (WaveWatch-III) are used to estimate the total setup along the coasts, combining storm surge maxima, tidal constituents and near-shore irregular wave breaking. The model is applied in the North Aegean Sea and in the nested domain of Thermaikos Gulf. Both areas are of high environmental and socioeconomic value, with extensive low-elevation planes, protected (Natura 2000 and Ramsar) sites and a broad spectrum of ...

Extreme storm surge events pose a great threat to low-elevation coastal areas and can cause loss ... more Extreme storm surge events pose a great threat to low-elevation coastal areas and can cause loss of land and property, damages to structures and defenses, and even human casualties. Hereby, we explore the trends of meteorologically induced extremes of sea level in the Mediterranean Sea, with a specific focus on the Greek seas, for a period of 150 years (1951-2100). The analysis is based on hydrodynamic simulations of storm surges with a couple of high spatial resolution model implementations for 2D shallow water equations, the Greek Climate Surge Model (GreCSM), which is nested to the coarser domain of the Mediterranean Climate Surge Model (MeCSM). The latter are implemented under IPCC’s A1B climate scenario that considers increasing future concentrations of atmospheric greenhouse gases. In this framework, in situ measurements from several areas, during the last 50 years, are used to evaluate the models’ results. Statistical indices and spatial distributions of extremes, from both h...

A state-of-the-art forecasting system (WaveForUs: Wave climate and coastal circulation Forecasts ... more A state-of-the-art forecasting system (WaveForUs: Wave climate and coastal circulation Forecasts for public Use) is implemented, delivering 3-day forecasts of spectral wave characteristics, hydrodynamic circulation and storm surges for the Thermaikos Gulf (North Aegean Sea). The forecasts are disseminated to the public via television broadcasts and internet applications. The WaveForUs platform is fully functional and aspires to provide users with an invaluable tool for their sea-based activities in Greece. The simulations are based on a storm surge hydrodynamic model, a circulation ocean model and a wave model, while necessary atmospheric input data are provided by a well-validated atmospheric model. The main characteristics of the WaveForUs system and the sea-state models that comprise the core of the modelling system are presented and discussed, while results from calibration/validation tests support the accuracy of the forecasts.

Extreme storm surge events pose a great threat to coastal areas and can cause loss of land and pr... more Extreme storm surge events pose a great threat to coastal areas and can cause loss of land and property, damages to structures and even human casualties. We explore the trends of sea level over the Greek Seas for a period of 150 years (1951-2100) under the A1B future climate scenario, using a high-resolution storm surge model. Our results suggest that there is a general decreasing trend in storminess under the considered climate scenario. More extreme events may occur over the Ionian region, while the southern regions reveal stronger decreasing trends.

Proceedings of virtual Conference on Coastal Engineering 2020, 2020

Karambas and Memos (2009) have presented a protocol version of a post-Boussinesq type wave model ... more Karambas and Memos (2009) have presented a protocol version of a post-Boussinesq type wave model with a system of 2-DH equations for fully dispersive and weakly nonlinear irregular waves over any finite water depth. The model in its two-dimensional formulation, involves in total five terms in each momentum equation, including the classical shallow water terms and only one frequency dispersion term. The latter is expressed through convolution integrals, which are estimated using appropriate impulse functions. In this work, an updated version of the aforementioned model is introduced. It is implemented for wave propagation and transformation (due to shoaling, refraction, diffraction, bottom friction, wave breaking, runup, wave-structure interaction etc.) in nearshore zones and inside ports. One of the main goals is the model's thorough validation, thus it is tested against experimental data of wave transmission over and through breakwaters, uni-and multi-directional spectral wave ...

Sea state (wave, circulation, storm surge) modelling and forecasting in Greece, are notions well ... more Sea state (wave, circulation, storm surge) modelling and forecasting in Greece, are notions well understood, investigated and implemented but only within the scientific community and mainly for research purposes. When it comes to practical implementations, there is poor distribution of the available information to every-day Greek users. Especially for Thermaikos Gulf (NW Aegean Sea), an area of high environmental significance and where a broad spectrum of sea-based activities (tourism, aquacultures, marine transportations, sea-related recreational and nautathletic activities etc) takes place, the availability of high-resolution, gridded sea state prognoses is very low. Under this reasoning, a state-of-the-art forecasting system (WaveForUs: Wave climate and coastal circulation Forecasts for public Use) is implemented that will deliver 3-day forecasts of wave, circulation and storm surges for the Thermaikos Gulf; the forecasts will be disseminated to the public via television broadcas...

Dynamics of Atmospheres and Oceans, 2015

ABSTRACT The trends of storm surge extremes in the Mediterranean Sea for a period of 150 years (1... more ABSTRACT The trends of storm surge extremes in the Mediterranean Sea for a period of 150 years (1951–2100) are explored, using a high-resolution storm surge model. Numerical simulations are forced by the output of regional climate simulations with RegCM3, which uses IPCC’s historical data on greenhouse gasses emissions for the (past) period 1951–2000, and IPCC’s A1B climate scenario for the (future) period 2001–2100. Comparisons between observations and modeling results show good agreement and confirm the ability of our model to estimate the response of the sea surface to future climatic conditions. We investigate the future trends, the variability and frequency of local extremes and the main forcing mechanisms that can induce strong surges in the Mediterranean region. Our results support that there is a general decreasing trend in storminess under the considered climate scenario, mostly related to the frequency of local peaks and the duration and spatial coverage of the storm surges. The northward shift in the location of storm tracks is a possible reason for this storminess attenuation, especially over areas where the main driving factor of extreme events is the inverted barometer effect. However, the magnitudes of sea surface elevation extremes may increase in several Mediterranean sub-regions, i.e., Southern Adriatic, Balearic and Tyrrhenian Seas, during the 21st century. There are clear distinctions in the contributions of winds and pressure fields to the sea level height for various regions of the Mediterranean Sea, as well as on the seasonal variability of extreme values; the Aegean and Adriatic Seas are characteristic examples, where high surges are predicted to be mainly induced by low pressure systems and favorable winds, respectively.

ABSTRACT Low-elevation areas along the Mediterranean coastline are under high inundation risk in ... more ABSTRACT Low-elevation areas along the Mediterranean coastline are under high inundation risk in cases of extreme storm surge events. We explore the trends of sea level extremes for a period of 150 years due to severe atmospheric conditions under a future climate scenario that considers increasing concentrations of atmospheric greenhouse gases. The climate change scenario used in the study is the A1B, one of the 35 Emission Scenarios of the Intergovernmental Panel on Climate Change. The A1B scenario is applied on the 3rd version of the Regional Climate Model (RegCM3) and, in turn, the RegCM3 model forces the hydrodynamic Mediterranean Climate Surge Model, for the period of 1950-2100. In situ measurements from several areas are used to evaluate the storm surge results; spatial distribution of extreme values from both historical data and modeling and statistical comparisons support the good performance of the model. Morphological differences between the Mediterranean regions reveal significant respective differences on the sea level height evolution and especially on the magnitude and occurrence frequency of extreme events under the future climate scenario. The atmospheric distribution of pressure and winds on the storm surge extremes variation and evolution and the general trends of the extremes during the entire study period are also under investigation.

Sustainability

This paper is intended to review the current practices and challenges regarding the corrosion of ... more This paper is intended to review the current practices and challenges regarding the corrosion of the Greek sewer systems with an emphasis on biocorrosion and to provide recommendations to avoid it. The authors followed a holistic approach, which included survey data obtained by local authorities serving more than 50% of the total country’s population and validated the survey answers with field measurements and analyses. The exact nature and extent of concrete biocorrosion problems in Greece are presented for the first time. Moreover, the overall condition of the sewer network, the maintenance frequency, and the corrosion prevention techniques used in Greece are also presented. Results from field measurements showed the existence of H2S in the gaseous phase (i.e., precursor of the H2SO4 formation in the sewer) and acidithiobacillus bacteria (i.e., biocorrosion causative agent) in the slime, which exists at the interlayer between the concrete wall and the sewage. Biocorrosion seems to...

Continental Shelf Research, 2021

Thermaikos Gulf is a typical, river-fed, microtidal, semi-enclosed, coastal inlet of the east-cen... more Thermaikos Gulf is a typical, river-fed, microtidal, semi-enclosed, coastal inlet of the east-central Mediterranean Sea. It is an important coastal ecosystem susceptible to several anthropogenic pressures, strong river discharges and variable meteorological and ocean (met-ocean) conditions. One of the most significant environmental problems of the region is the occasional formation of extended eutrophication phenomena (red tides, mucilaginous aggregates), especially over the Northern Thermaikos Gulf (NTG). Herein, we investigate the contribution of hydrodynamic processes on the formation of such events, under the effects of different meteorological and river discharge conditions during the annual cycle. We conducted field observations (physical-chemical measurements), microscopy analysis of phytoplankton samples, satellite ocean color image analysis, and implemented high-resolution numerical hydrodynamic simulations with updated river discharge outflows to detect eutrophication even...

Environmental Modeling & Assessment, 2021

In deltaic areas, riverine and coastal waters interact; hence, these highly dynamic environments ... more In deltaic areas, riverine and coastal waters interact; hence, these highly dynamic environments are particularly sensitive to climate change. This adds to existing anthropogenic pressures from irrigated agriculture, industrial infrastructure, urbanization , and touristic activities. The paper investigates the estimated future variations in the dynamics of surface and coastal water resources at a Mediterranean deltaic environment for the twenty-first century. Therefore, an Integrated Deltaic Risk Index (IDRI) is proposed as a vulnerability assessment tool to identify climate change impact (CCI) on the study area. For this purpose, three regional climate models (RCM) are used with representative concentration pathways (RCPs) 4.5 and 8.5 for short-term (2021-2050) and long-term (2071-2100) future periods. Extensive numerical modeling of river hydrology, storm surges, coastal inundation, water scarcity, and heat stress on irrigated agriculture is combined with available atmospheric dat...

Global OCEANS 2020 Online Proceedings, 2020

The ability to reliably forecast sea states (most importantly sea level, wind, and wave condition... more The ability to reliably forecast sea states (most importantly sea level, wind, and wave conditions) within or close to the entrance of ports is a critical tool for all involved stakeholders. In this paper, we present our work on a prototype decision support system capable of providing accurate sea state forecasts based on three high-resolution hydrodynamic models, i.e. a spectral wave model (model A), a mild-slope equation wave model (model B), and a barotropic hydrodynamic circulation model (model H). We present an end to end novel data processing pipeline, capable of handling the challenges posed by the volume of related data and capable of providing high-resolution wave forecasts by exploiting parallelization.

Proceedings of virtual Conference on Coastal Engineering 2020, 2020

Karambas and Memos (2009) have presented a protocol version of a post-Boussinesq type wave model ... more Karambas and Memos (2009) have presented a protocol version of a post-Boussinesq type wave model with a system of 2-DH equations for fully dispersive and weakly nonlinear irregular waves over any finite water depth. The model in its two-dimensional formulation, involves in total five terms in each momentum equation, including the classical shallow water terms and only one frequency dispersion term. The latter is expressed through convolution integrals, which are estimated using appropriate impulse functions. In this work, an updated version of the aforementioned model is introduced. It is implemented for wave propagation and transformation (due to shoaling, refraction, diffraction, bottom friction, wave breaking, runup, wave-structure interaction etc.) in nearshore zones and inside ports. One of the main goals is the model's thorough validation, thus it is tested against experimental data of wave transmission over and through breakwaters, uni-and multi-directional spectral wave ...

<p&amp... more <p>Thermaikos Gulf, located in the Northwestern Aegean Sea (Greece), is a marine ecosystem of major importance, not only environmentally (as an area of the deep water formation with contribution to the renewal of the North Aegean deep waters), but also due to the various socioeconomic activities associated with the area. Observational and simulated data are used to investigate the evolution of eutrophication events during the last two years in order to evaluate the current (2017-2019) quality state of the seawater in the Gulf. The quality of the marine environment of Thermaikos Gulf was appraised by measuring physical, chemical and biological parameters. Specific physical-chemical characteristics (temperature, salinity, density along with pH and dissolved oxygen) and biological parameters (chl-a and phytoplankton biomass) throughout the water column were evaluated by conducting in situ measurements during the sampling campaigns. Current fields, derived from a high-resolution 3-D ocean model, together with ADCP measurements, are used to describe the major circulation patterns, the river plume dynamics and the renewal pathways of the Gulf. The obtained results are discussed with regards to seasonal and spatial variability, and the water column stratification. Satellite ocean color data were also used to discuss the in-situ findings and confirm “Dirty” Sea and Red Tide phenomena, that were detected and analyzed based on the physical dynamics and especially the renewal patterns of the Gulf. Moreover, we compare these recent findings to respective observations from a previous period (1997 to 2007) to evaluate potential changes in the quality state of the Gulf with respect to meteorological and river discharge conditions.     </p>

The aim of the present research is the development of a state-of-the-art, high resolution, sea-st... more The aim of the present research is the development of a state-of-the-art, high resolution, sea-state forecasting system (WaveForUs) in the Thermaikos Gulf. The operational system includes mathematical models for the prognosis of: waves (WaveWatch-III), circulation (POM) and storm surges (HRSS). Atmospheric forcing is obtained by the WRF-ARW meteorological model. The WaveForUs system provides 3-day forecasts of waves, circulation, seawater thermohaline properties and sea level height via television broadcasts and web-based applications. The present paper focuses on the basic parameters of the forecasting system and on results from the calibration and validation of the sea-state forecasting models.

Proceedings of the ASLO 2015 Aquatic Sciences Meeting, Feb 26, 2015

Extreme storm surge events pose a great threat to densely populated, low-elevation areas at the c... more Extreme storm surge events pose a great threat to densely populated, low-elevation areas at the coastal zones of the Aegean, Ionian and (northern) Libyan Seas (regional Greek seas of the Mediterranean). Historically, similar events have caused human casualties, damages to coastal structures, and environmental pressures on ecologically sensitive and protected Greek sites (RAMSAR, NATURA 2000). Hereby, we explore the trends of meteorologically induced extremes of sea level, the variability and the occurrence frequency of storm surge extremes at the near-shore regions of Greek Seas for a period of 150 years (1951-2100), under IPCC’s A1B climate scenario (increasing future concentrations of greenhouse gases). In this framework, we use a high resolution (1/20˚) model of 2-D shallow water equations, which is nested to the coarser Mediterranean Climate Surge Model (MeCSM). In situ measurements from Greek tidal gauges are used to evaluate the results. Statistical indexes, high-order percent...

Proceedings of the ASLO 2015 Aquatic Sciences Meeting, Feb 26, 2015

WaveForUs is a high-resolution forecasting system for public and emergency use that delivers 3-da... more WaveForUs is a high-resolution forecasting system for public and emergency use that delivers 3-day sea-state prognoses. In this framework, a prognostic tool for total coastal surges (storm surge, tidal extremes and wave-induced setup) was implemented, aiming at the notification of the authorities and the public in cases of high coastal inundation risk; more specifically, the results of a 2D hydrodynamic model (HRSS) that simulates the free surface elevation due to the combined effect of atmospheric forcing (pressure and wind) and tides and the results of a spectral wave model (WaveWatch-III) are used to estimate the total setup along the coasts, combining storm surge maxima, tidal constituents and near-shore irregular wave breaking. The model is applied in the North Aegean Sea and in the nested domain of Thermaikos Gulf. Both areas are of high environmental and socioeconomic value, with extensive low-elevation planes, protected (Natura 2000 and Ramsar) sites and a broad spectrum of ...

Extreme storm surge events pose a great threat to low-elevation coastal areas and can cause loss ... more Extreme storm surge events pose a great threat to low-elevation coastal areas and can cause loss of land and property, damages to structures and defenses, and even human casualties. Hereby, we explore the trends of meteorologically induced extremes of sea level in the Mediterranean Sea, with a specific focus on the Greek seas, for a period of 150 years (1951-2100). The analysis is based on hydrodynamic simulations of storm surges with a couple of high spatial resolution model implementations for 2D shallow water equations, the Greek Climate Surge Model (GreCSM), which is nested to the coarser domain of the Mediterranean Climate Surge Model (MeCSM). The latter are implemented under IPCC’s A1B climate scenario that considers increasing future concentrations of atmospheric greenhouse gases. In this framework, in situ measurements from several areas, during the last 50 years, are used to evaluate the models’ results. Statistical indices and spatial distributions of extremes, from both h...

A state-of-the-art forecasting system (WaveForUs: Wave climate and coastal circulation Forecasts ... more A state-of-the-art forecasting system (WaveForUs: Wave climate and coastal circulation Forecasts for public Use) is implemented, delivering 3-day forecasts of spectral wave characteristics, hydrodynamic circulation and storm surges for the Thermaikos Gulf (North Aegean Sea). The forecasts are disseminated to the public via television broadcasts and internet applications. The WaveForUs platform is fully functional and aspires to provide users with an invaluable tool for their sea-based activities in Greece. The simulations are based on a storm surge hydrodynamic model, a circulation ocean model and a wave model, while necessary atmospheric input data are provided by a well-validated atmospheric model. The main characteristics of the WaveForUs system and the sea-state models that comprise the core of the modelling system are presented and discussed, while results from calibration/validation tests support the accuracy of the forecasts.

Extreme storm surge events pose a great threat to coastal areas and can cause loss of land and pr... more Extreme storm surge events pose a great threat to coastal areas and can cause loss of land and property, damages to structures and even human casualties. We explore the trends of sea level over the Greek Seas for a period of 150 years (1951-2100) under the A1B future climate scenario, using a high-resolution storm surge model. Our results suggest that there is a general decreasing trend in storminess under the considered climate scenario. More extreme events may occur over the Ionian region, while the southern regions reveal stronger decreasing trends.

Proceedings of virtual Conference on Coastal Engineering 2020, 2020

Karambas and Memos (2009) have presented a protocol version of a post-Boussinesq type wave model ... more Karambas and Memos (2009) have presented a protocol version of a post-Boussinesq type wave model with a system of 2-DH equations for fully dispersive and weakly nonlinear irregular waves over any finite water depth. The model in its two-dimensional formulation, involves in total five terms in each momentum equation, including the classical shallow water terms and only one frequency dispersion term. The latter is expressed through convolution integrals, which are estimated using appropriate impulse functions. In this work, an updated version of the aforementioned model is introduced. It is implemented for wave propagation and transformation (due to shoaling, refraction, diffraction, bottom friction, wave breaking, runup, wave-structure interaction etc.) in nearshore zones and inside ports. One of the main goals is the model's thorough validation, thus it is tested against experimental data of wave transmission over and through breakwaters, uni-and multi-directional spectral wave ...

Sea state (wave, circulation, storm surge) modelling and forecasting in Greece, are notions well ... more Sea state (wave, circulation, storm surge) modelling and forecasting in Greece, are notions well understood, investigated and implemented but only within the scientific community and mainly for research purposes. When it comes to practical implementations, there is poor distribution of the available information to every-day Greek users. Especially for Thermaikos Gulf (NW Aegean Sea), an area of high environmental significance and where a broad spectrum of sea-based activities (tourism, aquacultures, marine transportations, sea-related recreational and nautathletic activities etc) takes place, the availability of high-resolution, gridded sea state prognoses is very low. Under this reasoning, a state-of-the-art forecasting system (WaveForUs: Wave climate and coastal circulation Forecasts for public Use) is implemented that will deliver 3-day forecasts of wave, circulation and storm surges for the Thermaikos Gulf; the forecasts will be disseminated to the public via television broadcas...

Dynamics of Atmospheres and Oceans, 2015

ABSTRACT The trends of storm surge extremes in the Mediterranean Sea for a period of 150 years (1... more ABSTRACT The trends of storm surge extremes in the Mediterranean Sea for a period of 150 years (1951–2100) are explored, using a high-resolution storm surge model. Numerical simulations are forced by the output of regional climate simulations with RegCM3, which uses IPCC’s historical data on greenhouse gasses emissions for the (past) period 1951–2000, and IPCC’s A1B climate scenario for the (future) period 2001–2100. Comparisons between observations and modeling results show good agreement and confirm the ability of our model to estimate the response of the sea surface to future climatic conditions. We investigate the future trends, the variability and frequency of local extremes and the main forcing mechanisms that can induce strong surges in the Mediterranean region. Our results support that there is a general decreasing trend in storminess under the considered climate scenario, mostly related to the frequency of local peaks and the duration and spatial coverage of the storm surges. The northward shift in the location of storm tracks is a possible reason for this storminess attenuation, especially over areas where the main driving factor of extreme events is the inverted barometer effect. However, the magnitudes of sea surface elevation extremes may increase in several Mediterranean sub-regions, i.e., Southern Adriatic, Balearic and Tyrrhenian Seas, during the 21st century. There are clear distinctions in the contributions of winds and pressure fields to the sea level height for various regions of the Mediterranean Sea, as well as on the seasonal variability of extreme values; the Aegean and Adriatic Seas are characteristic examples, where high surges are predicted to be mainly induced by low pressure systems and favorable winds, respectively.

ABSTRACT Low-elevation areas along the Mediterranean coastline are under high inundation risk in ... more ABSTRACT Low-elevation areas along the Mediterranean coastline are under high inundation risk in cases of extreme storm surge events. We explore the trends of sea level extremes for a period of 150 years due to severe atmospheric conditions under a future climate scenario that considers increasing concentrations of atmospheric greenhouse gases. The climate change scenario used in the study is the A1B, one of the 35 Emission Scenarios of the Intergovernmental Panel on Climate Change. The A1B scenario is applied on the 3rd version of the Regional Climate Model (RegCM3) and, in turn, the RegCM3 model forces the hydrodynamic Mediterranean Climate Surge Model, for the period of 1950-2100. In situ measurements from several areas are used to evaluate the storm surge results; spatial distribution of extreme values from both historical data and modeling and statistical comparisons support the good performance of the model. Morphological differences between the Mediterranean regions reveal significant respective differences on the sea level height evolution and especially on the magnitude and occurrence frequency of extreme events under the future climate scenario. The atmospheric distribution of pressure and winds on the storm surge extremes variation and evolution and the general trends of the extremes during the entire study period are also under investigation.

Sustainability

This paper is intended to review the current practices and challenges regarding the corrosion of ... more This paper is intended to review the current practices and challenges regarding the corrosion of the Greek sewer systems with an emphasis on biocorrosion and to provide recommendations to avoid it. The authors followed a holistic approach, which included survey data obtained by local authorities serving more than 50% of the total country’s population and validated the survey answers with field measurements and analyses. The exact nature and extent of concrete biocorrosion problems in Greece are presented for the first time. Moreover, the overall condition of the sewer network, the maintenance frequency, and the corrosion prevention techniques used in Greece are also presented. Results from field measurements showed the existence of H2S in the gaseous phase (i.e., precursor of the H2SO4 formation in the sewer) and acidithiobacillus bacteria (i.e., biocorrosion causative agent) in the slime, which exists at the interlayer between the concrete wall and the sewage. Biocorrosion seems to...