Scour effects in piled structures—A sensitivity analysis

A sensitivity analysis is presented in this paper to judge the importance of several parameters influencing scour effects on piles of offshore foundations. The decrease of the pile reliability due to scour is also studied by applying the first-order reliability method. Suggestions for lateral pile resistance in design are included.     

Shear-wave Velocity Structure around Teide Volcano: Results Using Microtremors with the SPAC Method and Implications for Interpretation of Geodetic Results

Deformation analysis and simulation of volcanic edifices require the construction of models of elastic properties of those structures. In this paper we present an analysis of microtremor measurements recorded during the performance tests of two temporary seismic arrays installed in the eastern portion of the Teide caldera in 1994. We take advantage of recent developments of the SPAC method and use spatial cross-correlation computations to estimate phase velocity dispersion of Rayleigh waves at the location of the arrays. We show that the extension of the standard SPAC method is valid in the case of our data, justifying its use and supporting the generalization of the SPAC method to single station pairs. The phase velocity dispersion curve obtained was inverted to recover the shear-wave profile at the site of the arrays. Our results indicate that the subsoil structure of the caldera is laterally homogeneous at the scale of a few km about the location of the arrays. We obtained about 315 m of volcanic sediments overlying rocks with a shear-wave velocity of 2 km/s. These results are robust and are a starting point to further modelling of deformation, permanent or transient, at this volcanic edifice, which can be useful in the interpretation of different observed fields. In fact, the computation of deformations and gravity changes due to possible volcanic intrusions in two models; one considering the volcanic sediments and the other without considering them, provided different results in the near field.     

Energy poverty in Greek mountainous areas: a comparative study

The paper studied the energy poverty in the mountainous areas of Greece through parallel primary surveys, in comparison with the country-level conditions. The surveys are based on objective financial and expenditure data as well as on subjective views about housing conditions. The objective approach showed that mountainous areas of Greece are burdened with much higher energy expenditure while also having lower annual incomes. Under these circumstances, the energy poverty rate skyrocketed to 73.5%. The subjective indicators reveal significant aspects of the problem, such as the intense problem of damp walls and mold growth at home or the restriction of other basic needs in order to cover heating needs. However, despite the proven high vulnerability of Greek mountainous areas, current energy policy actually ignores the special features of mountainous areas, implementing horizontal policies. Therefore, a specialized energy plan targeted to alleviating energy poverty in mountainous areas in Greece is an urgent imperative.     

Macrobenthic community structure over the continental margin of Crete (South Aegean Sea, NE Mediterranean)

Macrobenthic faunal composition, abundance, biomass and diversity together with a suite of sedimentary environmental parameters were investigated on a seasonal basis in order to determine factors regulating faunal distribution over the oligotrophic continental margin of the island of Crete (South Aegean Sea, North Eastern Mediterranean). Macrofaunal species composition was similar to that of the western Mediterranean and the neighboring Atlantic having several common dominant species. Mean benthic biomass, abundance and diversity decreased with depth, with a major transition zone occurring at 540 m, beyond which values declined sharply. At comparable depths biomass and abundance values were considerably lower to those found in the Atlantic, high-lighting the extreme oligotrophy of the area. The continental margin of Crete was characterised by a high diversity upper continental shelf environment (dominated by surface deposit feeding polychaetes) and a very low diversity slope and deep-basin environment (dominated by carnivorous and filter feeding polychaetes). Classification and ordination analyses revealed the existence of four principle clusters divided by a faunal boundary between 200 and 540 m, as well as beyond 940 m depth. Significant correlations between macrofauna and sediment parameters led to the conclusion that besides depth, food availability (as manifested by the concentration of chloroplastic pigments) is the principle regulating factor in the system. Such being the case, the prevailing hydrographic features that structure the pelagic food web and are directly responsible for the propagation of organic matter to the benthos also affect its community structure.     

Safety level of damaged RoPax ships: Risk modelling and cost-effectiveness analysis

This paper elaborates on results of a recent risk analysis study for RoPax vessels, carried out as part of the activities of the SAFEDOR Integrated Project, targeting possible improvements on safety levels following large scale flooding. The study is based on a comprehensive analysis of accident statistics for the period 1994–2004, through which a high-level risk model (in the form of event trees) is established. This is then used to determine the current safety level of RoPax vessels (in various risk metrics, such as individual risk, potential loss of life and on an F–N curve), reconfirming that even though safety levels are improving, risk is still “high in the ALARP region”. In search of ways to further improve the situation possible risk control options are examined, by performing a sensitivity analysis on the effects of the Attained Index of Subdivision A onto the safety levels and by evaluating their cost-effectiveness.     

Maximum urban heat island intensity in a medium-sized coastal Mediterranean city

This paper studies the maximum intensity of the urban heat island (UHI) that develops in Volos urban area, a medium-sized coastal city in central Greece. The maximum temperature difference between the city center and a suburb is 3.4°C and 3.1°C during winter and summer, respectively, while during both seasons the average maximum UHI intensity is 2.0°C. The UHI usually starts developing after sunset during both seasons. It could be attributed to the different nocturnal radiative cooling rate and to the different anthropogenic heat emission rate that are observed at the city center and at the suburb, as well as to meteorological conditions. The analysis reveals that during both seasons the daily maximum hourly (DMH) UHI intensity is positively correlated with solar radiation and with previous day’s maximum hourly UHI intensity and negatively correlated with wind speed. It is also negatively correlated with relative humidity during winter but positively correlated with it during summer. This difference could be attributed to the different mechanisms that mainly drive humidity levels (i.e., evaporation in winter and sea breeze (SB) in summer). Moreover, it is found that SB development triggers a delay in UHI formation in summer. The impact of atmospheric pollution on maximum UHI intensity is also examined. An increase in PM10 concentration is associated with an increase in maximum UHI intensity during winter and with a decrease during summer. The impact of PM10 on UHI is caused by the attenuation of the incoming and the outgoing radiation. Additionally, this study shows that the weekly cycle of the city activities induces a weekly variation in maximum UHI intensity levels. The weekly range of DMH UHI intensity is not very large, being more pronounced during winter (0.4°C). Moreover, a first attempt is made to predict the DMH UHI intensity by applying regression models, whose success is rather promising.     

Assessing the economic value of vernacular architecture of mountain regions using contingent valuation

Human pressure on mountain resources poses certain threats to their natural and man-made environment. Although there are many parameters involved, one of the driving forces behind this situation is the emphasis given so far only to the market value of mountain goods and services, ignoring the true social and environmental costs of using mountain resources. Towards this direction, the use of non-market valuation techniques could prove to be beneficial. Bearing in mind the above remarks, the paper presents an application of the Contingent Valuation Method, which aims at estimating the monetary value of a mountain settlement’s vernacular architecture, namely Metsovo. For this purpose, the survey focuses on Metsovo visitors’ willingness to pay a single annual voluntary contribution to an institution that would be founded in order to undertake all necessary actions required to preserve the town’s traditional character. The results are very promising and indicate that vernacular architecture holds a significant economic value that could justify the implementation of appropriate policies towards the protection of vernacular settlements in mountain areas.     

Seismotectonic regionalization of the Red Sea area and its application to seismic risk analysis

A seismological evaluation of the Red Sea margin is presented in this contribution based on the concept of seismotectonic regionalization. The geology and the tectonic structure are critically reviewed to define regions of homogeneous seismicity in the study area, and available seismicity data are implemented to estimate the seismic parameters of the region. The results of the study are applied to evaluate the seismic hazard of an offshore platform site.